Alpine-scale 3D geospatial modeling: Applying new techniques to old problems

Abstract

The investigation of geologically complex settings in Alpine or mountainous terrains is still dominated by traditional data collection and analytical techniques. The application of computer-aided geometric design and threedimensional (3D) visualization and interpretation is rarely applied to such settings, despite its signifi cant benefi ts. This contribution uses the Gosau Muttekopf Basin (Eastern Alps, Austria) to demonstrate that the application of 3D geospatial models can both provide new insights into our understanding of such settings and result in a more robust and reproducible synthesis of a complex region.The objective of studying the Muttekopf Basin is to investigate the 3D structural control on the deposition of the deepwater sedimentary basin fi ll. Data for the investigation only consist of that which would be collected in a traditional fi eld study (e.g., structural mapping, stratigraphic logging, and data localities derived from hand-held GPS [global positioning system]). The 3D basin confi guration is initially derived using traditional analysis techniques (e.g., cross-section construction, photo-panel mapping, block diagrams, etc.). Using these analysis techniques, signifi cant thickness variations are observed in the basin fi ll and are related to temporal and spatial variations in displacement of the controlling structure on the southern basin margin. However, there are signifi cant limitations to this approach. In particular, because of the uncertainty in projection and spatial positioning, these techniques can only be used in an illustrative or qualitative fashion. To overcome these limitations, a 3D geospatial model is constructed from the same input data and illustrates that 3D geospatial modeling is a powerful technique for understanding complex geological settings. Integration of map data, stratigraphic section data, photographic images, structural data, and rock property data (gamma ray) into a single geospatial model maximizes the constraints of the limited data set. It also facilitates a deeper data analysis by signifi cantly decreasing the time involved in generating multiple surfaces required for isopach generation.The use of the isopach maps in the Muttekopf Basin provides signifi cant insights into the basin's evolution. In the Schlenkerkar section, the isopach maps reveal: (1) there was very little sediment thickness variation across the basin during the early basin fi ll;(2) the intermediate episode was characterized by a very thick accumulation in the basin's axis with signifi cant thinning onto the southern uplifted margin; and (3) a north-ward migration of accumulation occurred during the late stage of the basin fi ll. Overall, the isopach maps suggest that the structure on the southern margin was the primary control on accommodation space creation and that it was most active during the intermediate basin-fi ll episode. Using similar observations from isopach maps for the entire basin reveals that the change in structural style of the southern margin from a fold-to a faultdomi...

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Palinspastic restoration of an exhumed deepwater system: A workflow to improve paleogeographic reconstructions

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