--> ABSTRACT: Opening History of the Mesozoic Equatorial Atlantic Continental Margins, by Mark Hempton; #91020 (1995).

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Opening History of the Mesozoic Equatorial Atlantic Continental Margins

Mark Hempton

Computer reconstructions based on exploration data from the equatorial continental margins of South America and Africa suggest the following history for opening of the Equatorial Atlantic Ocean:

Mid Jurassic - South America and Africa stretch slightly, yielding swarms of diabase dikes from the Guinea plateau to Ghana. However, there is no evidence for Triassic-Jurassic rift basins south of the Guinea/Demerara Plateau.

Barremian/Aptian - Fossil data suggest that rift basins in the proto-Equatorial Atlantic began to open between Africa and South America during the Barremian. Extension propagated from the Demerara and Guinea plateaus eastward toward the Liberian coast between NW-oriented strike-slip faults. Extension associated with the opening South Atlantic was accommodated by rifting between NE-striking wrench faults in the Benue Trough and to the west toward the Marajo Basin, Brazil.

Albian - In the Demerara/Guinea plateau area, nonmarine sedimentation was accompanied by significant mafic volcanism and intrusion. In the Ghana/Ivory Coast area, some rift basins began to accumulate marine shales in the Mid Albian as access to the South Atlantic improved. By the Late Albian, widespread uplift and erosion of rift zone margins marked the initiation of significant sea-floor spreading between major strike-slip fault pairs.

Cenomanian-Turonian - Continental stretching and nonmarine sedimentation ceased between NE Brazil and NW Africa as extensional strain concentrated at spreading center segments.

Campanian-Maastrictian - Oceanic spreading center segments linked to form contiguous oceanic crust in the Equatorial Atlantic. As a result equatorial margins separated and subsided rapidly.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995