Evolution of Lamayuru palaeolake in the Trans Himalaya: Palaeoecological implications

Abstract

About 35,000-40,000 yr BP, an episode o f neotectonicactivity on the Indus Suture Zone created a lakeat Lamayuru (Ladakh) that has preserved an over105 m thick sequence of fluvio-lacustrine deposits. Thelacustrine horizons (carbonaceous muds) and a numberof carbonate-rich strata interlayered with clay/silt/sand have yielded freshwater ostracods, gastropodsand charophytes. A total of nine fossiliferous horizonsare located. The prominent ostracod taxa are llyocypris(I. gibba and /. bradyi), Eucypris and Candona. Thegastropods are dominated by Lymnaea, Succinea andGyraulus. The charophytes can be identified as Charaglobularis. The palaeoecological interpretation isbased on the characteristic faunal and floral content andthe nature of deposits. It is suggested that the lake,throughout its existence, was shallow with cold, extremelylow salinity and slow flowing plant-rich waters. Asan open basin, it may have had continuous outflow duringits existence. The depletion of the lake was causedby structural disruption of the lake floor and by depositionof a huge mass of debris flow, triggered by a furtherpulse of tectonic instability in the Late Holocene.