New insights for origin of fine-grained sediments from the early neogene Qaidam Basin: Wind and fluvial–lacustrine source-to-sink processes

Abstract

Fine-grained sediment deposition is widely distributed in lacustrine and marine facies and significant for petroleum geology. However, the causes of fine-grained sediment deposition remain controversial. In this study, we examine the cause of fine-grained sedimentation in the Neogene saline lacustrine Qaidam Basin, and propose a new insight into the sedimentary process for fine-grained sediments. Various sedimentary structures identified from the fine-grained sediments such as erosional structures with lag deposits, hummocky cross-stratification (HCS)-like structures, asymmetrical ripples, or sandy ball-and-pillow structures, are generated by winter storms. These winter storms are related to the winter winds that cause eolian sedimentation in Asia. Abundant detrital material may be rapidly transported into lakes by winter storms, favoring extensive terrigenous detrital deposition in the lacustrine basin, hardly controlled by the division of sedimentary facies and topographical differentiation. The genetic features and shallow-water origin with wind and fluvial–lacustrine source-to-sink processes, may be the main reason for the poor hydrocarbon potential of the Neogene fine-grained sediments in the Qaidam Basin.