Cyclic gravity flow deposits constrained by alternating dry/wet climates in a middle‒late Eocene saline lake, Jianghan Basin, Hubei Province, China

Lacustrine sediments serve as valuable archives of extreme events and past environmental changes. However, the formation mechanisms and distribution patterns of gravity flow deposits in inland hypersaline lakes under climatic controls remain underexplored. In the Eocene Jianghan Basin, rhythmic strata influenced by climatic cycles provide a unique opportunity to investigate the relationship between gravity flow deposits and paleoclimate. According to core descriptions, thin section analysis, logging data, and grain size analysis, seven lithofacies and four lithofacies associations related to gravity flow deposits were identified. Frequent turbidity flows, primarily flood-induced gravity flows, are widely distributed in the saline lake. Proximal gravity flow deposits are characterized by thick, massive sandstones with minimal mud debris, occasionally featuring deformed lamination and scoured bases. Distal gravity flow deposits comprise clast-bearing massive sandstones, planar laminated sandstones, and graded siltstones. Paleoclimate analysis, based on trace elements and rock salt thickness, reveals a strong linkage between gravity flow deposits and climatic cycles. Correlations were established by systematically identifying short-term base-level cycles, which were subsequently grouped into medium-term base-level cycles through stacking pattern analysis. Short-term base-level changes, corresponding to stable climatic cycles, are marked by rhythmic salt layers. In contrast, medium-term base-level cycles, controlled by orbital periods, govern the deposition of gravity flow deposits. Under arid climatic conditions, reduced vegetation coverage and pronounced temperature variations lead to intensified erosion and increased suspended particle concentration. The deposition of sandstone layers is more substantial, and the frequency of turbidity flows is significantly higher under arid climatic conditions compared to humid climatic conditions. This research highlights how climatic cycles influence gravity flow deposits in hypersaline lake environments.