Abstract The non-marine sedimentary successions of the Berriasian and lower Valanginian of NW Germany are described. The stratigraphical distribution of ostracods allow this interval to be subdivided into 10 biozones, which can be used for regional correlation in the central part of the NW German Basin. Three ostracod taxa ( Fabanella ansata, Cypridea alta formosa and Pachycytheridea compacta ) can be used for interregional correlation between Germany, Denmark, France and England. The middle part of the Katzberg Member, which yields F. ansata , allows correlation with the Lower Purbeck of S England, the Paris Basin, and the Boulonnais. The first occurrence of this species can be used to define the Portland/Purbeck boundary. Fluctuations in the taxonomic content of ostracod assemblages reflect changes in salinity. Brackish conditions dominated deposition during the earliest Berriasian (Munder Formation) and earliest Valanginian (Osterwald Member). Sediments of the late Berriasian Obernkirchen Member were deposited under freshwater conditions. A short-lived marine transgression marked the mid Berriasian (base Wealden 4). The Platylenticeras Beds of mid-Valanginian age indicate a return to fully marine conditions.