Diachronous Accumulation of Mid-Pleistocene Gravel Beds Driven by Tectonics Across the Tibetan Plateau

Abstract

Deciphering how the widespread late Cenozoic conglomerates were formed across the Tibetan Plateau is crucial for understanding the competition between tectonics and climate. Here we target the mid-Pleistocene conglomerate cap along the northern Saishiteng range (SR), North Tibet. ²⁶Al/¹⁰Be burial dating constrains the onset accumulation of the conglomerate cap to 828 ⁺¹¹⁶/₋₁₀₅ to 679 ^+55.0/_−51.1 kyr ago. Newly-discovered seismites and localized unconformities indicate the mid-Pleistocene growth of the SR, leading to accumulation of the conglomerate cap. Integrating our new observation with previous studies on other gravel beds across the Tibetan Plateau, we reveal diachronous depositional ages of these gravel beds ranging from 1.37 to 0.56 Myr. Given the spatial and temporal distribution patterns of gravel beds, we infer that tectonic uplift primarily governed the accumulation of the low-elevation (<2,400 m) gravel beds, whereas the interplay between tectonics and climate change shaped most high-elevation (>2,400 m) gravel beds across the plateau.