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Abstract
Elemental abundance variations across a Devonian Carboniferous (D'C) boundary section located at Huangmao, Guangxi Zhuang Autonomous Region. China, have been investigated by INAA and RNAA. Abundances of Ir, Au. Ni, Co. Cr, As. Sb, Se, U and V at the D/C boundary shale (14 cm thick) are 156ppt, 14.5ppb. 494ppm. 51.4ppm, 113ppm. 109ppm, 16.4ppra. 16.8ppm. 55.3ppm and 709ppm, higher than the background values of the underlying and overlying stratigraphic samples by factors of 20–100.
The geochemical anomaly at the D/C boundary is correlated with the biological mass extinction, e.g. of Palmatolepic gracilis expansa. Pseudopolygnathus trigonicus and other conodont species, and especially of the Clymenides. It implies that an event occurred at the end of the Devonian. But neither volcanic eruption, nor extraterrestrial impact can explain the geochemical anomaly.