Seismic stratigraphy evolution and crustal structure of the Atlantic margin offshore Safi (Morocco)

Abstract

A recent marine seismic survey (Mirror cruise) was conducted by Ifremer (France), BGR (Germany) and the Universities of Brest, El Jadida and Lisbon. The main aim of the Mirror survey was to characterize the deep crustal structure and the seismic stratigraphy structure of the Northern Atlantic Moroccan margin. In this study the multi-channel seismic (MCS) reflection and wide angle-data of Mirror survey will be presented. In order to have a detailed imaging of the sedimentary layers and the basement structures, the network of multi-channel seismic profiles was additionally densified by existing datasets from the M-203 German cruise.

The analysis of the final velocity models from wide-angle data modeling image an continental crustal domain subdivided in unthinned continental crust with a thickness of 36 km, and a necking domain in which the crustal thickness thins to only 10 km. Seismic interpretation of the MCS data, in the necking domain shows some Palaeozoic tilted blocks and salt structures beneath the shelf and the slope overlain by Mesozoic and Cenozoic sediments. The salt bodies deform overlying sedimentary strata and correspond to the Late Triassic-Early Jurassic deposit and it was deposited during the last stage of rifting prior to the continental break-up (Hafid, 2000). All the identifiable salt structures are situated east of the magnetic anomaly S1 and occur over a distance of 100 km length. The largest variations in sediment thickness occur on the shelf and the slope. Sediment thickness generally decreases oceanward.

West of the magnetic anomaly S1, 8 km thickness oceanic crust were modeled using two layers. MCS data show a thick sedimentary layers affected by faults. Interpretation of the MCS data enabled the identification of a tectonic uplift of the basement, seen as a bulge on the seismic profiles. This bulge seems to be continuous to the North, offshore El Jadida.

Basement depth has been mapped from seismic data. It generally increases toward the north, and shallow basement has also been mapped towards the south near of the Canary Islands. MSC data indicate also an increase in volcanic activity towards the south whichs may be related to the Canary Hot Spot.

AAPG Datapages/Search and Discovery Article #90226 © 2015 European Regional Conference and Exhibition, Lisbon, Portugal, May 18-19, 2015