274 / 2019-07-08 17:17:18

A comparison of marine and lacustrine aggradational to progradational clinothem pairs: Insights into some critical differences in sediment delivery and partitioning between marine and lacustrine basin

Sequence stratigraphy; sediment delivery and partitioning; shelf-edge trajectories; endorheic lacustrine basins; clinothem pairs

Marine vs. lacustrine clinothem pairs were recognized and analyzed in marine basins of Qiongdongnan deepwater, Adriatic foredeep, Northern Carnarvon Basin, and Washakie Basin and in lacustrine basins of Pannonian Basin and Dongying Depression. A comparison of them highlights some critical differences in sediment delivery and partitioning between marine and closed lacustrine basins. In marine Qiongdongnan Basins, 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 the lacustrine 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 partitioning across lacustrine clinoforms is that a wet-dry climate model needs to be used to explain sediment dispersal to the floor of deep Lake Pannon or Dongying. 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 flow and thick bottomsets on the lake-basin floor. During the semi-arid half-cycle, lake level was fairly stable and both the water and sediment flux into Lake Pannon or Dongying 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 stratigraphy to lacustrine basins.