Second‐order Sequence Stratigraphy of the Palaeozoic of North Africa

Abstract

A synthesis of the sedimentology and sequence stratigraphy of the Palaeozoic succession of North Africa is presented. Two chronostratigraphic correlation panels have been constructed at roughly right angles to each other across North Africa, in WNW-ESE and NNW-SSE orientations. The panels illustrate the way in which sedimentology and hydrocarbon geology vary across the continent through time. The Palaeozoic succession is divided into five second-order sequences (NA 1, Early Cambrian to Late Ordovician; NA 2, Late Ordovician to Late Silurian; NA 3, Devonian; NA 4, Carboniferous; NA 5, Permian), with sequence boundaries, maximum flooding surfaces and systems tracts being defined for NA 1 to NA 4. Palaeogeographic reconstructions for the North African region from the Cambrian to the Carboniferous are illustrated, and a sea-level curve based on the panels and palaeogeographic reconstructions is compared to other published sea-level curves. The proximity of the North African region to the South Pole during the Palaeozoic and its relative tectonic stability suggest that sea-level curves derived from the area should closely reflect Palaeozoic glacio-eustasy. This study may be used to investigate the occurrence of reservoir, seal and source rocks away from areas of data control, and is intended to provide a useful framework for future third-order studies. SECOND-ORDER SEQUENCES WITHIN THE NORTH AFRICAN PALAEOZOICIn this section, each sequence is described in terms of key surfaces and general characteristics; within each sequence, systems tracts have been defined by age, bounding

The Fadnoun area, Tassili-n-Azdjer, Algeria: Fracture network geometry analysis

“…These are characteristic of a cratonic domain and stable tectonic conditions (Boote et al, 1998;Badalini et al, 2002;Fabre, 2005). The sedimentology of the Palaeozoic interval is characterized by braided fluvial systems building out braid-plain deltas into intacratonic Palaeozoic Basins (Aliev et al, 1971;Beuf et al, 1971;Fekirine and Abdallah, 1998;Carr, 2002;Fabre, 2005).…”

The Cambrian-Ordovician succession in the Ougarta Range (western Algeria, North Africa) and interference of the Late Ordovician glaciation on the development of the Lower Palaeozoic transgression on northern Gondwana

“…Fluvial successions in the SSE graded towards the NNW in storm-to-tide dominated successions. Multiphased Palaeozoic to Mesozoic tectonic uplifts have differentiated several intracratonic basins, the present geometry of which bears little relation to the much broader North Gondwana platform that had an off-shelf gradient towards the NNW during the whole of the Early Palaeozoic (Beuf et al 1971, Boote et al 1998, Carr 2002.…”

“…It is well defined and synchronous (base of Hirnantian) at the geological time scale everywhere in North Gondwana (Ghienne et al in press and references therein). Based on its prominent erosional character, this bounding surface is generally considered to be a major unconformity that includes a tectono-stratigraphic component and separating two major, long-term depositional sequences (Sharland et al 2001, Carr 2002, Eschard et al 2005. The overlying glacially related strata are sometimes regarded as an individual major depositional sequence (Fekirine & Abdallah 1998, Eschard et al 2005.…”

Sedimentological and sequence stratigraphic analysis of Carboniferous deposits in western Libya: Recording the sedimentary response of the northern Gondwana margin to climate and sea-level changes

“…According to Carr (2002), the base and the top of Carboniferous deposits represent second-order sequence boundaries throughout North Africa. These two sequence boundaries are very prominent in parts of western Libya.…”