THE MESOZOIC AND EARLY TERTIARY TECTONIC EVOLUTION OF THE SOCOTRA AREA, EASTERN GULF-OF-ADEN, YEMEN

Recent interpretation and mapping of seismic data covering the area to the south and west of the Island of Socotra have enhanced the underst anding of the Mesozoic and Early Tertiary tectonic history of the Soco tran Platform. Lineament orientations, after restoration to account fo r Oligo-Miocene Gulf of Aden rifting, indicate: 1. The most significan t basin forming lineament has a 140 degrees orientation. Basin initiat ion, based on onshore Yemen analogues, occurred in the Late Jurassic-E arly Cretaceous (Oxfordian to Hauterivian) and is believed to be assoc iated with Neo-Tethys rifting between the Afro-Arabian and Laurasian P lates; 2. The presence of a 45 degrees lineament orientation associate d with the extension and subsequent opening of the North Somali Basin. Separation of the Indian Plate from the African Plate during Callovia n-Oxfordian times resulted in the opening of a number of en-echelon ri ft basins (Mozambique, West Somali and North Somali Basins) offset by major north-south orientated fracture zones (Davie Ridge and A.R.S.-V. L.C.C. Fracture Zones); 3. Cretaceous post-rift carbonate platform dev elopment in the study area was followed by several phases of later str uctural evolution. These have characteristic translational aspects to their movements and occurred in the Late Cretaceous-Palaeocene, furthe r modifying The structural geometry of the Socotran sub-basins. The ma jority of the translational features and faults evident on seismic dat a, and mapped at late Cretaceous and Palaeocene time horizons, suggest an 80 degrees Principal Displacement Zone (PDZ) orientation; seismica lly derived isochrons indicate that movement along this zone was inter mittent. (C) 1997 Elsevier Science Ltd.