A PALEOENVIRONMENTAL AND PALEOECOLOGICAL ANALYSIS OF FINE-GRAINED PALEOGENE ESTUARINE DEPOSITS OF NORTH GERMANY

The lower Tertiary successions of the North German Basin predominantly consist of shallow marine, fine-grained siliciclastic rocks which gra de towards the SE and S into continental deposits infilling bays and e stuaries. In the study area around the Gorleben salt dome, glauconitic sandstones, siltstones and mudstones were laid down together with tuf fs in a depositional environment that is interpreted as a shelf-estuar y transition. Syngenetic salt tectonics strongly affected the basin ar chitecture and the composition of the sediments under study. Analysis of the depositional environment is based on sedimentological, mineralo gical and chemical data. Although bathymetry and salinity may be often calibrated by means of microfossils by analogy with present-day speci es, there is much debate as to their validity for palaeodepth reconstr uctions in the North Sea. Interdisciplinary interpretation of data fro m biological and sedimentological studies on the same material may imp rove the quality of the palaeoenvironmental reconstruction. Core exami nation and the investigation of wireline logs form the basis of the pa laeogeographical model of the North German Basin. This model shows a d eepening of the basin from the Paleocene through the late Eocene, lead ing eventually to the transgression of the Rupelian sea into the estua ry. The history of the palaeo-shelf and estuary area during the Tertia ry is described in analogy with modern depositional environments, such as the present-day Celtic Sea, the western end of the English Channel , the German Eight and the Isle of Helgoland, which is situated above a salt diapir off the North German coast. The climate in this area, ho wever, was much warmer during the Paleogene than today.