252 C. SCHUCHERT MORRISON AND TENDAGURU FORMATIONS 



deposits in Colorado and Wyoming. A presentation of all of the more 

 important sections can be had in Mook's paper of 1916 on the Morrison. 



OIL CREEK, BELOW GARDEN PARK, COLORADO 



About one mile south of the Marsh dinosaur quarry. Adapted from 

 Stanton, Journal of Geology, volume 13, 1905, page 666. 



Feet 



Dakota massive gray sandstone overlain by Benton shale 100 



Break in deposition. 

 Comanchian (Purgatoire). Marine dark gray shales with thin-bedded 



sandstones. Marine fossils (Washita) 35 feet from top 85 



Massive gray sandstone with conglomerate near top 35 



Probable break in deposition. 

 Morrison (typical). Chocolate, reddish, and variegated shales? and variable 

 sandstones. All of the dinosaurs were collected in the upper half. Asso- 

 ciated with or just above and below the dinosaurs occur also the bivalves 

 Unio felchii, U. toxonotus, U. macropisthus, U. iridoides, and U. lapil- 

 loides; the snails Limncca ativuncula, L. consortis, PlanorMs veternus, 

 and Valvata scahrida; the ostracods Metacypris forhesii, Darwinula 

 leguminella, etcetera. Probable total thickness 400 



COMO BLUFF, WYOMING 



Six miles east of Medicine Boav. Seen by Schuchert July 29, 1899. 



Feet 



Comanchian. Cloverly heavy-bedded sandstone. About 45 



Probable break in deposition. 



Morrison formation. Green shales with thin zones of gray and buff and 



beds of dark chert. In places variegated green and red shales. Toward 



the top appear intercalated thin sandstones. Main horizon for dinosaurs 



(especially Stegosam^us) , mammals (at the very top), Unio nucalis, and 



Vorticifex stearnsii. About 75 



Reddish shales with local sandstone zones and many ironstone 

 concretions. Dinosaurs here also. Above, variegated with 



green shales. About 75 



Green shales with thin beds of brown limestone, and pyrite con- 

 cretions. About 20 



Whitish to buff sandstone. About 15 



Total (estimated) 185 



Darton gives the thickness as 202 feet. 

 Break in sedimentation. 

 Jurassic. Sundance formation. Greenish to buff sandy shale with an 

 abundance of Belemnites densus throughout. Much marked with 



caudagalli-likP' burrows. About 50 



Coarse white sandstone 5 



Buff and red sandy shale with chert horizons. Weathers rapidly. 

 Belemnites at about 5 and 35 feet from base. About 50 



