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A critical look at the creation of accommodation space for salt in the Gulf of Mexico

James Pindell, Rod Graham and Brian Horn
A critical look at the creation of accommodation space for salt in the Gulf of Mexico (in Papers presented at the 33rd annual GCSSEPM Foundation Bob F. Perkins research conference; Sedimentary basins; origin, depositional histories, and petroleum systems, James Pindell (editor), Brian Horn (editor), Norman Rosen (editor), Paul Weimer (editor), Menno Dinkleman (editor), Allen Lowrie (editor), Richard Fillon (editor), James Granath (editor) and Lorcan Kennan (editor))
Papers presented at the Gulf Coast Section, Society of Economic Paleontologists and Mineralogists Foundation Annual Bob F. Perkins Research Conference (2014) 33: 393-412

Abstract

Interpretation of ION-GXT long-offset 2D depth-imaged and other seismic data suggests that outer continental margins collapse and tilt basinward rapidly as rifting yields to seafloor spreading. The outer continental margin, already thinned by rifting processes, can be viewed as the hanging wall of a mega-half-graben associated with a landward dipping shear zone. The footwall of the shearmega is the serpentinised or serpentinising sub-continental mantle that commonly becomes exhumed as it rises from beneath the thinned and embrittling continental margin. We call this shear zone between the continental crust and the rising sub-continental mantle the "outer marginal detachment." At magma-poor margins, the outer continental margin collapses to tilt basinward ("outer marginal collapse") to depths up to 3-3.5 km sub-sea at the continent-ocean transition, so that it normally lies deeper than the adjacent oceanic crust (accreted later by seafloor spreading). We use the term "collapse" because of the rapidity of the deepening, which seems to be < 3 Ma, and possibly < 1 Ma. Salt deposition or rapid clastic (deltaic) sedimentation at non-magmatic margins, or SDRs and less organised magmatism at magmatic margins, may accompany the collapse, with salt thicknesses rapidly reaching 5 km and volcanic piles reaching 15-20 km, as controlled by isostasy. This mechanism of rapid salt deposition allows some megasalt basins (e.g., Gulf of Mexico) to be deposited on synrift sections at global sea level, although other salt basins may form in air-filled depressions below sea level. Outer marginal collapse is "postrift" from the perspective of the continental crust, but of tectonic, and not of thermal, origin, owing to shear on outer marginal detachments. We examine how outer marginal collapse can migrate diachronously along strike, much like the onset of seafloor spreading, as is required in models of ocean creation. We suggest that backstripping estimates of lithospheric thinning (beta) at outer continental margins may be excessive, because they probably attribute outer marginal collapse to thermal subsidence.


ISSN: 1544-2462
Serial Title: Papers presented at the Gulf Coast Section, Society of Economic Paleontologists and Mineralogists Foundation Annual Bob F. Perkins Research Conference
Serial Volume: 33
Title: A critical look at the creation of accommodation space for salt in the Gulf of Mexico
Title: Papers presented at the 33rd annual GCSSEPM Foundation Bob F. Perkins research conference; Sedimentary basins; origin, depositional histories, and petroleum systems
Author(s): Pindell, JamesGraham, RodHorn, Brian
Author(s): Pindell, Jameseditor
Author(s): Horn, Brianeditor
Author(s): Rosen, Normaneditor
Author(s): Weimer, Pauleditor
Author(s): Dinkleman, Mennoeditor
Author(s): Lowrie, Alleneditor
Author(s): Fillon, Richardeditor
Author(s): Granath, Jameseditor
Author(s): Kennan, Lorcaneditor
Affiliation: Rice University, Department of Earth Science, Houston, TX, United States
Pages: 393-412
Published: 2014
Text Language: English
Publisher: Society of Economic Paleontologists, Gulf Coast Section (GCSSEPM) Foundation, Houston, TX, United States
ISBN: 978-0-9836097-9-0
Meeting name: 33rd annual GCSSEPM Foundation Bob F. Perkins research conference
Meeting location: Houston, TX, USA, United States
Meeting date: 20140126Jan. 26-28, 2014
References: 23
Accession Number: 2016-100167
Categories: Solid-earth geophysics
Document Type: Serial Conference document
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., geol. sketch maps
N18°00'00" - N30°04'00", W98°00'00" - W80°30'00"
Secondary Affiliation: ION Geoventures, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 201649
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