3-DIMENSIONAL MODELING OF QUATERNARY FLUVIAL DYNAMICS IN A CLIMO-TECTONIC DEPENDENT SYSTEM - A CASE-STUDY OF THE MAAS RECORD (MAASTRICHT, THE NETHERLANDS)

A three-dimensional model (MATER) simulating Quaternary terrace development along the river Maas at Maastricht was made. Simulation results indicate that Maas terraces are most probably the result of both climatic and tectonic changes in time. Terrace formation is mainly climatically determined but their long-term preservation is closely related to the prevailing tectonic regime. Quaternary uplift of the Maastricht area has known several phases with different ''constant'' uplift rates. These differences in uplift rate are a main cause of the general valley morphology near Maastricht. Whereas the deep-ocean climatic record is clearly dominated by the tilt cycle between 2.4 and 0.9 Ma, the continental record in the form of the cold-stage floodplain aggradation-dominated periods appears to register primarily modulations of the eccentricity cycle over this episode. During the last 0.9 Ma, when the general uplift rate was of the order of 0.1 m/ka, a ''complete'' climate-related terrace sequence developed. Every 100 ka climatic cycle is registered in this part of the terrace sequence. Both model and field evidence suggest that Maas terrace sediments are mainly records of the ''cold'' periods. As such they are valuable continental counterparts of palynological records registering ''warm'' episodes. Tectonism determines long term terrace preservation and the value of a specific fluvial system as record of past climatic change.