10Be Exposure Age of the Third Terrace in Bingzhongluo Reach of Nujiang River

Date: 4/24/2019

Time: 06:00 PM

Room: Grand Ballroom

Fluvial terraces are common in the Nujiang River valley, while the third level is widest and mostly distributed. Three granite boulders were taken as samples at the posterior margin of the third terrace of the Nujiang River at Bingzhongluo. The diameters of all boulders are large (>2m) and buried in soil layers. Sample NJ2-1 was collected from one large granite boulder on floodplain, which is used to estimate the inheritance. Sample BZL43 was chiseled about 1.5cm from the surface of a quartz vein, that insets a sandy slate of the third terrace at downstream about 2km. The ¹⁰Be concentrations of BZL43 is highest of the four samples from the third terrace. Weathering processes have a greater impact on the exposure ages of boulder samples according to the relief, environmental features and ¹⁰Be concentration. Assuming the erosion rate of sample BZL43 from the quartz vein as 0.05cm/ka, the erosion rate of granite boulders is represented graphically as 0.3cm/ka by the relationship among effective exposure age, exposure time and erosion rate. The exposure ages of the three granite boulders on the third terrace were obtained after the correction for erosion and ignoring inheritance. Combined with the corrected exposure age of sample BZL43, it is considered that the third terrace of Nujiang River at Bingzhongluo was developed during 150~203ka.

Presenting Author: Yanwu Lv

Authors