456 



MESOZOIC TIME. 





3. 



5. 



taceous occurs in the Coast ranges, becoming most prominent to the north of San Fran- 

 cisco, and along the foot-hills of the Sierra Nevada, from Placer County to Shasta; and 

 in Oregon, east of the Cascade range (Marsh). 



As the Cretaceous formation is very fully represented in the region of the Upper 

 Missouri, a detailed section of it, by Meek & Hayden, is here given, beginning 

 below, the Laramie group excluded : — 



1. Dakota Group. — Yellowish, reddish, and whitish sandstones and clays, with 



lignite and fossil Angiospermous leaves : thickness, 400 feet. Location, near Da- 

 kota, and reaching southward into northeastern Kansas. This division may re- 

 quire to be united with No. 2 (M. & H.). 



2. Benton Group. — Gray laminated clays, with some limestone: thickness, 800 feet. 



Location, near Fort Benton, on the Upper Missouri, also below the Great Bend; 

 eastern slope of the Rock) 7 Mountains. 

 Niobrara Group. — Grayish calcareous marl: thickness, 200 feet. Location, Bluffs 



on the Missouri, below the Great Bend, etc. 

 Pierre Group. — Plastic clays : thickness, 700 feet ; — middle part barren of fossils. 

 Located on the Missouri, near Great Bend, about Fort Pierre and out to the Bad 

 Lands, on Sage Creek, Cheyenne River, White River above the Bad Lands. 

 Fox-Hills Gkoup. — Gray, ferruginous, and yellowish sandstones and arenaceous 

 clays : thickness, 500 feet. Location, Fox Hills, near Moreau River, above Fort 

 Pierre near Long Lake, and along the base of Big Horn Mountains. 

 Nos. 2, 3, and 4, correspond collectively to the Colorado group (p. 454). 

 No. 1 occurs at different points in New Mexico (Newberry). No. 2, on the north 

 branch of the Saskatchewan, west of Fort a la Corne, lat 54° N.; in New Mexico 

 (Meek). No. 3, over the region from Kansas through Arkansas to Texas, in the Pyra- 

 mid Mountain. No. 4, in British America, on the Saskatchewan and Assiniboine; on 

 Vancouver Island; Sucia Islands, in the Gulf of Georgia No. 5, at Deer Creek, on the 

 North Platte, and not identified south of this. (Meek & Hayden.) 



King gives for the Dakota group, in the Uinta Range, a thickness of 500 feet, for the 

 Colorado group, where thickest, 2,000 feet; the Fox Hills group, 3,000 to 4,000 feet. The 

 conglomerate at the base of the Dakota separates it from the underlying Jurassic beds. 

 The fossil plants of the Cretaceous in the Rocky Mountains come from the lower part 

 of the Dakota group. At the very base of the group in the Uinta region there is an ex- 

 cellent coal-bed, which does not occur to the eastward. 

 In Mississippi, Hilgard has made out the following subdivisions: — 



1. (Lowest) J'Jutaw (/roup (Coffee group of Safford), consisting of clays, with usually 

 some sand beds above, and containing beds of lignite and rarely other fossils, the thick- 

 ness 300 to 400 feet. 



2. Botten-Limestone group, not less than 1,200 feet thick, made up of soft, chalky, 

 white limestones, underlying the prairies, and containing Placuna scabra Mort., Neithea 

 Mortoni Gabb, Gryphcea convexa Mort., G. mutabilis Mort., G. Pitcheri Mort., Ostrea 

 falcata Mort., Eudistes, Mosasaurus, and including the " Tombigby Sand," in which 

 occur many Selachian relics and the gigantic Ammonites Mississippiensi^. 



3. The Ripley group, hard white limestones, often glauconitic and sandy, underlaid 

 by black or blue micaceous marlytes, 300 to 350 feet thick, and containing Cucullcea 

 capax Con., Gervillia ensiformis Con., Baculites Spillmani Con., Scaphites Conradi 

 D'Orb., Ammonites placenta Dekay, etc., forming the Pontotoc ridge in Mississippi, the 

 Chunnenugga ridge in southeastern Alabama, and occurring also at Eufaula, Ala. 1 

 Is Hayden's No. 1; 2, his No. 4; and 3, his No. 5 (Hilgard, Am. J. Sci., III. ii. 392). 



In Tennessee, there are the Coffee Sand, 200 feet thick; the Green-sand or Shell bed 

 (Rotten Limestone), 200 to 350 feet; the Ripley group, 400 to 500 feet thick, consisting 

 mostly of stratified sands. 



In Alabama, the thickness of the Cretaceous is 2,000 feet, 900 to 1,100 of it the Rotten 

 Limestone. 



In Texas, the beds consist mainly of compact limestone, and the larger part are of the 

 Later Cretaceous. Shumard gives the following subdivisions: Marly clay, 150 feet 



