太阳集团网tyc9728(百度)有限公司

Lacustrine organic matter (OM) accumulation is a critical Earth's carbon sink and a source of hydrocarbon resources. The Upper Cretaceous Qingshankou Formation in the Songliao Basin archives an organic-rich sedimentation alongside paleoclimatic fluctuations, yet the mechanistic links between climate and OM enrichment remain unclear. Previous single-well studies are contentious and insufficient to unravel the complex, coupled sedimentary environmental feedbacks at the depression scale. This investigation integrates organic petrology and geochemical analyses of 24 core samples from the first (K2qn1) and second (K2qn2) members in the Central Depression, complemented by published data from 33 wells. Paleoclimate proxies reveal a climatic transition from the relatively humid K2qn1 interval to arid K2qn2 interval. This shift reconfigured the depositional system, altering terrestrial input, sedimentation rates, redox conditions, salinity, OM sources, and productivity. Crucially, it drove a fundamental OM accumulation change: high productivity in the relatively humid K2qn1 interval was offset by oxygenated waters conditions that limited preservation, whereas the arid K2qn2 interval, despite lower productivity, developed strong salinity stratification and benthic anoxia that dramatically enhanced OM preservation. Therefore, a climate-driven OM-preservation model for the study area was proposed, where aridity-controlled enhancement of water-column stratification and redox conditions dominated OM accumulation, overriding the productivity increases associated with relatively humid conditions. This model provides a new framework for understanding the formation of organic-rich lacustrine source rocks.