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The AAPG/Datapages Combined Publications Database

CSPG Special Publications

Abstract


Shelf Sands and Sandstones — Memoir 11, 1986
Pages 341-342
Symposium Abstracts: Storm-Dominated Shelves

Controlling Factors and Important Differences of Sedimentary Processes and Patterns in Unidirectional-Current-Dominated Epicontinental (Epeiric) Shelves: Abstract

C. Hans Nelson1

Abstract

The northeastern Bering epicontinental shelf is a large (200 by 500 km) shallow (<50 m) epeiric seaway that is surrounded by a peripheral coastline; it is characterized by a major sediment source (the Yukon River) and a permanent northward geostrophic current. The strong, unidirectional flow, reinforced by episodic storm-associated currents, controls: 1. the distribution of sediment facies that may or may not be parallel to shorelines; 2. the distribution of biofacies that are related to current-controlled substrate gradations, not to shoreline proximity; 3. the formation of lee-side sand bodies extending as far as 100 km behind islands and westward-projecting land masses; 4. major sediment advection from the Yukon River to depocentres 100 to 1000 km northward; 5. the progradation of storm-sand layers more than 100 km northward from the Yukon delta; and 6. the formation of major unidirectional sand-wave and scour-depression fields on the east sides of straits. This environment is also subject to synergistic combinations of gas-charged sediment, storm-wave loading with sediment liquefaction, and unidirectional ebbflow from storm surge that results in significant sediment resuspension and transport to depocentres far from sources.

Thus, the interpretation of sedimentary processes, and patterns, and paleogeo-graphic reconstructions in epeiric seaways, cannot be based on depositional models of marginal shelves where sedimentation is associated with diminishing energy seaward from waves and storm-driven currents. Biofacies and lithofacies gradations in epeiric seaways dominated by unidirectional currents are controlled by topographic setting and current shear, not by distance from shoreline or depth. Depocentres may be laterally extensive, thin, and displaced far from river sources. Large linear sand bodies with innershelf biofacies and lithofacies may form oblique to, and tens to hundreds of kilometres from, the coastline or sediment sources.


 

Acknowledgments and Associated Footnotes

1 U.S. Geological Survey, Menlo Park, California 94025, U.S.A.

Copyright © 2008 by the Canadian Society of Petroleum Geologists