Distribution of recent planktonic foraminifera in surface sediments of the Basque shelf (S Bay of Biscay): Oceanographic implications

Abstract

In this work we describe for the first time the distribution of planktonic foraminifera assemblages preserved in recent surface sediments that cover the Basque shelf (southern Bay of Biscay), and their relationship with diverse oceanic currents that affect this area. In the 83 studied samples a total of 18 (morpho)species of planktonic foraminifera have been identified, being the most abundant species: Neogloboquadrina pachyderma dex., Globigerinoides ruber, Globigerina bulloides, Globoconella inflata, Orbulina universa and Turborotalita quinqueloba. These species represent the 92.8% of the total hand-picked specimens. The preferential accumulation of planktonic foraminifera shells in fine sediments deposited in the eastern margin of the Basque shelf, and the random distribution of the dominant species in this area, seem to respond to the general surface current that affect the Basque shelf, which flows eastward during most of the year. Moreover, the input of certain currents and deeper water masses in this area has an important impact on assemblage distribution. Thus, the presence of abundant individuals of Globigerinoides ruber indicates the entrance of the warm and salty Iberian Poleward Current (IPC). Likewise, the dominance of subpolar species Globigerina bulloides, Neogloboquadrina pachyderma dex. and Turborotalita quinqueloba, together with the occurrence, as accessories species, of Neogloboquadrina pachyderma sin., Globorotalia scitula, Globorotalia truncatulinoides and Neogloboquadrina dutertrei, suggest the impact of upwelling processes on the Basque shelf. In conclusion, in this work we have evidenced the useful application of planktonic foraminifera assemblages preserved in surface sediments as indicators of oceanic currents and water masses in shallow continental shelves, such as the Basque shelf.