From the beginning of his study of the flora of Fort Union, to his last statement on the subject, he insisted on their separation. Barnum Brown" published a valuable contribution on the geology of the Hell Creek region of northeastern Montana.
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 1 89 Corylus amcricana Newb
FORSYTH, MONTANA
The characteristic dark sandstones and clays of the lower Fort Union are known to extend for some distance as a surface formation. HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS A stretch of nearly 20 miles along both sides of the Yellowstone River west of.
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 191 of nearly 20 miles along both sides of the Yellowstone River west of
CUSTER, MONTANA, AND VICINITY
A section several hundred feet thick, resting on one of the upper members of the Pierre, is.
BULL MOUNTAIN, MONTANA, AREA
MELVILLE, MONTANA, AREA
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS I93 in this general region is somewhat obscure — to judge by the different
Gidley and considered by him to be of Torrejon affiliation, although scattered remains of mammals have been found almost to the horizon of plants. Subsequently, however, large collections from Livingston were made and studied with the result of showing that it.
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS I95
RED LODGE, MONTANA
GLENDIVE, MONTANA, AND VICINITY
HELL CREEK BEDS, CERATOPS BEDDS AND EQUIVALENTS 197 agree with the Fox Hills beds of the Hell Creek section, and belong.
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 1 97 agree with the Fox Hills beds of the Hell Creek section, and should
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 1 99
GLENDIVE, MONTANA, TO MEDORA, NORTH DAKOTA
Leonard and Smith,2° has a depth of from 420 to 440 feet below the surface of the plain in which it was eroded, and may have cut into the beds of the lower member, although the deep pit was sunk in Medora. The entire thickness of the section in this area, including the beds fed by the Medora well, is 1720 feet, and it is possible that the upper part of the lower member of the Fort Union may be exposed, but as it is not is not definitely known, it is omitted from the present consideration. In any case, all the numerous finely preserved plants obtained in this region are clearly of the Fort Union period.
BISMARCK, NORTH DAKOTA, AND VICINITY
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 20I lowing plants in shaley sandstone about loo feet above the top of
YULE, BILLINGS COUNTY, NORTH DAKOTA, AND VICINITY
- PROBABLE AREA OF LOWER FORT UNION IN NORTHWESTERN SOUTH DAKOTA
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 20Ilowing plants in shaley sandstone about loo feet above top of. Gidley that he has observed dinosaur-bearing beds stratigraphically and lithologically similar to the "Ceratops beds" of Converse County, W^yoming, in the country between the Grand and Moreau rivers in South Dakota, on both the east and west sides of the Long Pine Hills. HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 203horizon is about 250 feet above the Fox Hills and embraces.
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 203 horizon is about 250 feet above the Fox Hills and embraces the
AREA IN WESTON COUNTY, WYOMING
NORTHWARD EXTENSION OF WESTON COUNTY AREA CONNECTING WITH THE MILES CITY AREA
At least in some places they rest on seafloors that contain invertebrate fossils characteristic of the Fox Hills deposits. The fact remains, however, that the fossil-rich part of the "Ceratops beds" is mainly the upper part, with the highest point at which dinosaurs were found being only 30 to 50 meters below Fort Union. The different layers of the series are not always continuous; a layer of sandstone gives way to a layer of shale, and vice versa.
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 207 Following is the list of plants thus far obtained from the " Ceratops
For several years, however, data have been collected in neighboring and more distant areas, which have a special relevance to the problem, as a result of which the present writer has completely changed his opinion about the proportions and age of the beds in question. The affinity of the undescribed forms is also quite clear to the true Laramieflora, and as nearly as can be discerned the plants confirm the Laramie age of the Ceratops beds. Since the publication of the above-mentioned paper, the plants have been more closely examined, which has increased their number to 48 forms, as already enumerated, although it still shows a large proportion of new forms, with more modern characteristics.
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 209
AREA TO THE EASTWARD OF THE BIGHORN MOUNTAINS, WYOMING
Its north and south hex nearly coincide with faults which, according to Darton, have attended an uplift of about 9,000 feet of this portion of the Bighorn Mountains. That the unconformity at the base of the Kingsbury is not of wide significance is shown by the fact that it has not been detected in a section made at Parkman, only about 25 miles north of the northern part of the Kingsbury, and nor was it found a few kilometers south of the southern limits of the formation. Along the eastern margin of the Kingsbury it can be observed that there are fingers in the soft shales and sandstones of the De Smet Formation.
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 211 Cissiles parroticcfolia Lesq
BIGHORN BASIN, WYOMING
In the extreme northwestern part of the basin, the lower Fort Union undoubtedly connects the area around Red Lodge, Montana. Fisher's paper had been prepared, sufficient paleontological data had not been obtained to determine the limits of this, as well as underlying and overlying beds, and the entire series, totaling more than 5000 feet in thickness, was described and mapped as the 'Laramie and Associated Formations' . As shown on Fisher's map, these beds are exposed continuously around the outer margin of the basin, with their maximum areal extent in the northeastern part and their 34;massive gray to buffsandstone," which is lithologically similar to the supposed 'Fox Hills' on the eastern side of the Bighorn Mountains, and for this reason was tentatively referred to the 'Fox Hills'. The few invertebrates do not serve to definitively establish the age, according to Stanton,'* as they may occur below the Judith River as well as in the.
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 213 tion the sandstones are usually fine-grained and massive, and sand-
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 213tion the sandstones are usually fine-grained and massive, and sand-.
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 215 Taxodium occidentale Newb
POSSIBLE DISTRIBUTION OF LOWER FORT UNION IN OTHER AREAS
The beds in which they are located belong to the so-called "upper Laramie" of Veatch and others, which is above the conformity to the upper Laramie, but whether or not this series of beds is a unit is currently an open question. To the west, in the Evanston area, some Fort Union species have been recorded, but in all these cases additional data are required. Having traced the surface distribution of what is here called the lower member of the FortUnion formation, a brief summary may be made, as the present facts seem to warrant, of the relations shown of this to the underlying beds.
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 21'J
This interpretation by Brown makes the unconformity at the base of the lower Fort Union member the same as that demonstrated by Mr. Whitman Cross to occur at the top of the Laramie in the Denver basin of Colorado. We can now proceed to consider the various lines of paleontological data, beginning with that of plants.
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 219 at over fifty localities, and when these are brought together in a single
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 221
From the above table it appears that of the whole number of forms now known in the lower member of the Fort Union, only 16 species are common to it and the Cretaceous, this including both Laramie. Thus, Ficus trinervis, found only in the lower beds at Glendive, Montana, is a species of wide distribution in the Montana and Laramie, and has been found in the Shoshone. Juglans rugosa, of which there is but a single specimen in the dinosaur beds at Yule, is of very wide distribution.
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 223 occurring at Point of Rocks, Rock Springs, Bhick Buttcs, Evanston,
He saw this clearly enough and pointed them out, but the prevailing opinion at the time, especially among invertebrate paleontologists, misled him that it could not be separated from 'Laramie', just as Newberry had previously been misled into referring Fort Union to the Miocene, on based on the then valid correlation of some plant-bearing horizons in Greenland, England and elsewhere. Dawson^^ has preserved the Eocene age of Fort Union (the "Upper Laramie" of Canadian geologists), and neither, so far as the writer knows, has ever been altered. The flora of Fort Union, as stated by Newberry, has a botanical facies which at first sight admits of its separation from the flora of Laramie.
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 225
INVERTEBRATE EVIDENCE
The invertebrates of the lower member of the Fort Union are comparatively much less numerous, both in species and in individuals, than the plants, but fortunately considerable collections have been secured in the critical areas. It should be noted, however, that this total includes eight unnamed but putative new Unio species, which are listed by Stanton as occurring in the "Ceratops beds". The distribution of these invertebrates is.
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 227 species preceded by a cross (x) are common lo these beds and the Colorado
However, it is very likely that at least some of the undescribed Unios from Converse County may turn out to be identical to those from Hell Creek. This indicates either that the "Hell Creek Beds" are relatively recent, or that the Unios are not of great value as time markers. 34;The fossiliferous, dinosaur-bearing bed of Black Buttes, Wyoming, is not admitted to be definitely referable to Laramie, but rather to post-Laramie or Shoshone.
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 229
VERTEBRATE EVIDENCE
Hatcher'', when speaking of the Ceratops fauna, honestly said that due to the fact that very few vertebrates had previously been described from the typical Laramie, as first defined by Mr. Thedinosaurs of the Ceratops- beds, are highly modified and specialized forms hitherto unknown in other parts of the world, except: perhaps in the Gosau Formation of Austria, and the conclusion that they necessarily indicate a Mesozoic implies a reason why. They are covered by hundreds of meters of fossiliferous marine Cretaceous, and the dinosaur fauna, together with associated fossil plants, indicates an age approximately that of the Judith River.
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 23
The causes that led to the extinction of the dinosaurs are of course unknown and may always remain so. An orogenic movement with the effect it would have had on climate and vegetation; the draining of the waters in which, or by which they lived; the sudden invasion of mammalian enemies they can handle; the outpouring of volcanic material; this, or any one of them, may be responsible for their disappearance, but we have no evidence of the occurrence of either of these phenomena. Gilmore says: "It appears to represent a typical fauna of the so-called Laramie, or better, Ceratops beds."
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 233 was continuous. No more plausible theory occurs to the writer
The gap between Laramie and Puerco was relatively short as indicated by the relatively limited evolution of both Plagiaulacidae and Trituberculates. I do not hesitate to say, judging from the known forms, that the differences between the mammals of the Jurassic and those of the Ceratops beds are at least ten times greater than those between the mammals of the Ceratops beds and those of the Puercos. . Leaving aside the multituberculates at present, the pattern of tooth crowns, especially of the upper molars, in Jurassic mammals is fundamentally different from.
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 235
Of them Eastman says, "As a whole the collection has not a definite Cretaceous aspect," adding that "it would be useless to reason from this that the beds in question are of the Eocene age, for there are numerous fishes of the dominant Eocene type in the FortBenton Cretaceous of Wyoming." From this it appears that the fish remains are not likely to be much of a factor in fixing the age of these beds, although they favor the Eocene age at all. If a locality could be founded on which sedimentation was continuous, it would probably be necessary to draw an arbitrary line, but we know of no portion of such completeness in this country. HELL CREEK BEDS, CERATOPS BEDDS AND EQUIVALENTS 237of the Rocky Mountains, the general elevation of the country, and.
HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 237 of the Rocky Mountains, the general elevation of the country, and
The mammals of the lower Fort Union show very little rela- tionship with Jurassic or Cretaceous forms, but find their closest
