GEOMORPHIC ANALYSIS OF THE MØRE-TRØNDELAG FAULT COMPLEX IN SOUTHERN NORWAY

The topography of the Norwegian passive margin is atypical of an area that has allegedly been absent of tectonic influence for 50 million years, as has been suggested by many workers. The 2-3 km high seaward-facing escarpment is uncharacteristic of passive margins where subsidence and cooling are the dominant processes. Various models have been proposed to explain the puzzling landscape. One model suggests that the topography is a remnant of the Caledonian Orogeny, while others propose that glacial erosion in combination with isostatic rebound or mantle processes are the driving mechanisms for the morphology. Though the exact mechanism responsible for the atypical margin is under debate, based on previous offshore geophysical data, onshore geomorphology, thermochronology, and structural geology, it is largely accepted that the region has undergone topographic rejuvenation.

Study of the Møre-Trøndelag Fault Complex, a fault system that has a complex history and has undergone several periods of fault reactivation, may provide evidence for a tectonic uplift model as the mechanism responsible for the high relief. To address this model, we are using 3 techniques to investigate the high, rugged topography that has been maintained tens of millions of years after tectonic activity had concluded. These techniques comprise of tectonic geomorphology, low temperature thermochronology and structural geology to test the normal fault displacement gradient as well as constrain the timing of faulting within the Møre-Trøndelag Fault Complex. Tectonic geomorphic analysis will be completed through fluvial knickpoint analysis, a technique that has provided a great deal of data exhibiting a relationship between channel steepness and uplift. Knickpoint analysis will be compared with the geology and geomorphology of the area to tease out lithologically and glacially controlled knickpoints, in order to determine tectonic knickpoints. Multichronometer dating will be used on samples collected in the field to constrain the minimum timing of uplift, as there is currently not enough data to do so. Combination of these techniques will allow us to identify whether recent tectonic uplift is a valid model.