Critical Differences in Sediment Routing From Deltas to Deep-Water Fans Between Marine and Lacustrine Basins: A Comparison of Marine and Lacustrine Aggradational to Progradational Clinothem Pairs
Twenty-seven marine vs. twenty-three lacustrine clinothem pairs were recognized and analyzed in Qiongdongnan and Pannonian Basins, respectively. A comparison of them highlights some critical differences in sediment routing from deltas to deep-water fans between marine and closed lacustrine basins. In marine delta to deep-water fan source-to-sink systems in Qiongdongnan Basin, rising but forward-moving shelf-edge trajectories and clinoforms with a height of 100s m, commonly link downdip to a lack of or limited sandy bottomsets, whereas the opposite occurs in lacustrine delta to deep-water fan source-to-sink systems in Pannonian Basin where very thick bottomsets commonly occur in front of highly aggradational clinofoms. A further comparison of strongly progradational clinothem sets with fairly flat shelf-edge trajectories shows that relatively thick vs. thin or absent sandy bottomsets occur in the marine and lacustrine settings, respectively. The main reason for this marked contrast in sediment routing from deltas to deep-water fans on lake floors is that a wet-dry climate model needs to be used to explain sediment dispersal to the floor of deep Lake Pannon. During the humid half-cycle, catchment precipitation and sediment flux into Lake Pannon was probably high, while a coeval rising, but reduced salinity lake likely increased shelf accommodation and caused topset aggradation of the forward-moving clinothems. This, in turn, resulted in enhanced hyperpycnal flows and thick bottomsets on the lake-basin floor. During the semiarid half-cycle, lake level was fairly stable and both the water and sediment flux into Lake Pannon were probably reduced, causing some increase in the salinity, less frequent hyperpycnal flow and the resultant short down-lapping clinothems lacking or with only thin bottomsets. Critical differences in sediment delivery and partitioning between marine and lacustrine basins, as highlighted by a comparison of aggradational to progradational clinothem pairs, draw attention to the pitfall of mechanically applying conventional marine sequence stratigraphic concepts of sediment routing from deltas to deep-water fans to lacustrine basins.
AAPG Datapages/Search and Discovery Article #90350 © 2019 AAPG Annual Convention and Exhibition, San Antonio, Texas, May 19-22, 2019