A re-examination of the Pliensbachian and Toarcian Ostracoda of Zambujal, west-central Portugal

Abstract

Abstract. Pliensbachian and Toarcian Ostracoda first described by Exton (Geological Paper, Carleton University, Ottawa, 79: 1–104 1979) from the Lusitanian Basin, west-central Portugal have been re-examined. As a result, a greater diversity in the Ostracoda (80 species) is now recognized. Two species are newly described (Eucytherura zambujalensis sp. nov., Ektyphocythere mediodepressa sp. nov.) from the marls and calcareous shales of the Maria Pares Hill section near the village of Zambujal. Poor preservation precludes a complete taxonomic review of the present material. Five ostracod zones are proposed; Gammacythere ubiquita–Ogmoconchella gruendeli Zone, Poly cope cerasia–Polycope cincinnata Zone, Liasina lanceolata–Ogmoconcha convexa Zone, Bairdiacypris rectangularis–Kinkelinella sermoisensis Zone, and Cytherella toarcensis-Kinkelinella costata Zone. Although the ostracod assemblages possess strong similarities to those described from Northwest Europe, some of the Zambujal assemblages are dominated by the genus Polycope. A marked faunal turnover, in association with the extinction of the Metacopina occurs in the lower Subzone of the tenuicostatum Zone of Lower Toarcian age. These faunal events are discussed in relation to changing environmental conditions.