Q 



36 R. T. HILL — GEOLOGY OF RED RIVER. 



For instance, we know that the Trinity level of deposition has been 

 elevated to 4,000 feet in New Mexico, the Dakota and Eocene (Laramie) 

 to 10,000, and the Miocene to 5,000 feet, while all are found below 500 

 feet in Arkansas. 



Nearly all these movements, except the Comanche, have been recog- 

 nized if not correlated in the Rocky mountain region, but the Comanche 

 has not been noticed because it had not been differentiated when our 

 great physical geologists studied that region and when the Dakota was 

 supposed to be the lowest Cretaceous baselevel epoch. When the Cor- 

 dilleran region is studied in the light of this later knowledge of the 

 Comanche it will reveal a volume of history now unknown. 



Conclusions as to the Cretaceous Section. 



Limited space prevents the amplification in this paper of much desira- 

 ble detail, but the writer hopes that he has presented the salient facts 

 concerning the structure, especially of the Cretaceous formations. A 

 study of these as here presented cannot but emphasize the fact that in 

 the Arkansas-Texas region they have a completeness of stratigraphic and 

 paleontologic succession such as can be found nowhere else in America, 

 from which many important deductions can ultimately be drawn, and 

 which lead to conclusions somewhat different from those currentl}^ ac- 

 cepted. 



The writer believes that without the aid of this section, deductions 

 concerning correlation have been in general premature and unreliable, 

 and will be until the paleontology of the six* distinct faunas of the 

 Comanche series are studied, compared and published. These faunas 

 are as distinct one from another as they can be, and each contains impor- 

 tant data without which it is utterly impossible for any one to properly 

 understand the life relations of the North American Cretaceous. While 

 species-making has continued until nearly every form has received many 

 names, not a single one of these faunas has been fully published, so that 

 its full meaning can be interpreted, and only two of them approximately 

 published.f Several of them are briefly mentioned in this paper for the 

 first time. W^ith the exception of the Echinodermata,:|; not a single class 

 has been studied systematically with reference to stratigraphic occur- 



* These faunas are those of 1. The Trinity division; 2. The Comanche peak beds and Caprina 

 limestone; 3. The Preston beds (Kiamitia and Duclc creek) ; 4. The Fort Worth limestone; 5. The 

 Denison beds; 6. The Shoal creek limestone. 



fThe faunas of the Trinity division and Caprina limestone. See Proc. Biol. Soc, Washington, 

 1893. 



X'Vhe Mesozoic Echinodermata of the United States, by W. B. Clark. Bull. 97, U. S. Geological 

 Survey, Washington, Ism. 



