资源环境科技发展态势分析平台

Twenty-seven marine and 23 lacustrine clinothem pairs were recognized and analyzed in Qiongdongnan Basin and Pannonian Basin, respectively. A comparison of their architecture highlighted some critical differences in sediment delivery and partitioning between the marine and closed lacustrine basins. In marine Qiongdongnan Basin, rising but forward-moving shelf-edge trajectories and clinoforms with a height of hundreds of meters commonly link downdip to absent or limited sandy bottomsets, whereas the opposite occurs in the lacustrine Pannonian Basin, where very thick bottomsets developed in front of highly aggradational clinoforms. A further comparison of strongly progradational clinothem sets with fairly flat shelf-edge trajectories suggests that relatively thick versus thin or absent sandy bottomsets occur in the marine and lacustrine settings, respectively. The main reason for this marked contrast in sediment partitioning across marine versus lacustrine clinoforms is climate, where 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 were probably high, and coeval lake-level rise and reduced salinity 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 catchment precipitation and sediment flux into Lake Pannon were probably reduced, causing some increase in the salinity, less frequent hyperpycnal flows, and resultant short downlapping 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 documented herein, draw attention to the pitfall of mechanically applying conventional marine sequence stratigraphy to lacustrine basins.