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Salt tectonics on passive margins: examples from Santos, Campos and Kwanza basins

By
Dave G. Quirk
Dave G. Quirk
Maersk Olie og Gas AS, 50 Esplanaden, 1263 Copenhagen K, Denmark
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Niels Schødt
Niels Schødt
Maersk Olie og Gas AS, 50 Esplanaden, 1263 Copenhagen K, Denmark
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Birgitte Lassen
Birgitte Lassen
Maersk Olie og Gas AS, 50 Esplanaden, 1263 Copenhagen K, Denmark
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Steven J. Ings
Steven J. Ings
Department of Oceanography, Dalhousie University, Halifax, NS, B3H 3J5, Canada
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Dan Hsu
Dan Hsu
Maersk Oil America, 2500 City West Boulevard, Suite 1350, Houston, Texas 77042, USA
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Katja K. Hirsch
Katja K. Hirsch
Maersk Olie og Gas AS, 50 Esplanaden, 1263 Copenhagen K, Denmark
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Christina Von Nicolai
Christina Von Nicolai
German Research Centre for Geosciences (GFZ), Section 4.4 Basin Analysis, Telegrafenberg, D-14473 Potsdam, Germany
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Published:
January 01, 2012

Abstract

Salt flows downslope, irrespective of overburden. In salt basins on passive margins, the salt will tilt and flow towards the ocean immediately after continental rifting has ended due to thermal subsidence. Using real examples, as well as physical and numerical models, tilting is shown to be relatively rapid, enhanced by isostatic rebound updip and loading downdip where salt pools and inflates behind an outer high. In the Santos, Campos and Kwanza basins, this outer high is represented by an embryonic mid-Atlantic ridge, amplified in height by the differential weight of the inflating salt. Widespread extension and translation of overburden, utilizing both seaward- and landward-dipping normal faults, characterizes the early evolution of the inboard region. Inflation and contraction occur outboard, the effects of which tend to expand in a landward direction over time. Rapid accumulation of salt implies wholesale dewatering of pre-salt sediments, the water possibly permeating the salt once it has reached a burial depth of c. 3 km. The process of thermal subsidence, salt drainage and isostatic amplification is an efficient mechanism for moving sediment on passive margins tens of kilometres seaward during a relatively short period and helps explain why great thicknesses of salt can accumulate there in the first place.

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Contents

Geological Society, London, Special Publications

Salt Tectonics, Sediments and Prospectivity

G. I. Alsop
G. I. Alsop
University of Aberdeen, UK
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S. G. Archer
S. G. Archer
University of Aberdeen, UK
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A. J. Hartley
A. J. Hartley
University of Aberdeen, UK
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N. T. Grant
N. T. Grant
ConocoPhillips UK Ltd, Aberdeen, UK
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R. Hodgkinson
R. Hodgkinson
Bowleven plc, Edinburgh, UK
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Geological Society of London
Volume
363
ISBN electronic:
9781862396111
Publication date:
January 01, 2012

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