Browsing by Author "Ju, YT"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Fluctuation history of the interior East Antarctic ice sheet since mid-pliocene
    (Cambridge University Press, 2008-04) Huang, FX; Liu, XH; Kong, P; Fink, D; Ju, YT; Fang, AM; Yu, LJ; Li, XL; Na, CG
    Cosmogenic Be-10 and Al-26 measurements from bedrock exposures in East Antarctica provide indications of how long the rock surface has been free from glacial cover. Samples from the crests of Zakharoff Ridge and Mount Harding, two typical nunataks in the Grove Mountains, show minimum Be-10 ages of 2.00 +/- 0.22 and 2.30 +/- 0.26 Ma, respectively. These ages suggest that the crests were above the ice sheet at least since the Plio -Pleistocene boundary. Adopting a 'reasonable' erosion rate of 5-10 cm Ma(-1) increases the exposure ages of these two samples to extend into the mid-Pliocene. The bedrock exposure ages steadily decrease with decreasing elevation on the two nunataks, which indicates similar to 200 m decrease of the ice sheet in the Grove Mountains since mid-Pliocene time. Seven higher elevation samples exhibit a simple exposure history, which indicates that the ice sheet in the Grove Mountains decreased only similar to 100 in over a period as long as 1-2 Ma. This suggests that the East Antarctic Ice Sheet (EAIS) was relatively stable during the Pliocene warm interval. Five lower elevation samples suggest a complex exposure history, and indicate that the maximum subsequent increase of the EAIS was only 100 in higher than the present ice surface. Considering the uncertainties, their total initial exposure and subsequent burial time could be later than mid-Pliocene, which may not conflict with the stable mid-Pliocene scenario. © 2008, Cambridge University Press
  • No Thumbnail Available
    Item
    Minimum bedrock exposure ages and their implications: Larsemann Hills and neighboring Bolingen Islands, East Antarctica
    (Wiley-Blackwell, 2010-06-01) Huang, FX; Li, GW; Liu, XH; Kong, P; Ju, YT; Fink, D; Fang, AM; Yu, LJ
    Considerable controversy exists over whether or not extensive glaciation occurred during the global Last Glacial Maximum (LGM) in the Larsemann Hills. In this study we use the in situ produced cosmogenic nuclide 10Be (half life 1.51 Ma) to provide minimum exposure ages for six bedrock samples and one erratic boulder in order to determine the last period of deglaciation in the Larsemann Hills and on the neighboring Bolingen Islands. Three bedrock samples taken from Friendship Mountain (the highest peak on the Mirror Peninsula, Larsemann Hills; ∼2 km from the ice sheet) have minimum exposure ages ranging from 40.0 to 44.7 ka. The erratic boulder from Peak 106 (just at the edge of the ice sheet) has a younger minimum exposure age of only 8.8 ka. The minimum exposure ages for two bedrock samples from Blundell Peak (the highest peak on Stornes Peninsula, Larsemann Hills; ∼2 km from the ice sheet) are about 17 and 18 ka. On the Bolingen Islands (southwest to the Larsemann Hills; ∼10 km from the ice sheet), the minimum exposure age for one bedrock sample is similar to that at Friendship Mountain (i.e., 44 ka). Our results indicate that the bedrock exposure in the Larsemann Hills and on the neighboring Bolingen Islands commenced obviously before the global LGM (i.e., 20–22 ka), and the bedrock erosion rates at the Antarctic coast areas may be obviously higher than in the interior land. © 2010, Wiley-Blackwell.