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A new consistent sequence stratigraphic model is set up for the Oligocene sedimentary pile at the southern rim of the Northwest European Tertiary Basin. Using well-log analysis of 230 exploration and research wells six Oligocene sequences (R 1 - R 3 and C 1 - C 3) are established for the working area that correspond well with the sequences of HARDENBOL et al. (1998). Hence, the Lower Rhine Embayment is showing one of the most complete sedimentary fillings of European Oligocene basins. Despite strong subsidence basinwide sea-level changes can be traced. The Oligocene sequences are based on the establishment of flooding and erosion surfaces, respectively.
At the beginning of the Rupelian period the North Sea transgressed onto the southern foreland filling up the existing topography. During RU-2 a SW-NE trending system of barrier sands developed parallel to the palaeocoast at the southwestern Lower Rhine Embayment forced by tidal conditions. These sands are preserved due to a strong sea-level rise at the beginning of RU-3 that led up to the development of a condensed section. Starting with RU-4 the basin became shallower caused by the initiation of a regressive phase. It was filled with clastic material due to the uplift of the Rhenish Massif in the hinterland.
The beginning of the Chattian was again initiated by a basinwide transgression. Sediments rich of glauconite indicate low sediment supply rates from the hinterland. The transgression reached its maximum during CH-2 leading to water depths of up to 60 metres. For the rest of the Chattian the Oligocene North Sea was repeatedly regressing and transgressing. In this Ph.D. thesis the marine Veldhoven Clay and Grafenberg Sands are correlated with the continentally influenced Cologne Series ("Köln-Schichten") for the first time ever.
During Rupelian and Chattian times the Lower Rhine Embayment and its adjacent
areas were forced by the alpine compressional tectonic regime as well as by
an increasing extensional tectonic influence due to the Cenozoic Central European
rift system. At the beginning of the Rupelian the subsidence at the northern
margin of the variscan fold belt was very consistent from Belgium to Saxony-Anhalt.
Variscan structures perpendicular to the main stress orientation NNW-SSE have
been reactivated due to the influence of the Alpine orogeny upon the central
european earth crust. These structures were affecting the sedimentation patterns
to a high degree. Today's architecture of the Lower Rhine Embayment was already
initiated from RU-4 onwards. This is in contradiction to ZAGWIJN (1989) who
assumed the initiation in the Upper Oligocene. During the Chattian the Lower
Rhine Embayment was differentiated into several blocks that were predominantly
facing separate sedimentation histories.
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Table of contents
Part 1. Pages 5 - 50 (1,8 MB)
Part 2. Pages 51 - 103 (2,0 MB)
Part 3. Pages 104 - 151 (1,9 MB)