Palynofacies analysis for interpreting paleoenvironment and hydrocarbon potential of Triassic–Jurassic strata in the Sichuan Basin, China

The Sichuan Basin is one of the largest petroliferous basins in China. continental fluvial‒lacustrine sediments Upper Triassic Xujiahe Formation and Lower Jurassic Zhenzhuchong yield diverse fossil organisms host most important gas reservoirs basin. However, paleontological implication for paleoenvironment hydrocarbon source less documented. Here, we report, first time this basin, results from palynofacies analyses combined with thermal alteration data Early Mesozoic deposit Qilixia section, northeastern Basin. show that, organic matters are dominated by phytoclasts, abundant palynomorphs a few amorphous (AOMs). Four assemblages were identified, reflecting depositional settings general proximal oxic fluvial‒deltaic environment, two distal–proximal sedimentary cycles. prominent dominance opaque phytoclasts within lower may be related to frequent wildfires across Triassic–Jurassic transition. Palynofacies (especially relative abundance phytoclasts) reflect 405 kyr eccentricity cyclicity pattern. index (TAI), geochemical indicate presence type III kerogen mature post-mature phases, suggesting potential formations This study provides significant implications better understanding variations during transition future exploration area.