Astronomical controlling factors of hyperpycnal flow and its impact on organic matter enrichment: A case study from the Ordos Basin

ABSTRACT

Astronomically forced climate cycles and hyperpycnal flow deposits are the forefront of contemporary geological research. Climate significantly influences the formation of hyperpycnal flows, with these changes being driven by astronomical cycles. However, the relationship between astronomical cycles and hyperpycnal flows has not been sufficiently explored. Additionally, although hyperpycnal flows can transport terrigenous clastic particles to the deep-water areas of basins, their impact on organic matter enrichment remains inadequately studied. Therefore, this study analyzed the characteristics of hyperpycnal flow deposits within the Chang 7 Oil Member (Chang 7 Member) in the southern Ordos Basin, assessed their frequency of occurrence, and investigated their correlation with long-eccentricity cycles. By examining the geochemical signatures and sedimentary accumulation rates (SARs) of different genetic types of deposits, this study also explored the controlling factors of hyperpycnal flows on organic matter enrichment. The analysis indicates that hyperpycnal flows within the Chang 7 Member exhibit periodic development, significantly influenced by long-eccentricity cycles. Hyperpycnal flows not only transport nutrients into the lake basin but also increase SARs, thereby facilitating the rapid burial of organic matter and promoting its enrichment. These findings underscore the significant role of astronomical cycles in governing the development of hyperpycnal flows and highlight their positive influence on organic matter enrichment.