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Provenance Analysis of Neogene Guantao Formation in Bodong Sag, Bohai Bay Basin, Eastern China: Implicaitons for Sediment Routing

Abstract

The Bohai Bay Basin (BBB) is one of the most petroliferous basins in China, accounting for nearly one third of the total oil production of the country. This study focuses on the Neogene Guantao Formation in Bodong Sag where sediment source areas and the sediment-routing history are pivotal factors controlling oil and gas reservoir distribution and quality. Long-standing interpretations have concluded that the primary siliciclastic sediment inputs to the Bodong Sag were sourced from the Jiao-Liao-Ji belt (including Jiaodong Uplift and Liaodong Uplift) through fluvial systems without accurate provenance analysis. Here we perform an integrated detrital zircon geochronologic and petrographic analysis of the Guantao strata to investigate the evolution of Guantao Formation provenance and the sediment-routing history in Bodong Sag, BBB. Guantao strata include grain age populations from Yanshanian granite (140-100 Ma), the late Jurassic (160-150 Ma), the early Jurassic (180-170 Ma), and Indo-China period provinces (270-200 Ma), with minor contributions from Paleoproterozoic (2500-1600Ma), and Archean (>2.5 Ga) provinces. Zircon core-rim ages and petrographic characteristics combined with drainage networks and relict paleogeomorphology analysis suggest significant siliciclastic sediment delivery from Liaodong Uplift to the northern part of Bodong Sag and Jiaodong Uplift to the southern part of Bodong Sag. However, the data from the central part of Bodong Sag indicate siliciclastic sediment delivery from both Liaodong Uplift and Jiaodong Uplift. Therefore, we find a characteristic age signature represented a reference for distinguishing the dominated sediment source areas in double-source areas, which suggests that Liaodong Uplift source areas are more important to sediment delivery during the early sedimentary period of Guantao Formation than previously thought. Knowledge of Jiao-Liao-Ji belt source area for the siliciclastic sediment filling the Bodong sag during Guantao Formation contributes to our understanding of depositional evolution and the sediment-routing history from mountainous source areas to depositional sinks during Neogene time in the Bodong sag. To sum up, this study will extend our knowledge about a more accurate prediction of reservoir quality in this type of system by understanding the sediment routing.