Carbon isotopes of pedogenic carbonate are often used to study paleoenvironments, but the existence of detrital carbonate changes the carbon isotopic composition. To develop an experimental method to determine existence of detrital carbonate in carbonate nodules, and to avoid it during isotope analysis, 23 pedogenic carbonate nodules in Miocene loess from the Loess Plateau of China were studied through micromorphology and carbon isotope analysis. The difference in carbon isotopic composition between matrix carbonate (B) and pore carbonate (A) (δ 13C(B-A)) ranges from 0.27‰ to 0.44‰ in nodules containing detrital carbonate and -0.16‰ to 0.13‰ in nodules where detrital carbonate is absent. The latter is within measurement error, but the former is beyond it. Here we propose an isotopic approach to determine if nodules contain detrital carbonate: if δ 13C(B-A) is within the measurement error, the nodules do not contain detrital carbonate, and vice versa. We suggest that it is better to analyze pore carbonate instead of matrix carbonate when using carbon isotope of carbonate nodules to reconstruct paleoenvironments.
The geomorphic evolution of northwestern China during the Cenozoic has been a subject of much geological inter...
ZHAN Tao~(1,2),GUO ZhengTang~(1*),WU HaiBin~1,GE JunYi~1,ZHOU Xin~1, WU ChunLin~(1,2) & ZENG FangMing~(1,2) 1 Key Laboratory of Cenozoic Geology and Environment,Institute of Geology and Geophysics, Chinese Academy of Sciences,Beijing 100029,China
