TIGHT COUPLING BETWEEN THE CYCLICITY OF DEEP-WATER SYSTEMS AND RISING-THEN-FLAT SHELF-EDGE PAIRS ALONG THE SUBMARINE SEGMENT OF THE QIONGDONGNAN SEDIMENT-ROUTING SYSTEM

摘要

On the basis of shelf-edge (SE) trajectory analysis, the present study demonstrates the tight coupling between the cyclicity of deep-water systems and contemporaneous SE trajectories with a paired rising-then-flat trajectory tendency (termed "SE pairs'') along the submarine segment of the mid-Pleistocene Qiongdongnan sediment-routing system, contributing to a better understanding of how to predict internal architecture and stacking patterns of deep-water systems. At the outlying deep-water reaches of the mid-Pleistocene Qiongdongnan sediment-routing system, Qiongdongnan deep-water systems are shown to have grown in a cyclic fashion that is stratigraphically manifested as the underlying mass-transport deposits (MTDs) systematically capped by submarine channels or sheet-like turbidites (i.e., MTD-channel and MTD-turbidite cycles, respectively). At the SE staging areas of the mid-Pleistocene Qiongdongnan sediment-routing system, Qiongdongnan shelf edges (SEs) have grown in a paired rising-then-flat fashion. The lower stratigraphic fill level of Qiongdongnan deep-water sedimentation cycles correlates to rising SE trajectories, during which the far shoreline to SE proximity (i.e., the long shoreline to SE distance of tens of kilometers) coupled to positive shelf accommodation [represented by positive SE trajectory angles (T-se) of 4.38 degrees to 10.45 degrees] most likely promoted passive sediment-transport agents and resultant MTDs. The upper stratigraphic fill level of mid-Pleistocene Qiongdongnan sedimentation cycles, in contrast, corresponds to flat SE trajectories, during which the close shoreline to SE proximity (i.e., the short shoreline to SE distance of < 5 km) coupled to negative shelf accommodation (represented by T-se of -0.17 degrees to -1.32 degrees), in contrast, favored active sediment-transport agents and resultant submarine channels or sheet-like turbidites.