22 COLORADO FORMATION AND ITS INVERTEBRATE FAUNA, [bull. 106. 



tal and the Tertiary deposits are not very thick, the streams have cut 

 through into the Cretaceous for some distance within the Tertiary area, 

 thus making its boundary very irregular. Only a part of it has been 

 accurately mapped. 



Until recently all of the Cretaceous strata of Kansas have been 

 referred to the Dakota and the Colorado formations, and there is no 

 doubt that these two formations do cover a large area within the state, 

 but it has been shown ] that a part of the Lower Cretaceous Comanche 

 scries, with some of its characteristic species of fossils, occurs in several 

 of the southern counties, and the probable existence of the Montana 

 formation in the northwestern part of the state has been reported. 



Prof. B. F. Mudge, who spent several seasons in collecting vertebrate 

 fossils from the Niobrara division in Kansas and visited the most of 

 the Cretaceous outcrops in the state, estimated 2 the total thickness of 

 the Cretaceous at 900 feet, of which 500 feet was assigned to the 

 Dakota and the remainder to the Niobrara. 



The fact that the beds above the Dakota contain a greater propor- 

 tion of calcareous material than usual led Prof. Mudge to conclude that 

 they all belong to the Niobrara and that the Fort Benton shales are 

 absent, but it is evident from the description that his Niobrara repre- 

 sents the whole of the Colorado formation. The data for the following 

 section of the Upper Cretaceous strata of Kansas :i are taken from the 

 paper last cited: 



Kansas Upper Cretaceous section.. 



Feet. 



1. Dakota formation. 



Brown and variegated sandstone of varying degrees of hardness, frequently 

 with ferruginous concretions, and usually interstratified witlitliiu beds of 

 clay shales, and one or more seams of lignite. Fossil plants abundant; ani- 

 mal 3 remains rare. Estimated thickness 50O 



2. Colorado formation. 



a. Interstratified shales and thin layers of limestone containing Inoceramus 

 labiatus and a few other mollusks, with occasional fish remains 140 



b. Bluish black or slate colored shale with many concretions containing 

 Prionotropis ivoolgari, Scajrirftes, Inoceram us, etc 60 



c. Massive chalky limestone with Inoceramus deformis, Osti-ea congesia, and 

 occasional remains of fish and saurians 60 



d. Buff and white chalk or chalky limestone with calcareous shales. Fossils : 

 Uintacrinus socialis, Inoceramus labiatus, I. deformis?, Ostrca congesta, Badio- 

 litcs?, Baculites ancepst and great numbers of vertebrates, including birds, 

 reptiles, and fishes. Thickness 200 : 



Est ima ted total thickness of the Colorado 460' 



* 



1 Cragin, F. W. The Cheyenne Sandstone and the Ncocomian Shales of Kansas. Washburn College- 

 Lab, of Nat. nist. Bull., vol. II, No. 11, and Am. Geologist, vol. VI, p. 233, and vol. vn, p. 23. 



2 Mudge, B. F. Notes on the Tertiary and Cretaceous Periods of Kansas, U. S. Geol. Sur. Terr: 

 Ann. Rept. for 1875, pp. 277-294. 



3 15 species of invertebrates, none of which have been found in the overlying strata, have been de- 

 scribed by Meek (U. S. Geol. Sur. Terr., vol. IX) and White (PiOC. U. S. National Museum, vol.11) from' 

 this horizon in Saline county, Kansas. 



