Integrated Mineral Magnetic and Lithologic Studies to Delineate Dynamic Modes of Depositional Conditions in the Leh Valley Basin, Ladakh Himalaya, India

Abstract

We present here lithofacies and mineral magnetic results from a ~50 m thick composite record of fluvial, lacustrine and aeolian facies within the Leh valley basin of Indus River in Ladakh Himalaya. Mineral magnetic studies decipher interplay of two contrasting sediment sources viz., the unimodal ferrimagnetic source derived from Ladakh batholithic glacial domain and mixed ferri- to antiferromagnetic source derived from Indus sedimentary sequence. The lithofacies variability expresses dynamic changes in the depositional regimes controlled by base level fluctuations that are governed by the interaction of basin fill conditions and the response to Late Quaternary climatic perturbations. A three stage evolution of the Leh valley basin is proposed after comparison to other characteristic lithofacies changes within the valley as: (I) the basin under-fill conditions marked by fluvial and fluvio-lacustrine phase till ~24m (~64 Ka OSL age) above modern base level followed by (II) predominantly varved, glacio-lacustrine, basin overfill phase till 38m (~28 Ka) gradually passing into an aeolian phase; and (III) basin incision that began at the earliest Holocene warming. Advancement and retreat of glaciers from the transverse valleys, attributed to climatic oscillations, appears to have greatly controlled the basin-fill conditions in the Leh valley. The present approach demonstrates its larger scope in recording the Late Quaternary response of individual valley basins to delineate local and regional attributes of climate change in the Himalayan and Karakoram region.

Late Quaternary Palaeoclimate and Contemporary Moisture Source to Extreme NW India: A Review on Present Understanding and Future Perspectives

“…Similarly, the three other age brackets using OSL/IRSL technique are ∼72 to ∼32 ka (Sangode et al, 2013), ∼177 to ∼72 ka (Blöthe et al, 2014) and 78.8-46.7 ka (Figure 6) (Mujtaba et al, 2017;Lal et al, 2018) showing considerable variation beyond the error range. The discrepancy observed in ages indicates that more work is required to address this issue, at least for regions like Himalaya or similar orogen.…”

“…In our endeavor to revisit the palaeolake deposits of Spituk area near Leh city in Ladakh, the 14 C AMS dates that we have received are much younger (Phartiyal et al, 2013) than the one we have analyzed by the conventional 14 C dating techniques of the same sequence (Phartiyal et al, 2005). Optical ages from this sequence have yielded age estimates that are similar or older than conventional radiocarbon ages (Sangode et al, 2013;Blöthe et al, 2014;Lal et al, 2018) as shown in Figure 6.…”

“…• E) exposed on the right bank of the Indus river. Several workers study this sedimentary sequence and have given the chronology for the same sequence (Phartiyal et al, 2005(Phartiyal et al, , 2013Sangode et al, 2013;Blöthe et al, 2014;Mujtaba et al, 2017;Lal et al, 2018) (Figure 6). So far as the sediment facies present in the entire >50 m sequence is concerned, there is a fairly good understanding among the authors that how incision followed by the fluvial aggradation and subsequent lacustrine facie deposition took place in the Spituk locality, however, the chronology is disturbed.…”

“…Altogether three dating techniques were applied for establishing the chronology of the Spituk section, i.e., conventional 14 C radiometric and AMS dating by Phartiyal et al (2005Phartiyal et al ( , 2013, respectively. All other authors used the OSL/IRSL technique to date this sequence (Sangode et al, 2013;Blöthe et al, 2014;Mujtaba et al, 2017;Lal et al, 2018). The conventional 14 C radiometric date bracketed between ∼50 and ∼30 ka.…”

Sedimentary characteristics of palaeolake deposits along the Indus River valley, Ladakh, Trans‐Himalaya: Implications for the depositional environment

“…Tibetan lakes have experienced significant changes in water level since the LGM (Gasse et al ., ), inferred mainly from lacustrine sediment records (Gasse et al ., , ; van Campo & Gasse, ; Gu et al ., ; Wei & Gasse, ; Wu et al ., ; Mügler et al ., ) and the chronostratigraphy of lake terraces (Long et al ., ). This suggestion is supported by field surveys which show that many Tibetan lakes are surrounded by multiple palaeo‐shorelines (Zhao et al ., ; Zheng et al ., ; Lee et al ., ; Kong et al ., ) and stacks of lacustrine deposits along the river valleys (Sangode et al ., , ; Phartiyal et al ., , ; Blöthe et al ., ; Nag & Phartiyal, ). These shorelines and the palaeo‐lacustrine deposits provide information on the timing and volume of former high lake levels, as well as the ancient/past lake extent and environment.…”