USING LIDAR TO DISTINGUISH BETWEEN COMPETING MODELS OF TERRANE ACCRETION IN THE WESTERN SEGMENT OF THE SAINT ELIAS OROGEN, ALASKA

One of the most dramatic structural features of the Saint Elias orogen is the 90 degree change in strike of the the thin-skinned thrust belt west of the Bering Glacier. New research in the region suggests that the thrust belt is being refolded around a subvertical axis. The Indentor and Train Wreck models have been proposed as end member models to explain the refolding. These models each predict distinct fault patterns. Key to distinguishing between these models is documenting locations of surface ruptures and their sense of offset. As part of the STEEP project 1 m posted LiDAR data was flown by NCALM north of Katalla, Alaska in 2005. Hillshade DEMs were generated from the LiDAR data to map in detail bedding orientation, faults, folds, and geomorphic indicators of active deformation. Mapping indicates the east-west striking thrust belt in the northern portion of the scene is folded around a subvertical axis near the center of the scene. Strata near the hinge of this fold are intensely disrupted and approaching broken formation. There are several types of faults that accommodate the refolding: faults parallel to bedding, gravity driven uphill facing scarps (possibly sackung), and faults that are discordant to bedding. The sense of offset for most faults are difficult to extract from the LiDAR data as many are likely flexural slip faults. Preliminary field work in 2006 documented the presence of dip slip faults, left oblique-slip normal faults, and reverse faults throughout the area. We will be visiting faults on both both sides of the hinge during the 2007 field season checking for the sense of motion on faults.