Journal of Petroleum Geology, Vol.11, No.2, pp. 157-168, 1988

©Copyright 2000 Scientific Press, Ltd.

FOLDING OF THE MESOZOIC COVER IN SW SOMALIA: A COMPRESSIONAL EPISODE RELATED TO THE EARLY STAGES OF INDIAN OCEAN EVOLUTION

M. Boccaletti(1) , P. Dainelli(2) , A. Angelucci(3) , M.A. Arush(4) , M.M. Cabdulqaadir(4) , P. Nafissi(2) ,
G. Piccoli(5) , E. Robba(6)

(1) Diartimento di Scienze della Terra, University of Florence, Via La Pira, 4, 50121 Florence, Italy.
(2) GEOMAP, Via Della Robbia, 28, 50132 Florence, Italy.
(3) Dipartimento di Scienze della Terra, University of Rome, "La Sapienza", Piazzale A. Moro, 5, 00100 Rome, Italy.
(4) Faculty of Geology, Somali National University, P. O. Box 1081, Mogadishu, Somalia.
(5) Istituto di Geologia, University of Padua, Via Giotto, 1, 35137 Padua, Italy.
(6) Dipartimento di Scienze della Terra, University of Milan, Piazzale Gorini, 15, 20133 Milan, Italy.

Abstract

The tectonic-sedimentary evolution of SW and central Somalia is characterized by two main depositional cycles. The first cycle (Triassic to Early Cretaceous) is characterized by subsiding basins related to a process of crustal thinning, and is associated with the separation of Madagascar from Africa, between 165 and 121 Ma*. The second cycle, starting in the Late Cretaceous with a regional unconformity, is related to the separation and NEward drift of India, at approximately 80 Ma. The folds that affect the Jurassic and Early Cretaceous formations of the Lugh-Mandera basin in SW Somalia are the result of a compressive phase connected with dextral transcurrent movements along NE-SW trending fracture zones. These zones are developed parallel to the oceanic system of transform faults, in connection with the change in the stress regime intervening at the shift ofthe direction of spreading between the first and the second stages of evolution of the Indian Ocean.