10Be analysis of the rock samples from the northeastern shore of Lake Pumoyum Co in south Tibetan Plateau

Lake Pumoyum Co is located at the south Tibetan Plateau (28 degrees 34 & PRIME;N, 90 degrees 24 & PRIME;E;-5030 m asl; lake surface area 281 km2; present maximum water depth -65 m). On the northeastern shore of the Lake Pumoyum Co, rock samples (quartzose arenite) were obtained from four areas at different altitudes (T1,-5060-5070 m asl; T2,-5120 m asl; T3,-5160-5170 m asl; T4,-5190 m asl). In this study, 10Be/9Be ratios of the quartz in the rock samples were measured by a 5.0 MV AMS system (JAEA-AMS-TONO-5MV; 15SDH-2, National Electrostatics Corporation) at Tono Geoscience Center, Japan Atomic Energy Agency. The 10Be concentrations of the quartz in the rock samples ranged from 3.78 to 10.8 x 106 atoms/g. The calculated minimum 10Be exposure ages and maximum erosion rates ranged from -41 ka to -247 ka and from -4.8 m/Myr to -14.2 m/Myr, respectively. Relatively young 10Be exposure ages (-41 ka) were observed in the T4 (-5190 m asl). Furthermore, the 10Be exposure ages became older from -41 ka to -247 ka with decreasing altitude on the northeastern shore of the Lake Pumoyum Co (from -5190 m asl to -5060 m asl). Although further geomorphological and chronological researches are needed to understand factors controlling the 10Be exposure ages and erosion rates, the trend in this study may be caused by 1) tectonic activity, 2) retreat of regional alpine glacier or 3) downward migrate of rocks on the area.

Automated summary

In this study, the 10Be/9Be ratios of quartzose arenite rock samples obtained from Lake Pumoyum Co in the southern Tibetan Plateau were measured to calculate the minimum 10Be exposure ages and maximum erosion rates. The results showed that as the altitude decreased, the 10Be exposure ages became older, indicating possible factors such as tectonic activity, regional alpine glacier retreat, or downward migration of rocks.