SB profiling

The overall acoustic signature of the sea-bottom was poor due to the occurrence of rocky outcrops or bioclastic coarse sands. This prevented acoustic penetration (especially on Ampére  and Seine smt that are shallower with a grater production of bioclastic material). However, in some instances, a fairly good acoustic response was detected.

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Figure 18: Sub-bottom profile across the Ampére  smt. Note poor or null penetration over the top of the seamount due to rocky outcrops or to coarse bioclastic sands.

Two sparker profiles have been acquired across the Seine Semount in order to get information on thickness and hopefully the internal geometry of stratigraphic units above the volcanic basement. The sparker system operated at 1 kJ, with shot rate of 1 sec. The acquired data revealed that the Seine Seamount is covered by a well-layered stratigraphic succession 60- 80 m thick (unit 2) which over-lies a lower unit (unit 1) characterized by patchy occurrence and relatively modest stratigraphic thickness, mostly corresponding to sedimentary infill of pre-existing erosional scours or channels shaping the volcanic basement.

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Figure 19: Detail of sparker profile CL_1 acquired on Seine Seamount and preliminary interpretation. Note the gentle tilting of unit 2 , seemingly associated with low-angle truncation of strata at the sea-floor.