Wave-Enhanced Sediment-Gravity Flows in Bohai Bay Lacustrine Basin, Eastern China

摘要

Sequences of wave-enhanced sediment-gravity flows (WESGFs) have been widely recognized in the marine shelf environment.In this study,we show observations of WESGF deposits in lacustrine settings using well core and thin section data from the Paleogene in the Jiyang sub-basin,Bohai Bay basin,eastern China.The findings of this study include the following:1) the sequence of WESGFs in the lacustrine basin is similar to that of marine;it consists of three units,MF1 unit:siltstone with basal erosion surface,MF2 unit:silt-streaked claystone,and MF3 unit:silty-mudstone;and 2) prodelta sand sheets are found in the lacustrine WESGF sequence and are classified as the MFd unit:clay-streaked siltstone.However,because the system size and variability in hydrodynamic conditions are different between the lacustrine and marine basins,lacustrine WESGFs do appear to have three distinguishable features:1) the sediment grain size and sand content are slightly higher than those of the marine WESGFs;2) lacustrine WESGFs may contain prodelta sediments or sedimentary sequences of other types of gravity flows,such as hyperpycnal flows;and 3) the scale of the sedimentary structures for lacustrine WESGFs is smaller.The WESGFs found in the continental lacustrine basin provide a new model for sediment dispersal processes in lake environments and may be helpful to explain and predict the distribution of sandy reservoirs for oil and gas exploration.