Palaeovalleys and fault-controlled depocentres in the Late-Ordovician glacial record of the Murzuq Basin (central Libya)

ln the Gargaf area, the stratigraphic architecture of the Late-Ordovician glacialdrift results from successive glacial erosion events, with the location of the main glacial valleys partly controlled by inherited Panafrican structural trends, and by the existence of glacio-isostatically induced fault-related depocentres. Four laterally discontinuous, depositional units correspond to the filling of palaeovalleys. Each of the corresponding basal bounding surfaces was incised during a major ice front advance, reaching at least the northern Gargaf (> 28degreesS). The bulk of the glacial record is made up of fluvial to shallow-marine sediments deposited in relatively distal glacial environments. Each unit, which recorded a glacial-interglacial climatic cycle, can be used for correlation throughout the Murzuq Basin and even at the scale of the North Gondwana platform. (C) 2003 Academie des sciences. Published by Elsevier SAS. All rights reserved.