File:Map showing the distribution of the Cretaceous formation in North America – Geology (1907) (14589719039).jpg

Identifier: geology00cham (find matches)
Title: Geology
Year: 1907 (1900s)
Authors: Chamberlin, Thomas C. (Thomas Chrowder), 1843-1928 Salisbury, Rollin D., 1859- joint author
Subjects: Geology
Publisher: New York, H. Holt and co.
Contributing Library: Internet Archive
Digitizing Sponsor: Internet Archive

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
ibution of the Cretaceoussystem has much in common with that of the Comanchean, theyounger system is much more widespread (Fig. 388). The Atlantic border region.1—The Cretaceous beds of the Atlanticcoast come to the surface in a belt near the western margin of theCoastal Plain, immediately east of the outcrop of the Lower Creta-ceous system. The principal exposures are in New Jersey, Delaware,Maryland, and Virginia. The lowest beds are not believed to repre-sent the earliest beds of the system as developed elsewhere. TheCretaceous beds have been but little disturbed, and still dip, as whendeposited, slightly to seaward. In that direction the beds passbeneath later formations. The Cretaceous formations of the Coastal Plain are made up ofconformable (probably) beds of clay, sand, limestone, and greensand 1 Besides the State Reports referred to under the Comanchean, see Clark, BullGeol. Soc. of Am., Vol. 8, 1897, pp. 315-358, and Weller, Jour, of Geol., Vol. XIII,p. 71. 137 138 GEOLOGY
Text Appearing After Image:
FlG. 388.—Map showing the distribution of the Cretaceous formation in North AmericaThe conventions are the same as in preceding maps. THE CRETACEOUS PERIOD. 139 marl, the last being rather characteristic of the system. The bedsof sand and clay are mainly unindurated, and do not differ notablyfrom other sedimentary beds of similar materials. Of limestone,there is but little on the Atlantic coast, but more about the Gulf. A chief constituent of the greensand marl is glauconite, primarilya hydrous silicate of potash and iron,1 occurring in grains. Glauconiteis now making in some parts of the sea, and from the positions in whichit occurs, the following are inferred to be the conditions necessary forits origin:2 (1) water of moderate depth, 100 to 200 fathoms beingthe most favorable; (2) a meagre supply of land-derived sediment,and (3) the presence of foraminifera. The production of the glau-conite seems to be effected by chemical changes induced in the sedi-ments as the result of the de

Note About Images