¹⁰Be study of rapid erosion in Taiwan

Cosmogenic ¹⁰Be was measured using accelerator mass spectrometry in soils and sediments to study the erosion of Taiwan, which has the highest denudation rate in the world. The river sediments in Taiwan have very low ¹⁰Be concentrations, around 5 million atoms per gram, about 1 45 the world wide average. This is the direct consequence of its high sediment yield of more than 1000 mg/cm²/yr, 70 times the world average. Combining these values we found that, for Taiwan as a whole, the ¹⁰Be output to the sea only slightly exceeds the input from the rain, a situation typical of many areas around the world. Therefore, even in this example of extremely rapid erosion, ¹⁰Be seems to remain a useful indicator for erosion status. The total ¹⁰Be inventory found in a soil profile from a geologically stable area is at least 18% of the maximum possible inventory. The minimum age thus estimated for the soil is 0.11 Ma, in reasonable agreement with estimates from other means. The maximum erosion rate for this area thus estimated is at most 0.14 mg/cm²/yr, four orders of magnitude slower than the average value observed for Taiwan. We also demonstrate that the shelf sediments around Taiwan have received the admixing of a ¹⁰Be rich component from the ocean and would give a poor estimate for material eroded from Taiwan.