Date of Award

Fall 1985

Document Type


Degree Name

Master of Science (MS)


Ocean & Earth Sciences


Geological Sciences

Committee Director

Stephen J. Culver

Committee Member

Dennis A. Darby

Committee Member

G. Richard Whittecar

Committee Member

P. A. Bull

Call Number for Print

Special Collections LD4331.G4M33


Field and hand sample descriptions were supplemented with petrographic and textural analyses derived from thin sections, and scanning electron microscopy (SEM) to determine environments of deposition for the late Precambrian Gibi Mountain Formation, Liberia, Tabe

Formation, Sierra Leone, and the basal Mali Group, Senegal, West Africa.

The Gibi Mountain Formation consists of a glaciomarine tillite, marine laminites with dropgrains, and shallow water arkoses. A shale facies remains unresolved in origin.

The Tabe Formation is composed of three members: Tibai, Dodo, and Taban. The Tibai Member contains a glaciomarine tillite deposited in a shallow shelf marine environment, marine laminites, and shallow water arkoses. The Dodo Member consists of shallow water arkoses, and the Taban Member consists of arkoses derived from the Guinea-Senegal area deposited in a fluvial braided stream environment.

The basal Mali Group consists of shallow shelf glaciomarine tillites and shallow water arkoses.

These interpretations suggest that the southwestern margin of the West African Craton experienced widespread glaciation during the late Precambrian. The glacigenic interpretation for the Gibi Mountain Formation extends the known range of late Precambrian glacigenic sediments in West Africa. It is suggested that the Gibi Mountain Formation was possibly deposited in an extension of the depositional basin of the Rokel River Group to the north in Sierra Leone. If true, this extends the basin of deposition another 200 km south.


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