To understand the underlying geochemical mechanism of the heavy metal element (HME) enrichment in weathering profiles of black marlstone, this study characterized 8 kinds of HME, including Cr, Ni, Cu, Zn, Cd, Pb, Th and U, along a weathering profile of black marlstone (DM profile) in the northwestern Hunan Province, China, and compared with two weathering profiles of black shales (XT and HZ profiles) from the same region. The results showed that: (1) Geochemical characteristics of HMEs in processes of black marlstone weathering and pedogenesis could be summarized as relatively low background v...