Formation and evolution of the Erlangjian lacustrine spit in Qinghai Lake, northeastern Qinghai–Tibetan Plateau

Abstract Lacustrine spits are one of the important hydrocarbon reservoir types, yet their formation mechanisms remain poorly understood, which has constrained further oil and gas exploration and development. This study aims to elucidate their formative processes and sedimentary evolution through investigations of modern lacustrine spits. The Erlangjian (Elj) spit at Qinghai Lake, located on the northeastern Qinghai–Tibetan Plateau, initially formed 2,370 yr BP and has continuously evolved to the present day. This spit serves as an ideal model for reconstructing the evolutionary history of lacustrine spits and understanding associated sediment transport. This study employs ground-penetrating-radar surveys, historical satellite images, and contemporary beach observations to investigate the formation and evolution of the lacustrine spit. Results indicate that lake-level variations control periodic changes in sediment supply and accommodation space, which strongly influence spit formation. Lateral accretion of the spit occurs due to the welding of sandbars during a low lake-level stage. As the lake level rises, large-scale recurved ridges develop on the low-stand-generated swash bars, resulting in vertical spit accretion. Sediments are sourced primarily from the southern proximal alluvial fan and are transported alongshore by wind-driven waves and currents. Additionally, changes in topography alter hydrodynamic conditions on the landward side of the spit, which in turn reshape the original spit. Thus, cyclical lake-level fluctuations are critical to the growth and complex architecture of spits in Qinghai Lake. This study contributes to a more comprehensive understanding of sedimentary evolution and sediment transport mechanisms for lacustrine spits.