Browsing by Author "Ding, L"

Now showing 1 - 4 of 4
  • No Thumbnail Available
    Item
    Cosmogenic 10Be inferred lake-level changes in Sumxi Co basin, Western Tibet
    (Elsevier, 2007-03-01) Kong, P; Na, C; Fink, D; Huang, F; Ding, L
    Most Tibetan lakes are surrounded by conspicuous regressive shorelines attesting to high-water levels in the past. Concentrations of the in situ produced cosmogenic radionuclide Be-10 in bedrock from the three highest terraces surrounding Sumxi Co, situated in Western Kunlun, indicate that the highest lake-level appeared before 10,000-11,500 yr, and most likely between 11,000 and 12,800 yr. Younger ages for the two lower terraces imply regression of Sumxi Co during the early-mid Holocene. The concurrency of the highest lake-level with orbitally induced maximum northern hemisphere summer insolation suggests that the increase in water supply to Sumxi Co was most likely associated with increased recharge from melting glaciers. We conclude that the enhanced Indian monsoon during the early Holocene did not penetrate the Tibetan plateau and affect the northwestern part of Tibet significantly. © 2006, Elsevier Ltd.
  • No Thumbnail Available
    Item
    Erosion in northwest Tibet from in-situ-produced cosmogenic 10Be and 26Al in bedrock
    (Wiley, 2007-01) Kong, P; Na, C; Fink, D; Ding, L; Huang, F
    Concentrations of in-situ-produced cosmogenic nuclides 10Be and 26Al in quartz were measured by accelerator mass spectrometry for bedrock basalts and sandstones located in northwest Tibet. The effective exposure ages range between 23 and 134 ka (10Be) and erosion rates between 4·0 and 24 mm ka−1. The erosion rates are significantly higher than those in similarly arid Antarctica and Australia, ranging between 0·1 and 1 mm ka−1, suggesting that precipitation is not the major control of erosion of landforms. Comparison of erosion rates in arid regions with contrasting tectonic activities suggests that tectonic activity plays a more important role in controlling long-term erosion rates. The obtained erosion rates are, however, significantly lower than the denudation rate of 3000–6000 mm ka−1 beginning at c. 5-3 Ma in the nearby Godwin Austen (K2) determined by apatite fission-track thermochronology. It appears that the difference in erosion rates within different time intervals is indicative of increased tectonic activity at c. 5–3 Ma in northwest Tibet. We explain the low erosion rates determined in this study as reflecting reduced tectonic activity in the last million years. A model of localized thinning of the mantle beneath northwest Tibet may account for the sudden increased tectonic activity at c. 5–3 Ma and the later decrease. Copyright © 2006 John Wiley & Sons, Ltd.
  • No Thumbnail Available
    Item
    Erosion in northwest Tibet from in-situ-produced cosmogenic Be-10 and Al-26 in bedrock
    (John Wiley & Sons, 2007-01) Kong, P; Na, CG; Fink, D; Ding, L; Huang, FX
    Concentrations of in-situ-produced cosmogenic nuclides Be-10 and Al-26 in quartz were measured by accelerator mass spectrometry for bedrock basalts and sandstones located in northwest Tibet. The effective exposure ages range between 23 and 134 ka (Be-10) and erosion rates between 4.0 and 24 mm ka(-1). The erosion rates are significantly higher than those in similarly and Antarctica and Australia, ranging between 0.1 and 1 mm ka(-1), suggesting that precipitation is not the major control of erosion of landforms. Comparison of erosion rates in and regions with contrasting tectonic activities suggests that tectonic activity plays a more important role in controlling long-term erosion rates. The obtained erosion rates are, however, significantly lower than the denudation rate of 3000-6000 mm ka(-1) beginning at c. 53 Ma in the nearby Godwin Austen (K2) determined by apatite fission-track thermochronology. It appears that the difference in erosion rates within different time intervals is indicative of increased tectonic activity at c. 5-3 Ma in northwest Tibet. We explain the low erosion rates determined in this study as reflecting reduced tectonic activity in the last million years. A model of localized thinning of the mantle beneath northwest Tibet may account for the sudden increased tectonic activity at c. 5-3 Ma and the later decrease. © 2006, John Wiley & Sons Ltd.
  • No Thumbnail Available
    Item
    Late miocene ice sheet elevation in the Grove Mountains, East Antarctica, inferred from cosmogenic Ne-21-Be-10-Al-26
    (Elsevier, 2010-05) Kong, P; Huang, FX; Liu, XH; Fink, D; Ding, L; Lai, QZ
    The Grove Mountains, lying in the interior of East Antarctica, consist of 64 nunataks. Geomorphic characteristics of the nunataks suggest that past ice sheet elevations have overtopped the summits of the Grove Mountains. Cosmogenic 21Ne, 10Be and 26Al dating yields surface exposure ages of five bedrock samples taken from the crest of Mount Harding, a typical nunatak in the Grove Mountains. Using multi-nuclide fitting, we have calculated the time that the ice sheet retreated below the crest of Mount Harding; all data point to the late Miocene, ~ 6.3 Ma ago. The results provide the first land-based evidence of the elevation of the East Antarctic Ice Sheet in the Grove Mountains in Late Miocene, which reached 2300 m, 200 m higher than the current ice sheet level. The higher than current ice sheet elevations during the late Miocene together with contemporaneously higher temperatures in the Southern Ocean suggest that moisture transport plays an important role in ice sheet expansion in the interior of East Antarctica. © 2010, Elsevier Ltd.