Andreas Schaefer1, Frank Eichhorst2, Michael Klett2
(1) Universitaet Bonn, Bonn, Germany
(2) Geological Institute, University of Bonn
ABSTRACT: Rifting and Marginal Marine to Fluvial Environments of Cenozoic Lower Rhine Basin (NW Germany)
The Lower Rhine Basin is part of the southeastern Dutch-German Cenozoic rift system, subsiding into the north-western headlands of the Rhenish Massif, where it forms a 100 km long and 50 km wide NE-ward dipping halfgraben. The Tertiary and Quaternary siliciclastic fill of the Lower Rhine Basin is of 1300 m in thickness. Toward the North, the basin deepens to 2000 m to form the Roer Valley Graben in the Netherlands. The basin has been seismically active until today, therefore earthquakes are frequent.
From the Palaeogene onward, the Tertiary North Sea transgressed onto the lowlands of today Belgium, the Netherlands, and Germany. During the Oligocene, the North Sea lapped onto the Rhenish Massif and reworked the fill of the Lower Rhine Basin which was shed by fluvial input from the heights in the South. The ingression of the sea is well documented by marginal marine medium-energy beach associations which were deposited under tidal conditions with a rich variety of trace fossils. The North Sea reached its highstand with the early Miocene. As a consequence, a coastal plain was formed, covered by marshes, swamps, mires, and forests - the today lignite coal of about 100 m in total that have intensely been mined for decades by the local lignite coal industry in open-cast mines in the south-eastern Lower Rhine Basin. Meandering and, later, braided fluvial systems followed the stepwise progradation of the coast in late Miocene and Pliocene, when the North Sea retreated again. In the Pleistocene, the Rhenish Massif was lifted to its present elevation, and the Rhine River shed a thick, gravelly and coarse-grained fluvial outwash-fan towards the North.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado