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AAPG Bulletin

Abstract

AAPG Bulletin, V. 94, No. 5 (May 2010), P. 615–642.

Copyright copy2010. The American Association of Petroleum Geologists. All rights reserved.

DOI:10.1306/10270909055

Seismic geomorphology of offshore Moroccoprimes east margin, Safi Haute Mer area

Dallas B. Dunlap,1 Lesli J. Wood,2 Chad Weisenberger,3 Haddou Jabour4

1Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Austin, Texas 78713-8924; [email protected]
2Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Austin, Texas 78713-8924
3EOG Resources, Inc., 6101 S. Broadway, Suite 200, Tyler, Texas 75703
4National Office of Hydrocarbons and Mining, 5 Avenue Moulay Hassan B.P. 99, Rabat 10050, Morocco

ABSTRACT

The lower continental slope of Morocco's west coast consists of Triassic-age salt manifested in the form of diapirs, tongues, sheets, canopies, and toe thrusts. Active salt diapirism and regional tectonics greatly influence the morphology of the modern sea floor, forming a severely rugose expression with ongoing minibasin development and episodic submarine failure. Detailed mapping of a 1064-km2 (411-mi2) seismic survey acquired in the Safi Haute Mer area revealed that Jurassic to Holocene salt mobilization continually affected distribution of sediment, causing a range of depositional flow styles, from slumps to sheet slides and mass-transport complexes (MTCs). Large sediment waves (20 km [12 mi] long, 1.5-km [0.9-mi] wavelength) were also documented at the end of the Aptian. An east-west–trending structural anticline downdip of the salt activated during initiation of the Atlas uplift in the latest Cretaceous to earliest Tertiary and shaped much of the lower slope into the Tertiary with a persistent canyon system and slope channels. The largest of the debris flows is a Cretaceous-age MTC, a 500-m (1640-ft)-thick flow that spans an area of up to 20,000 km2 (7722 mi2). Composing the MTC are (1) chaotic, mounded seismic facies; (2) internal syndepositional thrusts; and (3) transported megablocks (3.3 km2 [1.3 mi2]) with preserved internal stratigraphy. The MTC originated from an upslope collapse of a narrow shelf during the earliest phases of the Alpine orogeny.

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