Quaternary glaciation of the Himalaya and Tibet
Shortcut URL: https://serc.carleton.edu/60233
Location
Continent: Asia
Country: Pakistan, India, Nepal and China
State/Province:N/A
City/Town: N/A
UTM coordinates and datum: none
Setting
Climate Setting: Tropical
Tectonic setting: Continental Collision Margin
Type: Stratigraphy, Chronology
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Description
The mountains of the Himalaya and Tibet are the most glaciated regions outside of the polar realm. The countries within and bordering the Himalaya and Tibet depend greatly on the glacial and associated hydrological systems that provide much of the water to these regions. Future natural and/or human-induced changes in these glacial and hydrological systems will profoundly effect the people and economies of these counties. Study of the Quaternary glacial geological record in the Himalaya and on the Tibetan Plateau can be used to reconstruct the effects of environmental change on the regional climate and hydrology. As such, interest and study of the Quaternary glacial geologic record of the region has increased in recent years.
Yet, despite the importance of determining the past extent and timing of glaciation and the associated hydrological and climatic responses in the Himalaya and Tibet, glacial geologic studies are still in their infancy. This is partially due to the logistical and political inaccessibility of the region, but also because accurate reconstructions of former ice extent have been hindered by the difficulty of mapping glacial landforms. Reconstructing the timing of glaciation has been difficult because of the lack of organic material for radiocarbon dating (the most common dating method used for glacial successions) throughout the region. Radiocarbon dating has been undertaken, but the dating has been generally limited to the wetter parts of the Himalayan–Tibetan region, and is mostly are restricted to dating Holocene (<11,600 years to present) sediments and landforms. Moreover, most of the dated landforms poorly define the timing of glaciation.
Newly developing dating techniques that include optically stimulated luminescence (OSL) and terrestrial cosmogenic nuclide (TCN) surface exposure dating, however, are now allowing glacial successions throughout Tibet and the bordering mountains to be dated and correlated.
OSL dating is used to date sediment and it determines the time elapsed since a sediment sample was exposed to daylight. This method has been proven successful in many areas. OSL dating relies on the acquired luminescence signal within mineral that is produced by ionizing radiation due to radioactive elements in the ground. The acquired luminescence signal is produced and measured by exposing the buried sample to light in an OSL reader in the laboratory. Ages can be determined from <100 yrs to >100,000 years, with errors as low as 5%.
TCN dating is used to date moraine boulders and glacially eroded surfaces. TCNs are produced by the interaction of cosmic ray particles (mostly neutrons at Earth's surface) with minerals in rock and/or sediment at Earth's surface. The concentration of TCNs increases with time in an exposed surface. Notable TCNs include Be-10, C-14, Al-26 and Cl-36. The rate of production for a particular TCN depends on latitude and altitude, but when accurately determined the TCN concentration in a rock or sediment surface provides an estimate of the time that surface has been exposed to cosmic rays. Both OSL and TCN dating have their associated errors, but when used in combination can accurately help to define the ages of glacial landforms. This has been done successfully around Mount Everest, and in the Hunza Valley and around K2 in Northern Pakistan.
These recent studies have provided new insights into the nature of latest Pleistocene (~70,000-11,600 years ago) and Holocene (last 11,600 years) glacier oscillations. They provide abundant evidence for significant glacial advances throughout the last glacial (~ the last hundred thousand years). In most high Himalayan and Tibetan regions, glaciers reached their maximum extent early in the last glacial, significantly before the Northern Hemisphere ice sheets reached their maximum extent (at time known as the Last Glacial Maximum at about 20,000 years ago). However, glaciers did advance in some areas of the high Himalaya and Tibet during the Last Glacial Maximum, but their advances were significantly less extensive than earlier in the last glacial cycle. Other notable glacier advances occurred during the Late Glacial (~15,000 – 13,000 years ago) and the early Holocene (~ 11,000 - 9,000 years ago), with minor advances in some regions during the mid-Holocene (~ 5,000 – 3,000 years ago). There is abundant evidence for multiple glacial advances throughout the latter part of the Holocene (last thousand years ago), although these are generally very poorly defined, and were less extensive than the early Holocene glacier advances.
The poor dating control on glacial successions makes it difficult to construct correlations across the region, and with other glaciated regions in the world. This makes it hard to assess the relative importance of the different climatic mechanisms that force glaciation in this region, which are needed to help predict future changes. The Lateglacial and Holocene glacial record is particularly well preserved in several regions, notably in the Mount Everest region. Despite these problems, a picture of the timing and extent of Himalayan and Tibetan glaciation is beginning to emerge, and there is hope that detailed reconstructions of glaciation may be established throughout the region in the coming years (Fig. 1). The Everest region is one particular notable area where well-defined glacial advances have been determined for the latter part of the last glacial and Holocene (Figs. 2 and 3).
These glacial geologic studies are beginning to shed light on the complex interaction between climate, glaciation and hydrology in the Himalaya and Tibet. The glacial geologic record is also being used to help test tectonic–climatic–geomorphological theories and models.
Yet, despite the importance of determining the past extent and timing of glaciation and the associated hydrological and climatic responses in the Himalaya and Tibet, glacial geologic studies are still in their infancy. This is partially due to the logistical and political inaccessibility of the region, but also because accurate reconstructions of former ice extent have been hindered by the difficulty of mapping glacial landforms. Reconstructing the timing of glaciation has been difficult because of the lack of organic material for radiocarbon dating (the most common dating method used for glacial successions) throughout the region. Radiocarbon dating has been undertaken, but the dating has been generally limited to the wetter parts of the Himalayan–Tibetan region, and is mostly are restricted to dating Holocene (<11,600 years to present) sediments and landforms. Moreover, most of the dated landforms poorly define the timing of glaciation.
Newly developing dating techniques that include optically stimulated luminescence (OSL) and terrestrial cosmogenic nuclide (TCN) surface exposure dating, however, are now allowing glacial successions throughout Tibet and the bordering mountains to be dated and correlated.
OSL dating is used to date sediment and it determines the time elapsed since a sediment sample was exposed to daylight. This method has been proven successful in many areas. OSL dating relies on the acquired luminescence signal within mineral that is produced by ionizing radiation due to radioactive elements in the ground. The acquired luminescence signal is produced and measured by exposing the buried sample to light in an OSL reader in the laboratory. Ages can be determined from <100 yrs to >100,000 years, with errors as low as 5%.
TCN dating is used to date moraine boulders and glacially eroded surfaces. TCNs are produced by the interaction of cosmic ray particles (mostly neutrons at Earth's surface) with minerals in rock and/or sediment at Earth's surface. The concentration of TCNs increases with time in an exposed surface. Notable TCNs include Be-10, C-14, Al-26 and Cl-36. The rate of production for a particular TCN depends on latitude and altitude, but when accurately determined the TCN concentration in a rock or sediment surface provides an estimate of the time that surface has been exposed to cosmic rays. Both OSL and TCN dating have their associated errors, but when used in combination can accurately help to define the ages of glacial landforms. This has been done successfully around Mount Everest, and in the Hunza Valley and around K2 in Northern Pakistan.
These recent studies have provided new insights into the nature of latest Pleistocene (~70,000-11,600 years ago) and Holocene (last 11,600 years) glacier oscillations. They provide abundant evidence for significant glacial advances throughout the last glacial (~ the last hundred thousand years). In most high Himalayan and Tibetan regions, glaciers reached their maximum extent early in the last glacial, significantly before the Northern Hemisphere ice sheets reached their maximum extent (at time known as the Last Glacial Maximum at about 20,000 years ago). However, glaciers did advance in some areas of the high Himalaya and Tibet during the Last Glacial Maximum, but their advances were significantly less extensive than earlier in the last glacial cycle. Other notable glacier advances occurred during the Late Glacial (~15,000 – 13,000 years ago) and the early Holocene (~ 11,000 - 9,000 years ago), with minor advances in some regions during the mid-Holocene (~ 5,000 – 3,000 years ago). There is abundant evidence for multiple glacial advances throughout the latter part of the Holocene (last thousand years ago), although these are generally very poorly defined, and were less extensive than the early Holocene glacier advances.
The poor dating control on glacial successions makes it difficult to construct correlations across the region, and with other glaciated regions in the world. This makes it hard to assess the relative importance of the different climatic mechanisms that force glaciation in this region, which are needed to help predict future changes. The Lateglacial and Holocene glacial record is particularly well preserved in several regions, notably in the Mount Everest region. Despite these problems, a picture of the timing and extent of Himalayan and Tibetan glaciation is beginning to emerge, and there is hope that detailed reconstructions of glaciation may be established throughout the region in the coming years (Fig. 1). The Everest region is one particular notable area where well-defined glacial advances have been determined for the latter part of the last glacial and Holocene (Figs. 2 and 3).
These glacial geologic studies are beginning to shed light on the complex interaction between climate, glaciation and hydrology in the Himalaya and Tibet. The glacial geologic record is also being used to help test tectonic–climatic–geomorphological theories and models.
Associated References
- Owen, L.A., Caffee, M.W., Finkel, R.C. and Seong, B.Y., 2008. Quaternary glaciations of the Himalayan-Tibetan orogen. Journal of Quaternary Science. 23, 513-532.
- Owen, L.A., 2009. Latest Pleistocene and Holocene glacier fluctuations in the Himalaya and Tibet. Quaternary Science Reviews, 28, 2150-2164.
- Owen, L.A., 2010. Landscape development of the Himalayan-Tibetan orogen: a review. Special Publication of the Geological Society of London, 338, 389-407.
- Owen, L.A., Robinson, R., Benn, D.I., Finkel, R.C., Davis, N.K.*, Yi, C., Putkonen, J., Li, D. and Murray, A.S., 2009. Quaternary glaciation of Mount Everest. Quaternary Science Reviews, 28, 1412-1433.