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The AAPG/Datapages Combined Publications Database

CSPG Special Publications

Abstract


Shelf Sands and Sandstones — Memoir 11, 1986
Pages 333-333
Symposium Abstracts: Sediment Source, Supply and Dispersal

Generation of Transgressive Stratigraphy: Abstract

Ron Boyd1, Shea Penland2

Abstract

A range of continental shelf sand bodies can be produced when a shoreline transgresses. Four categories of transgression can be recognized, each of which is responsible for producing a characteristic shelf stratigraphy: 1. rapid erosional transgression, which generates a discontinuous stratigraphy of overstepped coastal barriers separated by a thin transgressive veneer; 2. slow erosional transgression, which generates a thin transgressive veneer overlying an unconformity; 3. slow erosional transgression followed by a stillstand, which generates a thin transgressive veneer terminated updip by a fully preserved coastal sequence; and 4. slow depositional transgression during which a variable component of the coastal sequence is incorporated into the shelf stratigraphic record. These four categories are not discrete, but represent intervals of a transgressive spectrum that is governed by sediment supply, regional gradient, relative sea level, wave energy and coastal oceanography. The preservation potential of transgressive stratigraphy is largely governed by the translation path of the shorefacc. A simple coastal stratigraphy may consist of a pre-existing substrate, fine-grained backbarrier deposits, sandy barrier deposits and a shelf mud. Horizontal translation of a deep shoreface incises an erosional unconformity into the pre-existing substrate, which is in turn overlain by a sandy lag veneer and a shelf mud. Horizontal and vertical translation of a shallower shoreface leaves the pre-existing substrate intact, preserves: a. part of the backbarrier deposits; b. all of the backbarrier deposits; or c. all the backbarrier deposits plus part of the barrier deposits, overlain by an erosional unconformity, a sandy lag veneer and a shelf mud. Very rapid horizontal and vertical shoreface translation is incapable of reworking the entire shelf retreat path of the coastal zone. In this case, partly reworked segments of the coastal sequence are therefore also incorporated into the shelf stratigraphic record and in turn overlain by a shelf mud. The final stratigraphic sequence results from the horizontal and vertical translation of a shallow shoreface receiving active sediment supply. Under these circumstances the coastal stratigraphy may be preserved intact and erosional unconformities may be absent.


 

Acknowledgments and Associated Footnotes

1 Centre for Marine Geology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 3J5

2 Louisiana Geological Survey, Baton Rouge, Louisiana 70803, U.S.A.

Copyright © 2008 by the Canadian Society of Petroleum Geologists