Coastal Phenomena and Isostatic Uplift Around Fildes Peninsula of King George Island, South Shetland Islands, Antarctica

After a field work on recently raised coastal features in South Shetland Islands, we conclude that there are three kinds of recent coastal features, i.e, fragmental coast, rock coast, and ice cliff coast. The processes and forms of the fragmental cost formed by wave action with floating ice are studied. Systematic study of the raised coasts enables us to distinguish two groups of the coasts by an elevation of 20m a.s.l. The raised coasts above 20m a.s.l. belong to older group and those below 20m a.s.l. belong to younger group. Mean uplift rate of coast in this area is 6.7mm/a

Grain size characteristics and environmental indication of the sediments around Great Wall Station, Antarctica

The Great Wall Station of China (62°13'S. 58°58'W) is located at the Fildes Peninsula of King George Island, South Shetland Islands, Antarctica. Sediments in the area can be divided into glacial, periglacial, fluvial lacustrine and littoral deposits in origin. Analysis of the fine particals (below 3.52 mm) shows obviously difference among grain size composition, frequency curve, accumulative curve and scatter diagram. In order of periglacial-glacial-fluvial-littoral deposit, sand increases, silt and clay decreases; sorting changes from poor to good; mean grain size is at very fine-fine-medium-coarse sand respectively; skewness changes from very positive to near symmetric. Scatter diagram of grain size parameters shows difference in the sediments. Variation among frequency curves reflects processing and forming condition of the sediments. The fluvial and littoral deposits follow normal distribution, they are straight line in normal accumulative diagram. The glacial and periglacial deposits follow Rosin's distribution, they are straight lines in Rosin's accumulative diagram

An evaluation of multiple working hypotheses to explain cosmogenic exposure age data from glacial deposits in the Bayan Har Shan, NE Tibetan Plateau

Many questions remain unanswered regarding the Quaternary glaciations of the Tibetan Plateau. We have used terrestrial cosmogenic nuclide (TCN) exposure age dating of glacial deposits to examine the style, extent, and timing of past glaciations of the Bayan Har Shan, a mountain region on the northeastern Tibetan Plateau. This area lies within a transition zone between the dry interior of the Tibetan Plateau and the wetter eastern margin affected by the Asian monsoon. Bayan Har Shan has many glacial landforms and deposits that provide evidence for former glaciation ranging from cirque and valley glaciers to ice-fields and ice caps. In an attempt to constrain the timing of glaciations in Bayan Har Shan, we have performed TCN exposure dating on 65 samples in central Bayan Har Shan from glacial deposits. boulders (39 samples), on surface pebbles/cobbles (12 samples), and on pebbles in sediment depth profiles (14 samples from four profiles) allow us to examine the timing and extent of glaciations in this area. As is often the case, there are some challenges in interpreting the range of TCN apparent exposure ages that is found in data from several samples and sample types on a single deposit and from samples taken at various sites. Thus we evaluate multiple working hypotheses to explain apparent exposure ages on glacial deposits, which in this case range from 3 ka to 129 ka. We consider three different hypotheses; 1) some samples have erroneously old exposure ages due to inheritance, 2) samples have been preserved under cold-based, non-erosive ice, and 3) samples have experienced only post-glacial shielding. Only when we adopt a hypothesis that assumes no prior exposure, and thus that maximum apparent exposure ages constrain the minimum age of formation of a feature (working hypotheses 3), do we find broad consistency between apparent exposure ages from different sample types (erratic boulders, surface pebbles/cobbles and pebbles from depth profiles). This leads to the conclusion that all of the sites of former glaciations we examined are at least 50ka in age, and that there has been no large-scale expansion of glaciers in the central Bayan Har Shan over the last 50ka.Presented at The 5th International Symposium on Tibetan Plateau / The 24th Himalaya-Karakorum-Tibet Workshop, Beijing, China, August 11-14, 2009</p

A paleoglaciological reconstruction for Bayan Har Shan, NE Tibetan Plateau

The paleoglaciology of the Tibetan Plateau has remained elusive because extensive areas still lack detailed scrutiny. We here present a paleoglaciological reconstruction for the Bayan Har Shan region, NE Tibetan Plateau, which could serve as a working model to investigate other poorly investigated regions. The reconstruction is primarily based on three methods for revealing the glacial history; 1) remote sensing (geomorphology), 2) field studies (stratigraphy), and 3) numerical dating techniques. Remote sensing (SRTM elevation data, Landsat ETM+ satellite imagery and Google Earth) of a 136 500 km2 area reveals an abundance of glacial landforms in the highest mountain areas and an absence of glacial landforms on intervening plateau surfaces. Stratigraphical data collected during three field seasons supplement the picture emerging from remote sensing. Glacial deposits (including erratic boulders and till) occur in the elevated mountain areas but are absent on the intervening plateau areas. Marginal moraines in central Bayan Har can be grouped to represent at least three separate glacial extents and scattered observations of glacial deposits indicate the presence of a fourth (and maximum) glacial extent. To tie the glacial geological record to a chronology we have employed terrestrial cosmogenic nuclide (TCN) exposure and optically stimulated luminescence (OSL) dating. Beryllium apparent exposure ages of 65 glacial boulders, surface cobbles/pebbles and depth profile samples yield minimum ages for the three youngest glacial extents of 40-65 ka, 60-100 ka, and 95-165 ka (with the wide age ranges due to TCN dating uncertainties). A preliminary OSL age of c. 160 ka from glacial sediments of the oldest of these glacial extents supports our interpretation based on TCN dating. The glacial extent presented here is more restricted than most previous reconstructions, most notably with very restricted glaciers over at least the last 40-65 ka. These results indicate that while continental-scale ice sheets evolved and disappeared in North America and Eurasia over the last half of the last glacial cycle, the NE corner of the Tibetan Plateau experienced relatively minor glacial fluctuations

The extent of permafrost in China during the local Last Glacial Maximum (LLGM)

Recent investigations into relict periglacial phenomena in northern and western China and on the Qinghai-Tibet Plateau provide information for delineating the extent of permafrost in China during the Late Pleistocene. Polygonal and wedge-shaped structures indicate that, during the local Last Glacial Maximum (LLGM, between ~35 and 10.5ka BP), the southern limit of latitudinal permafrost in northern China advanced southward at least to ~38-40°N in the east and to ~37-39°N in the west. This represents an advance of about 5-10° of latitude beyond present-day permafrost limits. The lower limits of elevationally controlled permafrost on the Qinghai-Tibet Plateau and its peripheries were about 1000m lower: this permafrost was largely continuous during the LLGM. This suggests a cooling of between 4 and 10°C, or more. This paper discusses the extent of permafrost during the LLGM and presents maps that have been constructed on the basis of extensive and integrative analysis of all reliable and pertinent data. The results indicate that the extent of LLGM permafrost in China was between ~3.8 and 4.3×1