CARBONATE BUILDUP FLANK DEPOSITS - AN EXAMPLE FROM THE PERMIAN (BARENTS SEA, NORTHERN NORWAY) CHALLENGES CLASSICAL FACIES MODELS

Mounds seen on seismic in the Barents Sea, offshore northern Norway, o ccur in the upper Palaeozoic of the Finnmark Platform. A 160-m-long co red section from such a mound, dated as unspecified Asselian-Artinskia n (Lower Permian), documents a carbonate buildup of microbial origin a nd rich in Stromatactis fabric. The cored section documents the flank of a buildup where depositional dip angles vary from a few degrees to about 45 degrees. Approximately 2/3 of the flank consists of in-situ m icrobial boundstone with abundant Stromatactis and, in the upper part, bryozoan-cement framestone. The remainder is gravity flow sediment de posited on the flank and at the toe of the buildup consisting of argil laceous sediment alternating with crinoid grainstones. Modal thin-sect ion analysis indicates that biogenic particles make up 38% of the buil dup flank, diagenetic products such as early, fibrous cement, microcry stalline cement and late, blocky calcite 46%, and lime mud, including that interpreted as microbially induced, 16%. The studied core interva l shows that steeply inclined buildup flanks can be largely in-situ de posits rather than allochthonous as predicted in classical facies mode ls.