--> Abstract: Shelf-Margin Delta Myths and Misconceptions, by Donald I. Cummings, R.W.C. Arnott, and Bruce Hart; #90039 (2005)

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Shelf-Margin Delta Myths and Misconceptions

Donald I. Cummings1, R.W.C. Arnott2, and Bruce Hart3
1 Queen's University, Kingston, ON
2 University of Ottawa, Ottawa, ON
3 McGill University, Montreal, QC

Since being first identified seismically in the Gulf of Mexico in the 1960s, shelf-margin deltas have received considerable attention, not only because they commonly host large hydrocarbon accumulations, but because they form the basic building blocks of accretionary continental margins, are useful in identifying fossil shelf edges, and commonly act as staging areas for sediment delivered to slope turbidite systems. However, despite their significance, detailed case studies remain few and focus predominantly on Late Pleistocene deposits from the Gulf of Mexico: this adds considerable bias to popular shelf-margin delta depositional models. Using examples of Mesozoic shelf-margin deltas from the passive margin basin offshore Nova Scotia, it is argued that several features apparently common or in fact unique to shelf-margin deltas are perhaps artifacts of the small dataset. In particular, it is argued that 1) tides as well as waves can be important in controlling shelf-margin delta morphology and architecture; 2) shelf-margin delta lobes can be stacked vertically as well as in an offset fashion; 3) associated incised valleys can be progradationally or transgressively infilled and are not necessarily long, linear and thin; and 4) lowstand shelf-margin delta topsets are not always restricted to the shelf edge, but can onlap considerably in a landward direction.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005