The collection of extended and updated abstracts presented here resulted from a two-day workshop of the Collaborative Research Centre ‘Interactions between and Modelling of Continental Geo-Systems’ (SFB 350) held on 19th and 20th November, 1999 at the Rheinische Friedrich-Wilhelms-Universität Bonn. This workshop was entitled ‘Rift Tectonics and Syngenetic Sedimentation - the Cenozoic Lower Rhine Graben and Related Structures’. Its central topic was devoted to various approaches of understanding the evolution of a young graben structure, with the aim to trace the interaction of tectonics, sedimentation, facies development, burial history, and coherent structural behaviour by integration of geodetic, seismological, gravimetric, sedimentological, paleontological, and climatological data.

Since the beginning of the development of the North German Basin in Stephanien to Early Rotliegend times, rifting played a major role. Nearly all structures in NW-Germany and the German North Sea - (more than 800) - salt diapirs, grabens, inverted grabens and inversion structures - are genetically related to rifting. Today, the rifting periods are well dated. We find signs of dilatation at all times except from the Late Aptian to the end of the Turonian. To the contrary, the period of the Coniacian and Santonian, lasting only five million years was a time of compression, transpression, crustal shortening and inversion. Rifting activities decreased notably after inversion in Late Cretaceous times. Tertiary movements concentrated on a limited number of major, long existing lineaments. Seismically today NW-Germany and the German North Sea sector is one of the quietest regions in Central Europe.

Within the Cenozoic sedimentary section of the Roer Valley Graben ten seismostratigraphic units have been identified. They are closely related to the lithological framework which makes it possible to recognize diem also on well logs in this region. The Lower Tertiary seismic units, representing mainly marine sediments, have a uniform development mat can be correlated over large distances into the German part of the Roer Valley Graben. The marine to continental Upper Tertiary and Quaternary seismic units display a more complex development due to lateral facies changes (including prograding delta systems) and rift tectonics.

The Cenozoic fill of the Lower Rhine Basin is investigated with data from industry wells and open-cast mines on lignite coal. The geophysical logs of digitised well data are used to calculate lithofacies logs with a newly developed technique. The lithofacies logs allow the interpretation of shallow marine and continental environments in a sequence stratigraphie approach. In addition, base level analysis with both the lithofacies logs and the geophysical logs provide a stratigraphical frame for environment interpretation, modelling, and simulation.

This paper discusses the faunal content, the mammal biostratigraphy, and the environmental ecology of three important continental Tertiary vertebrate faunas from the Lower Rhine Embayment. The sites investigated are Rott (MP 30, Late Oligocene), Hambach 6C (MN 5, Middle Miocene), Frechen and Hambach 11 (both MN 16, Late Pliocene). Comparative analysis of the entire faunas shows the assemblages to exhibit many conformities in their general composition, presumably resulting from their preference for wet lowlands. It appears that very similar environmental conditions for vertebrates reoccurred during at least 20 Ma although the sites are located in a tectonically active region with high subsidence rates. Differences in the faunal composition are partly due to local differences in the depositional environment of the sites: lake deposits at the margin of the embayment (Rott), coal swamp and estuarine conditions in the centre of the embayment (Hambach 6C), and flood plain environments with small rivulets (Frechen and Hambach 11). The composition of the faunal assemblages (diversity and taxonomy) also documents faunal turnovers with extinctions and immigrations (Oligocene/Miocene and postMiddle Miocene), as a result of changing climate conditions.

Additional vertebrate faunal data were retrieved from two new assemblages collected from younger strata at the Hambach mine (Hambach 11C and 14). They are important for the understanding of the Plio-Pleistocene transition in the southern part of the Lower Rhine Embayment and for correlating depositional sequences in the Dutch/German borderland.

Based on recent studies, the impact of global sea-level and climate change on the paleogeographic and sedimentary evolution of the Tertiary of the Lower Rhine Basin is analysed. It is shown that major changes in global climate and sea-level, such as the high-stand during the Middle Miocene climate optimum, the extreme low-stands near the base of the Tortonian and within the Messinian, are clearly reflected in the sedimentary succession. Continental climate curves, as reconstructed from Tertiary macrofloras of the Lower Rhine Basin, can be correlated with the marine, long-term isotope record. As shown by the analyses, a warm and humid climate with mean annual temperatures above 13°C and mean annual precipitation not below 1000 mm, persisted throughout the Late Miocene to Early Pliocene. Continental, high-resolution, climate data show that Late Miocene alternations of lignites and elastics are rather caused by tectonic and sedimentary processes (such as the repeated migration of the river system) than by major climate changes.

More than 400 samples for paleobotanical and sedimentological investigations were collected from Late Pliocene and earliest Pleistocene beds in the open-cast lignite mine Hambach. They were analysed to obtain information about the paleoecology and paleoclimate of this time interval. The sedimentation type changed from a high-energy meandering fluvial system to floodplain, swamp and oxbow lake sedimentation. The typical Tertiary floral elements decreased with the onset of increasingly cooler climatic conditions and disappeared at the beginning of the Pleistocene to be substituted by a impoverished and coldadapted flora. These combined litho- and biostratigraphic investigations led to an improved and reproducible separation of Late Pliocene from Early Pleistocene deposits.

During the Pleistocene the drainage pattern in the Lower Rhine Basin changed twice, from a flooding of the whole basin by the river Rhine from SW to NE to an influence restricted to the NE only.

The first dominance of the river Rhine is documented from the Reuverian to the Tiglian, the second one in the Cromerian. In between this time, the Meuse River drained the central Lower Rhine Basin in NE direction. For the sediments of that river, the term ‘Holzweiler Formation’ is introduced. Since the Late Cromerian, the influence of the Rhine is again restricted to the NE of the Lower Rhine Basin. The central part of the basin is drained by small local rivers.

Using marine planation surfaces, fluvial terraces and a digital terrain model, the amount of eroded rock volume versus time for the Meuse catchment has been computed. A comparison of the amount of eroded volume with the volume of sediment preserved in the Roer Valley Rift System shows that 12% of the eroded volume is trapped in this rift. The neotectonic uplift evolution of the Ardennes is inferred from the incision history of the Meuse River system and compared to the subsidence characteristics of the Roer Valley Rift System. Both areas are characterized by an early Middle Pleistocene uplift event.

Uplift of the Rhenish Massif can be demonstrated by means of the stream-made river terrace system that accompanies the Rhine river and its tributaries along their way through or within this part of the Variscan fold and thrust belt. The height difference between a former valley floor, especially that of the Younger ‘Hauptterrasse’ (Main Terrace), and the recent one allows to quantify the uplift by the amount of downcutting erosion. The uplift velocity increased just after the BRUNHES / MATUYAMA boundary, i.e. about 0.8 Ma B.R Since that time, a domal uplift of more than 250 m is documented in the eastern Hunsriick and in the south-eastern Eifel. The area of this maximum height anomaly is situated just between the East-and West-Eifel Quaternary volcanic districts. Thus, causal connections are supposed. The domai uplift is affected by normal faulting partly inherited since Tertiary rifting.

As part of the activities of the Collaborative Research Centre ‘SFB 350’, measurements of geodetic and geodynamic changes in the area of the Lower Rhine Embayment and the Rhenish Shield are being performed at different scales in space and time. Continuous borehole tilt measurements and repeated microgravimetric surveys yield information on the local stability of the ground and changes in horizontal gravity gradients that are both dominated by seasonal fluctuations. Results of more than seven years of regular GPS campaigns are discussed in terms of vertical and horizontal point motions. The most prominent motions are man-induced effects occurring in or near the browncoal mining areas, where groundwater withdrawal produces subsidence of up to 2.2 cm/y in the area under investigation. Horizontal and vertical motions at other GPS points are smaller by one order of magnitude and in most cases are only marginally detectable. The eastward motion of two points in the Bergisches Land and the westward motion of two points in the Eifel near the Belgian border may be interpreted as a result of the ongoing extension of the Cenozoic rift system in the western part of the Eurasian plate.

Kinematic geological models can greatly enhance our understanding of the interaction and timing of processes involved in the formation of sedimentary basins. The prototype tool for the calculation and visualisation of such models presented here is aimed at studying subsidence rates and patterns at basin scale: A backstripping algorithm is applied to a geometrical 3D-model consisting of prismatic volumes, constructed from an initial set of stacked triangulated surfaces. As a result, we obtain a collection of palinspastically restored volumes for each timestep of basin evolution. The backstripped volumes of each layer are then arranged within a timescene, and the set of timescenes collected as a hierarchical timetree. By interpolating between succeeding key-frames, the subsidence history of the basin can be viewed as an interactive, continuous animation. The approach is illustrated using a high-resolution dataset from the German part of the Cenozoic Lower Rhine Basin.

In the context of the investigation of the sedimentary and structural evolution of the Cenozoic Lower Rhine Basin, the construction of a volume-balanced kinematic model of a small faulted domain with detailed spatial information on strata and fault geometry from a set of parallel geological sections is under development. A 3D geometry model is built that allows for relative movements of blocks at fault surfaces. Rouby’s method of restoration in the map plane is used to determine horizontal displacement fields. The 3D and 3D(t) geometry models are supported by the object-oriented geometry database tool GeoToolKit for storage and retrieval of selected parts of the model using queries referring to spatial and temporal criteria, while visualization is based on key frame technique.

Within the collaborative research centre SFB350 at the University of Bonn a component software called GeoToolKit has been developed, which is intended to facilitate the design and implementation of 3D/4D geological applications. It provides a range of geo-oriented software building blocks for application developers involving database management system based spatial and temporal data maintenance, support for efficient spatial and temporal retrieval, communication, visualization and graphical interfaces which the user could assemble in a ready-to-use application. As such, GeoToolKit is not a GIS-in-a-box package - rather it is a library of C++ classes that allows the incorporation of spatial functionality within an application under development. It is primarily oriented towards software engineers with the C++ experience involved in the development of specialpurpose geological applications, which can hardly be modelled within standard GISs. We present applications using GeoToolKit, which have been developed to support the geological reconstruction of the Lower Rhine Basin.