Geometric Parameters as Key Factors for the 3D-modeling of Fluvial Deposits

Abstract

GIS is an established and appropriate tool for the management and evaluation of geodata which is being increasingly used for the three-dimensional modeling of strata. An advanced technique for the GIS-based 3D-modeling is developed here in order to integrate genetic aspects of deposition into the modeling process. The ArcView® software (ESRI, Inc., Redlands, California) and the extensions 3D-Analyst and Spatial Analyst have been used for the data management and layer rendering. The tools VirGIL and GSI-3D (Insight Corp., Germany) have been applied for the purpose of visualization of the layers in 3D. The main topic of the work is the generation of geometrically consistent models of fluvial terrace bodies, which represent monogenetic fills of Pleistocene palaeovalleys. One peculiarity of the investigated Illerglacier foreland, southern Germany, is the occurrence of highly eroded terrace remnants. The preserved deposits are tied to several accumulation levels, but the usual way of morphostratigraphic interpretation is limited and results in lots of different stratigraphies and palaeogeographic ideas presented in literature. The sediment fill of meltwater valleys, which can be identified in the Illerglacier area is reconstructed based upon intense field mapping. The terrace accumulations are defined by the base and surface layers, which are thought to be isochronous. Some 1,400 data points were used to model these layers in 3D. The geometry of the sediment deposits is defined using basic parameters, e.g. the gradient and the thickness of the terrace, which are used as bench levels for the modeling process. The quality of the calculated maps and cross-sections far surpasses that of those derived in the classic way without a genetic concept and without using the 3D-modeling technique. The results derived from the terrace models are relevant for the stratigraphy and palaeogeography of the investigated region of the Alpine foreland. The advanced modeling technique can be used for the detail analyses of terrace sequences of other regions.