The aim of the sampling operations was twofold: obtaining information of the volcanic basement rock) of this segment of the HS chain (through dredging) and sample the sedimentary cover and benthic fauna associations (through dredging and grabbing) at the top of the smts. Four sites were dredged for rock samples from slope and escarpment, namely four on Seine smt and two on Unicorn smt. A total of 13 grabs were sampled mostly over the tops of the smts in the upper hundreds metres depths. Only in a few cases (on the upper escarpment of Seine and at Unicorn) were grabs collected at greater depths. Almost every grab recovered, contained coarse to fine bio-clastic sands (planctonic and benthonic Foraminifera, Gasteropods Bivalves, Polychaetes, Echinids and Crustaceans rarely Bryozoans) and rarely basaltic clasts.
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