Geomorphic signature of late Quaternary climate change and tectonic upheaval: Insights from the Pinggu Basin, Beijing

Understanding the relative influence of tectonics and climate on landscape evolution is a fundamental challenge in geomorphology, particularly in tectonically active intraplate regions experiencing significant climatic shifts. This study investigates the Pinggu Basin, located at the transition between the Yanshan Mountains and the North China Plain, to decipher the interplay of these forces in shaping fluvial landscapes during the late Quaternary. Through detailed geomorphological mapping, stratigraphic analysis, and multi-proxy chronological dating (OSL, ¹⁴C, ¹⁰Be-²⁶Al, paleomagnetism), we reconstruct the basin's geomorphic and sedimentary history. Our results reveal a critical, previously undocumented tectonic regime shift around the late Late Pleistocene (∼17 ka), transitioning from a prolonged period of subsidence-dominated deposition (∼141 ka - 17 ka), characterized by > 50 m of alluvial fan-braided river and aeolian sediment accumulation, to a phase of regional uplift promoting sustained fluvial incision. Following this fundamental tectonic reorganization, we demonstrate that the five distinct fluvial river terraces levels (T1-T5) along the Ju River, was primarily paced by Late Pleistocene to Holocene climate variability. Terrace ages correlate strongly with major climate transitions, including MIS 3/4, the Last Glacial-Holocene transition, and subsequent Holocene climatic fluctuations influencing the East Asian Monsoon. This climate-driven formation mechanism, operating within the context of regional uplift that provided the potential for incision, contrasts with previous interpretations emphasizing localized fault control. Furthermore, we reconstruct the evolution of the Ju River system, documenting headward erosion, river capture and at least three major channel migrations, as a response to this combined tectonic and climatic forcing. This study provides critical insights into the complex interplay and hierarchical controls of intraplate tectonics and climate change in shaping continental landscapes, offering a valuable, well-constrained analogue for similar tectonically active, climate-sensitive regions globally.