Revised lithostratigraphy of the Mesozoic-Cenozoic succession of the onshore Rovuma Basin, northern coastal Mozambique

摘要

A revised formal lithostratigraphy for the Mesozoic-Cenozoic succession of the onshore portion of the Rovuma Basin in northern Mozambique replaces a previous mixture of informal lithostratigraphical and biostratigraphical names. The new lithostratigraphy is based on fieldwork carried out in 2005 by mapping teams from the Geological Survey of Norway (NGU), British Geological Survey (BGS) and the Mozambique Direcção National de Geologia (DNG) , combined with information taken from published papers and maps, and unpublished reports at the DNG made available to the project. The following formations are formally described: Rio Mecole Formation (Jurassic? age), N'Gapa Formation (Jurassic? age), Pemba Formation (late Jurassic and early Cretaceous age), Macomia Formation (Aptian-Albian age), Mifume Formation (Albian (offshore)/Campanian (onshore)-Maastrichtian age), Alto Jingone Formation (Paleocene-Eocene age), Quissanga Formation (middle Eocene to Oligocene age), Chinda Formation (Neogene age) and Mikindani Formation (Neogene age). The thickest accumulation of sediments occurred during the Cretaceous concomitant with intense erosion of the uplifted African interior. The Basin’s geology records the temporal development of the coastline of northern Mozambique and southern Tanzania over the last 200 or so million years. Throughout this period, intermittent, mostly extensional faulting parallel to the approximately N-S to NNW-SSE coastline strongly influenced sedimentation, and the faults remain active along this ‘passive’ continental margin. These faults cut across the ENE-WSW structural grain of the underlying Precambrian crystalline rocks of the East African Orogen. However, transfer faults identified in the offshore part of the Rovuma Basin are parallel to the Precambrian structural grain, and may well represent reactivated major ductile shear zones, e.g. in the area between Pemba and Quissanga.