608 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



feet. Lithologically and stratigraphically this is identical with the Morrison beds seen on 

 the Purgatoire, where characteristic dinosaurs were collected. Fragmentary, undetermined 

 dinosaur remains were seen in it on the Cimarron near Exter, N. Mex. 



Beneath the recognized Morrison some localities show 40 to 50 feet of gypsum and gypsif- 

 erous shales resting on a massive white or pinkish sandstone which Mr. Lee has described as 

 the Exter sandstone. It varies greatly in thickness, the maximum observed being 80 feet. 

 The Exter is separated from the red beds by a striking angular unconformity, wherever the 

 red beds are folded in local uplifts. The red beds show the usual character and at Tod's 

 ranch, 15 miles east of Folsom, they yielded fragmentary Triassic vertebrates. 



Summing up the evidence presented by the sections quoted and also by those 

 at Tucumcari and Canon City, Stanton says: 



The question whether the Morrison formation is Jurassic or Cretaceous is still to be 

 answered, and if a satisfactory answer is ever received it will doubtless be from vertebrate 

 paleontology, aided by careful stratigraphic methods. If the Morrison is Cretaceous, the 

 proof that it is so will not be by tracing it directly into marine Cretaceous strata. It has been 

 shown that the beds supposed to be thus connected with it overlie it for more than 100 miles 

 across the strike. But these overlying beds are by no means the earliest Cretaceous, and there 

 is still room for the Morrison within that system if the fauna requires such a reference. On 

 the other hand, there is ample space for it in the Jurassic " not otherwise represented in the 

 region by sediments, and before the final decision is made the character of the flora in the 

 Fuson formation of the Black Hills and in the Kootanie of Montana should be given due weight 

 and these formations should be closely studied and searched for other evidence. 



I-K 17-18. ATLANTIC COASTAL PLAIN, MASSACHUSETTS TO NORTH CAROLINA, INCLUSIVE. 



The following statement, prepared by WiUiam B. Clark, is an elaboration 

 of a briefer article "^ covering the northern part of the Atlantic Coastal Plain : 



General conditions of occurrence. — The oldest deposits of the Atlantic Coastal Plain which 

 outcrop at the surface are of Cretaceous age. Well borings at many points throughout the 

 district have not afforded strata of earlier age, although such deposits may exist to the east 

 toward the margin of the continental shelf. 



The deposits as a whole have been but little changed since they were originally laid down 

 along the continental border, but the strata present much complexity due to the variation in 

 the angle and direction of tilting during the successive oscillations of the sea floor during Cre- 

 taceous time. The sediments in general form a series of tliin sheets which are inclined sea- 

 ward, so that successively later formations are encountered in a journey from the inland border 

 of the region toward the coast, yet at no place accessible to our study do we find a complete 

 sequence of deposits, although sedimentation must have been continuous over a large part of 

 the continental shelf. The incompleteness, therefore, must be regarded as a purely marginal 

 condition due to the transgressions and retrogressions of the sea along the coastal border. 



The Cretaceous formations are variously transgressed in the different areas by deposits of 

 Tertiary and Quaternary age, these later formations in places reaching to the Piedmont border 

 or beyond and entirely concealing the earlier strata along the outcrop. The full sequence of 

 Cretaceous deposits can therefore be observed only at favorable points and chiefly along the 

 main river channels, although even here the later formations are buried over many wide areas 

 in consequence of the attitude of the strata to the present sea level. 



The Atlantic Coastal Plain deposits afford representatives of both the Lower and the 

 Upper Cretaceous, the former being most extensively developed in Maryland and northern 

 Virginia and in North Carolina, the latter in New Jersey, whence the strata gradually 

 thin out northeastward along the New England coast and southward through Delaware and- 



o The marine Jurassic Sundance formation, characterized by Cardioceras cordiforme M. and M., etc., on which the 

 Morrison rests in the northern area, does not represent tlie latest Jurassic according to European standards. 



