Preliminary study on the erratic exposure ages of Grove Mountains,East Antarctica

The first study of erratic boulder exposure ages in the Grove Mountains, interior Antarctica, indicates the two erratic boulders （060131-1 and 060131-2, collected from a typical nunataks, Zakharoff Ridge in the Grove Mountains） have 10 Be minimum exposure ages of 1.24 ±0. 11 Ma, 1.37 ±0. 12 Ma, and ^26Al ages of 0.90 ±0.12 Ma,0.44 ±0.04 Ma, respectively. Meanwhile, another erratic boulder sample 060131-4, coming from vicinal ice surface, has ^10Be and ^26Al minimum exposure ages of 0.47 ±0.3 Ma and 0. 44 ±0.04 Ma, respectively. The exposure ages of the three erratic boulders are nearly similar to the bedrocks with the similar elevation. Thus, using the technique of in situ produced terrestrial cosmogenic nuclides, the ice sheet evolution histories in the Grove Mountains reflected by erratic boulder and bedrock exposure ages are basically consistent.

LATE PLEISTOCENE—HOLOCENE RAPID UPLIFT AND EROSION IN TIBET: CONSTRAINTS FROM COSMOGENIC EXPOSURE AGE DATA

Tibet is the largest and highest plateau on the Earth (having 82% of the world’s land surface area falling >4km above sea level) attributed to the India and Asian convergence tectonics. Recently, high\|resolution digital topography data (Fielding et al., 1994) confirmed the earlier observations about flat erosional surfaces in the central part of the plateau (Jujin, et al., 1995) and suggested extraordinary flatness at a wide range of scales. Much of the Tibetan plateau across different accreted terranes has shallow slopes between 5°～10° and variation in relief of about 1 km, except in its marginal parts (Himalayan ranges; Kunlun mountains) where rough and high topography with intense fluvial dissections (variations in relief up to 7km) is quite frequent. However, in the southern and south\|central part of the plateau along the Pliocene\|Quaternary grabens, slopes generally steepen.

Paleoglacial and paleoclimate reconstructions during the global Last Glacial Maximum in the Longriba area, eastern Tibetan Plateau

Owing to the remoteness of the Longriba area and the lack of dating records,it is extremely challenging to reconstruct the chronology and extent of the paleoglaciers in this area.In this paper,we combined limited observational data with automated modelling for paleoglacial reconstructions.We first identified a broadly distributed paleoglacier from satellite imagery and field investigation based on the sediment-landform assemblage principle and dated it to 23.1±1.4~19.5±1.2 ka by ^(10)Be exposure dating,corresponding to the global Last Glacial Maximum(gLGM).Then,we reconstructed the extent and ice surface of 171 paleoglaciers formed during the similar period based on geomorphological evidence and‘ice surface profile’modelling.The results showed that the paleoglacial coverage was 426.5 km2,with an ice volume of 38.1 km^(3),in the Longriba area.The reconstructed equilibrium line altitudes(ELAs)based on modelled ice surfaces yielded an average of 4245±66 m above sea level(asl),~725±73 m lower than the present ELA(4970±29 m asl).The temperature was~5.51-6.68℃lower,and the precipitation was~30-34%less in Longriba,during the gLGM compared to the present day.This glacial advance was mainly driven by colder climate that was synchronous with Northern Hemisphere cooling events.