--> ABSTRACT: Tectono-Sedimentary Evolution of Southern Part of Benue Trough: From an Asymmetric Basin in Middle Albian to an Infilled Basin in Mid-Cenomanian, by K. A. Ojoh and M. Popoff; #91022 (1989)

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Tectono-Sedimentary Evolution of Southern Part of Benue Trough: From an Asymmetric Basin in Middle Albian to an Infilled Basin in Mid-Cenomanian

K. A. Ojoh, M. Popoff

Before the opening of the Equatorial domain of the South Atlantic, the initiation and installation of most intracontinental basins within Gondwanaland took place before the Albian in northeastern Brazil and west Africa. The first pronounced marine incursion in the southern part of the Benue Trough was in the middle Albian.

Subsidence was localized in the deep asymmetrical middle Albian basin. The latter, combined with a lowstand marine ingression in the southern Benue Trough and the progressive rifting-drifting of Africa and South America, engendered an unstable, tectonically active, oversupplied basin characterized by megaslumps and turbidites.

During the late Albian, differential subsidence installed a stable platform with organic-rich fossiliferous black shales and littoral deposits contemporaneous with a highstand of sea level and the interconnection of the Central and South Atlantic oceans in the proto Gulf of Guinea. Volcanosedimentary tendencies have been documented from the littoral deposits, and pyroclastics containing molluscan fragments in the southern Benue Trough have also been attributed to the upper Albian.

The high rate of subsidence during the Albian became very slow in the Cenomanian. It corresponds to a period of eustatic fall of sea level during the early and middle Cenomanian with high clastic influx into the basin. The middle Cenomanian is characterized as the period of an infilled basin with subaerial-submarine erosional surface (unconformity type 2) in the southern Benue Trough. This may be attributed to the global character of the Cenomanian lowstand of sea level.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.