Quaternary carbonate-rocky talus slope successions (Eastern Alps, Austria): sedimentary facies and facies architecture

摘要

Quaternary carbonate-lithic talus slope succes-sions of the Eastern Alps record an overall correlationbetween prevalent sedimentary facies, depositional geo-metry, and geomorphic maturity of the slope. After exposureof high cliffs by deglaciation or rocksliding, a low-dippingimmature talus dominated by unsorted rockfalls initiallyaccumulates. With progressive talus buildup, slope segmentsof different dips develop. Concomitantly, prevalent deposi-tional processes change to grain flows and sorted rockfalls inthe proximal, steep-dipping (35°-30°) slope segment, whiledeposits of cohesive debris-flows, ephemeral fluid flows andlarger rockfalls prevail in the distal, lower-dipping slopesegment. In mature talus deposy stems, the proximal slopesuccession overlies the lower-dipping package of the distalslope along a thin `downlap interval'. Immediately after cliffexposure by deglaciation or rocksliding, talus may aggradeat rates of up to a few tens of meters per 1,000 years, but theaccumulation rate slows strongly with progressive maturityof slopes.