Influence of late Quaternary climate change and Neo-tectonic on fluvial aggradation and incision in the Markanda valley, NW Himalaya

Tectonics and surface processes shape the Earth, and the Himalayas are a key region for studying the relationship between fluvial dynamics and active tectonics. Our study focuses on the monsoon-dominated Markanda River Valley, in NW Himalaya, aiming to reveal the river geomorphology and sedimentation history and elucidate the interactions between monsoonal variability and tectonic activity. Through detailed field mapping, sedimentological measurements and Optically Stimulated Luminescence (OSL) dating, we identified at least five major aggradation phases (>45 to 38 ka, >27–23 ka, ∼17–12 ka, 10–5.8 ka and 3.4–3 ka) with intermittent incision phases. These phases are the reflection of the changes in the strength of the Indian Summer Monsoon (ISM), aligning with global climatic events during the Pleistocene-Holocene transition. Geomorphological, sedimentological, and geochronological analyses reveal fan inter-fingering with fluvial facies from > 45 ka to 38 ka, indicating a high-energy environment and strong monsoons. Incision during the Last Glacial Maximum (∼25 ka) reflects weakened ISM, reducing sediment flux, while rapid aggradation (∼17–12 ka, 10–5.8 ka), corresponds to strengthened ISM. We estimate an average uplift rate of 4.4 ± 0.4 mm/year along the HFT over 7 ka and the regional comparisons confirm the climatic coherence. The evidence of HFT reactivation aligns with documented tectonic events, however, ISM fractionations significantly influenced aggradation and incision in the Markanda Valley.