(super 10) Be, (super 14) C distribution, and soil production rate in a soil profile of a grassland slope at Heshan Hilly Land, Guangdong

Abstract

Concentrations of organic carbon, carbon isotopes ( (super 13) C and (super 14) C), atmospheric (super 10) Be in soil, and in situ (super 10) Be in bedrock and weathering rock were determined in a study of a profile of a grassland slope at the Heshan Hilly Land Interdisciplinary Experimental Station, Chinese Academy of Sciences, in Guangdong Province, China. A good linear relationship between depth and the (super 14) C apparent age of the organic carbon demonstrates that the rock weathering process and the accumulation process of organic matter in the slope are relatively stable. Both (super 14) C and (super 10) Be results show that about 34% of soil in the grassland slope has been eroded during the past 3800 yr. The (super 10) Be results for interstitial soil from weathered rocks show that the 90-cm-thick weathering rock layer above the bedrock has evolved over a period of 1.36 Myr. The concentrations of in situ (super 10) Be in the weathered rock and bedrock are 10.7X10 (super 4) atoms/g and 8.31X10 (super -4) atoms/g, respectively. The weathering rate of the bedrock, equivalent to the soil production rate, was estimated at 8.8X10 (super -4) cm/yr, and the exposure ages of the weathered rock and the bedrock were 72 kyr and 230 kyr, respectively.