Geomorphological and chronological evidence of middle to Late Pleistocene glaciation in the Chaka North Mountains, northeastern Qinghai-Tibet Plateau

The northeastern Qinghai-Tibet Plateau (NQTP) is a region highly sensitive to climate fluctuations. However, detailed evidence regarding the timing and processes of its Quaternary glaciations remains limited in many subregions. Here, we systematically identify, quantify, and date glacial landforms in the Chaka North Mountains using an integrated approach that combines high-resolution remote sensing, digital elevation model (DEM) morphometric analysis, and optically stimulated luminescence (OSL) dating, supplemented by field mapping. Our morphometric results demonstrate that cirques, U-shaped valleys, and distinctive moraine ridges are widely distributed throughout the region, providing evidence of significant Quaternary glacial activity. OSL dating of sediments mantling frontal moraines provides minimum stabilization ages of 111.5 ± 9.3 ka and 110.7 ± 11.2 ka, indicating a major glaciation during the penultimate glacial period (Marine Isotope Stage 6, MIS 6). Additional OSL ages of 112.7 ± 23.6 ka and 74.9 ± 11.5 ka from glacial lacustrine sediments indicate two distinct phases of lacustrine sedimentation: one during MIS 6 and the other during late MIS 5a. These findings suggest that the Chaka North Mountains experienced more extensive glaciation during MIS 6 than during the Last Glacial Maximum (LGM), as reflected by a significantly lower equilibrium line altitude (ELA). Our study provides a foundational chronostratigraphic framework for a key transitional region, offering critical constraints on the spatiotemporal evolution of the Quaternary cryosphere and the drivers of glacial asynchrony in the NQTP. • First OSL chronology for the Chaka North Mountains constrains a major glaciation to MIS 6. • Paleo-ELA reconstruction (∼3174 m) indicates peak glaciation occurred in MIS 6, not the LGM. • Morphometric analysis and sedimentology resolve the tectonic vs. glacial origin of U-shaped valleys.