Pliensbachian–Toarcian ostracod biogeography in NW Europe: Evidence for water mass structure evolution

This paper examines the role played by palaeoceanographic and climatic conditions on the palaeobiogeography of the Pliensbachian–Toarcian ostracods (Early Jurassic) in the European Epicontinental Sea (EES). The influence of the palaeogeography, ocean currents and sea level, temperature and salinity variations on ostracod abundance, diversity and migration patterns is reconstructed. Ostracod migration follows an anticlockwise circulation in the eastern side of the EES, with a leading northeast–southwest movement, and the frequent arrival of Tethyan faunas into the central and western parts of the EES during the Pliensbachian. A three-fold classification of water masses based on salinity, temperature, lithological and fossil data is proposed. The repeated inflow of Tethyan ostracods into the EES ended by the earliest Toarcian. This ostracod event is related to the opening of the Hispanic Corridor and to the reorganization of the surface and deep circulations that may have generated a cold episode at the beginning of the Toarcian.