Quaternary glaciation of the Himalayan–Tibetan orogen

Abstract

Glacial geological evidence from throughout the Himalayan-Tibetan orogen is examined to determine the timing and extent of late Quaternary glaciation in this region and its relation to similar changes on a global scale. The evidence summarised here supports the existence of expanded ice caps and extensive valley glacier systems throughout the region during the late Quaternary. However, it cannot yet be determined whether the timing of the extent of maximum glaciation was synchronous throughout the entire region or whether the response was more varied. The lack of organic material needed for radiocarbon dating has hindered past progress in glacial reconstruction; however, application of optically stimulated luminescence and terrestrial cosmogenic radionuclide methods has recently expanded the number of chronologies throughout the region. Limits to the precision and accuracy available with these methods and, more importantly, geological uncertainty imposed by processes of moraine formation and alteration both conspire to limit the time resolution on which correlations can be made to Milankovitch timescales (several ka). In order to put all studies on a common scale, well-dated sites have been re-evaluated and all the published terrestrial cosmogenic nuclide ages for moraine boulders and glacially eroded surfaces in the Himalayan-Tibetan orogen have been recalculated. Locally detailed studies indicate that there are considerable variations in the extent of glaciation from one region to the next during a glaciation. Glaciers throughout monsoon-influenced Tibet, the Himalaya and the Transhimalaya are likely synchronous both with climate change resulting from oscillations in the South Asian monsoon and with Northern Hemisphere cooling cycles. In contrast, glaciers in Pamir in the far western regions of the Himalayan-Tibet orogen advanced asynchronously relative to the other regions that are monsooninfluenced regions and appear to be mainly in phase with the Northern Hemisphere cooling cycles. Broad patterns of local and regional variability based on equilibrium-line altitudes have yet to be fully assessed, but have the potential to help define changes in climatic gradients over time.

Late Quaternary paleoclimatic and geomorphological evolution at the interface between the Menyuan basin and the Qilian Mountains, northeastern Tibetan Plateau

“…Any MIS 3 advance in the Qilian Mountains must have been smaller than the LGM advance. This chronology differs from that of the southern Tibetan Plateau as established by Owen et al (2008) in that there the LGM advances were smaller than the MIS 3 advances.…”

“…A glacial advance during the MIS3 when Asian monsoon enhanced in the southern Tibetan Plateau has been considered as the response to changes in insolation-controlled monsoon precipitation (Owen et al, 2008;Owen, 2009). But glaciers advanced extensively in the southern Qilian Mountains at~21 ka, at the same time as in the northern hemisphere including the eastern Tibetan Plateau, reaching their maximum extent since the late Pleistocene (Ou et al, 2012).…”

Rates of river incision across the main tectonic units of the Pamir identified using optically stimulated luminescence dating of fluvial terraces

“…Cosmogenic nuclide dating of the moraine yielded two age clusters of 136 -93 kyr and 86 -60 kyr (Zech et al, 2005a;Abramowski et al, 2006;Röhringer et al, 2012). The oldest glacial moraine from the Lake Yashilkul, the Southern Alichur Range and the Ailuitek Pass indicates the presence of paleo-glaciers down to the intra-plateau valley floors at ∼3600 m a.s.l.. Hummocky moraines accompanied by two lateral moraine ridges indicate a glacial advance during MIS 3, which is synchronous with an increased influence of the ISM (Zech et al, 2005a;Röhringer et al, 2012) as reported from the Hindu Kush, Karakoram Range and Tibet (e.g., Owen et al, 2002bOwen et al, ,a, 2008Owen et al, , 2012. Additional scattered younger ages are interpreted as prolonged ice degradation and/or glacial recession (Zech et al, 2005b).…”

“…2), indicating the dominance of the Westerlies (Abramowski et al, 2006;Owen et al, 2008). Progressively less extensive advances suggest links to an increasing aridity throughout the Late Quaternary in Central Asia due to a strengthened Siberian High (Abramowski et al, 2006).…”

Landscape evolution of a bedrock peneplain on the southern Tibetan Plateau revealed by in situ-produced cosmogenic 10Be and 21Ne

“…In summary, the discussion above reveals that the most significant uncertainty associated with the 10 Be denudation rates of this study is the uncertainty introduced by the scaling model that is used to calculate the local nuclide production rates. This important point has also been highlighted by Owen et al (2008) and Chevalier et al (2011) and emphasizes the urgent need for a production rate calibration site at high elevation of ~5 km -ideally such a site should be located on the Tibetan Plateau.…”