Sedimentation in the ephemeral landslide dammed paleolake in Indo-Burmese Range: Late Pleistocene-Holocene climatic variability and surface processes coupling

Abstract

The Late Pleistocene-Holocene marks a sharp transition in climate perturbation affecting landform patterns and depositional sequence in tectonically active regions. We investigate the fluvial landforms and Holocene fluvial-lacustrine sedimentary sequences in an ephemeral landslide-dammed intra-montane paleolake, which acts as an archive for reconstructing extreme events driven surface processes and paleo-climatic history along the Daili-Imphal River in the Indo-Burmese Range. The effect of climate-tectonic coupling on surface processes is explored through quantitative geomorphologic analysis of the landscape and sedimentological proxies, including grain size and shape analysis, geochemistry, and optically stimulated luminescence (OSL) dating of the lacustrine sequence. This analysis helps constrain the climatically sensitive hydrodynamics during the Late Pleistocene-Holocene period. The lack of grain size, geochemical variations in the sediment column, and geochemical affinity with the substrate, the Disang Shale Formation, point towards the dominance of erosion from a proximal sediment source. We argue that the pre-Holocene Bølling-Allerød (12–12.9 ka) climatic extreme caused excessive mass wasting, which blocked the Daili-Imphal River and formed a paleolake, paradoxically resulting in a low sedimentation rate during the early Holocene. The sedimentation rate increased during the Mid-Late Holocene due to local climatic optima. This unique setup highlights the role of local climatic fluctuations on the ephemeral growth of geomorphic and sedimentary archives.