THE MUTTEKOPF-GOSAU BASIN (LECHTAL ALPS, TYROL, AUSTRIA) - SEDIMENTOLOGY AND BASIN FORMATION

In the Eastern Alps compression during orogeny in the Upper Cretaceous caused crustal thickening, isostatic uplift and gravitational adjustm ent of the unstable orogenic wedge. This process triggered extensional basin formation on the back of the orogen (Gosau Basins). The basin f ill of the Muttekopf Gosau Basin is arranged in megacycles, the first one comprising alluvial fan sediments and ''Inoceramus marls'' of the Lower Gosau Complex (Faupl et al. 1987) of Santonian age. Three other cycles follow (Upper Gosau Complex, Campanian to Maastrichtian), consi sting of turbiditic fining upward sequences, that are indicative for e xtensional tectonics during basin formation, as subsidence events prev ent formation of autocyclic coarsening upward sequences and therefore prograding of the turbidite system. Deposition of the 1st and 2nd Mega cycle occured below the CCD (Carbonate Compensation Depth). The carbon ate rich 3rd Megacycle was deposited probably below the CCD after a pe riod of palaeogeographic reorganisation (uplift?) in the source area.