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5.1.1. Substratum
Up to now the shoals, which isolate the AB, have been considered as sand banks (Prevost, 1746 and Sevrin-Reyssac, 1993). However in the northern part of AB, the bedrock shows a relief similar to the isolated erosional hills (“guelbs”) observed inland and the seismic data clearly show that shoals continue the Tafaritian outcrops described inland (Giresse et al., 1989) (Fig. 7). This mid-Quaternary continental/littoral formation was eroded during the different glacio-eustatic cycles. Inland the erosion was due to the sheet-flood common in arid zones, but in the marine part, it 5-Azacytidine is attributable to more condensed flows producing deep gullies (Fig. 4A). The result is an irregular topography, marked by small depressions that seem to be connected to each other, and may have outlets to the gametophyte ocean.
5.1.2. Early preserved deposits
The well-stratified U1 filling the incisions in the bedrock may correspond to relict, coarse detritic sediment. This may be interpreted as the remnants of previous filling during the LGM, accumulated in the form of lag deposits during the phase of scouring/winnowing (Fig. 8 and Fig. 9). Tides could accentuate the process by scouring meters of sediments in estuarine environments (Chaumillon et al., 2010, Tessier et al., 2010a and Tessier et al., 2010b). These AB erosional processes could correspond to the proximal processes related to the Timiris Canyon distal deposition of sandy turbidites (Antobreh and Krastel, 2006, Wien et al., 2006, Wien et al., 2007, Zühlsdorff et al., 2007, Hanebuth and Lantzsch, 2008 and Hanebuth and Henrich, 2009).