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Role of magmatic evacuation in the production of SDR complexes at magma-rich passive margins

James Pindell, Rod Graham and Brian Horn
Role of magmatic evacuation in the production of SDR complexes at magma-rich passive margins (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: 1-15

Abstract

Seaward dipping reflector or SDR complexes comprise piles of individual basaltic flows and inter-bedded sediments that are thought to have formed subaerially at the flanks of tholeiitic shield volcanoes like those in the Afar or at larger magmatic complexes like Iceland. During the rift process, these flows subsequently acquire very steep true dips (up to 25 degrees ) almost always in the seaward direction. Past explanations for the acquisition of these dips involve progressive burial, loading and flexure by subsequent flows or listric, landward-dipping faulting and magmatic dilation. These factors no doubt play a role, but we feel that such models fall short of a full explanation by exceeding reasonable amounts of flexure and the amount by which huge blocks of continental crust can rotate by faulting alone. Such models also do not provide an explanation for how the topmost SDR layer subsides rapidly to the depth of normal oceanic crust as the latter begins to form, a problem that has been apparent since Mutter et al. (1982). Here, we present and discuss some of the main observations visible in long-offset, depth imaged seismic reflection records of SDR complexes at magma rich passive margins and propose a new but simple magmatic evacuation model for their production. Having conducted a global review of seismic data imaging SDR complexes, we present a line from the southern Brazilian margin to serve as a template example that shows most of the important criteria worldwide. After identifying the main observations, we propose a simple model of magmatic evacuation, similar to salt or mud evacuation in sedimentary sequences, to explain the observations. We hope that this simple proposal will spawn new avenues of research to refine and support the general model.


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: Role of magmatic evacuation in the production of SDR complexes at magma-rich passive margins
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: Tectonic Analysis, Sussex, United Kingdom
Pages: 1-15
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: 6
Accession Number: 2016-100143
Categories: Igneous and metamorphic petrologyApplied geophysics
Document Type: Serial Conference document
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects.
S30°00'00" - S23°00'00", W48°00'00" - W40°00'00"
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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