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A. Zámolyi, B. Székely:
"Revealing the micro-scale fault pattern from ALS-DTM data in an Alpine environment (Vorarlberg, Austria)";
Poster: EGU 2009, Vienna; 2009-04-19 - 2009-04-24; in: "Geophysical Research Abstracts", 11 (2009), Paper ID EGU2009-13142, 1 pages.

The post-glacial geologic history of the Eastern Alps is dominated by erosion of over-steepened valley slopes,
increased fluvial erosion and gravitational mass-movements. Increased erosion enhances the morphology of and
observability of structural features, especially in high-resolution LiDAR-DTM data. The study area is located at
the northern margin of the Penninic Units in Vorarlberg, Western Austria. Here, between the NW-margin of the
Silvretta nappe and the Northern Calcareous Alps (NCA) a NW-SE striking fault zone supports the formation of
crystalline duplex structures. Additionally, the generally E-W striking NCA units bend towards SW reflecting the
overthrusting of the Alpine nappes.
A further focus lies on the mountain slopes bounding the Gargellen valley that were subjected to surface and
erosional processes related to glaciation. The Gargellen valley joins the Ill-valley in the northern part of the study
area. Both valleys hosted minor glaciers during the Pleistocene; the confluencing glaciers caused an increased
stress on the bedrock. Thus, in this area effects of deglaciation are amplified. Typical processes acting on the
slopes are: (i) frost shattering, (ii) gelifluction and after deglaciation (iii) surface runoff erosion due to increased
precipitation, (iv) fluvial erosion by incising rivers. Since the beginning of the Holocene further mass wasting
by sliding, slumping, fall, toppling and creep occurred. Assessment of the aforementioned micro- and mesoscale
geomorphic features is needed to detect the ongoing processes and to determine the rates of deformation, incision
and sediment production.
Because of their high-accuracy, LiDAR-DTMs are often applied to extract information on microtopography. A
one-meter resolution LiDAR DTM was analyzed using a structural geologic approach. Results indicate that surface
processes follow and reveal tectonic features. Also, a remarkable difference in geomorphologic characteristics
is observable between the NW-side of the Gargellen valley and the mountain slopes on the SE-side. Whereas
in the NW areas cockpits are abundant in the higher elevated regions and glacial features (e.g. moraines) can be
traced very accurately, the mountain slopes on the SE-side are steep, straight slopes with triangular facets and
a drainage pattern that follows a systematic grid most probably provided by fault locations. This distribution of
geomorphologic features is likely to indicate different exhumation rates and neotectonic activity. A picture that is
supported at a much larger scale by apatite fission track measurements form the EasternWestern Alps (e.g. Vernon
et al., 2008).

http://publik.tuwien.ac.at/files/PubDat_175583.pdf