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Topset-dominated deltas; a new model for river delta stratigraphy

Douglas A. Edmonds, John B. Shaw and David Mohrig
Topset-dominated deltas; a new model for river delta stratigraphy
Geology (Boulder) (December 2011) 39 (12): 1175-1178


In the late 1800s, G. K. Gilbert provided the first stratigraphic description of river delta deposits, but later work revealed that the "Gilbert-type" model, long thought to be universal, did not apply to all deltas. Here we propose that, in addition to "Gilbert-type" deltas (herein called foreset-dominated), there is a class of deltas with a basic, first-order stratigraphy that is topset dominated. We develop a geometric model that predicts the occurrence of each delta type by calculating the topset and foreset thicknesses under different fluvial and basinal conditions. Our model predicts that topset-dominated deltas have a novel characteristic: their distributary channels commonly incise into pre-delta sediment. This type of delta should be common on shelves where the slope is less than approximately 0.05 degrees and the river feeding the delta has a discharge greater than approximately 200 m (super 3) /s. Field data from Gulf of Mexico deltas confirm the prediction that distributary channels often incise into pre-delta sediment. Finally, we propose a new stratigraphic model for topset-dominated deltas and suggest that future stratigraphic interpretation must distinguish between delta types because the cause of channel incision for each is different and may be unrelated to allogenic changes.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 39
Serial Issue: 12
Title: Topset-dominated deltas; a new model for river delta stratigraphy
Affiliation: Boston College, Department of Earth and Environmental Sciences, Chestnut Hill, MA, United States
Pages: 1175-1178
Published: 201112
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 34
Accession Number: 2012-007725
Categories: GeomorphologySedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2011346
Illustration Description: illus. incl. sect.
N18°00'00" - N30°04'00", W98°00'00" - W80°30'00"
Secondary Affiliation: University of Texas at Austin, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201204
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