File:Annals of the New York Academy of Sciences (1916) (18415742961).jpg

Title: Annals of the New York Academy of Sciences
Identifier: annalsofnewy27191617newy (find matches)
Year: 1877 (1870s)
Authors: New York Academy of Sciences
Subjects: Science
Publisher: New York, New York Academy of Sciences
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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118 ANNALS NEW YORE ACADEMY OF SCIENCES The presence of small stratigraphic breaks at many localities and levels in the Morrison formation emphasizes the force of the statements of Hatcher, that in the production of a continental formation of the char- acter of the Morrison, the main process of deposition is not continuous for any given area. The process is rather one of alternating deposition and erosion, deposition being the dominant factor. The situation is analogous with the conditions at the front of a glacier, v^^here the ice front may stand still, while the actual ice advances, through melting at the front. If melting goes on faster than ice advance, the front retreats; '-^^-^
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I o I a I "I ° I ■" ■ ir-r . ( o I * I o I A I o 1 o I oi o I o I o I — -a I — o \ o~r Pig. 83.—Diagrammatic section of the exposure of the Morrison formation at the Marsh- Hatcher dinosaur quarry, near Canon City, Colorado. if melting goes on slower than ice advance, the front advances. In the case of a continental formation ultimate deposition of a considerable thickness would be brought about by excess of deposition over erosion. If erosion predominated over deposition, there would be no formation produced, but a great stratigraphic break. In considering the age of such a formation as the one under considera- tion, it must be remembered that deposition under the conditions indi- cated above will be much slower in producing a great thickness of beds than under conditions of continuous deposition. A total thickness of

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