| Based on the understanding for the formation and preservation conditions of the beach and bar sand bodies in
Qinghai Lake, using the basic principle of “the present is the key to the past” in geology, this paper carried out a
comparative study on shore-shallow lacustrine beach and bar deposits in modern Qinghai Lake and ancient Ordos Basin
from the the aspects of provenance supply, topography of lake basin, (wind) hydrodynamic force, lake shoreline
morphology and lake level cycle (base level). It is considered that during the deposition of Yanchang Formation in Upper
Triassic, Chang 9-Chang 82-Chang 7 sedimentary period is not only in the early stage of second-order sequence, but also
in the lake transgressive system tract of third-order sequence, which is very conducive to the preservation of terrigenous
clastic beach and bar. The prediction model of the distribution of shore-shallow lacustrine beach and bar of Yanchang
Formation is established. It is pointed out that the southern basin (including southwest and southeast) is a favorable area
for the development and preservation of the beach and bar sand bodies of Chang 9-Chang 82-Chang 7, and is also a
favorable area for looking for the favorable beach and bar reservoirs in the future. |
