¹⁰Be, ¹⁴C 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 ( 13 C and 14 C), atmospheric 10 Be in soil, and in situ 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 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 14 C and 10 Be results show that about 34% of soil in the grassland slope has been eroded during the past 3800 yr. The 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 10 Be in the weathered rock and bedrock are 10.7 × 10 4 atoms/g and 8.31 × 10 4 atoms/g, respectively. The weathering rate of the bedrock, equivalent to the soil production rate, was estimated at 8.8 × 10 -4 cm/yr, and the exposure ages of the weathered rock and the bedrock were 72 kyr and 230 kyr, respectively.