Paleoglaciology of the Dalijia Shan, northeastern Tibetan Plateau
Abstract
Understanding past variations in the extent of glaciers is important for reconstructing past climates and predicting future climate change, and mountain glaciers provide a particularly sensitivity record of paleoclimate. Investigating the paleoglacial history of the Dalijia Shan, a small mountain range on the northeastern margin of the Tibetan Plateau, is important both regionally and as a contribution to the growing knowledge of paleoglaciation on the Tibetan Plateau; the Dalijia Shan is one of the northeasternmost mountain ranges of the Tibetan Plateau that has a glacial record and it is located near the transition zone between the two major climate systems influencing the Plateau. A variety of techniques are used here to investigate the record of paleoglaciation of the Dalijia Shan: (1) glacial landform mapping from a combination of remote sensing imagery (Digital Elevation Models, Landsat 7 ETM+ satellite imagery, and Google Earth™), (2) calculating valley morphometry to determine valley type (fluvial or glacial), and (3) 10Be terrestrial cosmogenic nuclide (TCN) exposure age dating to determine the timing of glacial events. Paleoglaciation in the Dalijia Shan was relatively limited in extent. Most of the glacial landforms (moraines and "U-shaped" valleys) are located around Dalijia Peak, covering ∼1.3% of the study area (10,730 km2). Quantifying valley morphometry confirms the classification of "U-shaped" versus "V-shaped" valleys in this region. The extent of glaciation in valleys that have experienced both glacial and fluvial erosion is identified from the exponent values of the power law function, confirming the mapping results. Four glacial events are identified based on the TCN ages from moraines within the Deheisui Valley: ∼38.6 +32.4/-6.85 ka (MIS3), ∼23.5 +3.38/-1.43 ka to 21.8 +3.24/-1.42 ka (MIS2), ∼17.3 +1.05/-0.61 ka (MIS2), and ∼11.7 +0.24/-0.22 ka (Younger Dryas). Based on the locations of the associated moraines, glaciation appears to have been more extensive during the MIS3 event, which is similar to observations made in western, central, and southern regions of the Tibetan Plateau and less extensive during the global Last Glacial Maximum (MIS2). This study provides insights on the influence of climate systems and the timing of paleo-glaciations along the northeastern margin of the Tibetan Plateau, as it shows that the glacial chronology of this region is consistent with that of other regions on the Plateau and is asynchronous with the Northern Hemisphere ice sheets during the Late Quaternary.
Degree
M.S.
Advisors
Harbor, Purdue University.
Subject Area
Geomorphology
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