Climatically- and tectonically-controlled development of the late quaternary alluvial fan in the north piedmont of Zhongtiao Shan (ZTS), north China

Abstract

The evolution of alluvial fans is controlled by the tectonic setting and climatic fluctuations. This study focused on the Lidian alluvial fan in the northern piedmont of Zhongtiao Shan, north China, to study the fluvial responses to paleoenvironmental changes since the late Last Glacial Maximum. In combination with series of accelerator mass spectrometry (AMS) 14C dating data on fan sediments, sedimentary analyses indicated that the primary fan accumulation was controlled by episodic millennium-scale debris and sheet flood flow related aggradation during 13.3–13.0, 12.7–11.3, 6.2–4.5, and 4.5–2.8 cal ka BP. Between the accumulation periods, the fan process was dominated by aeolian paleosol-and-loess sequence development and the reworking of fan clasts. Considering regional hydraulic conditions and sediment flux, we proposed that the millennium-scale episodic debris flow related fan aggradation during 13.3–13.0, 12.7–11.3, and 4.5–2.8 cal ka BP was controlled by high-volume sediment influx of the permafrost and physical weathering during cold events. The millennium-scale sheet flood-dominated fan aggradation event during 6.2–4.5 cal ka BP was related to the abrupt coarsening and high sediment yield forced by tectonic uplift. We also suggest that the scattered distributed channelized floods and debris backfilling sediments within the fine-grain layers indicate that the deposition of irregular fan lobe accumulation coincided with hydraulic shifts over shorter temporal scales.