Structural development of Southern Morocco; interaction of tectonics and deposition.

Michalnemcok
Energy and Geoscience Institute at University of Utah, 423 Wakara Way, Suite 300, Salt Lake City, UT 84108, USA, e-mail: mnemcok@egi.utah.edu

Steven A. Hermeston*
Kerr-McGee Oil and Gas Corporation, 16666 Northchase, Houston, TX 77060, USA *present address: Repsol YPF, 1330 Lake Robbins Drive, Suite 300, The Woodlands, TX 77380, USA

Ian Davison
Earthmoves Ltd., Chartley House, 38-42 Upper Park Road, Camberley, Surrey GU15 2EF, UK

Charles Stuart, Marylin P. Segall, Richardson B. Allen, Chelsea Christensen
Energy and Geoscience Institute at University of Utah, 423 Wakara Way, Suite 300, Salt Lake City, UT 84108, USA

Abstract

Interpretation of magnetic, gravity, seismic and geological data shows that the curvilinear Late Paleozoic orogen affected the location of Central Atlantic syn-rift faults. While northeast-southwest striking thrust faults were perpendicular to extension, prominent curvatures, such as the Pennsylvania salient, introduced structural complexities. Eastnortheast-westsouthwest striking dextral transpressional strike-slip faults of this salient became reactivated during Carnian-Toarcian rifting. They formed sinistral transtensional strike-slip “rails” that prevented the Georges Bank – Tarfaya Central Atlantic segment from orthogonal rifting, causing formation of a pull-apart basin system. Central Atlantic segments to the south and north of this one underwent almost orthogonal rifting. “Rails” lost their function after the continental break-up, except for minor younger reactivations. They were not kinematically linked to younger oceanic fracture zones.

Atlantic segments initiated by normal rifting differ from the segment initiated by the Georges Bank – Tarfaya strike-slip fault zone. They contain Upper Triassic-Lower Jurassic evaporites with salt-detached gravity glides, while the connecting transfer segment does not. Their structural grain is relatively simple, divided mostly by northeast-southwest striking normal faults. Northwest-southeast striking oceanic fracture zones kinematically link with continental faults in a few places, controlling the sediment transport pathways across the uplifted continental margin.

The connecting Georges Bank – Tarfaya Central Atlantic segment, initiated as a sinistral transfer-zone, and has a complex structural grain, characterized by numerous small depocenters and culminations. Their boundaries are formed by eastnortheast-westsouthwest striking sinistral strike-slip, northnortheast-southsouthwest striking normal and westnorthwest-eastsoutheast striking dextral strike-slip faults. Sediment transport pathways have complex trajectories, weaving through local depocenters. Key words: rifting, strike-slip faulting, Central Atlantic, Southern Morocco, tectonics, structural development, deposition.