The Quaternary glacial history of the Zanskar Range, north-west Indian Himalaya

Abstract

Three glacial Stages and a minor advance are recognised from the Zanskar range of the north-western Indian Himalaya. A glaciated palaeosurface >280 m above river level (a.r.l.) with associated erratics represents the oldest and most extensive glaciation, the Chandra Stage. This ice covered a landscape of broad, gentle valleys probably as an ice-cap with an erratic distribution indicating that the ice-shed lay to the south over the High Himalaya. A change in valley form from broad glacial troughs to narrow V-shaped gorges along with large subdued moraine ridges delimits a separate later extensive valley glaciation, the Batal Stage, with its maximum at ∼78.0±12.3 ka BP. Distinct sets of moraine ridges represent a less extensive younger glaciation, the Kulti Stage, which dates close to the global Last Glacial Maximum. A minor advance, the Sonapani, is represented by sharp crested moraine ridges within 2 km of current ice bodies, possibly belonging to the Little Ice Age. Glacier Elevation Indexes (GEIs) calculated for this and adjacent areas, show a rise in elevation from the south-west to the north-east, but dip again to the Indus valley for both the Batal and Kulti Stages, reflecting attenuation of the south-westerly monsoon and possible channelling of westerly depressions along the broad upper Indus valley. GEI depression are ∼500 and ∼300 m for the Batal and Kulti Stages, respectively. The change in extent and style from the Chandra Stage to the later glaciations may be related to uplift of more southerly ranges blocking monsoon precipitation and incision of the landscape such that ice reached lower altitudes over shorter horizontal distances. Why ice extent was greater during Oxygen Isotope Stage (OIS) 4 than 2 is not clear, although recent high-resolution plaeomonsoon records show complex peaks in monsoon intensity, and it is possible that there was a more favourable combination of precipitation and temperature earlier rather than later during the last glaciation.