Late Quaternary (Marine Isotope Stage 3 to Recent) sedimentary evolution of the Basque shelf (southern Bay of Biscay) BLANCA MARTÍNEZ-GARCÍA, ARANTXA BODEGO, JONE MENDICOA, ANA PASCUAL AND JULIO RODRÍGUEZ-LÁZARO Martínez-García, B., Bodego, A., Mendicoa, J., Pascual, A. & Rodríguez-Lázaro, J.: Late Quaternary (Marine Isotope Stage 3 to Recent) sedimentary evolution of the Basque shelf (southern Bay of Biscay). Boreas. 10.1111/ bor.12079. ISSN 0300-9483. Late Quaternary (MIS 3 to Recent) oceanographic evolution of the Basque 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 San Sebastian canyon. The variability of the percentage of the planktonic foraminifera species Neogloboquadrina pachyderma sin. and of δ 18 Obull allowed us to identify the influence of colder and warmer waters in the Basque shelf during the late Quaternary. From ∼56 cal. ka BP to the end of the Last Glacial Maximum (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 Deglaciation (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 Holocene, 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 Deglaciation 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 Basque shelf are attributed to both regional and eustatic sea-level changes. Blanca Martínez-García (blancamaria.martinez@ehu.es), Jone Mendicoa, Ana Pascual and Julio Rodríguez-Lázaro, Universidad del País Vasco UPV/EHU, Facultad de Ciencia y Tecnología, Dpto. Estratigrafía y Paleontología, B. Sarriena s/n, Apartado 644, E-48080 Bilbao, Spain; Arantxa Bodego, Universidad del País Vasco UPV/EHU, E.U.I.T. de Minas y de Obras Públicas, Dpto. de Ingeniería Minera y Metalúrgica y Ciencia de los Materiales, Paseo Rafael Moreno 2, E-48013 Bilbao, Spain; received 9th October 2013, accepted 14th March 2014. Marine sedimentary processes in the North Atlantic Ocean have been controlled by numerous climate- dependent factors that respond to astronomical cycles and non-astronomical forcings of different temporal scales during the late Quaternary (e.g. Heinrich 1988; Bond & Lotti 1995; Bond et al. 1997, 1999; Hemming 2004). Several analyses based on marine sedimentary cores have compiled the late Quaternary sedimentary evolution of the Bay of Biscay (e.g. Grousset et al. 2000; Zaragosi et al. 2001; Ménot et al. 2006; Eynaud et al. 2007, 2012; Toucanne et al. 2008, 2009, 2012; Penaud et al. 2009), and show the relationship between the hydrography of this area and the advances and retreats of European ice sheets and continental glaciers. Never- theless, very few studies concerning the southern Bay of Biscay, that is, the Basque shelf, have been published. Studies that have focused on recent sedimentary pro- cesses of the Basque shelf suggest a hydrodynamic (both oceanic currents and river discharges) control on sedi- ment distribution along the shelf and on the generation of some sedimentary structures, such as ripples and other bedforms (Castaing et al. 1999; Jouanneau et al. 2008; Galparsoro et al. 2010). The aim of this study was to reconstruct, for the first time, the variability of the sedimentary record of the Basque shelf during the late Quaternary (from almost the beginning of Marine Iso- topic Stage 3 until Recent), in relation to internal (mor- phology and/or regional hydrodynamic processes) and external (climatic forcing and eustatic changes) factors that control the spatial distribution of sediments and their variations through time in this area. The study was based on sedimentological analyses (mean grain size, calcium carbonate content and mineralogical nature of lithic grains), on the percentage variability of Neogloboquadrina pachyderma (Ehrenberg) left coiling (sin.) and on the oxygen isotopic signal (δ 18 Obull) of three sedimentary cores obtained from the middle and outer Basque shelf. The specific objective was to discriminate between regional and North Atlantic Ocean environ- mental signals in a shallow area close to the North Iberian continental margin, in order to better constrain the influence of each signal in the Basque shelf. By depicting the impact of eustatic sea-level changes, regional currents and river discharges and/or estuarine progradation or retrogradation, the evolution of the shelf can be better understood. Morphological, hydrological and sedimentological background The Bay of Biscay is a wedge-shaped inlet of the North Atlantic Ocean (Fig. 1A). Its margins are non-volcanic conjugates: the southern E−W trending margin corre- DOI 10.1111/bor.12079 © 2014 Collegium Boreas. Published by John Wiley & Sons Ltd