Terrestrial cosmogenic nuclide surface exposure dating of the oldest glacial successions in the Himalayan orogen: Ladakh Range, northern India

Abstract

Terrestrial cosmogenic nuclide surface exposure dating of moraine boulders and alluvial fan sediments defi ne the timing of fi ve glacial advances over at least the last fi ve glacial cycles in the Ladakh Range of the Transhimalaya. The glacial stages that have been identifi ed are: the Indus Valley glacial stage, dated at older than 430 ka; the Leh glacial stage occurring in the penultimate glacial cycle or older; the Kar glacial stage, occurring during the early part of the last glacial cycle; the Bazgo glacial stage, at its maximum during the middle of the last glacial cycle; and the early Holocene Khalling glacial stage. The exposure ages of the Indus Valley moraines are the oldest observed to date throughout the Himalayan orogen. We observe a pattern of progressively more restricted glaciation during the last fi ve glacial cycles, likely indicating a progressive reduction in the moisture supply necessary to sustain glaciation. A possible explanation is that uplift of Himalayan ranges to the south and/or of the Karakoram Mountains to the west of the region may have effectively blocked moisture supply by the south Asian summer monsoon and mid-latitude westerlies, respectively. Alternatively, this pattern of glaciation may refl ect a trend of progressively less extensive glaciation in mountain regions that has been observed globally throughout the Pleistocene.

Can glacial erosion limit the extent of glaciation?

“…The trend has been documented also on other continents (e.g., Kaufman et al, 2004;Owen et al, 2005Owen et al, , 2006. Owen et al (2006) described the pattern in the Himalaya and invoked decreased moisture flux into the region as the mountains have uplifted.…”

“…Owen et al (2006) described the pattern in the Himalaya and invoked decreased moisture flux into the region as the mountains have uplifted. On the other hand, they recognized that similarities may exist between the Himalayan record and an apparent global trend.…”

Quaternary glaciation of the Himalayan–Tibetan orogen

“…Defining the ages of landforms and sediments throughout much of the HimalayanTibetan orogen has been particularly difficult because of the Shiraiwa, 1993;Sharma and Owen, 1996;Phillips et al, 2000;Richards et al, 2000a,b;Owen et al, 2001Owen et al, , 2002aOwen et al, ,b, 2003aOwen et al, ,b,c, 2005Owen et al, , 2006aSchäfer et al, 2002;Tsukamoto et al, 2002;Yi et al, 2002;Finkel et al, 2003;Zech et al, 2003Zech et al, , 2005Barnard et al, 2004aBarnard et al, ,b, 2006aMeriaux et al, 2004;Spencer and Owen, 2004;Chevalier et al, 2005;Abramowski et al, 2006;Colgan et al, 2006;Seong et al, 2007Seong et al, , 2008a. The red dots in part (A) highlight regions where TCN surface exposure dating has been undertaken.…”

“…The possibility of numerous glacier advances also complicates correlations between regions based on TCN dating, especially because the TCN dating method is relatively imprecise ($8% systematic error; Balco et al, 2008). A detailed interpretation of the interregional variability therefore requires more comprehensive Owen et al, 2001Owen et al, , 2002aOwen et al, ,c, 2003aOwen et al, ,b,c, 2005Owen et al, , 2006aSchäfer et al, 2002;Finkel et al, 2003;Zech et al, 2003Zech et al, , 2005Barnard et al, 2004aBarnard et al, ,b, 2006aMeriaux et al, 2004;Chevalier et al, 2005;Abramowski et al, 2006;Colgan et al, 2006;Seong et al, 2007Seong et al, , 2008a. The number of samples used to produce each probability plot is indicated by 'n' All data 20 30 40 50 60 70 80 90 100 110 120 20 30 40 50 60 70 80 90 100 110 120 20 30 40 50 60 70 80 90 100 110 120 20 30 40 50 60 70 80 90 100 110 Figure 9 Probability density functions of TCN 10 Be ages for all published data from the Himalayan-Tibetan orogen plotted for each major climatic region.…”

“…The number of samples used to produce each probability plot is indicated by 'n' All data 20 30 40 50 60 70 80 90 100 110 120 20 30 40 50 60 70 80 90 100 110 120 20 30 40 50 60 70 80 90 100 110 120 20 30 40 50 60 70 80 90 100 110 Figure 9 Probability density functions of TCN 10 Be ages for all published data from the Himalayan-Tibetan orogen plotted for each major climatic region. (A) All published data; (B) MIS 1 and MIS 2; and (C) MIS 3 to MIS 5e (data from Phillips et al, 2000;Owen et al, 2001Owen et al, , 2002aOwen et al, ,b, 2003aOwen et al, ,b,c, 2005Owen et al, , 2006aSchäfer et al, 2002;Finkel et al, 2003;Zech et al, 2003Zech et al, , 2005Barnard et al, 2004aBarnard et al, ,b, 2006aMeriaux et al, 2004;Chevalier et al, 2005;Abramowski et al, 2006;Colgan et al, 2006;Seong et al, 2007Seong et al, , 2008a. The number of samples used to produce each probability plot is indicated by 'n' in the order of the regions shown in the legend of part (A).…”