Late Q uaternary ( M arine I sotope S tage 3 to R ecent) sedimentary evolution of the B asque shelf (southern B ay of B iscay)

Late Q uaternary ( MIS 3 to R ecent) oceanographic evolution of the B asque shelf has been analysed for the first time based on the sedimentological analysis of three cores obtained from the middle and outer shelves. The cores are located in two interfluves separated by the S an S ebastian canyon. The variability of the percentage of the planktonic foraminifera species N eogloboquadrina pachyderma sin. and of δ 18 O bull allowed us to identify the influence of colder and warmer waters in the B asque shelf during the late Q uaternary. From ∼ 56 cal. ka BP to the end of the L ast G lacial M aximum (19 cal. ka BP ) the sedimentary record shows a decreasing trend in the mean grain size that correlates with the eustatic sea‐level fall. The last D eglaciation (19–11.5 cal. ka BP ) is characterized by a sea‐level rise that produced an important hiatus in the western outer shelf. During the H olocene, the middle and outer shelves present different behaviours. From 11.5 to 6.7 cal. ka BP , in the outer shelf the sea‐level rise that started during the D eglaciation produced a hiatus, whereas in the middle shelf the sedimentary succession records the presence of warm to temperate waters. Between 6.7–4.9 cal. ka BP , the entrance of cold surface water‐masses that only affected the middle shelf has been identified, and temperate to warm waters occurred in the outer shelf. The cold surface water‐masses retreated during 4.9–4.3 cal. ka BP in the middle shelf. Finally, from 4.3 cal. ka BP to Recent, the middle shelf registers a hiatus due to sea‐level stabilization after a generalized transgression, synchronous to a decrease in the energy of the water‐masses in the outer shelf. In conclusion, the environmental changes detected in the B asque shelf are attributed to both regional and eustatic sea‐level changes.