Temporal changes in an epeiric paralic deposition during a third-order relative sea-level cycle (Late Pennsylvanian, western North China): Insights from integrated facies and sequence stratigraphic analysis

摘要

The upper Chinssu Member (Late Pennsylvanian) of the Taiyuan Formation in the Linxing block of western North China records a complex sedimentological and stratigraphic arrangement of sandstone, mudstone and coal attributed to paralic environments that developed in an epicontinental setting with a tropical rainforest climate. Facies analysis of core TB01 through the upper Chinssu Member from the Linxing block is used to distinguish seven facies associations, reflecting successive depositions in the tide-dominated estuary, transgressive vegetation-dominated coastal plain, back-barrier tide- and wave-influenced lagoon, storm-wave-dominated inner shelf, tide-dominated open-coast tidal flat, and regressive vegetation-dominated coastal plain. Sequence stratigraphic analysis of core TB01 and nearby boreholes and outcrops is used to construct a framework of transgressive and highstand systems tracts and their bounding surfaces. Within the framework, nine types of facies contacts are identified to distill the internal makeup of systems tracts. The high-resolution framework enables the deconvolution of various controls on temporal changes in the epeiric paralic deposition during a third-order relative sea-level cycle. The high-amplitude third-order sea-level change is the dominant control on the stratal stacking patterns. The channel migration, peat compaction, shoreline autoretreat, and bedrock inheritance modified the depositional response to overall rise in relative sea level through time. This study contributes to a better understanding and prediction of the changes in depositional processes in the cratonic interior in response to relative sea-level changes.