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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 53 (1969)

Issue: 3. (March)

First Page: 709

Last Page: 709

Title: Shallow Shelf Sedimentation in Rock Record--Introduction to Symposium: ABSTRACT

Author(s): James E. Brooks, E. G. Wermund, Thomas E. Williams

Article Type: Meeting abstract

Abstract:

A shelf is defined in Webster's Third International Dictionary as "1 a : a thin, flat, usually long and narrow piece of wood or other material fastened horizontally at a distance from the floor (as on a wall or in a frame) to hold objects"; and "2 : something resembling a shelf in form or position."

"Something resembling a shelf" in the contemporary geologic scene cannot be well defined. For example, modern continental shelves are defined in different ways by hydrographers, by geographers, and by geologists. Some describe the continental shelf as a surface marginal to continents and lying between the strandline and that place where the sloping surface of the lithosphere steepens toward a deeper part of the ocean basin, regardless of water depth. Others define the shelf as that surface between sea level and a particular depth (commonly 100 fm), irrespective of steepening of the surface. Still others apply the term "shelf" to surfaces formed under the control of erosional, depositional, or structural agencies, or by various more specific biologic or sedimentologic agencies. In most cases, a surface so defined displays the same topographic habit for a distance in either direction from the strandline. With so many apparent variations, can any consensus definition of "shelf" be established within the geologic community?

The presumably representative AGI Glossary and the pertinent literature demonstrate that the term "shelf" is applied to any shallow marine sediment. Examples include deposits formed in a great range of physical and tectonic environments. Among these are continental shelves, broad shallow intracontinental basins (epeiric seas), "stable shelves" at cratonic margins, shallow intracratonic basins, and various types of geosynclines. Physical environments in which shelf deposits form are neritic, littoral, and paralic.

For the purpose of this symposium, "shelf" is used in a broad sense. Shelf sediments are subaerial and submarine sediments which were deposited on a relatively shallow, uniformly, gently sloping surface which includes the marine-land interface of the strandline. The zone of shelf sedimentation as here defined is terminated landward and seaward by a perceptible change in the slope and topographic character of the depositional interface.

The purpose of this symposium is to bring together various contemporary viewpoints on shelf sediments. To this end authors representative of the various schools of thought and subdisciplines of shelf studies have been invited to contribute basic papers related to the geology, biology, and chemistry of shelves, or papers illustrating "typical" shelves from various parts of the rock record. It is hoped that such an enunciation of principles and examples will bring into focus the parameters that have controlled sediment accumulation in shallow seas associated with the continental masses and will lead to the construction of reliable theoretical models for their interpretation.

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Copyright 1997 American Association of Petroleum Geologists