Hatcher's excellent descriptions of the stratigraphy and general features of the region have been supple-. The freshwater invertebrate fauna and flora as well as the vertebrate fauna of the Converse County "Ceratops Beds" have been collected primarily from the upper half of the formation. If Barton's observations are correct, the rapid northward thinning of the sandstones beneath the "Ceratops Beds" is not the result of erosion of the upper parts, but of lateral replacement of the lower parts by shale.
On faunal and stratigraphic evidence, Brown's correlation of the "Hell Creek Beds" with the "Ceratops Beds" of Converse County, Wyoming, is fully justified. The base of the section is a marine chalk shale referred to the Pierre, which is overlain by 80 feet. The "Laramie" and older rocks in the section are not described in Woolsey's report, but from the exposures I visited with Mr.
Brown records-^ a similar discovery of a dinosaur in the upper part of the Pierre Shale in the Hell Creek region. Whatever may be true of Livingston in the type area near the town of that name, the rocks assigned to it by Weed are east. Stanton on a fork of Big Elk Creek gives a thickness of 5592 feet from the bottom.
The base of the formation is a particularly massive, coarse-grained sandstone that forms pronounced forested ridges.
266 STANTON
34;CERATOPS beds" OF WYOMING AND_MONTANA 267 tain light-colored sandstone strata in the upi:)er part of the lower. Some brownish and yellow sandy strata lying still higher, near the top of the same member on Tongue River, appear to thin out toward the south and gives way to dull colored shale or sandy strata on Goose and Beaver creeks in T. The sandstone throughout is dull in color, and near the southern boundary of the mapped area the sandstone beds contain pebbles of limestone, quartz, and chert.
The constituent parts of the conglomerate become coarser rather abruptly as we approach the Paleozoic rocks of the Bighorn Mountains, on which the conglomerates are unconformably overlain. The exposed portion of the conglomerate strata is more than 1,000 feet thick between Little Goose and Sandy Creek valleys, at the base of the Big Horn Mountains, on the southern border of the Sheridan field. Gale produced a planetable map (unpublished) and a structural section of several land sections in the southwestern part of T.
82 W., which enabled him to determine with precision the stratigraphic positions of the various collections, and to demonstrate that there was one large. All the evidence, both paleontological and stratigraphic, tends to prove that the unconformity at the base of the Kingsbury conglomerate is quite widespread at Fort Union. The most prominent feature of the section at Black Buttes is the massive sandstone bed, somewhat over 100 feet thick at the base of the exposure, forming steep hills and cliffs northeast of the railroad in front of the station and passing below the surface from its dip of 9 or 10 degrees near the coal mine.
All Laramie fossils, whether plants, invertebrates, or vertebrates, hitherto described or cited as originating in the BlackButtes, have been obtained from the overlying beds about 100 feet from the top of this massive sandstone. The freshwater element of the invertebrate fauna shows a close relationship and specific identity with the HellCreek and Converse County faunas, while the brackish-water species are similarly related on the one hand to the Laramie fauna of Crow Creek, Colorado, which is in the Denver Basin, and on the other to the. Of the freshwater forms, Tulotoma thompsoni also extends to Mesaverde, and some Unios are represented by related species in this formation.
While this line removes such species from the list of distinct Laramie species, it does not impair their value as evidence of the Cretaceous age of the beds in which they occur. The flora is apparently more closely related to that of Point of the Rocks, which is located in the upper part of the Mesa-. Lesquereux" recognized the close relationship of the flora of these two localities, stating that they had 9 species in common.^^ That progress in science in the last 30 years has not altered this relationship is shown by two small collections taken in past. near Table Rock from the Black Buttes horizon in which the following species were identified by Dr. Knowlton and referred to "probably the same age in the BlackButtes."
274 STANTON
34;CERATOPS Beds" OF WYOMING AND MONTANA 275 in the bed of mostly brackish-water shells, among which the following have been identified from a locality inT. Above the Mesaverde is the Lewis Shale, about 1500 feet thick, with a few layers of fossiliferous sandstone which is often Near the middle of the formation in T.22N., R.89W., in line across the strike of the Mesaverde and Lewis localities noted above, Corbula suhtrigonalis M.
This is clearly a sharply modified repetition of the basal brackish-water fauna of the upper Mesaverda and is virtually identical to the brackish-water element of the Zeza fauna. Stratigraphic, surface, and structural relationships and faunal evidence appear to justify correlation of the "Laramie" of this area with the BlackButtescoal Group. Above his Laramie Smith distinguishes two unconformities between which there are coal-bearing seams with a total thickness estimated at 8,780 feet which he treats as **undifferentiated Tertiary."
Above the upper unconformity are from 900 to 1,800 feet of coal seams, which Smith listed in the Wasatch. Veatch's "Upper Laramie" of this area, with the addition at the top of the 1,200 feet of beds referred to FortUnion, apparently agrees very well with Smith's "Undifferentiated Tertiary." The "Upper Laramie" has a basal conglomerate "composed largely of pebbles derived from the underlying Cretaceous rocks" and overlies several older formations in part of the area.
The localities and horizons of the various lots given on the field labels have been compared with the published geological map and the evidence will be recorded as such. In some other localities Tulotoma thompsoni White was collected with other gastropods of this list. Veatch believes, however, that the dinosaurs were found incomplete in the "Upper Laramie" about a mile and a half above the mouth of the Medicine Bow.
His belief, it is said, is based on statements by a native of the region that large fossils were once collected there. Mr. Gardner believes the bed he collected from belongs to the Puerco and that there are several. CERATOPS BEDS OF WYOMING AND MONTANA In this respect the evidence in Carbon County tends to do so.
CERATOPS BEDS OF WYOMING AND MONTANA 279 So far as it goes the evidence in the Carbon County field tends to
There is no more intermingling of the two kinds of forms than might be expected, where slight fluctuations in the level alternately bring them over the same area, and where currents. Some areas in the Rocky Mountain region must have been subject to erosion for long periods before the end of the Cretaceous. The hypothesis is that erosion did not begin until near Laramie in the Denver region, for example, and that there must be time between Laramie and Arapahoe before erosion can cut through 15,000 or 20,000 feet of sediments to the granite in this region istom, but it is incredible and creepy.
The turtles, rhynchocephals, and crocodiles of the "Ceratopsbeds" may be very closely related to those of Fort Union, Puerco, and Torrejon, but the faunas are generally very distinct. In France, the Montien stage now referred to the uppermost Cretaceous contains dinosaurs closely related to those of the Tricera-topsfauna, according to DeLapparent.^^. A Comparison of the Laramie Invertebrates of the Denver Basin with the Invertebrates of the "ceratops Beds" of HellCreek and Converse Countyisa, for any such value.
The invertebrates of the "Ceratops beds" and indeed practically all non-marine forms of the Cretaceous such as the plants of. This element of the fauna is best developed in the Hell Creek and Converse County areas, where they are not associated with brackish water beds, but the distribution of some of the species is. Laramie of the upper Missouri, named by Hayden, FortUnion group, and which, in my judgment, must be considered basal.
King regarded this as the uppermost member of the Cretaceous system, and excluded from it the Fort Union beds of Hayden, which, on the evidence I gave him, he agreed with me to consider tertiary. Rocky Mountain region; it forms a marginal belt on the east side of the mountains, extending from central Mexico into the British possessions. On the west side of the Rocky Mountains it extends to the Wasatch, but has not been recognized at any point west of the crest of that range.
Six are the same as those from the Lower European Miocene and seven are analogous; two are identical with the Arctic, and one is related to it. Seven of them are closely related to the plants of the Lower European Eocene, Sezanne and Gelinden, two localities forming a subdivision separated at the base of the Tertiary, under the name. The plant assemblages at Point of Rocks have, in addition to the Eocene representatives, six species identified with and related to those of the European Miocene.
Of course I leave the so-called Upper Cretaceous floras of Europe whose. One of the oldest floras in Europe containing angiosperms is that of Aix-la-Chapelle, and even this we have seen is comparatively modern; but these are not referable in all equal degree to existing genera, and even the conifers are embarrassed by their highly transitional character.
CERATOPS BEDS OF WYOMING AND MONTANA 293 The Fort Union formation, properly restricted, is of early Eocene
