,as the ,nation's principal conservation agency1 the ,department of the ,interior has basic responsibilities for water1 fish1 wildlife1 mineral1 land1 park1 and recreational resources4 ,indian and ,territorial affairs are other major concerns of ,america's 8,department of ,natural ,resources40 ,the ,department works to assure the wisest choice in managing all our resources so each will make its full contribution to a better ,united ,states--now and in the future4 ,this publication is one in a series of research studies devoted to special topics which have been explored in connection with the various areas in the ,national ,park ,system4 ,it is printed at the ,government ,printing ,office and may be purchased from the ,superintendent of ,documents1 ,government ,printing ,office1 ,washington1 ,d4,c4 #bjdjb4 ,library of ,congress ,cataloging in ,publication ,data ,mc,grew1 ,paul ,orman1 #aiji- ,the geological history of ,fossil ,butte ,national ,monument and ,fossil ,basin4 7,national ,park ,service occasional paper2 no4 #c7 ,bibliography3 p4 ,includes index4 #a4 ,geology--,wyoming--,fossil ,butte ,national ,monument4 #b4 ,geology1 ,stratigraphic--,eocene4 #c4 ,paleontology--,eocene4 #d4 ,fossil ,butte ,national ,monument1 ,wyo4 ,i4 ,casilliano1 ,michael1 joint author4 ,,ii4 ,title4 ,,iii4 ,series3 ,united ,states4 ,national ,park ,service4 ,national ,park ,service occasional paper2 no4 #c4 ,,qe#ahb4;,f#fg,m#c #eeg4hg'hb #ge-ageaa ,the ,geological ,history of ,fossil ,butte ,national ,monument and ,fossil ,basin ,paul ,o4 ,mc,grew ,michael ,casilliano ,department of ,geology1 ,university of ,wyoming ,,national ,,park ,,service ,,occasional ,,paper ,,number ,,three ,illustration3 ,excavations in progress ,contents ,,introduction #a ,,location #a ,,historical ,,background ,,of ,,research #a ,,stratigraphy #e ,thaynes ,limestone #g ,evanston ,formation #g ,wasatch ,formation #g ,basal ,conglomerate ,member #i ,lower ,member #i ,main ,body #aa ,sandstone ,tongue #aa ,mudstone ,tongue #ab ,bullpen ,member #ab ,tunp ,member #ab ,age of the ,wasatch ,formation #ab ,depositional ,environment #ac ,green ,river ,formation #ac ,fossil ,butte ,member #ac ,angelo ,member #ad ,age of the ,green ,river ,formation #ad ,depositional ,environment #ad ,fowkes ,formation #ae ,sillem ,member #ae ,bulldog ,hollow ,member #ae ,gooseberry ,member #ae ,age of the ,fowkes ,formation #ae ,depositional ,environment #ae ,,quaternary #ae ,,the ,,geologic ,,structure ,,of ,,fossil ,,basin #ae ,,paleontology #ai ,flora #ai ,invertebrates #bj ,vertebrates #bj ,fish #bj ,amphibians #bd ,reptiles #bd ,birds #bd ,mammals #be ,,paleoecology ,,and ,,taphonomy #cj ,,glossary #cd ,,references #ce ,,bibliography #cg ,,acknowledgments #cg ,,introduction ,fifty million years ago the southwestern corner of what is now ,wyoming was part of a system of three freshwater lakes that covered that area plus adjacent parts of ,colorado and ,utah4 ,these lakes began with ,lake ,flagstaff and later became ,lake ,gosiute1 ,lake ,uinta1 and ,fossil ,lake 7,fig4 #a74 ,these lakes developed in intermontane basins that were created as a result of the geologic events that formed the ,rocky ,mountains4 ,the three lakes1 collectively known as the ,green ,river ,lake ,system1 had a long1 complex history of expansion and contraction4 ,varying climatic and geologic conditions were responsible for the changes in lake size and distribution4 ,the shores surrounding the lakes were blanketed by a lush1 green canopy of palm1 cinnamon1 maple1 oak1 and other familiar trees4 ,hazel and lilac covered the forest floor4 ,rushes and other aquatic plants lined the lake shore4 ,the air was humid and warm4 ,streams flowing down from the hills and mountains built up flood plains and fed sediment into the lake1 where it was deposited in shallow water near the shore4 ,deposits formed by chemical processes settled to the bottom further from shore in deep1 quiet water4 ,from these processes were formed the rocks from which the past history of ,green ,river ,lake ,system is read4 ,in the forest and undergrowth lived the ancestors of modern mammal groups4 ,ancestral rodents and tiny insectivores lived a furtive existence in the brush and mold that carpeted the forest floor1 or else they sought a livelihood among the branches of trees4 ,large1 bizarre animals with strange names lumbered through the reed-covered streamsides eating soft1 succulent plants4 ,the earliest members of the horse family browsed on the soft vegetation4 ,the trees overhead were alive with the chattering and antics of early primates4 ,carnivorous mammals preyed on their plant-eating neighbors and so maintained a balanced community4 ,crocodiles and turtles basked in the sun on the beach4 ,flamingos concentrated in large nesting grounds4 ,snakes and lizards crawled about in the undergrowth4 ,insects1 many exceedingly similar to modern types1 flew about in the warm air or crept about on the plants4 ,the waters of the lakes teemed with many types of fish4 ,relatives of the perch1 herring1 and sting ray swam in the warm lake water4 ,occasionally1 large-scale mortalities of the fish occurred4 ,as the fish died1 they sank to the bottom of the lake1 and were preserved in the lake sediments4 ,today1 the lakes are gone and where once there were lush tropical forests there is now a semi-desert covered with sagebrush and greasewood4 ,the history of these lakes1 forests1 and animal life can be read in the thick sediments deposited so long ago4 ,this report concerns itself with one of these lakes1 the smallest of the three1 ,fossil ,lake4 ,famous for its fossil fish beds1 part of this ancient lake is now ,fossil ,butte ,national ,monument4 ,it is the purpose of this report to relate the history of ,fossil ,lake and its now fossilized inhabitants1 thereby1 hopefully presenting the order of events in a landscape obscured by #ej million years of time4 ,,location ,fossil ,butte ,national ,monument is near the geographical center of ,fossil ,basin4 ,the basin itself is located in the extreme southwestern part of ,wyoming in ,uinta and ,lincoln counties1 near the ,utah-,idaho border 7,fig4 #b74 ,the monument is situated about #aj miles west of ,kemmerer1 ,lincoln ,county1 ,wyoming 7,fig4 #c74 ,u4,s4 ,highway #cj,n runs just south of the monument as does the ,union ,pacific ,railroad line to ,oregon4 ,the abandoned town of ,fossil is also immediately south of the monument4 ,the ,kemmerer and ,sage quadrangles of the ,united ,states ,geological ,survey cover the entire monument and the surrounding area4 ,,historical ,,background ,,of ,,research ,the principal rocks involved at ,fossil ,butte are the ,green ,river and ,wasatch formations4 ,the first published notice of these two rock units was by ,hayden 7#ahfi74 ,although short1 ,hayden's descriptions were the basis for later refinement of the stratigraphy of the ,green ,river and ,fossil basins4 ,hayden also mentioned the quantities of fossil fish from the ,green ,river ,formation4 ,the work done by ,hayden was conducted under the auspices of the ,u4,s4 ,department of the ,interior1 ,geological and ,geographical ,survey of the ,territories4 ,the survey lasted from #ahfg to #ahgh1 during which time ,hayden and his associates published annual reports of their findings4 ,in the #ahgj report1 ,hayden 7#ahga7 mentioned the discovery of the ,petrified ,fish ,cut4 ,this cut is located on the main line of the ,union ,pacific ,railroad about #b miles west of ,green ,river1 ,wyoming4 ,a4 ,w4 ,hilliard and ,l4 ,e4 ,rickseeker1 employees of the ,union ,pacific ,railroad1 discovered the cut and obtained many fossil fish which they turned over to ,hayden4 ,previous to ,hayden1 rocks now known as the ,green ,river and ,wasatch formations were occasionally mentioned in the various diaries1 journals1 and reports of early missionaries like those of ,s4 ,a4 ,parker or those of explorers like ,fremont 7,knight #aiee74 ,illustration3 ,fig4 #a4 ,paleocene-,eocene lake system 7after ,schaeffer and ,mangun #aife74 ,illustration3 ,fig4 #b4 ,geographic features of southwest ,wyoming and adjacent areas 7from ,oriel and ,tracey #aigj74 ,illustration3 ,fig4 #c4 ,physiography of the ,fossil ,butte ,national ,monument region 7from ,u4,s4 ,department of the ,interior #aifd74 ,hayden's report 7#ahga3dbe-dcg7 included a description of the fish fossils from ,petrified ,fish ,cut by ,e4 ,d4 ,cope1 a vertebrate paleontologist4 ,several years earlier ,leidy 7#ahef71 another paleontologist1 described a fish from an unknown locality in the ,green ,river ,formation4 ,hayden divided this survey area into several districts4 ,the ,green ,river district was put in charge of ,a4 ,c4 ,peale4 ,peale's 7#ahgi3ece7 report contained the first geologic description of ,fossil ,butte itself1 as well as a short discussion of the fish fossils obtained there4 ,the description of the butte is quoted here3 444 ,in the lower part of the bluff from which these specimens are taken1 the bright coloured beds of the ,wasatch are seen outcropping1 although the entire section cannot be seen1 as their softness causes them to weather so that the debris conceals the strata4 ,the fossils are found at several horizons in the shales4 ,near the top of the bluff is a band of hard1 bituminous1 or oily shale1 which burns rather freely with a strong bituminous odor4444 ,it is brownish-black in color and on the weathered surfaces a bluish white4444 ,the next major publication dealing with ,fossil ,basin was that by ,veatch 7#aijg74 ,he mapped the rocks in certain areas of the basin in an attempt to bring a semblance of order to ,hayden's 7#ahfi7 broad stratigraphic descriptions4 ,his work resulted in the designation of most of the rock units in ,fossil ,basin from ,jurassic to ,recent4 ,schultz 7#aiad71 an associate of ,veatch1 published a paper dealing with the structures to the north and east of ,fossil ,basin4 ,this helped to delineate the features surrounding and forming the basin4 ,subsequent work on the geology of southwest ,wyoming mainly has been concentrated on the ,green ,river ,basin just east of ,fossil ,basin4 ,significant work on ,fossil ,basin has been done by ,rubey et al4 7#aifh;a1 b7 who mapped the northern part of the basin1 and by ,oriel and ,tracey 7#aigj7 who have published results of the latest study on the stratigraphy and age of the rock units in ,fossil ,basin4 ,this latest work is the culmination of many years of study and incorporates and refines data presented in shorter1 earlier papers4 ,,stratigraphy ,the complete geologic history of the ,fossil ,basin involves many stratigraphic units4 ,most of these are not exposed within the monument itself but are well known from outcrops outside the boundaries of the monument and from deep wells 7,fig4 #d74 ,at the base of the stratigraphic section are rocks of ,precambrian age4 ,these have not been penetrated by wells within the ,fossil ,basin but should occur as much as #be1jjj ft beneath the surface4 ,they probably consist of metamorphic and intrusive rocks4 ,beginning about #fjj million years ago1 at the beginning of ,cambrian time1 sedimentary deposits accumulated4 ,these are both marine and continental in origin and range in age from early ,cambrian 7#fjj million years old7 to early ,tertiary 7#ej million years old74 ,some #cd geologic formations are recognized in this thick section1 a list of which follows3 ,eocene ,fowkes ,formation ,wasatch-,green ,river ,formations ,paleocene ,evanston ,formation 7upper part7 ,upper ,cretaceous ,evanston ,formation 7lower part7 ,adaville ,formation ,lazeart ,sandstone ,hilliard ,shale ,frontier ,formation ,lower ,cretaceous ,aspen ,shale ,bear ,river ,formation ,gannett ,group ,jurassic ,stump ,sandstone ,preuss ,sandstone ,twin ,creek ,limestone ,nugget ,sandstone 7upper part7 ,triassic ,nugget ,sandstone 7lower part7 ,thaynes ,limestone ,woodside ,formation ,dinwoody ,formation ,permian ,phosphoria ,formation ,pennsylvanian ,wells ,formation ,mississippian ,brazer ,limestone ,madison ,limestone 7upper part7 ,devonian ,madison ,limestone 7lower part7 ,darby ,formation ,silurian ,not ,present ,ordovician ,leigh ,dolomite ,bighorn ,dolomite ,cambrian ,gallatin ,limestone ,gros ,ventre ,formation ,precambrian ,complex of metamorphic and intrusive rocks ,within the monument itself the oldest rocks exposed are those of the ,thaynes ,limestone near ,prow ,point4 ,as will be seen in the discussion of the structure of the ,fossil ,basin1 all of the rocks beneath the ,evanston ,formation are folded and faulted and within the monument are buried by deposits of ,tertiary age4 ,for this reason detailed discussion of stratigraphic units will be confined to those rocks that can be seen within the boundaries of the monument or closely adjacent to it 7,fig4 #e 74 ,the distribution of the various formations within the monument is illustrated in ,figs4 #g and #h4 ,illustration3 ,fig4 #d4 ,geologic time scale4 ,era_/,period_/,epoch ,age ,major ,biological ,geologic ,events 7,millions of years7 ,,cenozoic ,quaternary ,ice ,age begins and evolution of modern mammals2 man reaches ,n4 ,a42 general uplift of continent4 ,holocene 7,recent7 4#ja ,pleistocene #c ,tertiary ,evolution and ,development of major mammal groups2 ,cascadian ,orogeny in northwestern ,united ,states2 in latest ,cenozoic1 ,eocene lake system4 ,pliocene #e4e ,miocene #be4e ,oligocene #cf ,eocene #ed ,paleocene #fe ,,mesozoic ,cretaceous #acj ,extinction of dinosaurs2 flowering plants flourish2 height of ,cordilleran ,orogeny4 ,jurassic #ahe ,first birds1 dinosaurs and mammals continue to evolve2 beginning of ,cordilleran ,orogeny which formed the ,rocky ,mountains4 ,triassic #bcj ,conifers evolved2 first dinosaurs2 first mammals2 ,appalachian ,orogeny2 some orogeny in ,cordillera4 ,,paleozoic ,permian #bfe ,archaic reptiles and mammal-like reptiles evolve4 ,appalachian ,orogeny4 ,pennsylvanian #caj ,first reptiles1 coal swamps formed2 beginning of the ,appalachian ,orogeny4 ,mississippian #cee ,expansion of amphibians2 much carbonate deposition2 ,antler ,orogeny in ,cordilleran ,mobile ,belt 7,rocky ,mountain area74 ,devonian #dac ,first land plants2 first jawed fishes1 sharks and bony fish2 amphibians appear2 ,acadian ,orogeny in the ,appalachian belt4 ,silurian #dbe ,jawless fishes evolved2 much reef development2 evaporite mineral development4 ,ordovician #dge ,first vertebrate remains known from this time2 ,taconic ,orogeny in ,appalachian belt4 ,cambrian #fjj ,first shelled invertebrates2 major flooding of ,north ,america4 ,notes3 ,reformatted table to combine #8,era'1 #8,period'1 and #8,epoch' columns into one column in outline form4 ,beneath heading #8,epoch'3 87,cenozoic only702 beside other periods1 8,epochs for these periods are not definitely established0 ,as the last line1 8,precambrian time began #e billion years ago40 ,thaynes ,limestone ,at the very northeastern corner of ,fossil ,butte ,national ,monument can be seen an outcrop of the ,thaynes ,limestone of ,triassic age1 a marine unit deposited some #bjj million years ago4 ,this formation is noted for its rich and varied assemblage of marine fossils1 mostly forms related to oysters and clams4 ,the ,thaynes ,limestone consists predominantly of sandy1 gray limestone and green-gray limey siltstones4 ,the formation weathers to a dark brown in the lower part and a grayish-yellow in the upper4 ,the fact that the ,thaynes ,limestone is exposed in the monument at all is because of the faulting that took place just prior to the deposition of the ,evanston ,formation of latest ,cretaceous and earliest ,tertiary age 7refer to section on structure7 and the erosion of the ,tertiary rocks that once covered it4 ,evanston ,formation ,although not seen within the boundaries of the ,fossil ,butte ,national ,monument1 the ,evanston ,formation is exposed just south of ,highway #cj,n1 #a4e miles southeast of the southeast corner of the monument4 ,the ,evanston was not involved in the complex folding and faulting but it is somewhat disturbed and rests under the ,wasatch ,formation with angular uncomformity4 ,the ,evanston ,formation bridges the time boundary between the ,cretaceous and ,tertiary periods4 ,in the lower part of the unit are found many fossil leaves1 pollen1 and spores and a jaw of the horned dinosaur ,triceratops that prove its ,cretaceous age1 and in the upper part are found fossil mammals of ,paleocene age4 ,the ,evanston ,formation has been studied in detail by ,oriel and ,tracey 7#aigj74 ,these authors divide the formation into three members4 ,the lowest1 which they called the ,lower ,member1 is predominantly 8gray to very dark gray mudstone1 siltstone1 claystone and gray carbonaceous sandstone40 ,the ,lower ,member reaches a thickness of #ejj ft in some places4 ,above and in part interfingering with the ,lower ,member is a #ajjj ft thick unit that was named the ,hams ,fork ,conglomerate ,member4 ,this unit consists of beds of boulder conglomerate interstratified with thick beds of coarse1 partly conglomeratic brown sandstone and gray mudstone4 ,where the ,lower ,member of the ,evanston is missing1 the ,hams ,fork ,conglomerate forms the base of the formation4 ,the ,upper ,member of the ,evanston ,formation is termed by ,oriel and ,tracey 7#aigj7 the ,main ,body4 ,it is more than a thousand feet thick and the lower part intertongues with the ,hams ,fork ,conglomerate4 ,the ,main ,body is 8light to dark gray carbonaceous sandy to clayey siltstone interbedded with gray1 tan1 yellow and brown sandstone and conglomerate and carbonaceous to lignitic claystone40 ,it is this ,main ,body that can be seen along the highway just southeast of the monument4 ,the types of sediments and fossils found in the ,evanston indicate that the formation was deposited by streams on flood plains and in marshes and ponds4 ,a subtropical climate is indicated and the area was heavily wooded4 ,wasatch ,formation ,the term ,wasatch was first used by ,hayden 7#ahfi3ia7 as follows3 ,immediately west of ,fort ,bridger commences one of the most remarkable and extensive groups of ,tertiary beds seen in the ,west4 ,they are wonderfully variegated1 some shade of red predominating4 ,this group1 to which ,i have given the name of ,wasatch group1 is composed of variegated sands and clays4 ,very little calcareous matter is found in these beds4 ,in ,echo and ,weber ,canyons are wonderful displays of conglomerates1 fifteen hundred to two thousand feet in thickness4 ,although this group occupies a vast area1 and attains a thickness of three to five thousand feet1 yet ,i have never known any remains of animals to be found in it4 ,i regard it1 however1 as of middle ,tertiary age4 ,the ,wasatch is well exposed in ,fossil ,basin4 ,there the unit was regarded by ,veatch 7#aijg7 as a group and divided by him into three formations3 the ,almy1 ,fowkes1 and ,knight4 ,he wrote 7#aijg3hh73 ,in the ,wasatch group as thus defined by ,hayden the field work of the season #aije showed three divisions3 #a7 a basal member composed of reddish-yellow sandy clays1 in many places containing pronounced conglomerate beds1 which has been named the ,almy ,formation2 #b7 a great thickness of light-colored rhyolitic ash beds containing intercalated lenses of white limestones with fresh-water shells and leaves--the ,fowkes ,formation2 and #c7 a group of reddish-yellow sandy clays with irregular sandstone beds 7the ,knight ,formation7 closely resembling #a7 lithologically and separated from #a7 #b7 by a pronounced period of folding and erosion4 ,veatch1 however1 erred in his field work and did not realize that the ,fowkes ,formation had been downfaulted into the position in which he saw it 7,tracey and ,oriel #aiei2 ,eardley #aiei74 ,the ,fowkes is actually the youngest of the three formations of ,veatch and is considerably later in age than the true ,wasatch4 ,the ,almy and ,knight formations are not separable 7,oriel and ,tracey #aigj3af71 and can be seen to grade into each other at the basin edges4 ,illustration3 ,fig4 #e4 ,intertonguing relationship of latest ,cretaceous and ,tertiary stratigraphic units of ,fossil ,basin4 ,recent1 ,pleistocene ,pleistocene and ,recent gravel and alluvium ,pliocene ,gooseberry ,member of ,fowkes ,formation ,oligocene to ,pliocene ,hiatus ,eocene ,bridgerian ,fowkes ,fm4 ,bulldog ,hollow ,member ,sillem ,member ,unconformity ,wasatchian3 ,wasatch ,formation1 ,tunp ,member ,bullpen ,member ,green ,river ,formation ,angelo ,member ,mudstone ,tongue ,fossil ,butte ,member ,sandstone ,tongue ,main ,body ,lower ,member ,basal ,conglomerate ,member ,paleocene ,possible hiatus or unconformity ,evanston ,formation ,main ,body ,hams ,fork ,conglomerate ,member ,latest ,cretaceous ,lower ,member ,,unconformity ,late ,cretaceous ,adaville and older formations ,illustration3 ,fig4 #f4 ,subdivisions of ,paleocene and ,eocene time4 ,eocene ,late ,eocene ,uintan ,mid ,eocene ,bridgerian ,early ,eocene ,wasatchian ,lostcabinian ,lysitean ,graybullian ,paleocene ,late ,paleocene ,tiffanian ,mid ,paleocene ,torrejonian ,early ,paleocene ,dragonian ,puercan ,the ,almy and ,knight1 as defined by ,veatch1 are probably different facies of ,wasatch1 the ,almy being a more peripheral facies and the ,knight a more basinal facies 7,oriel and ,tracey #aigj74 ,these authors proposed that the terms ,almy and ,knight be dropped and that the name ,wasatch be applied to all these rocks to avoid confusion4 ,the latest subdivision of the ,wasatch ,formation in the ,fossil ,basin is that of ,oriel and ,tracey4 ,the members of the ,wasatch ,formation they propose are described in order from oldest to youngest4 ,,basal ,,conglomerate ,,member4 ,this member has only local development in ,fossil ,basin4 ,where found1 it is a lenticular conglomerate with pebbles and cobbles of buff and tan sandstone from the ,nugget ,sandstone and limestone fragments from the ,thaynes and ,twin ,creek formations4 ,the basal conglomerate is essentially a channel fill in ancient stream beds cut into ,mesozoic rocks4 ,,lower ,,member4 ,this is an irregular sequence of flood-plain and stream-channel deposits4 ,it is exposed along the southern part of the ,tunp ,range and extends into the far western section of ,fossil ,butte ,national ,monument just below ,prow ,point4 ,mudstone is the main rock type4 ,it can be tan1 brown1 pink1 red1 or gray in color4 ,black1 carbonaceous siltstones are also present4 ,gray sandstone that weathers yellow or brown and coarse-grained1 cross-bedded conglomerate and sandstone are also prominent4 ,limestone occurs as thin lenses and is often brown1 platy1 and carbonaceous4 ,it is interesting to note that the ,lower ,member is intermediate not only in stratigraphic position but also in color and composition between the underlying ,evanston ,formation and overlying ,main ,body of the ,wasatch ,formation4 ,the ,lower ,member thus appears to represent a gradual change in either climatic and_/or sedimentary conditions in ,fossil ,basin 7,oriel and ,tracey #aigj74 ,illustration3 ,fig4 #g4 ,geologic map of ,fossil ,butte ,national ,monument 7after ,rubey et al4 #aifh74 ,,legend ,quaternary--,qg-,qaf--,gravel stream deposits ,eocene ,green ,river ,fm4 ,tga--,angelo ,member ,tgf--,fossil ,butte ,member ,wasatch ,fm4 ,twb--,bullpen ,member ,twm--,mudstone ,tongue ,tw--,main ,body ,twl--,lower ,member ,triassic ,,tr--,thaynes ,limestone ,illustration3 ,fig4 #h4 ,,nw-,,se section across ,fossil ,butte ,national ,monument1 ,sage and ,kemmerer quadrangles 7mapped by ,rubey et al4 #aifh74 ,eocene ,twb--,bullpen ,member of ,wasatch ,fm4 ,tga--,angelo ,member of ,green ,river ,fm4 ,twm--,mudstone tongue of ,wasatch ,fm4 ,tgf--,fossil ,butte ,member of ,green ,river ,fm4 ,tw--,main body of ,wasatch ,fm4 ,,main ,,body4 ,this unit of the ,wasatch ,formation is that part of the formation which produces the spectacular red-colored badlands in ,fossil ,butte ,national ,monument4 ,particularly typical exposures can be seen in the south-facing scarp of ,fossil ,butte where the ,main ,body makes up the lower portion of the butte4 ,the most remarkable feature of the ,main ,body is its color4 ,on the lower slopes of ,fossil ,butte are bands of bright to dull red1 pink1 purple1 yellow1 and gray color arranged in various patterns4 ,this unit is best observed at a distance1 especially after a rain4 ,the bright hues of the ,wasatch contrast markedly with the whites and tans of the overlying ,green ,river ,formation4 ,individual bands of color range from #a to #aj ft thick 7,oriel and ,tracey #aigj3gh74 ,the colors are brightest in the upper part of the member and drabber in the coarser-grained lower part4 ,the predominant rock types in the ,main ,body are banded1 variegated mudstone with interlayered sandstone1 conglomerate1 marlstone1 siltstone1 and claystone4 ,the upper part of the ,main ,body is mainly mudstone composed of fine silt and very fine1 bedded sand with a clay binder4 ,conglomerates occur as channel fills and contain calcium carbonate as cement as do a number of sandstone and siltstone layers in the upper ,main ,body4 ,conglomerates and sandstone are more common in the lower part of the ,main ,body4 ,some are part of ,veatch's old ,almy ,formation4 ,they are best developed along the edge of ,fossil ,basin4 ,the ,main ,body overlaps the ,evanston ,formation in some places and may rest directly on ,mesozoic or ,paleozoic rocks4 ,,sandstone ,,tongue4 ,this is a tongue of cross-bedded sandstone4 ,it is brown in color and is composed mostly of quartz with some black chert grains4 ,this unit is limited in distribution to the south of ,fossil ,butte ,national ,monument4 ,the ,sandstone ,tongue thins and pinches out to the north and is not present within the monument4 ,the area of pinchout represents the shoreline at one stage of ,fossil ,lake4 ,the ,sandstone ,tongue wedges into the ,fossil ,butte ,member of the ,green ,river ,formation4 ,the sediment sources were probably the ,uinta ,mountains at the south edge of ,fossil ,basin4 ,tectonic events caused an uplift and erosion of ,mesozoic and ,paleozoic rocks in the ,uintas and debris was deposited in ,fossil ,lake as an encroaching delta of sand4 ,when deposition of the sand halted1 the lake expanded and covered the sand1 encasing it within the shales of the ,green ,river ,formation4 ,the ,sandstone ,tongue can be traced into the ,main ,body of the ,wasatch1 hence its assignment to the ,wasatch ,formation4 ,,mudstone ,,tongue4 ,this tongue of the ,wasatch ,formation can be seen in the northwestern part of ,fossil ,butte ,national ,monument and over most of the northern part of ,fossil ,basin4 ,in the area of its distribution1 the ,mudstone ,tongue separates the underlying ,fossil ,butte ,member of the ,green ,river ,formation from the overlying ,angelo ,member of the ,green ,river ,formation4 ,the tongue thins and disappears to the south1 that is1 basinward4 ,as with the ,sandstone ,tongue1 the edges of the ,mudstone ,tongue where it pinches out represent an ancient shoreline of ,fossil ,lake4 ,to the north and west the ,mudstone ,tongue merges with the ,tunp ,member of the ,wasatch ,formation4 ,the ,mudstone ,tongue is a composite of dark-red mudstone which becomes lighter in color basinward1 changing to light red1 pink1 or greenish-gray claystone4 ,the unit is a mixture of silt and clay derived from the north and west1 and was deposited as a large delta in ,fossil ,lake4 ,an interesting aspect of the ,mudstone ,tongue is the presence of algal logs4 ,these are cylinders of limestone that apparently formed as an encrustation of calcium carbonate around logs and branches that fell into the edge of the lake4 ,the calcium carbonate resulted from the action of algae which grew around the log4 ,successive growths of algae resulted in successive layers of calcium carbonate being deposited4 ,,bullpen ,,member4 ,this uppermost member of the ,wasatch ,formation is found mostly to the west and south of the monument4 ,a few1 small1 isolated caps on the top of the ,green ,river ,formation east of ,prow ,point occur within the monument4 ,these low hills1 mere bumps1 are remnants of a once more extensive distribution of the ,bullpen ,member4 ,veatch 7#aijg3ii7 originally considered what is now called the ,bullpen ,member as being the ,bridger ,formation1 this was based mostly on the ,bullpen's position above the ,green ,river ,formation rather than on any lithologic resemblance to the ,bridger4 ,the ,bullpen is much redder in color than the ,bridger4 ,in early work ,tracey and ,oriel 7#aiei3gbi7 called these beds an upper tongue of the ,wasatch and have since named them the ,bullpen ,member4 ,the ,bullpen ,member is lithologically very like the ,main ,body of the ,wasatch and can be traced into the peripheral units of the ,wasatch ,formation4 ,the rocks included within the ,bullpen ,member are layered sequences of red1 pink1 gray1 and green claystone and mudstone4 ,bentonite is present in some claystone beds and causes sloughing because of its property of expanding when wet4 ,some sandstones are present in the northern areas of the member's distribution4 ,limestones are also present4 ,they are thin and slabby and have a brown1 white1 or gray color4 ,some contain varying amounts of clay4 ,a conglomerate is present in the upper part of the ,bullpen toward the basin periphery and merges with the ,tunp ,member of the ,wasatch ,formation4 ,the ,bullpen ,member is conformable with the underlying ,angelo ,member of the ,green ,river ,formation4 ,the contact is a transitional one reflecting a gradual change from the lake environment of the ,green ,river ,formation through a swamp environment to that of a flood plain4 ,the light-colored1 fine-grained shales1 marlstones1 and limestones of the ,green ,river ,formation grade upward into drabber1 coarser grained clay and mudstones of the ,bullpen ,member as a reflection of this change of environments4 ,,tunp ,,member4 ,this peripheral unit of the ,wasatch ,formation was first described by ,oriel and ,tracey in #aigj4 ,it is not exposed in the monument1 but forms a belt of outcrops around the edge of ,fossil ,basin and in channels cut at right angles to the basin edge4 ,the ,tunp ,member is seen to intertongue with nearly all of the ,wasatch and ,green ,river formations4 ,the member grades laterally basinward from coarse1 angular conglomerates to fine mudstone4 ,two limestone tongues of the ,green ,river ,formation are interbedded with the ,tunp1 indicating that at least twice there was major expansion of the lake4 ,lithologically1 the ,tunp ,member is a diamictite4 ,this is a sedimentary rock with a wide range of particle sizes4 ,the ,tunp is best described as a red1 conglomeratic1 sandy mudstone with angular1 poorly rounded to smooth1 well-rounded clasts with a size range from pebble to boulder4 ,there is no bedding or orientation of clasts4 ,the ,tunp ,member probably originated from mudflows and gravity sliding 7,tracey et al4 #aifa74 ,environmental studies indicate that the area had a warm1 humid climate4 ,this would cause deep weathering of the surrounding slopes4 ,this weathered material would then be a prime source to be acted upon by rain1 gravity1 and possibly earthquakes4 ,these agents of deposition would then cause the material to flow and be deposited with little chance for sorting and rounding of the rock particles4 ,the result was a belt of coarse1 unsorted detritus on the basin edges now called the ,tunp ,member4 ,,age ,,of ,,the ,,wasatch ,,formation4 ,the exact age of the units within the ,wasatch ,formation can be determined only if fossils are present4 ,none has been found in the basal conglomerates but it is believed to be earliest ,eocene4 ,the ,lower ,member is also not dated with fossils but is believed to be very early ,eocene4 ,a number of fossil mammals are known from the ,main ,body of the ,wasatch ,formation4 ,the lower part is early1 early ,eocene as demonstrated by the presence of a very primitive ungulate1 ,haplomylus speirianus4 ,in the upper part of the ,main ,body another primitive ungulate1 ,hyopsodus browni1 is found which indicates a mid to early ,eocene age4 ,the ,mudstone and ,sandstone tongues are not dated by means of fossils but the stratigraphic relationships indicate an early ,eocene age4 ,fossil mollusks in the ,bullpen ,member are not completely diagnostic but suggest either a late early ,eocene 7,lostcabinian7 7,fig4 #f7 or mid-,eocene age4 ,the ,tunp ,member interfingering as it does with the entire ,wasatch section represents all of early ,eocene age4 ,,depositional ,,environment4 ,the sediments that make up the ,wasatch ,formation in the ,fossil ,basin were deposited mainly by streams flowing into the basin from the surrounding uplands4 ,rock types are variable and for the most part individual types cannot be traced over large areas1 a condition typical of fluvial environments4 ,the mudstones and siltstones probably were deposited along flood plains1 while the lenticular sands and conglomerates were laid down in stream channels4 ,where streams entered the lake tongues of deltaic deposits1 sands or mudstones wedge into the ,green ,river ,lake sediments4 ,the reason for the red color of the ,wasatch ,formation is not fully known4 ,according to ,van ,houten 7#aidh71 the red is most likely the result of tropical1 red lateritic soils forming in the uplands and being deposited on flood plains4 ,the oxidation of organic material in a humid1 subtropical environment causes the red color4 ,the bands of purple1 gray1 orange1 and other colors are due to various stages in the reduction of the iron oxides in the rocks4 ,the presence of palms in the lake sediments and of bones of primates and crocodiles in both the lacustrine and fluvial sediments indicate a heavily forested1 tropical environment4 ,green ,river ,formation ,the ,green ,river ,formation is easily recognized by its light color and continuous bedding1 in strong contrast to the red1 discontinuous1 variegated ,wasatch ,formation below4 ,the ,green ,river ,formation can be thought of as a gigantic lens of lacustrine sediments enclosed in the fluvial ,wasatch ,formation4 ,the name ,green ,river ,formation is applied to all of the roughly contemporaneous deposits laid down in lakes of ,utah1 ,colorado1 and ,wyoming4 ,it is probable that at one time or another all of these lakes were connected4 ,oriel and ,tracey 7#aigj7 have divided the ,green ,river ,formation of the ,fossil ,basin into two members3 the ,fossil ,butte ,member and the ,angelo ,member4 ,,fossil ,,butte ,,member4 ,the type section for this member is near the southeastern end of ,fossil ,butte within the monument boundaries4 ,in the type area the ,fossil ,butte ,member can be seen to consist of four lithologic units4 ,the lowermost unit is predominantly mudstone4 ,it occurs in a sequence about #de ft thick and contains light gray1 fine-grained1 calcareous mudstone and siltstone4 ,the next overlying unit is about #ge ft thick and is mainly a limestone unit4 ,it consists of tan to gray limestone1 shaly limestone1 siltstone1 and paper shale which weathers into thin1 curled flakes4 ,a yellow-brown mudstone tops this unit4 ,the third unit in the sequence is #de ft thick and mainly composed of shales4 ,these shales weather a buff color and are calcareous4 ,oil shale1 organic rich paper shale1 and marlstone comprise the actual layers in the unit4 ,a few1 thin ash beds are also present4 ,this unit is the most significant one for ,fossil ,butte ,national ,monument4 ,about #aj ft below the top of this unit 7about #aee ft above the ,wasatch7 is a bed of varved shales1 one foot thick1 that contains the fossil fish for which the monument was established4 ,the uppermost unit contains a number of beds of oil shale that are brown on a fresh surface but weather a grayish-white4 ,an orange-yellow-weathering limestone caps the #dj-;ft thick upper unit4 ,ash beds are common and traceable over a wide area of ,fossil ,basin4 ,south of the monument the ,sandstone ,tongue of the ,wasatch ,formation wedges in between the lowermost unit and the overlying limestone unit of the ,fossil ,butte ,member4 ,in the ,fossil ,butte ,member an interesting sequence of facies changes can be seen which reflect lateral changes in the environment of ,fossil ,lake4 ,in those areas where the member represents a deep-water environment1 organically formed limestones and shales are predominant4 ,shoreward1 these rocks grade into ostracodal limestone1 gastrapodal limestone1 and1 closest to shore1 algal limestone4 ,then a muddy1 sandy beach facies is encountered where the ,green ,river and ,wasatch formations intergrade4 ,the contact with the underlying ,wasatch is conformable and sharp4 ,it is often marked by a bench or by slump blocks of ,green ,river ,formation4 ,the ,fossil ,butte ,member may in some cases overlap the ,wasatch ,formation and be deposited on ,paleozoic and ,mesozoic rocks4 ,this is a reflection of topographic relief during the ,eocene4 ,the thickness of the ,fossil ,butte ,member1 as reported by ,oriel and ,tracey 7#aigj3cg71 is from #bjh to #bfi ft4 ,,angelo ,,member4 ,in the northern part of ,fossil ,basin1 the ,mudstone ,tongue of the ,wasatch ,formation separates the ,angelo ,member of the ,green ,river ,formation from the ,fossil ,butte ,member4 ,further south1 the two members rest directly on one another4 ,the southern extent of the ,angelo ,member has not been determined as yet1 but ,oriel and ,tracey 7#aigj3cb7 believe it extends up to1 and intertongues with1 ,wasatch conglomerates near the ,uinta ,mountains4 ,toward other edges of ,fossil ,basin1 the ,angelo ,member thins and pinches out into the ,wasatch ,formation4 ,the ,bullpen ,member of the ,wasatch rests on top of the ,angelo ,member4 ,the ,angelo ,member consists of white to blue-white weathering limestone1 marlstone1 and mudstone4 ,some sandstone lenses1 claystone1 oil shale1 and siliceous limestone are present as well4 ,in general1 ,oriel and ,tracey 7#aigj7 have found that buff limestones prevail to the north and white1 siliceous limestone1 to the south4 ,like the ,fossil ,butte ,member1 the ,angelo ,member shows a facies change from deep-water to shore4 ,this member forms the very uppermost1 rounded slopes of ,fossil ,butte in contrast to the more vertical cliffs formed by the ,fossil ,butte ,member4 ,,age ,,of ,,the ,,green ,,river ,,formation4 ,the age of the ,green ,river ,formation is dated on its intertonguing relationships with the ,wasatch ,formation because the latter has datable mammal fossils4 ,the well-preserved fossils of fish1 leaves1 and insects from the ,green ,river are1 unfortunately1 of little value in dating the ,green ,river ,formation4 ,although no ,lostcabinian mammals are known from ,fossil ,basin1 the ,green ,river ,formation is believed to be of that age 7,gazin #aiei2 ,schaeffer and ,mangus #aife74 ,,depositional ,,environment4 ,the ,green ,river ,formation1 on the basis of its lithology and fossil content1 is a fresh-water1 lacustrine deposit4 ,clay and silt were dumped in ,fossil ,lake by streams4 ,most of this fine debris was deposited near the shore4 ,chemical and organic processes formed limestones and marlstones in the deeper central part of the lake4 ,examination of the edge of the ,green ,river ,formation indicates that ,fossil ,lake expanded and contracted several times4 ,fossil ,lake was eventually filled in with chemical precipitates and deltaic deposits4 ,the end of the lake was gradual as seen in the transitional and gradational ,green ,river-,bullpen contact4 ,although oil shale is not extensively developed in the ,green ,river ,formation of ,fossil ,basin1 it does occur in small quantities4 ,oil shale is a fine-grained sedimentary rock containing organic matter which was derived chiefly from aquatic organisms1 waxy spores and pollen grains 444 and of which a large portion is distillable into a liquid similar to petroleum4 ,despite the name1 most rich beds of oil shale in the ,green ,river ,formation cannot be regarded strictly as shale4 ,instead1 they are dolomitic marlstones rich in organic matter4 ,nevertheless1 a few are shaly 7,bradley #aifd;b3#ai74 ,oil shale has a structureless ground mass that is yellowish-orange to reddish-orange in color4 ,pyrite crystals are found indicating a partially anaerobic or reducing environment4 ,pollen1 waxy spores1 filaments of algae1 and other plant parts are preserved along with insects and larvae4 ,the preservation is akin to mummification4 ,crystals of calcite1 dolomite1 or authigenic feldspar are also found in the oil shale 7,bradley #aiff74 ,the exact mode of origin of oil shale is not positively known because of a lack of a modern analogue for comparison4 ,oil shale probably originated as an organic ooze on the bottom of the ,fossil ,lake4 ,this ooze was composed of the remains of phytoplankton1 blue-green algae1 zooplankton1 bacteria1 and some pollen and spores4 ,the ooze was dense and uncompacted4 ,little clastic debris is found1 either because the ooze accumulated in deep water or plants near the shore filtered out the debris4 ,decay was reduced effectively in the ooze because of either an antibiotic in the ooze which inhibited bacteria of decay or the ooze accumulated in waters where anaerobic conditions prevented decay4 ,with time and the weight of overlying sediments1 the ooze was compacted and most of its water driven off4 ,continuing pressure from compaction and heat generated by burial and compaction caused a variety of complex chemical reactions which converted the ooze into a petroleum product called kerogen4 ,kerogen is distillable and is the important constituent of oil shale4 ,an alternate hypothesis 7,eugster and ,surdam #aigc71 would have some oil shale forming in a desert-playa environment4 ,this is based on geochemical evidence found in ,gosiute ,lake sediments to the east of ,fossil ,lake4 ,there1 certain minerals are found in association with some oil shale that could only have been deposited during periods of extreme evaporation and in a shallow lake4 ,much study is now being directed toward a solution to these problems4 ,the combustible quality of oil shale has been known for a long time4 ,many of the pioneers used it as a fuel for cooking and heat4 ,hayden 7#ahga3adb7 wrote of how workmen on the ,union ,pacific accidently ignited the oil shale in a cut they were excavating4 ,the burning shale provided enough light for night work4 ,many of the shales of the ,green ,river ,formation appear to be varved4 ,a varve consists of two layers1 one of calcium or magnesium carbonate and one of organic material4 ,the limnological conditions that led to the formation of varves will be discussed in their proper place in the section on ,paleoecology4 ,fowkes ,formation ,this is the middle formation of ,veatch's 7#aijg7 tripartite division of the ,wasatch ,group4 ,it is now found to be the youngest formation in ,fossil ,basin4 ,it is not exposed in ,fossil ,butte ,national ,monument4 ,oriel and ,tracey 7#aigj7 have formally divided and named three members of the ,fowkes ,formation3 a lower ,sillem ,member1 a middle ,bulldog ,hollow ,member1 and an upper ,gooseberry ,member4 ,,sillem ,,member4 ,like most of the ,fowkes ,formation1 this sequence of rocks has been eroded extensively and is preserved as erosional remnants1 where protected by faulting1 in the western part of ,fossil ,basin4 ,the ,sillem ,member consists of a lower conglomeratic sequence with some sandstone and mudstone4 ,the conglomerate contains well-rounded clasts of gray quartzite1 chert1 and ,paleozoic limestone4 ,the sandstone is light gray1 calcareous to muddy1 and coarse to medium-grained4 ,the mudstone is pink1 gray1 or tan in color4 ,the upper part of the ,sillem ,member is a mudstone and claystone unit4 ,it ranges in color from pink and yellow to gray and green4 ,some volcanic debris is found4 ,there are also interbedded layers of marlstone and limestone4 ,some sandstone is present4 ,the ,sillem ,member is between #ajj and #djj ft thick and most probably rests unconformably on the ,bullpen ,member of the ,wasatch4 ,,bulldog ,,hollow ,,member4 ,this middle member of the ,fowkes ,formation has the thickest and most extensive outcrops4 ,the ,bulldog ,hollow ,member is exposed along the west side of the basin4 ,included rocks are green1 white1 and blue-green mudstone with ash beds1 green and buff claystone1 and tuffaceous1 limy sandstone4 ,a high percentage of the iron mineral1 magnetite1 occurs in the sandstone4 ,conglomerate occurs as lenses4 ,the ,bulldog ,hollow ,member has a gradational contact with the underlying ,sillem ,member4 ,the amount of volcanic material increases upward from the ,sillem1 indicating an increase in volcanic activity during the deposition of the ,bulldog ,hollow ,member4 ,,gooseberry ,,member4 ,oriel and ,tracey 7#aigj3ee7 place this uppermost member provisionally within the ,fowkes ,formation4 ,most of the ,gooseberry ,member is a puddingstone1 a lithology with well-rounded1 spherical pebbles in a marlstone1 sandstone1 or sandy limestone matrix4 ,the pebbles are too rounded for the rock to be a diamictite1 and too separated from each other to be called a conglomerate4 ,the nature of the ,gooseberry-,bulldog ,hollow contact is not completely known4 ,it appears to be gradational in some areas and to be an angular unconformity in others4 ,,age ,,of ,,fowkes ,,formation4 ,fossils date the ,sillem and ,bulldog ,hollow members as middle ,eocene in age4 ,these fossils consist of ostracodes1 gastropods1 leaves1 and vertebrates from the ,bulldog ,hollow ,member 7,nelson #aigc74 ,the ,gooseberry ,member has yielded a few vertebrate remains and is late ,miocene or early ,pliocene in age 7,oriel and ,tracey #aigj74 ,,depositional ,,environment4 ,the ,fowkes ,formation is an alluvial deposit1 much like the ,wasatch ,formation4 ,the chemical and climatic conditions of deposition were different from those of the ,wasatch1 and the extensive red-beds are not developed4 ,small lakes were present in which limestone and marlstone accumulated4 ,the puddingstone may be a mudflow4 ,volcanic activity left its record in the ash found in the ,fowkes ,formation4 ,in the past1 the ,fowkes ,formation had a greater distribution4 ,postdepositional faulting down dropped parts of the ,fowkes protecting them from subsequent erosion4 ,,quaternary ,rubey et al4 7#aifh;a1 b7 have mapped several forms of ,quaternary deposits in ,fossil ,basin4 ,these include stream alluvium1 rock and landslide debris1 river terraces1 and gravels1 all derived from local formations4 ,these deposits are the work of water1 wind1 and ice acting in relatively ,recent time4 ,,the ,,geologic ,,structure ,,of ,,fossil ,,basin ,the ,fossil ,basin is a small1 linear and structurally controlled basin in the southeastern part of the ,wyoming overthrust belt4 ,this 8overthrust belt0 is represented by a number of small mountain ranges and high ridges formed by the 8thrusting0 of sedimentary rocks over other sedimentary rocks4 ,topographically1 the ,fossil ,basin is bounded by the ,crawford ,mountains and ,tunp ,range on the west1 by ,oyster ,ridge on the east1 and by the ,uinta ,mountains on the south4 ,the ,crawford ,mountains1 ,tunp ,range1 and ,oyster ,ridge 7,fig4 #b7 are areas of high relief developed upon southerly extended salient ridges of deformed ,paleozoic and ,mesozoic strata4 ,in the center of the ,fossil ,basin1 these earlier rocks are covered by a veneer of early ,tertiary sediments4 ,superficially1 the ,fossil ,basin appears to be a broad syncline with tilted beds dipping sharply or gently basinward from the basin margins4 ,the ,tertiary sedimentary cover1 however1 partially obscures what is a more complex structural history4 ,following deposition of the ,late ,cretaceous ,adaville ,formation1 the ,fossil ,basin was included in a period of intense structural deformation4 ,this deformation was the result of compressional forces acting along a more or less east-west alignment4 ,the strain1 or the resolution of these forces1 was developed along a north-south alignment or perpendicular to the compressional forces4 ,as the stress level became too great1 the rocks were first folded and then faulted4 ,initial faulting of the rocks relieved some of the stress2 however1 with continued application of compressive forces many stages of folding and faulting were generated4 ,because the alignment of the compressive forces remained about the same throughout deformation 7i4e41 east-west7 and because the strongest relative compressive forces were from the west1 successively younger folds and faults were generated in an eastward direction4 ,the structural evolution of the ,fossil ,butte area may be interpreted as follows from the schematic diagrams3 #a4 ,the ,rock ,creek-,needles ,anticline is developed at the western edge of the ,fossil ,basin4 ,the present topographic highs developed on this structure are the ,crawford ,mountains and ,tunp ,range 7,fig4 #i-;,b74 #b4 ,with continued application of compressional forces1 ,paleozoic and ,mesozoic rocks to the east of the ,rock ,creek-,needles ,anticline are folded 7,fig4 #i-;,c74 #c4 ,the fold becomes sharply asymmetrical and when the rocks can no longer accommodate the compressional forces by further folding1 a low-angle fault is developed 7,absaroka thrust fault74 ,this fault probably began as a fracture parallel to bedding which rose to topographic surface at a low angle at the point of greatest strain in the fold4 ,most likely1 this fracture was an eastward extension of the fault underlying the ,rock ,creek-,needles ,anticline1 as depicted in ,fig4 #i-;,d4 #d4 ,the rocks to the west of the newly developed fault overrode those to the east4 ,this was accompanied by further downwarping in the syncline to the east of the fault and the erosion of uplifted sedimentary rocks on the west side of the fault 7,fig4 #i-;,e74 #e4 ,another cycle of folding and faulting was initiated to the east of the ,absaroka fault4 ,this post-,absaroka deformation instigated further downwarping of the ,fossil ,basin area between the ,tunp-,crawford ,mountains and ,oyster ,ridge4 ,tertiary sediments began to accumulate in the ,fossil ,basin 7,fig4 #i-;,f74 ,illustration3 ,fig4 #i4 ,structural development of the ,fossil ,butte area4 ,,legend ,t--,tertiary ,k1 ,k--,cretaceous ,j--,jurassic ,,tr--,triassic ,pz--,paleozoic ,x--,position of ,fossil ,butte 1 --,relative movement along faults ,illustration3 ,a4 ,pre-deformation3 ,paleozoic ,mesozoic ,formations ,illustration3 ,b4 ,pre-,absaroka ,deformation ,illustration3 ,c4 ,development of the ,absaroka thrust fault3 folding ,illustration3 ,d4 ,development of the ,absaroka thrust fault3 faulting ,illustration3 ,e4 ,development of the ,absaroka thrust fault3 faulting ,illustration3 ,f4 ,post-,absaroka ,thrust ,deformation ,illustration3 ,g4 ,simplified structure section through present-day ,fossil ,basin 7,oyster ,ridge is off the diagram to the ,east7 ,structural interpretation by ,dr4 ,d4,l4 ,blackstone ,in early ,eocene times1 the effects of continued downwarping allowed ,fossil ,lake to form in the ,fossil ,basin4 ,by the late ,eocene1 however1 basinal subsidence could no longer keep pace with deposition and the dominantly lacustrine 7lake7 sedimentation was replaced by a fluviatile 7riverine7 sedimentary regime4 ,deposition of fluviatile sediments probably continued into the later ,tertiary when1 in the late ,pliocene1 regional uplift of the ,rocky ,mountain interior reversed the sedimentary cycle from depositional to erosional4 ,the last #c or #d million years of geologic history have witnessed the excavation of much of the ,tertiary sedimentary fill from the ,fossil ,basin4 ,fossil ,butte and the ,ham's ,fork ,plateau to the northeast of the butte are high erosional remnants of this early ,tertiary basin fill4 ,the traces of the ,absaroka and other thrust faults are buried beneath these remaining ,tertiary deposits in the ,fossil ,basin4 ,while most of this complex structural history took place before the ,tertiary sediments were deposited1 some deformation continued into the early ,eocene4 ,near ,prow ,point1 for example1 is a fault that developed during early ,eocene time4 ,this can be noted in the very northwest corner of the monument1 just to the west of ,prow ,point 7,fig4 #f74 ,here1 the ,lower ,member of the ,wasatch ,formation on the west is faulted against the ,main ,body on the east 7,,usdi #aifd74 ,this fault also is responsible for elevating the ,thaynes ,limestone so it is exposed 7,fig4 #aj74 ,illustration3 ,fig4 #aj4 ,structural relation of older rocks to ,wasatch and ,green ,river formations near ,prow ,point in the northwest corner of the monument 7from ,u4,s4 ,department of ,interior #aifd74 ,,paleontology ,fossils of plants1 invertebrates1 and vertebrates are abundant in rocks exposed in the ,fossil ,basin4 ,for example1 ,oyster ,ridge received its name because of the well-preserved and abundant fossil oysters found there4 ,of course1 ,fossil ,butte and ,fossil ,butte ,national ,monument were so named because of the beautifully preserved fossil fish4 ,a brief review of the main groups of fossils to be found in the basin follows4 ,flora ,many of the sediments in the ,fossil ,basin contain an abundance of fossil plants4 ,these consist of pollen1 spores1 wood1 and leaf impressions4 ,those of the ,green ,river ,formation are best preserved and have received the most study4 ,brown 7#aibi1 #aicd7 and ,lesquereux 7#ahhc7 have presented the best information on the flora of the ,green ,river ,formation4 ,much of the present knowledge is based on their work4 ,brown 7#aibi1 #aicd7 concluded that the ,green ,river flora is a mixed forest type4 ,it contains some plants common to warm1 wet lowlands and others adapted to cooler1 drier uplands4 ,pollen studies support ,brown's original concept that several plant communities1 including mountain communities1 existed around ,fossil ,lake4 ,the flora was situated in an inland1 mountain basin4 ,fossil ,lake was in the middle of the basin4 ,swamps and flood plains bordered the lake1 while the flanking ridges and mountains provided altitudinal variations in the plant assemblage4 ,spruce1 fir1 and pine are indicated by fossil pollen4 ,the presence of these conifers suggest that at least some of the nearby mountains rose to heights of #fjjj-hjjj ft4 ,leaf imprints indicate that deciduous trees occurred on the lower slopes4 ,oak1 elm1 maple1 and beech were common forms4 ,closer to the lake where it was wetter and warmer there were willows1 laurel1 and fig trees4 ,palms grew in the sandier soils 7,fig4 #aa74 ,cypress grew in quiet embayments of ,fossil ,lake4 ,the shoreline plant assemblage had a rather subtropical appearance4 ,illustration3 ,fig4 #aa4 ,impression of a palm frond from the fish beds of ,fossil ,basin4 ,width of original1 #afj mm4 ,collection of ,university of ,wyoming4 ,ground cover was provided by a mold of dead leaves1 holly1 liverworts1 mosses1 and ferns 7,fig4 #ab74 ,prairie-type grasses are not present and large savanna areas probably were not developed4 ,illustration3 ,fig4 #ab4 ,a fern leaf from the ,green ,river ,shales of the ,green ,river ,basin4 ,width of original1 #d cm4 ,collection of ,university of ,wyoming4 ,in the lake itself small1 one-celled algae floated about in the waves and currents4 ,bacteria grew on the lake bottom and in the water and helped to contribute to the organic ooze that built up on the bottom4 ,fungi1 wonderfully preserved in oil shales1 are further indicators that ,fossil ,lake was a fresh-water lake and deep enough to have depths below the zone of sunlight penetration 7,bradley #aifd;a74 ,reeds1 rushes1 and similar lake-shore plants grew in shallow1 near-shore waters4 ,the large amount of organic material in the rocks is evidence of the prolific microscopic plant growth in the lake4 ,occasional dry periods in the ,fossil ,basin are indicated by fossils of a plant called ,ephedra4 ,this plant had leaves with a thick1 waxy cuticle to prevent desiccation during drought4 ,the absence of saline minerals in the ,green ,river ,formation in ,fossil ,basin suggests that these arid periods were never of the intensity that occurred in the ,green ,river ,basin to the east4 ,the flora of ,fossil ,basin1 especially that from the ,green ,river ,formation1 is usually compared to that of the present-day ,gulf ,coast4 ,seaward from the ,appalachians1 the composition of the flora is very similar to that of the ,green ,river4 ,spruce1 pine1 and fir grow in the ,appalachians at elevations of #fjjj or more feet1 supporting the idea that similar elevations existed near ,fossil ,lake and that a general ,gulf ,coast climate prevailed in ,fossil ,basin4 ,invertebrates ,molluscs1 ostracodes1 and insects comprise the invertebrate fauna of ,fossil ,basin4 ,a large number of marine forms are found in the earlier marine deposits1 while fresh-water and terrestrial forms are common in the ,tertiary units4 ,it is these later forms which are considered here4 ,the fresh-water and terrestrial molluscs from the ,wasatch and ,green ,river formations include bivalves 7clams7 and gastropods 7snails74 ,aquatic clams from the ,green ,river ,formation include ,unio and ,plesiellipta4 ,pisidium and ,sphaerium are common in the ,wasatch ,formation4 ,land snails from the ,wasatch include such genera as ,grangerella1 ,discus1 ,oreoconus1 and ,glypterpres4 ,oreoconus is also known from the ,green ,river ,formation4 ,fresh-water snails are very abundant from both the ,wasatch and ,green ,river formations4 ,physa1 ,planorbis1 ,elimia1 ,bioniphalaria1 ,virpains1 and ,omalodiscus are from the ,wasatch4 ,physa1 ,elimia1 ,diomphalaria1 and ,goniobasis are recorded from the lacustrine ,green ,river sediments4 ,in some areas of the ,green ,river ,formation1 these snail fossils are so abundant that they form a major constituent of the limestones4 ,the presence of land snails in the ,green ,river and fresh-water molluscs in the ,wasatch is evidence that the two formations are not totally representative of a single environment1 but represent several related ones4 ,most of these fresh-water snails were herbivorous and frequented the shallow1 well-lighted areas of ,fossil ,lake which had a good growth of plants and algae4 ,this naturally occurred close to shore1 hence the gastropodal limestones reported by ,bradley 7#aibf7 and ,oriel and ,tracey 7#aigj7 are interpreted as being near-shore facies4 ,ostracodes are extremely small arthropods that produce a two-piece1 hinged shell within which they live4 ,pseudocypus is the most common form4 ,like the snails1 the ostracodes were so abundant in areas that they1 too1 formed a large part of some ,green ,river ,formation limestones4 ,and like the snails they lived in a near-shore environment4 ,within the laminated shales of the ,green ,river ,formation is preserved an abundant and diverse assemblage of fossil insects 7,fig4 #ac74 ,these insects are important because they demonstrate that many modern families and even genera were in existence during the ,eocene4 ,in contrast to this1 knowledge of insect evolution prior to the ,eocene is rather poorly known4 ,scudder 7#ahij7 and ,cockerell 7#aibj7 have described most of the ,green ,river insects4 ,beetles are the most common forms1 followed by dragonflies4 ,maggots and larvae of flies are commonly preserved4 ,except for these insects preserved as whole mummies in the oil shales1 the majority of the insect fossils are preserved as distilled outlines4 ,this distillation process resulted from the weight and heat of overlying sediments of driving off the volatile substances from the buried insects1 leaving a hydrocarbon outline4 ,the process is so precise that the fine hairs and wing veins and even body-color markings are preserved4 ,illustration3 ,fig4 #ac4 ,an impression of a horse fly from the ,fossil ,lake deposits4 ,length of original1 #ab mm4 ,collection of ,university of ,wyoming4 ,vertebrates ,,fish4 ,the single factor that has made ,fossil ,butte world famous is the occurrence of literally millions of beautifully preserved fossil fish4 ,in one layer approximately #ad inches thick1 the fish are nearly black and preserved in a nearly white shale4 ,most of the fish are perfectly preserved1 retaining every detail of the skeleton and even undisturbed scales4 ,fish from ,fossil ,butte have been collected and sold since the #ahgjs and may be found on sales counters1 in museums1 and on living room walls throughout the world4 ,the fossil fish from the ,green ,river ,formation have a history of discovery stretching back to #ahef4 ,at that time ,leidy 7#ahef3bef7 described a fish given to him by a ,dr4 ,john ,evans4 ,leidy called the fish ,clupea humilis1 a type of herring4 ,exactly where ,dr4 ,evans obtained the specimen is not known4 ,he passed through the area of the ,green ,river ,formation several times and could have collected it during any one of those trips 7,knight #aiee3ab74 ,during the construction of the ,union ,pacific ,railroad in the #ahfjs1 workmen blasting a cut through ,green ,river shales1 about #b miles west of ,green ,river1 ,wyoming1 came upon remains of well-preserved fish4 ,hayden 7#ahga3gdb7 first mentions this cut as ,petrified ,fish ,cut4 ,many of the fish from this cut were given to ,cope who described them in ,hayden's 7#ahga7 report4 ,insects1 plants1 and a bird feather were also obtained from ,petrified ,fish ,cut at this time4 ,sometime in the #ahgjs the first fish were obtained from ,fossil ,butte itself4 ,cope 7#ahgg1 #ahgh7 described fish from the ,green ,river ,formation which may be from ,fossil ,butte4 ,his locality is nearer the mainline of ,wasatch ,mountains 7,cope #ahgg3hjg74 ,this may be ,fossil ,butte4 ,his #ahgh locality information is just as poor4 ,he does mention a specimen of ,priscacara peali given to him by ,a4 ,c4 ,peale4 ,since it was ,peale who first wrote about ,fossil ,butte1 the specimen may have come from the butte4 ,peale 7#ahgi7 first mentioned the quarrying of fish at ,fossil ,butte1 but he had no specific date as to the discovery of the butte or the beginning of quarrying of fish4 ,cope 7#ahhd7 published two large volumes about the ,tertiary vertebrates of the ,west4 ,here he mentioned three fossil localities for his ,green ,river ,fish3 ,petrified ,fish ,cut1 ,the ,mouth of ,labarge ,creek1 and ,twin ,creek4 ,twin ,creek is now known as the ,fossil ,butte site4 ,since that time1 the quarries at ,fossil ,butte have been extensively worked1 mostly by commercial collectors4 ,the fish from ,fossil ,butte form an unusual array of genera 7,table #a7 unlike any now found living together4 ,included in the assemblage are forms usually found in marine waters and tropical1 fresh-water fish 7,schaeffer and ,mangus #aife74 ,,table #a4 ,simplified classification of fish from ,fossil ,basin4 ,elasmobranchii ,trygonidae ,xiphotrygon 7sting ray7 ,chondrostei ,polyodontidae ,polyodon 7paddle fish7 ,holostei ,lepisosteidae ,lepisosteus 7gar7 ,amiidae ,amia 7bowfin7 ,isospondyli ,osteoglossidae ,phareodus ,gonorhynchidae ,notogoneus 7sand fish7 ,clupeidae ,diplomystus 7herrings1 shad7 ,knightia ,ostariophysi ,siluridae ,ameiurus 7catfish7 ,xenarchi ,aphredoderidae 7pirate perches7 ,erismatopterus ,asineopidae ,asineops ,acanthoptergii ,percidae ,mioplosus 7perches7 ,serronidae ,priscacara ,more than #dj species of fish have been described from the ,green ,river shales1 but authorities do not agree on how many of these are valid4 ,because of this1 only super specific groups will be considered in the following discussion4 ,illustration3 ,fig4 #ad4 ,xiphotrygon1 a fossil ray4 ,these forms are present but rather rare in the fish deposits of ,fossil ,butte4 ,length of original1 #ci cm4 ,collection of ,university of ,wyoming4 ,one of the strangest forms to come from ,fossil ,butte is that of ,xiphotrygon 7,fig4 #ad74 ,this is not a true fish1 but is a sting ray1 related to sharks4 ,closely related forms still survive1 with little change1 in coastal waters in many parts of the world4 ,like sharks1 sting rays have a skeleton composed of cartilage4 ,normally1 cartilage is not preserved as a fossil as it disintegrates readily4 ,the excellent skeletons of ,xiphotrygon are good evidence of how well the shales of the ,green ,river ,formation preserve the fossils4 ,xiphotrygon is characterized by being shortened from back to front and flattened from top to bottom4 ,it possesses a long1 whip-like tail and bears enormous1 flat pectoral 7anterior7 fins4 ,the mouth is on the underside of the body indicating that ,xiphotrygon1 like its modern relatives1 fed along the bottom of the lake4 ,the strong flattened teeth form something like a pavement in the mouth1 suggesting that it fed on clams and other hard-shelled invertebrates4 ,close relatives of ,xiphotrygon live mostly in marine waters1 but occasionally enter fresh water4 ,the paddlefish1 ,polyodon1 is rare but present at ,fossil ,butte4 ,similar forms still survive in ,china and the ,united ,states4 ,the prominent features of ,polyodon include a virtually scaleless body1 a long1 depressed snout1 and long gill rakers4 ,the skeleton1 unlike that of most modern fish1 is composed of cartilage1 hence skeletons of ,polyodon are rare4 ,the difference between the modern and ,eocene paddlefish are so slight that the two probably filled similar or the same ecologic niches4 ,this consists of feeding on plankton and other small organisms which can be obtained from the water4 ,the long gill rakers would provide a large surface area on which food could be trapped as the water passed out through the gill slits4 ,the large mouth would also provide a large surface area for catching and trapping food4 ,quite common to streams and rivers of ,north ,america from the ,cretaceous to the ,recent is the garfish1 ,lepisosteus 7,fig4 #ae74 ,the most striking feature of the gar is its diamond-shaped scales1 which are extremely hard and shiny4 ,the body is long1 essentially of the same depth throughout1 and ending in a broad-based tail that is slightly asymmetrical4 ,the mouth is armed with many small1 sharp teeth for catching prey4 ,one specimen over #e ft long has been found in the ,fossil ,butte area4 ,illustration3 ,fig4 #ae4 ,the fossil gar ,lepisosteus4 ,only a few gar have been found at ,fossil ,butte itself4 ,length of original1 #gj cm4 ,across the highway from the butte1 one specimen over #e ft long was found by ,carl ,ulrich4 ,collection of ,university of ,wyoming4 ,fossils of the bowfin ,amia 7,fig4 #af7 are recorded from the ,green ,river shales at ,fossil ,butte and in stream deposits from ,cretaceous to ,recent4 ,this fish is still another 8living fossil40 ,amia is a nocturnal predator4 ,presumably1 the ,eocene ,amia had similar habits4 ,the body in ,amia has become elongate1 as has the dorsal fin4 ,the thickness of the scales has been reduced1 but they are still rather heavy and cover the body4 ,specimens are rather large and deep-bodied4 ,the tail fin is nearly symmetrical above and below4 ,amia is rare in the ,fossil ,butte fish quarries4 ,by far the most abundant fish from ,fossil ,butte is the genus ,knightia 7,fig4 #ag1 #ah74 ,this fish is a member of the ,clupeidae1 a family that includes modern herrings1 shad1 and sardines4 ,the tail fin is small relative to the rest of the body4 ,a row of modified scales extends on the back from the skull to the dorsal fin4 ,possibly they aided in streamlining the fish4 ,knightia apparently fed on the large amounts of plankton1 especially algae1 which lived in the waters of ,fossil ,lake4 ,fossils of ,knightia are also known from ,eocene lake sediments in ,south ,america4 ,knightia appears to have been susceptible to mass mortalities4 ,some layers of shale at ,fossil ,butte contain literally hundreds of thousands of these fish that must have suffered catastrophic mass mortality4 ,possible reasons for the obvious sudden death of so many fish will be discussed in the section on paleoenvironment and taphonomy4 ,another ,eocene relative of the herring found at ,fossil ,butte is ,diplomystus 7,fig4 #ai1 #bj74 ,like ,knightia1 ,diplomystus bears a row of modified scales on its back4 ,diplomystus is the second most abundant fish at ,fossil ,butte4 ,the jaw in ,diplomystus has a rather pronounced oblique angle to it4 ,the deepest portion of the body is directly behind the gill region1 with a continuous narrowing of the body toward the tail region4 ,diplomystus is known from ,cretaceous rocks of ,brazil and ,syria and from ,tertiary sediments in ,brazil and ,west ,africa 7,schaeffer and ,mangus #aife74 ,close relatives of ,diplomystus now inhabit the waters off the coasts of ,peru and eastern ,australia4 ,illustration3 ,fig4 #af4 ,amia1 the bowfin4 ,this too is rare but present at ,fossil ,butte4 ,length of original1 #fg cm4 ,collection of ,american ,museum of ,natural ,history4 ,illustration3 ,fig4 #ag4 ,the fossil herring1 ,knightia4 ,this fish is by far the most abundant in the fish beds at ,fossil ,butte and at least in one layer was involved in a catastrophic mass mortality4 ,length of each fish1 #ac cm4 ,collection of ,university of ,wyoming4 ,illustration3 ,fig4 #ah4 ,the herring1 ,knightia4 ,illustration3 ,fig4 #ai4 ,diplomystus1 another type of herring1 is the second most abundant fish at ,fossil ,butte4 ,length of original1 #ab cm4 ,collection of ,university of ,wyoming4 ,illustration3 ,fig4 #bj4 ,a large ,diplomystus with four small bass1 ,priscacara4 ,length of ,diplomystus1 #de cm4 ,collection of ,university of ,wyoming4 ,phareodus 7,fig4 #ba7 belongs to a family of fish1 the ,osteoglossidae1 which began as marine forms and has since become a fresh-water family4 ,at present1 they are restricted to tropical rivers and lakes of ,south ,america1 ,africa1 and ,australia4 ,in the past they had a much greater distribution1 as its occurrence at ,fossil ,butte indicates1 including ,north ,america4 ,it is a deep-bodied fish with a large head4 ,the anal and dorsal fins are close to the tail fins4 ,the many sharp teeth in the mouth attest to the carnivorous habits of ,phareodus4 ,the family ,gonorhynchidae1 the living sandfish of the ,indo-,pacific area1 is represented at ,fossil ,butte by ,notogoneus 7,fig4 #bb74 ,notogoneus is very long-bodied and quite slender4 ,the body width does not vary much from head to tail1 although narrowing does occur in the tail region4 ,the tail fin is symmetrical1 forming a good rudder4 ,the anal1 dorsal1 pectoral1 and pelvic fins are all small4 ,the body is covered with small1 elongate scales4 ,notogoneus was apparently a bottom feeder1 living on small organisms picked off or out of the bottom of ,fossil ,lake4 ,the ,recent catfish1 ,ameuirus1 has also been found at ,fossil ,butte in the ,green ,river shales4 ,the form of the ,eocene catfish was very much like the ,recent one4 ,the habits of the ,eocene catfish were probably like those of the modern ,ameuirus1 i4e41 adaptations to a scavenger-type existence4 ,rather common in the sediments of ,lake ,gosiute1 but not yet known from the ,fossil ,basin1 is ,erismatopterus1 a member of the family ,aphredederidae or pirate perches4 ,this small1 elongate fish has few distinguishing characters1 the rounded front edge of the skull being most distinguishable4 ,asineops is an ,eocene relative of ,erismatopterus and also one of the pirate perches4 ,asineops is1 however1 placed in a different family1 the ,asineopidae4 ,asineops1 like ,erismatopterus1 is a rather plain-looking fish4 ,the dorsal fin is long relative to the rest of the body4 ,the body is slightly deeper behind the gills than elsewhere1 giving ,asineops a rather common appearance4 ,the ,percidae1 or perches1 are represented at ,fossil ,butte by ,mioplosus 7,fig4 #bc74 ,mioplosus1 as indicated by its well-developed teeth1 was a carnivore that probably preyed on its piscine relatives in ,fossil ,lake4 ,the large head blends in well with a strongly built1 long body4 ,the anal and dorsal fins are subequal in size and positioned opposite each other4 ,the tail fin is large and fan-shaped4 ,it is easily identified by the presence of two dorsal fins4 ,illustration3 ,fig4 #ba4 ,a large ,phareodus1 fairly common in the ,fossil ,butte fish beds4 ,length of original1 #ed cm4 ,collection of ,university of ,wyoming4 ,illustration3 ,fig4 #bb4 ,notogoneus1 a long1 slender bottom-feeder1 occasionally found at ,fossil ,butte4 ,length of original1 #ef cm4 ,collection of ,university of ,wyoming4 ,illustration3 ,fig4 #bc4 ,mioplosus1 a fairly common perch from ,fossil ,butte4 ,length of original1 #cj cm4 ,collection of ,american ,museum of ,natural ,history4 ,illustration3 ,fig4 #bd4 ,priscacara1 a small bass that is common in the ,fossil ,butte fish beds4 ,length of original1 #ac cm4 ,collection of ,university of ,wyoming4 ,the one genus for which no close living relatives can be found is ,priscacara 7,fig4 #bd74 ,the family ,priscacaridae is thought to be related to the bass4 ,the family is known only from the ,eocene4 ,the size of ,priscacara is extremely variable4 ,the body is deep and nearly round like that of the common sunfish1 the head blending in well with the body and its contours4 ,the most distinguishing feature of ,priscacara is the series of strong1 stout spines supporting the anal and dorsal fins4 ,these spines may have acted as cut-waters for better swimming and_/or they may have protected ,priscacara from its more voracious relatives4 ,,amphibians4 ,to date1 no amphibian fossils are known from ,fossil ,butte4 ,they must have been present1 as this class of animals is recorded from ,devonian rocks more than #cej million years old and from rocks younger than those at ,fossil ,butte4 ,living amphibians are typified by frogs1 toads1 and salamanders4 ,the lack of amphibian remains at ,fossil ,butte is more likely due to nondiscovery than nonexistence4 ,,reptiles4 ,reptile fossils are very abundant in the ,green ,river and ,wasatch formations4 ,also a jaw of the three-horned ,triceratops is known from the ,cretaceous part of the ,evanston ,formation4 ,small lizards are normally represented only by jaw fragments and vertebrae4 ,their remains are most often found by a process of washing and screening of the sediments containing the fossils4 ,snakes are also represented in the ,green ,river ,formation4 ,remains of these animals are also often restricted to jaws and vertebrae4 ,a complete skeleton of a fossil boa1 ,boavus idelmani1 has been recovered from the ,green ,river ,formation and is the most complete fossil snake from ,north ,america 7,schaeffer and ,mangus #aife74 ,turtles are among the most abundant reptile fossils4 ,they are usually found as isolated shell plates1 although many complete shells are known4 ,the turtles ,trionyx 7,fig4 #be71 ,emys1 ,baena1 and ,notomorpha are known from the ,fossil ,basin4 ,the largest ,eocene reptiles were the crocodiles 7,fig4 #bf74 ,the presence of these predaceous animals is further evidence for a prevailing warm and humid climate during the ,eocene times since their tolerance ranges include only comparable conditions at the present time4 ,a few incomplete specimens have been recovered from near the monument4 ,,birds4 ,birds1 which first appeared in ,jurassic time1 are rare as fossils in rocks of any age because their skeletal remains are exceedingly fragile4 ,their fossilization requires special conditions because many of their bones are hollow as a weight-reducing adaptation for flight4 ,these hollow bones are especially susceptible to breakage and poor preservation4 ,scattered remains of birds1 mostly limb bones1 are found in the ,green ,river sediments4 ,feather imprints have also been recovered4 ,a complete skeleton of ,gallinuloides1 a bird related to the ,south ,american fowl-like chachalaca1 is one of the most significant finds from the ,green ,river ,formation4 ,recently1 ,brodkorb 7#aigj7 described the wings of puff birds similar to those now living in ,south ,america from near ,fossil ,butte4 ,illustration3 ,fig4 #be4 ,an aquatic turtle1 ,trionyx1 from the shore-line deposits of ,lake ,gosiute4 ,several turtles have been found in the fish beds near ,fossil ,butte4 ,illustration3 ,fig4 #bf4 ,the skull of a large crocodile from near the shoreline of ,lake ,gosiute4 ,several crocodile fragments have been found at ,fossil ,butte beds4 ,length of original1 #ge cm4 ,collection of ,university of ,wyoming4 ,in the adjacent ,green ,river ,basin to the east1 paleontologists from the ,university of ,wyoming have found nesting grounds of ,eocene flamingos in slightly younger sediments of the ,green ,river ,formation4 ,these 8rookeries0 have yielded many hundreds of fossil bones of this curious bird4 ,since these bird fossils were found proximal to ,fossil ,butte1 they demonstrate the near subtropical nature of the environment in the ,fossil ,butte area in ,green ,river times4 ,,mammals4 ,the rocks of the ,evanston1 ,wasatch1 and ,fowkes formations contain various fossilized remains of mammals which once inhabited the ,fossil ,basin4 ,mammal fossils are highly significant since they are used extensively for correlation and dating of the ,tertiary rocks of the ,west4 ,fossils which are readily recognizable1 limited in time1 and widely distributed geographically are called 8index fossils40 ,these fossils are restricted to a particular time horizon in the rock4 ,in this way1 rocks of unknown age which are found to contain index fossils can be dated relatively and hence correlated with other fossil-bearing rocks4 ,the small condylarth ,haplomylus 7,fig4 #bg7 is a very early ,eocene index fossil4 ,its presence in certain sediments in the ,fossil ,basin shows conclusively that these sediments were laid down in earliest ,eocene times4 ,illustration3 ,fig4 #bg4 ,a jaw of the primitive mammal ,haplomylus4 ,length of original1 #a4c cm4 ,collection of ,university of ,wyoming4 ,the mammal fossils found in ,fossil ,basin are also important in documenting the temporal changes in evolution and environment of the biotic community4 ,the picture of ,eocene ,wyoming drawn through interpretation of these fossils is vastly different than that of the present day4 ,mammals have a long evolutionary history that began over #bjj million years ago in the ,triassic period4 ,at that time mammals had only just evolved from their reptilian ancestors4 ,these earliest mammals were small1 furtive creatures4 ,however1 with the extinction of the dinosaurs some #fe million years ago at the end of the ,cretaceous1 the mammals were able to diversify rapidly and fill the empty ecologic niches that the dinosaurs once occupied4 ,this filling of ecologic niches voided by the dinosaurs coupled with the spreading of mammals into hitherto unoccupied niches resulted in the development of a large variety of mammals4 ,some became extinct1 others were the ancestors of modern mammals4 ,fossils of mammals found in sediments in the ,fossil ,basin are proof of the extent of this ,late ,cretaceous-early ,tertiary mammal radiation4 ,early mammals bore little resemblance to their later descendants4 ,general trends in mammalian evolution were increase in size and the tendency to become more 8modern0-looking through adaptation to changing ,tertiary environments4 ,most mammal fossils are extremely fragmentary4 ,teeth are most often preserved as they are the hardest part of the skeleton and therefore most resistant to wear and breakage4 ,thus1 it often happens that the knowledge of a particular fossil mammal is derived entirely from its preserved dentition4 ,this has obvious limitations for the completeness of our understanding about mammals in question4 ,the ,paleocene portion of the ,evanston ,formation has yielded mammals of ,torrejonian and ,tiffanian age 7,fig4 #f74 ,the ,torrejonian assemblage 7middle ,paleocene7 7,gazin #aifi7 is small and poorly preserved4 ,its main significance is that the fauna records a definite time interval for the ,evanston ,formation4 ,gazin's work has demonstrated this fauna to be intermediate in composition between similarly aged faunas recovered from sites to the north and south4 ,the major faunal elements are insectivores1 primates1 condylarths 7primitive ungulates71 and multituberculates 7a type of extinct rodent-like mammal1 with no known descendants74 ,the poorly preserved condition of these fossils makes discussion impossible except to note that they extend the known time range of mammalian habitation in the ,fossil ,basin4 ,the younger ,tiffanian fauna 7late ,paleocene7 7,gazin #aief7 is also known from largely fragmentary remains4 ,the multituberculate mammal ,ptilodus1 also present in ,torrejonian deposits1 is the most 8primitive0 mammal in the fauna4 ,the multituberculates first appeared in the ,jurassic 7,fig4 #d71 and are therefore the oldest lineage of mammals that survived into ,tertiary times4 ,the molar teeth of these animals are characterized by multiple cusps arranged in parallel rows4 ,ptilodus1 like most other multituberculates1 was specialized in that its fourth lower premolars were expanded into shearing blades1 the function of which is not known4 ,ptilodus was in many respects similar to rodents in the development of procumbant incisors and in general build and appearance4 ,multituberculates are1 however1 not related to rodents except that both are mammals4 ,the differentiation of rodents in the late ,paleocene and their diversification during the ,eocene probably presented strong competition for the multituberculates who were unable to compete successfully and so became extinct4 ,the primates were represented by ,plesiadapsis4 ,this animal was about the size of a squirrel and had chisel-like incisors4 ,flesh reconstructions of ,plesiadapsis1 based on skeletal remains1 show this primate to look much like a rodent with a long-snouted skull1 clawed feet1 long body1 and tail4 ,there is conceivable relationship between the rodents and ,plesiadapsis-like primates4 ,the dominant ,tiffanian herbivorous mammals were members of the ,order ,condylarthra4 ,these primitive ungulates were diverse in both size and appearance4 ,it is probable that later modern ungulates 7,artiodactyla1 ,perissodactyla7 evolved from the ,condylarthra2 however1 there are no surviving members of this group4 ,the ,paleocene condylarths were mostly small animals and include such forms as ,haplaletes1 ,litomylus1 and ,gidleyina4 ,these mammals had somewhat insectivore-like teeth1 and may have bridged the gap between insectivores and archaic hoofed mammals4 ,one of the larger ,tiffanian condylarths was ,phenacodus4 ,this mammal had a long1 massive skull and a long1 probably flexible body4 ,the limbs were stout and short4 ,the body ended in a long tail4 ,small hooves were present on all digits1 which numbered five per foot4 ,the length of the largest ,phenacodus was about #f ft4 ,carnivorous and omnivorous condylarthra were also common4 ,thryptacodon and ,claenodon are two types known from the ,evanston ,formation in the ,fossil ,basin4 ,the true carnivores 7,order ,carnivora7 were also present4 ,the ,paleocene carnivores were small and possibly arboreal in habit4 ,the stem carnivore stock was represented by the family ,miacidae4 ,in the ,fossil ,basin the miacid ,didymictis was common4 ,in ,didymictis1 the mouth was armed with small1 sharp teeth4 ,most important1 the typical carnivoran carnassial 7shearing7 teeth had developed4 ,among carnivores1 from ,paleocene to ,recent1 the shearing blades developed on the last upper premolar and the first lower molars4 ,various kinds of shearing teeth have evolved in other mammal lineages4 ,mammals from the ,wasatch ,formation in ,fossil ,basin represent the ,greybullian and ,lysitean provincial ages 7see ,fig4 #f74 ,these fossils are of earliest ,eocene and mid to early ,eocene age4 ,fossil localities in the ,wasatch ,formation of southwestern ,wyoming are ,knight ,station 7partly ,lysitean71 at ,elk ,mountain 7,greybullian71 and at ,fossil ,butte itself4 ,the age of the ,wasatch ,formation at ,fossil ,butte is ,lysitean4 ,the insectivores are represented by ,diacodon1 a small mammal known only from fragmentary material4 ,primates also continued to expand and diversify in ,wasatchian time4 ,microsyops was a very unusual type that belongs to the extinct family ,microsyopidae4 ,the teeth were sharp and adapted for eating fruit and_/or insects4 ,microsyops was about the size of a rat or slightly larger4 ,the microsyopid primates were limited to the ,paleocene and ,eocene and left no later known descendants4 ,another group of primates is represented by ,pelycodus4 ,this was a small lemur-like animal that may possibly have been an ancestor of higher primates 7monkeys1 apes1 and men74 ,pelycodus1 like ,microsyops1 was an arboreal 7tree-dwelling7 animal which inhabited the forests of the ,fossil ,basin during the early ,eocene4 ,the ,order ,taeniodonta is a strange and little known group of mammals4 ,in the sediments at ,fossil ,butte the taeniodonts are represented by ,ectoganus4 ,this was a moderately large animal4 ,the skeletal adaptations were similar to those of moles1 but there was no actual relationship between the two groups4 ,the front feet and legs were robust1 and bore large claws4 ,ectoganus probably used these structures to grub for food1 possibly roots4 ,the incisor teeth were rootless and persistently growing4 ,the tooth enamel was restricted to two bands on either side of the teeth4 ,the single pair of upper and lower incisors was greatly enlarged4 ,the taeniodonts became extinct in the ,eocene and left no descendants4 ,equally as strange a group of animals as the taeniodonts are mammals in the ,order ,tillodonta4 ,these were herbivorous animals1 some of which became quite large4 ,they have many rodent-like characters1 but were not related to rodents4 ,in many respects1 the morphology of rodents seems to have lent itself to convergence4 ,esthonyx was the most common tillodont from the ,fossil ,basin4 ,prominent1 rootless incisors were a characteristic of the later members of the group4 ,these incisors were chisel-like1 as in rodents4 ,the molars were unusual and bore certain resemblances to primitive carnivoran and insectivoran teeth4 ,the tillodonts1 however1 bore uncertain relationships to other mammals and left no descendants beyond the middle ,eocene4 ,in comparison with recent faunas1 ,paleocene rodents were rare faunal elements4 ,two early rodents were found in the ,fossil ,basin ,wasatch ,formation3 ,paramys was relatively unspecialized but was diverse in the number of species4 ,one species of ,paramys was about #b ft long and possessed a long tail4 ,the body was long and slender4 ,the skull was small and rather squirrel-like4 ,the cheek teeth were quadrate and had low1 blunt cusps4 ,the typical1 single pair of chisel incisors was present both on lower and upper jaws4 ,paramys was probably an arboreal form that did not look too unlike a modern squirrel and may have had a similar mode of life4 ,another rodent1 ,reithroparamys1 was somewhat similar to ,paramys in size and appearance4 ,the differences between the two animals were mainly in the teeth and hind limbs4 ,the latter showed certain very minor structural modifications that suggested a saltatorial 7jumping7 mode of locomotion for ,reithroparamys4 ,bats 7,order ,chiroptera7 are extremely rare as fossils because their volant and cave-dwelling habitat as well as a fragile skeleton did not lend their remains to preservation4 ,from the ,green ,river ,shales1 from near ,fossil ,butte1 a complete articulated skeleton of a bat has been found 7,jepsen #aiff74 ,this animal1 named ,caronycteris index1 was small and generalized in form4 ,superficially1 it looked much like a typical brown bat4 ,this fossil is important because it demonstrates that the bats had already become good fliers by early ,eocene time4 ,the condylarths were prominent in the early ,eocene but diminished in importance following this time4 ,phenacodus was still extant2 however1 it was replaced in importance by the smaller ,hyopsodus4 ,hyopsodus is perhaps the most commonly recovered ,eocene fossil mammal4 ,this animal was small and long-bodied and retained a more-or-less generalized structural pattern4 ,in some respects ,hyopsodus was similar to both insectivores and primates and was at one time or another regarded as belonging to either of these two orders4 ,some of the later condylarths paralleled the more advanced ungulates4 ,indeed1 the ,perissodactyla 7horses1 tapirs1 rhinos7 and ,artiodactyla 7bovids1 deer1 pigs1 sheep1 etc47 were derived from early ,tertiary condylarths4 ,meniscotherium was one such advanced condylarth4 ,the cusps on its molars1 instead of being blunt points1 had developed into crescentic patterns1 somewhat like those in deer or camels4 ,the relationship of ,meniscotherium to modern ungulates is only one of parallel dental development4 ,meniscotherium was a medium-sized animal1 but about the same build and size as that of a cocker spaniel4 ,meniscotherium1 however1 had hoofs on its toes and was a forest-living browser4 ,the condylarth ,haplomylus is found at the ,elk ,mountain ,wasatchian locality4 ,this small animal is typical of the ,greybullian level of faunal organization 7earliest ,eocene74 ,a supposed carnivorous condylarth was ,pachyaena4 ,pachyaena was a fairly large animal for its time4 ,the strong1 robust jaws and teeth and heavy build suggest that ,pachyaena was a predatory animal suited for preying on larger animals such as the amphibious pantodont ,coryphodon4 ,the affinities of ,pachyaena to the condylarths are uncertain and are based primarily on foot structure4 ,the miacid carnivores were abundant and varied4 ,didymictis persisted and both ,vassacyon and ,vulpavus continued the arboreal1 forest-dwelling habits of their ,paleocene precursors4 ,the main carnivorous animals of the ,eocene1 however1 were the creodonts 7,order ,creodonta7 which were essentially early experimenters in carnivorous habits4 ,as such they were diversely specialized4 ,proviverra 7,sinopa7 was one of the smaller1 predaceous creodonts that inhabited ,fossil ,basin during ,eocene times4 ,one of the most characteristic fossil mammals from the early ,eocene of ,fossil ,basin was ,coryphodon4 ,a specimen of ,coryphodon was also the first mammal fossil to be found in the ,fossil ,basin4 ,the order of mammals to which ,coryphodon belongs1 the ,pantodonta1 was a group of large and heavily built1 herbivorous mammals4 ,coryphodon was about the size of a small rhinoceros4 ,the skull was large and heavily built4 ,the brain1 however1 was small4 ,the canine teeth were somewhat enlarged and strong4 ,stout limbs supported the bulky body4 ,in habits1 ,coryphodon was possibly semi-aquatic4 ,the modern ungulates1 ,order ,perissodactyla 7odd-toed ungulates7 and ,order ,artiodactyla 7even-toed ungulates71 first appeared in the early ,eocene4 ,the earliest members of both orders were small and relatively unspecialized4 ,the earliest perissodactyls were the horses and tapirs4 ,the earliest horses were represented by ,hyracotherium4 ,this small1 slender1 and lightly built horse was about the size of a fox terrier4 ,the front feet had four toes1 and the hind feet three toes4 ,the teeth suggest that this animal was probably a browser1 living in the forests4 ,in the ,fossil ,basin1 tapirs were known from deposits of ,lysitean 7mid to early ,eocene7 age of which ,heptodon was representative4 ,the tapirs now live in the tropics of ,malaysia and ,latin ,america4 ,their present habitat suggests a similar environment may have been favored by the ,eocene tapirs of the ,fossil ,basin4 ,the first ,artiodactyls were pig-like forms1 although they are only distantly related to true suids4 ,protodichobune was small and may have looked much like some of the early ,perissodactyls4 ,there are1 however1 a complex of structural features which serve to distinguish these mammalian orders from each other4 ,the mammal fauna from the ,fowkes ,formation places a late ,bridgerian age on the ,sillem and ,bulldog ,hollow members 7,nelson #aigc74 ,small mammals were most abundant in the ,fowkes1 especially primates and rodents4 ,the marsupials were characterized by ,peratherium which was a small1 probably arboreal1 opossum-like animal4 ,peratherium was but one stage in a slow and relatively conservative evolution of opossums that began in the ,cretaceous4 ,the condylarths decreased in importance during ,fowkes time and were gradually replaced by more advanced ungulates1 the artiodactyls and perissodactyls4 ,only the small ,hyopsodus survived into the ,bridgerian of the ,fossil ,basin4 ,the horses continued to differentiate as evidenced by the appearance of ,orohippus1 an animal similar to ,hyracotherium1 but with minor dental differences4 ,the primitive tapirs were represented by ,hyrachyus1 a medium-sized herbivore which was nearly as closely related to the rhinoceroses as it was to the tapirs4 ,the primates were also diverse in ,fowkes time2 however1 this group began to decline in importance following ,bridgerian times4 ,as a group1 the primates were restricted mainly to warm and forested environments4 ,the lemur-like ,notharctus and the tarsier-like ,omomys and ,hemiacodon were common in the ,fowkes4 ,hemiacodon was typical of the late ,bridgerian 7an index fossil74 ,the true carnivores1 represented by ,miacis1 remained small in size1 perhaps to avoid competition with the larger surviving creodonts4 ,insectivores from the ,fowkes ,formation are abundant and varied4 ,unfortunately1 they are known almost exclusively from teeth4 ,fowkes insectivores include the hedge-hog-like ,nyctitherium1 ,talpavus1 and ,scenopagus4 ,apatemys is an insectivore of uncertain affinities4 ,the feeding habits of these early insectivores were probably similar to those of contemporary insectivore species 7moles and shrews72 however1 there is some evidence to suggest many of these small creatures may have been semi-arboreal4 ,one of the most unusual of middle ,eocene creatures is the giant ,uintatherium4 ,this was a large browsing animal1 about the size of a rhinoceros4 ,what was most unusual about ,uintatherium was its skull which was large and strongly built4 ,the large upper canines were apparently formidable defensive weapons4 ,the skulls of the males bore six prominent bony protuberances which grew from the frontal region of the skull4 ,the function of these structures is unknown4 ,they may have been of use for defense4 ,during ,bridgerian times1 the rodents underwent an explosive adaptive radiation which ultimately may have led to the near extinction of the less well-adapted multituberculates4 ,the diversity of ,bridgerian rodents from ,fossil ,basin is impressive4 ,species of ,leptotomus1 ,paramys1 ,thisbemys1 ,microparamys1 ,sciuravus1 ,mysops1 and ,pauromys demonstrate that a wide range of adaptations of environments was exploited by the rodents4 ,this diversity in life habits has been a mark of rodent evolution from the middle ,eocene to the present day4 ,the above descriptions of the known mammal fossils from the ,fossil ,butte area are intended to demonstrate the varied life forms that once existed in southwestern ,wyoming4 ,further collecting will almost certainly expand the number of fossil mammal species from ,fossil ,basin and increase our knowledge of the succession of ancient environments which prevailed at different times in the ,fossil ,basin area4 ,,table #b4 ,mammals known from ,fossil ,basin ,faunal lists--,middle ,paleocene3 ,torrejonian ,class ,mammalia ,multituberculata ,ptilodus ,neoplagiaulax ,ectypodus ,insectivora ,leptacodon ,aphronorus ,primates ,torrejonia ,pronothodectes ,condylarthra ,chriacus ,tricentes ,promioclaenus ,litaletes ,haplaletes ,late ,paleocene3 ,tiffanian ,multituberculata ,ptilodus8 ,primates ,plesiadapis ,condylarthra ,thryptacodon ,claenodon ,litomylus ,haplaletes ,gidleyina ,phenacodus ,carnivora ,didymictis ,pantodonta ,genus indeterminant4 ,early ,eocene3 ,graybullian ,primates ,pelycodus ,tillodontia ,esthonyx ,rodentia ,paramys ,creodonta ,proviverra ,carnivora ,didymictis ,vassacyon ,condylarthra ,pachyaena ,haplomylus ,hyopsodus ,phenacodus ,meniscotherium8 ,pantodonta ,coryphodon ,perissodactyla ,hyracotherium ,artiodactyla ,diacodexis ,early ,eocene3 ,lysitean ,insectivora ,diacodon ,primates ,pelycodus ,microsyops ,tillodontia ,esthonyx ,rodentia ,paramys ,reithroparamys ,creodonta ,proviverra ,carnivora ,didymictis ,vulpavus ,condylarthra ,pachyaena8 ,hyopsodus ,phenacodus ,meniscotherium8 ,pantodonta ,coryphodon ,perissodactyla ,hyracotherium ,heptodon ,artiodactyla ,protodichobune ,early ,eocene3 ,wasatchian 7general7 ,chiroptera ,icaronycteris ,late ,middle ,eocene3 ,late ,bridgerian ,marsupialia ,peratherium ,insectivora ,apatemys ,nyctitherium ,scenopagus ,talpavus ,primates ,hemiacodon ,omomys ,notharctus ,condylarthra ,hyopsodus ,rodentia ,leptotomus ,microparamys ,mysops ,paramys ,pauromys ,sciuravus ,thisbemys ,dinocerata ,uintatherium ,perissodactyla ,orohippus ,hyrachyus ,,paleoecology ,,and ,,taphonomy ,paleoecology is the study of ancient biotic communities and their relationship to the abiotic environment4 ,the conclusions of paleoecology are reached by studying in detail the fossils and sediments and whatever relationships exist between them4 ,its ultimate aim is to build a picture of the climate1 flora1 fauna1 and topographic setting of an area4 ,for this reason it borrows heavily from paleontology1 paleobotany1 sedimentology1 and climatology4 ,from studying modern environments1 it is observed that each has its own type of sediment4 ,when certain sediments are found in the rock record1 it is generally assumed that they represent environments similar to modern ones that produce similar deposits4 ,for example1 limestone is forming today in warm1 shallow1 well-lighted1 well-aerated water4 ,when limestone is found in a rock sequence1 it is usually assumed that the same or similar environmental conditions occurred in that area in the past4 ,fossils can further refine the interpretation4 ,as can be interpreted from foregoing discussions1 the sediments deposited in the ,fossil ,basin vary from stream and flood-plain fluvial to lacustrine4 ,at times1 material eroded from surrounding uplands was carried by streams throughout the basin4 ,these rocks are exemplified by the ,evanston and parts of the ,wasatch and ,fowkes formations4 ,when the lake appeared1 lacustrine sediments1 marlstone1 and shale were deposited in the lake1 while around the periphery of the basin1 fluvial sediments continued to accumulate4 ,plants found in the lake sediments of ,fossil ,basin tell us much about the climatic conditions that prevailed during the ,eocene4 ,the flora is quite similar to that now existing in the southeastern ,united ,states1 reflecting a warm and humid climate4 ,one of the striking examples is that of huge palm fronds that occasionally are found in the fish quarries at ,fossil ,butte4 ,these seem to be fronds that blew from the trees into the lake4 ,soon they became water-logged and settled to the bottom to be preserved4 ,the land animals indicate that a rather wide range of ecologic niches existed over the basin before the lake came into being1 around the lake during its presence1 and again all over the basin after the lake disappeared4 ,many of the smaller mammals1 some of the rodents1 and most of the primates were almost certainly arboreal4 ,the large mammals such as uintatheres1 pantodonts1 and tapiroids may have been stream-side or marsh dwellers4 ,probably inhabiting the forest floor and feeding on low bushes and undergrowth were such forms as the condylarths1 horses1 artiodactyls1 and some of the rodents4 ,feeding on the rodents and other smaller mammals were the creodonts and miacids4 ,tiny shrew-like forms scampered about the undergrowth and fed upon worms and insects4 ,bradley 7#aifc7 has estimated possible temperature and precipitation levels in southwestern ,wyoming during the ,eocene4 ,bradley's modern analogues were the ,gulf ,coast and ,great ,lakes regions4 ,from a series of calculations1 an average annual temperature of #fe;,f is postulated4 ,this could have fluctuated greatly in the inland setting of ,fossil ,basin4 ,precipitation amounts were possibly on the order of #cj-dc inches annually4 ,the amount of annual evaporation was also possibly in the range of #cj-dc inches4 ,it is believed that ,fossil ,lake was thermally stratified--that is1 with colder1 denser water at depth 7hypolimnion7 and warmer1 less dense water 7epilimnion7 nearer the surface4 ,the deeper waters probably would have been devoid of oxygen1 hence essentially uninhabited other than by anaerobic bacteria that survive without oxygen4 ,if the bottom had been oxygenated1 many types of life would have burrowed into the sediment thus destroying the delicate varves 7,fig4 #bh74 ,the lake was probably deep enough that wind and wave action did not roil the bottom sediments4 ,illustration3 ,fig4 #bh4 ,a section of shales from the fish beds showing thin laminae that are interpreted as varves4 ,enlarged six times4 ,there have been many attempts to interpret the taphonomy 7see glossary7 of concentrations of fish at ,fossil ,butte4 ,bradley 7#aidh7 interpreted the cause of death and the reason for their preservation as follows3 ,in this basin 7,fossil1 ,wyo47 hundreds of thousands of beautifully preserved fish are entombed in the varved sediments4 ,even the delicate fin and tail rays and other bones originally held in place only by tissue are virtually undisturbed1 and even the scales are in place almost completely undisturbed4 ,it seems to me that the picture of this lake as a thermally stratified water body provides nearly all the necessary information to account for the excellent preservation of these fish4 ,only in the stagnant hypolimnion could they have escaped being torn to pieces by scavengers or distorted by bottom feeders4 ,it is significant that all the well preserved fish are in varved sediments4 ,those in non-varved sediments are a disordered mass of broken and chewed up bones4 ,the only part of the story lacking now is how the fish died and got into the hypolimnion4 ,limnology offers two possible explanations4 ,sometimes when the surface of a lake gets excessively warm1 fish will plunge into deep water and might thus penetrate the hypolimnion1 be overcome by hydrogen sulphide1 and also have the gas in their swim bladders chilled so that they sank at once to the bottom4 ,once there1 only anaerobic bacteria would attack them4 ,the other hypothesis is that the thermally stratified lake was suddenly chilled so that it overturned more rapidly than the hydrogen sulphide could be oxydized and so killed off large numbers of fish4 ,this seems a little more probable as the fossil fish are of all ages and sizes4 ,the fish in these quarries have been collected since the #ahgjs but mainly by commercial collectors4 ,most museum collections were purchased from these commercial collectors1 hence they consist almost entirely of perfectly preserved fish1 as poorly preserved specimens would be discarded by the collectors as of no monetary value4 ,the result has been that most people1 including ,bradley1 were misled into believing all of the fish in the varved sediments of the quarry were perfectly preserved4 ,as nearly as can be determined1 the first attempt to systematically collect and study this concentration of fish was that by paleontologists from the ,university of ,wyoming 7,mc,grew #aigd74 ,this work threw much new light on the occurrence and made available much new data that permit new interpretations4 ,shales of the ,green ,river ,formation in general have been described by ,bradley 7#aica7 and he specifically mentioned those of the fish layer in the ,fossil ,basin as follows3 8,plate #a shows a thin section of the varved marlstone in the small1 unnamed ,green ,river ,lake west of ,gosiute ,lake1 where the varves are better developed4 ,each varve or annual deposit1 consists of a layer of microgranular carbonates and a thinner1 dark layer of organic matter0 7,bradley #aidh3fde74 ,the ,x-ray diffraction analyses performed by ,john ,ward ,smith of the ,laramie ,energy ,research ,center showed that the shales of the 8fish layer0 consist predominantly of calcite 7roughly #fj71 aragonite and dolomite 7approximately #bj71 and quartz 7up to #aj74 ,although fish are numerous throughout the thickness of this 8fish layer10 there are three laminae that contain so many fish that it is almost certain that they represent catastrophic mass mortalities4 ,two are made up primarily of ,priscacara and one consists almost exclusively of ,knightia4 ,x-ray photos show that a rather high percentage of the fish in the shales are not perfectly preserved but have undergone varying amounts of disarticulation4 ,there appears to be an orderly sequence of stages of decomposition--from essentially perfect articulation to total disarticulation4 ,disarticulation first appears in the most anterior vertebrae4 ,from there it rapidly proceeds anteriorly into the head region and appears to do so posteriorly at a slower rate4 ,in many specimens the head and anterior half of the body are completely disarticulated1 while the posterior part of the body shows no disarticulation whatever4 ,it is assumed that after the dead fish settled to the bottom of the lake1 external anaerobic bacteria found access to the 8innards0 of the fish via the opercular opening4 ,this would account for the first sign of decomposition and disarticulation being just back of the head4 ,in the blocks of shale covered by ,x-ray there were #che fish4 ,for convenience1 these were classified into six groups1 group ,i showing no discernable disarticulation and group ,,vi 7,fig4 #bi7 showing total disarticulation4 ,the number and percentage of fish in each group are as follows3 ,group ,i #bbc fish #eh ,group ,,ii #ch fish #aj ,group ,,iii #ad fish #d ,group ,,iv #bg fish #g ,group ,v #bd fish #f ,group ,,vi #ei fish #ae ,illustration3 ,fig4 #bi4 ,a partially disarticulated skeleton of a large ,priscacara1 ,group ,,iv4 ,because of the predominance of completely articulated fish throughout the quarry and the fact that the fish involved in the mass mortalities show no disarticulation1 it seems probable that some connection might exist between the death of the fish and conditions of the lake bottom that would cause their perfect preservation4 ,it would seem that rapid burial might be the most obvious reason for excellent preservation4 ,thus any factor or combination of factors that would cause rapid precipitation of carbonates and also would cause mortality of fish would satisfy our requirements4 ,one obvious factor that could1 at least theoretically1 fulfill these requirements would be an annual bloom of blue-green algae that are known to be toxic to fish 7,prescott #aidh74 ,such blooms usually occur during the warmest part of the summer when ,ca,c,o is least soluble4 ,by extracting ,,co from the water1 these algae are known to cause precipitation of ,ca,c,o4 ,thus we have a possible cause for some annual fish kill and perhaps an occasional superbloom that would bring about a catastrophic mass mortality4 ,the highest mortality of fish then might have occurred during late summer algal blooms and at this time also would occur the most rapid precipitation of ,ca,c,o4 ,it is not known how much deposition of ,ca,c,o would be required to protect a fish from disarticulation4 ,it may be that a very thin layer1 especially if mixed with organic ooze1 might provide an effective seal to slow decomposition and prevent disarticulation4 ,if sufficient ,ca,c,o was precipitated and deposited to cover the fish that died during this period1 one might expect perfect preservation4 ,such fish would fit into group ,i4 ,those fish that died just after this period might lie exposed on the lake bottom for most of a year and be subject to disarticulation4 ,if little or no deposition took place during the rest of the year1 fish that died just after the period of deposition should be the most completely disarticulated and fit into group ,,vi4 ,during the fall1 winter1 and spring1 fish that died of attritional mortality would be disarticulated according to the length of time they lay on the bottom prior to the next period of deposition4 ,if the foregoing is true1 one should be able to determine the approximate time of year fish died by the degree of disarticulation4 ,one might assume that blooms of blue-green algae and hence precipitation of ,ca,c,o would take place sometime during ,august and_/or ,september4 ,thus we should expect the most fish and those most perfectly preserved to have died during this time period 7group ,i74 ,those fish that died in ,october and_/or ,november should be the most completely disarticulated 7group ,,vi71 and those that died in ,june or ,july should show only a slight degree of disarticulation 7group ,,ii74 ,the distribution of the stages of disarticulation seems to fit almost exactly the pattern that one would expect if this interpretation is correct4 ,gunter 7#aidg7 has shown that annual periods of excess salinity in ,texas lagoons cause an annual increase in the death of fish and occasionally a catastrophic mass mortality4 ,because ,lake ,gosiute is known to have been saline1 it might be assumed that somewhat similar chemical conditions prevailed in the ,fossil ,lake4 ,it is not known definitely that the two lakes were ever connected but if they were1 it was most probably a narrow connection near the southern end of ,fossil ,lake and probably a rather temporary connection4 ,that a rather long period of aridity occurred in the general region is demonstrated by various depositional features1 primary structures1 and salt deposition in ,gosiute ,lake in a part of the ,green ,river ,formation4 ,these deposits appear to have settled down during ,lostcabinian 7late to early ,eocene7 times4 ,because the ,wasatch ,formation immediately underlying the ,fossil ,butte ,member of the ,green ,river ,formation in the ,fossil ,syncline ,basin is ,lysitean 7mid to early ,eocene71 it is probable that the fish deposits are of ,lostcabinian age4 ,thus it may well be that the long period of aridity occurred during the deposition of the fish beds4 ,while the ,fossil ,lake probably never reached the high degree of salinity present in ,lake ,gosiute1 it was probably sufficiently saline that periods of excessive evaporation could increase the salinity enough to contribute to the mortality of fish and occasionally cause a catastrophic mass mortality such as those described by ,gunter4 ,the presence of aragonite and dolomite in the shales suggests that at least some of the carbonate deposition might well have been because of excessive evaporation and high concentrations of carbonates 7,smith #aigd1 pers4 comm474 ,at the ,university of ,wyoming1 an attempt is being made to interpret scales of fish from the quarries4 ,in a number of specimens annuli can be observed and circuli counted4 ,although removal of scales for study is extremely difficult1 a number has been removed and photographed with a scanning electron microscope4 ,in ,lake ,george1 ,florida1 black crappie develop annuli during ,january1 ,february1 ,march1 and ,april 7,huish #aied74 ,climatic conditions in north central ,florida may be similar to those that existed in western ,wyoming during the early ,eocene4 ,thus annuli may have developed at the same time of year4 ,by counting the number of circuli between the last annulus and the edge of the scale1 it should be possible to determine the approximate time of death of a fossil fish4 ,if this should correlate with the degree of disarticulation1 a check on this interpretation should be possible4 ,sufficient data are not yet available1 however1 for the results to be conclusive4 ,it is not intended to suggest that the conditions outlined above could account for all of the fish concentrations in the ,green ,river ,shales4 ,in certain shales in the ,green ,river ,basin1 for example1 the concentrations of ,knightia in nonvarved shales appear to have been deposited in quite shallow water4 ,these fish are extremely well preserved but were obviously laid down under conditions quite different from those at ,fossil ,butte4 ,much study of these occurrences will be necessary before interpretations are possible4 ,the story1 as told here1 should make it clear that the earth is ever-changing4 ,what was once a beautiful1 deep lake in an area of lush tropical forests is now a dry1 sagebrush desert4 ,what was once an area in which sediments were accumulating is now an area of erosion1 occasioned by a broad uplift of the region near the end of ,tertiary time4 ,it is hoped that this brief story of the geologic history of ,fossil ,butte ,national ,monument will give the reader some appreciation of the geologic complexity not only of the monument itself but of the surrounding area as well4 ,certainly such knowledge will add to the enjoyment of a visit to the monument4 ,it may seem that geologists have all of the answers4 ,this1 however1 is not so4 ,interpretations are made on the basis of available evidence4 ,each time a geologist studies an area more geologic data and more evidence become available and our interpretations become a little more accurate4 ,it will be many years before all details of this fascinating history will be known4 ,,glossary ,,anaerobic4 ,usually in reference to organisms that can live without oxygen4 ,,angular ,,unconformity4 ,two rock layers which are not parallel2 the underlying older layer dips at a different angle 7usually steeper7 than the younger top strata4 ,,annuli4 ,marks on fish scales produced by periods 7usually winter7 of nongrowth4 ,,anticline4 ,a fold in stratified rock with the strata sloping downward in opposite directions from the fold crest4 ,,aragonite4 ,a carbonate mineral with specific characteristics4 ,,authigenic4 ,a mineral 7such as quartz or feldspar7 which is formed after the deposition of a sedimentary layer in which it occurs4 ,,bentonite4 ,a light-colored1 soft1 porous rock formed from the minute clay crystals of eroded volcanic ash4 ,it has the characteristic of swelling when wet 7water absorption7 and contracting when dry4 ,,brackish4 ,a condition in a body of water in which the salinity 7salt level7 is below that of sea water1 but higher than that of fresh water4 ,,carbonaceous4 ,rock or sediment which contains carbon or altered organic material such as coal4 ,,cherty4 ,containing chert3 a dull-colored1 flint-like quartz often found in limestone4 ,,circuli4 ,ridges on fish scales produced during growth of the scales4 ,,clast4 ,rock fragments which are the result of weathering of a larger rock mass4 ,,clastic4 ,rocks that consist of particles derived from pre-existing rocks or minerals4 ,,claystone4 ,an indurated clay without the lamination or fissility of shale4 ,,conglomerate4 ,a coarse-grained sedimentary rock composed of fragments larger than #b mm in diameter in a fine-grained matrix4 ,,cross-,,bedding4 ,an internal structure in sedimentary rock in which the upper sedimentary layer runs across the grain of the main bed2 it is caused by changing currents depositing sediment across the grain of the original deposits4 ,,diamictite4 ,a sedimentary rock containing a wide range of particle sizes4 ,,dip4 ,the downward inclination of a rock layer2 the vertical angle is determined by its relationship to a horizontal plane4 ,,dolomitic4 ,containing a measurable amount of the mineral dolomite2 a mineral consisting mainly of magnesium carbonate and calcium carbonate4 ,,facies4 ,lateral variations in the appearance or composition of a rock layer4 ,the variations can be lithologic or paleontologic4 ,,fault4 ,a fracture in the earth's crust along which displacement 7movement7 has occurred4 ,,fluvial4 ,pertaining to a river or rivers4 ,fluvial sediments are those transported and deposited by stream action4 ,,formation4 ,a rock layer that is mappable2 has a distinctive lithology or series of lithologies4 ,a mappable sequence of uniform or uniformly varying rocks4 ,,gastropodal4 ,a rock containing an abundance of gastropods4 ,,hogback4 ,a long1 narrow1 sharp-crested ridge formed by the outcropping edges of steeply inclined resistant rocks4 ,,igneous ,,rocks4 ,a rock or mineral that has solidified from molten or partly molten material4 ,,intrusive4 ,igneous rock formed by the forcing of molten material into a pre-existing rock4 ,,ironstone4 ,a rock composed of various iron minerals that accumulated during or shortly after deposition of the enclosing sediments4 ,,lacustrine4 ,pertaining to1 produced by1 or formed in a lake or lakes4 ,,lateritic4 ,containing laterite3 a red1 porous material usually developed in a tropical to temperate climate4 ,it is a residual or end-product of weathering4 ,,lignite4 ,a brownish-black coal that is intermediate in coalification between peat and subbituminous coal4 ,,lithology4 ,the scientific study of rocks3 composition1 texture1 color1 origin1 etc4 ,,magnetite4 ,a black1 opaque mineral that is strongly magnetic4 ,,marlstone4 ,an impure limestone4 ,,metamorphic4 ,rocks whose structure has been changed by pressure1 heat1 chemical reaction1 etc41 such as limestone into marble4 ,,mudstone4 ,an indurated mud without the lamination or fissility of shale4 ,,opercular ,,opening4 ,the gill opening of fish4 ,,ostracodal4 ,a rock1 usually a limestone1 that contains an abundance of the small crustacean1 ostracods4 ,,overthrust4 ,a low-angle thrust fault of large scale1 usually measured in miles4 ,,paleolimnology4 ,the study of ancient lakes4 ,,paper ,,shale4 ,a form of finely laminated shale that weathers into extremely thin1 curled flakes4 ,,phosphatic4 ,containing phosphates4 ,,phytoplankton4 ,floating microscopic plant life that occurs abundantly in lakes and oceans4 ,,platy4 ,rocks 7sandstone or limestone7 which separate into small slabs4 ,,porcellanite4 ,a dense cherty rock resembling porcelain4 ,,puddingstone4 ,a conglomerate consisting of well-rounded pebbles and cobbles sparsely packed in a fine-grained matrix4 ,,siltstone4 ,an indurated silt without the lamination or fissility of shale4 ,,strata4 ,rock layers of distinct composition and origin4 ,,syncline4 ,a fold in stratified rock in which the strata slope up from the axis of the fold forming a v opposed to anticline4 ,,taphonomy4 ,the branch of paleoecology which deals with the change from living animals to fossils4 ,,tectonic4 ,the forces which result in structural changes in the earth's crust4 ,,thrust ,,fault4 ,a fault in which an upper segment of rock 7hanging wall7 moves upward at a low angle 7less than #de7 relative to a lower segment 7footwall74 ,,tongue4 ,a rock unit that wedges into1 but disappears within1 another rock unit4 ,,tuffaceous4 ,sediment that contains up to #ej volcanic ash or dust4 ,,unconformity4 ,a substantial break or gap in the geologic or stratigraphic record4 ,,ungulates4 ,hooved mammals4 ,,varve4 ,a set of rock laminae in which different types of sediment were deposited in the winter and in the summer4 ,thus a couplet of each sediment type would represent the deposition of one year4 ,,well ,,sorted4 ,a rock in which nearly all of the sediment particles are of one grain size4 ,,zooplankton4 ,floating microscopic animal life that occurs abundantly in lakes and oceans4 ,,references ,,blackstone1 ,d4 ,l41 ,jr4 #aiga4 ,traveler's guide to the geology of ,wyoming4 ,wyo4 ,geol4 ,surv4 ,bull4 #ee3a-ij4 ,,bradley1 ,w4 ,h4 #aibf4 ,shore phases of the ,green ,river ,formation in northern ,sweetwater ,county1 ,wyoming4 ,pages #aba-aca in ,u4,s4 ,geol4 ,surv4 ,prof4 ,pap4 #adj-;,d4 ----4 #aibi4 ,the varves and climate of the ,green ,river ,epoch4 ,pages #hg-aaj in ,u4,s4 ,geol4 ,surv4 ,prof4 ,pap4 #aeh-;,e4 ----4 #aica4 ,origin and microfossils of the oil shale of the ,green ,river ,formation of ,colorado and ,utah4 ,pages #a-eh in ,u4,s4 ,geol4 ,surv4 ,prof4 pap4 #afh4 ----4 #aidh4 ,limnology and the ,eocene lakes of the ,rocky ,mountain region4 ,geol4 ,soc4 ,am4 ,bull4 #ei3fce-fdh4 ----4 #aifc4 ,paleolimnology4 ,pages #fba-feb in ,d4 ,g4 ,frey1 ed4 ,limnology in ,north ,america4 ,univ4 of ,wisconsin ,press4 ----4 #aifd;a4 ,geology of the ,green ,river ,formation and associated ,eocene rocks in southwestern ,wyoming and adjacent parts of ,colorado and ,utah4 ,u4,s4 ,geol4 ,surv4 ,prof4 ,pap4 #dfi-;,a4 ----4 #aifd;b4 ,aquatic fungi from the ,green ,river ,formation of ,wyoming4 ,am4 ,j4 ,sci4 #bfb3dac-daf4 ----4 #aiff4 ,tropical lakes1 copropel1 and oil shale4 ,geol4 ,soc4 ,am4 ,bull4 #gg3accc-acch4 ,,brodkorb1 ,p4 #aigj4 ,an ,eocene puffbird from ,wyoming4 ,contr4 ,geol4 7,univ4 of ,wyo47 #i7a73ac-ae4 ,,brown1 ,r4 ,w4 #aibi4 ,additions to the flora of the ,green ,river ,formation4 ,pages #de-gg in ,u4,s4 ,geol4 ,surv4 ,prof4 ,pap4 #ahe-;,c4 ----4 #aicd4 ,the recognizable species of the ,green ,river ,flora4 ,pages #de-gg in ,u4,s4 ,geol4 ,surv4 ,prof4 ,pap4 #ahe-;,c4 ,,cockrell1 ,t4 ,d4 ,a4 #aibj4 ,eocene insects from the ,rocky ,mountains4 ,u4,s4 ,natl4 ,mus4 ,proc4 #eg3bcc-bfj4 ,,cope1 ,e4 ,d4 #ahgg4 ,a contribution to the knowledge of the icthyological fauna of the ,green ,river ,shales4 ,u4,s4 ,geol4 ,geog4 ,surv4 ,territories ,bull4 #c7d73hjg-hai4 ----4 #ahgh4 ,descriptions of fishes from the ,cretaceous and ,tertiary deposits west of the ,mississippi ,river4 ,u4,s4 ,geol4 ,geog4 ,surv4 ,territories ,bull4 #d7a73fg-gg4 ,,cope4 #ahhd4 ,the vertebrata of the ,tertiary ,formations of the ,west4 ,book #a1 ,rep4 ,geol4 ,surv4 of the ,territories #c3a-ajji4 ,,eardley1 ,a4 ,j4 #aiei4 ,review of the geology of northeast ,utah and southwest ,wyoming4 ,pages #aff-aga in ,intermountain ,assoc4 of ,pet4 ,geol4 ,guidebook1 #ajth ,ann4 ,field ,conf41 ,wasatch and ,uinta ,mountains ,transition ,area4 ,,eugster1 ,h4 ,p41 and ,r4 ,c4 ,,surdam4 #aigc4 ,depositional environment of the ,green ,river ,formation of ,wyoming1 a preliminary report4 ,geol4 ,soc4 ,am4 ,bull4 #hd3aaae-aabj4 ,,gazin1 ,c4 ,l4 #aief4 ,the occurrence of ,paleocene mammalian remains in the ,fossil ,basin of southwestern ,wyoming4 ,j4 ,paleontol4 #ci7c73gjg-gag4 ----4 #aiei4 ,paleontological exploration and dating of the ,early ,tertiary deposits in basins adjacent to the ,uinta ,mountains4 ,pages #aca-ach in ,intermountain ,assoc4 of ,petrol4 ,geol4 ,guidebook1 #ajth ,ann4 ,field ,conf41 ,wasatch and ,uinta ,mountains transitional area4 ----4 #aifi4 ,a new occurrence of ,paleocene mammals in the ,evanston ,formation of southwestern ,wyoming4 ,smithson4 ,contr4 ,paleobiol4 no4 #b1 #ag p4 ,,gunter1 ,g4 #aidg4 ,catastrophism in the sea and its paleontological significance1 with special reference to the ,gulf of ,mexico4 ,am4 ,j4 ,sci4 #bde7aa73ffi-fgf4 ,,hayden1 ,f4 ,v4 #ahfi4 ,preliminary field report of the ,u4,s4 ,geological ,survey of ,colorado and ,new ,mexico 7#crd ,ann474 #add p4 ----4 #ahga4 ,preliminary report of the ,u4,s4 ,geological ,survey of ,wyoming and portions of contiguous territories4 #eaa p4 ,,huish1 ,t4 #aied4 ,life history of the ,black ,crappie of ,lake ,george1 ,florida4 ,trans4 ,am4 ,fish4 ,soc4 #hc3agf-aic4 ,,jepsen1 ,g4 ,l4 #aiff4 ,early ,eocene bat from ,wyoming4 ,science #aed7cged73 #accc-acci4 ,,knight1 ,s4 ,h4 #aiee4 ,review of the early geological explorations of the ,green ,river ,basin area1 #ahab-ahgi4 ,pages #aj-ag in ,wyo4 ,geol4 ,assn4 #ajth ,ann4 ,field ,conf4 ,guidebook 7,green ,river ,basin74 ,,leidy1 ,j4 #ahef4 ,notice of some remains of fishes discovered by ,dr4 ,john ,e4 ,evans4 ,acad4 ,nat4 ,sci41 ,phila4 ,proc4 #h3bef-beg4 ,,lesquereux1 ,l4 #ahhc4 ,contributions of the fossil flora of the western territories4 ,part #c in ,f4 ,v4 ,hayden1 ,the ,cretaceous and ,tertiary floras4 ,u4,s4 ,geol4 ,survey of the ,territories1 ,rept4 #h1 #bhc p4 ,mc,g,r,e,w1 ,p4 ,o4 #aigd4 ,taphonomy of ,eocene fish from ,fossil ,basin1 ,wyoming4 ,fieldiana #cc 7in press74 ,,nelson1 ,m4 ,e4 #aigc4 ,age and stratigraphic relations of the ,fowkes ,formation1 ,eocene1 of southwestern ,wyoming and northeastern ,utah4 ,contr4 ,geol4 7,univ4 of ,wyoming7 #ab7a73bg-ca4 ,,oriel1 ,s4 ,s41 and ,j4 ,i4 ,,tracey4 #aigj ,uppermost ,cretaceous and ,tertiary stratigraphy of ,fossil ,basin1 southwest ,wyoming4 ,u4,s4 ,geol4 ,surv4 ,prof4 ,pap4 #fce4 #ec p4 ,,peale1 ,a4 ,c4 #ahgi4 ,report on the geology of the ,green ,river district4 ,pages #eji-fdf in ,f4 ,v4 ,hayden4 #aath ,ann4 ,rept41 ,u4,s4 ,geol4 ,surv4 of the ,territories4 ,,prescott1 ,g4 ,w4 #aidh4 ,objectionable algae with reference to the killing of fish and other animals4 ,hydrobiologia #a3a-ac4 ,,rubey1 ,w4 ,w41 ,j4 ,i4 ,,tracey1 and ,s4 ,s4 ,,oriel4 #aifh;a4 ,preliminary geologic map of the ,kemmerer quadrangle1 ,lincoln ,county1 ,wyoming4 ,u4,s4 ,geol4 ,surv41 open file map4 ----4 #aifh;b4 ,preliminary map of the ,sage quadrangle1 ,lincoln ,county1 ,wyoming4 ,u4,s4 ,geol4 ,surv41 open file map4 ,,schaeffer1 ,b41 and ,m4 ,,mangus4 #aife4 ,fossil lakes from the ,eocene4 ,am4 ,mus4 ,nat4 ,hist4 #gd7d73aa-ba4 ,,schultz1 ,a4 ,r4 #aiad4 ,geology and geography of a portion of ,lincoln ,county1 ,wyoming4 ,pages #a-ada in,u4,s4 ,geol4 ,surv4 ,bull4 #edc4 ,,scudder1 ,s4 ,h4 #ahij4 ,the ,tertiary insects of ,north ,america4 ,rept4 #ac in ,f4 ,v4 ,hayden4 ,u4,s4 ,geol4 ,geog4 ,surv4 of the ,territories4 #gcd p4 ,,tracey1 ,j4 ,i41 and ,s4 ,s4 ,,oriel4 #aiei4 ,uppermost ,cretaceous and ,lower ,tertiary rocks of the ,fossil ,basin4 ,pages #abf-acj in ,intermountain ,assoc4 ,petrol4 ,geol4 ,guidebook4 #ajth ,annual ,field ,conf41 ,wasatch and ,uinta ,mountains transitional area4 ----1 and ,w4 ,w4 ,,rubey4 #aifa4 ,diamicitite facies in the ,wasatch ,formation in the ,fossil ,basin1 southwestern ,wyoming4 ,pages #adi-aej in ,short ,pap4 in the ,geol4 and ,hydrol4 ,sci41 ,u4,s4 ,geol4 ,surv4 ,prof4 ,pap4 #dbd;b4 ,,van ,,houten1 ,f4 ,b4 #aidh4 ,origin of red-banded early ,cenozoic deposits in the ,rocky ,mountain region4 ,pages #bjhc-babf in ,am4 ,assoc4 ,petrol4 ,geol4 ,bull4 #cb7aa74 ,u4,s4 ,,department ,,of ,,the ,,interior4 #aifd4 ,proposed ,fossil ,butte ,national ,monument4 ,national ,park ,service ,midwest ,region1 ,omaha1 ,neb4 ,,veatch1 ,a4 ,c4 #aigj4 ,geography and geology of a portion of southwestern ,wyoming with special reference to coal and oil4 ,u4,s4 ,geol4 ,surv4 ,prof4 ,pap4 #ef4 #agh p4 ,,bibliography ,,berry1 ,e4 ,w4 #aibe4 ,flora and ecology of the so-called ,bridger ,beds of the ,wind ,river ,basin1 ,wyoming4 ,pan-,am4 ,geol4 #dd3ceg-cfh4 ,,bradley1 ,w4 ,h4 #aiei4 ,revision of stratigraphic nomenclature of the ,green ,river ,formation of ,wyoming4 ,am4 ,assoc4 ,petrol4 ,geol4 ,bull4 #dc3ajgb-ajge4 ----4 #aigc4 ,oil shale formed in desert environment1 ,green ,river ,formation1 ,wyoming4 ,geol4 ,soc4 ,am4 ,bull4 #hd3aaba-aabd4 ,,bradley1 ,w4 ,h41 and ,h4 ,p4 ,,eugster4 #aifi4 ,geochemistry and paleolimnology of the ,trona deposits and associated authigenic minerals of the ,green ,river ,formation of ,wyoming4 ,u4,s4 ,geol4 ,surv4 ,prof4 ,pap4 #dif-;,b1 #gj p4 ,,brongersma-,,sanders1 ,m4 #aieg4 ,mass mortality in the sea4 ,pages #ida-ajaj in ,treatise on marine ecology and paleoecology4 ,g4,s4,a4 ,memoir #fg4 ,,gazin1 ,c4 ,l4 #aieb4 ,the lower ,eocene ,knight ,formation of ,wyoming and its mammalian faunas4 ,smithson4 ,misc4 ,coll4 #aag7ah73 #a-hb4 ----4 #aief;a4 ,the upper ,paleocene mammalia from the ,almy ,formation in western ,wyoming4 ,smithson4 ,misc4 ,coll4 #aca7g73 #a-ah4 ----4 #aifb4 ,a further study of the lower ,eocene mammalian faunas of southwestern ,wyoming4 ,smithson4 ,misc4 ,coll4 #add7a73a-ih4 ,,gary1 ,m41 ,r4 ,mc,a,f,e,e1 ,jr41 and ,c4 ,l4 ,,wolf 7eds474 #aigb4 ,glossary of ,geology4 ,amer4 ,geol4 ,inst41 ,washington1 ,d4,c4 #heg p4 ,,hesse1 ,c4 ,j4 #aici4 ,fossil fish localities in the ,green ,river ,eocene of ,wyoming4 ,sci4 ,monthly #dh3adg-aea4 ,,hutchinson1 ,g4 ,e4 #aieg4 ,a ,treatise on ,limnology1 vol4 #a 7,geography1 ,physics1 ,chemistry74 ,john ,wiley and ,sons1 ,new ,york4 #ajae p4 ,,oriel1 ,s4 ,s4 #aifa4 ,tongues of the ,wasatch and ,green ,river ,formation1 ,fort ,hill area1 ,wyoming4 ,pages #aea-aeb in ,short ,pap4 in the ,geol4 ,hydrol4 ,sci41 ,u4,s4 ,geol4 ,surv4 ,prof4 ,pap4 #dbd;b4 ----1 ,c4 ,l4 ,,gazin1 and ,j4 ,i4 ,,tracey4 #aifb4 ,eocene age of the ,almy ,formation1 ,wyoming1 in its type area4 ,am4 ,assoc4 ,petrol4 ,geol4 ,bull4 #df7aj73 #aicf-aicg4 ,,romer1 ,a4 ,s4 #aiff4 ,vertebrate paleontology1 #crd ed4 ,univ4 ,chicago ,press4 #dfh p4 ,,rubey1 ,w4 ,w41 ,s4 ,s4 ,,oriel1 and ,j4 ,i4 ,,tracey4 #aifa4 ,age of the ,evanston ,formation1 western ,wyoming4 ,pages #aec-aed in ,short ,pap4 in the ,geol4 and ,hydrol4 ,sci41 ,u4,s4 ,geol4 ,surv4 ,prof4 ,pap4 #dbd;b4 ,,sears1 ,j4 ,d41 and ,w4 ,h4 ,,bradley4 #aibd4 ,relations of the ,wasatch and ,green ,river formations in northwest ,colorado and southern ,wyoming with notes on oil shale in the ,green ,river ,formation4 ,pages #ic-ajg in ,u4,s4 ,geol4 ,surv4 ,prof4 ,pap4 #acb;f4 ,,thorpe1 ,m4 ,r4 #aich4 ,wyoming ,eocene fishes in the ,marsh collection4 ,am4 ,j4 ,sci4 #cf3bgi-bie4 ,,acknowledgments ,this report1 which was prepared under ,national ,park ,service ,contract ,,cx #fjjj-c-jjgf1 leans heavily on the publications of those many people who have studied various geologic aspects of the ,fossil ,basin4 ,we would like to cite particularly ,doctors ,steven ,oriel and ,joshua ,tracy of the ,united ,states ,geological ,survey1 whose studies have clarified the stratigraphic relationships of the sediments involved4 ,dr4 ,d4 ,l4 ,blackstone1 ,jr41 of the ,university of ,wyoming supplied information from his yet unpublished interpretations of the complicated structure of the ,idaho-,wyoming thrust belt4 ,mr4 ,tom ,bown helped with the structural part of the report and critically reviewed other parts4 ,the drafting1 except for ,figs4 #c and #i1 was done by ,mr4 ,evan ,groutage4 ,mrs4 ,elaine ,hertzfeldt1 secretary for the ,department of ,geology1 aided greatly in preparing this manuscript4 ,paul ,o4 ,mc,grew ,michael ,casilliano ,illustration3 ,,department ,,of ,,the ,,interior ,,march #c #ahdi2 ,,national ,,park ,,service ,transcriber's ,notes --,silently corrected a few typos1 including inconsistent spelling of 8,lostcabinian04 --,retained publication information from the printed edition3 this e,book is public-domain in the country of publication4 --,in the text versions only1 text in italics is delimited by underscores4