THE CAUSE OF BIOMASS EXTINCTION AT THE FRASNIAN-FAMENNIAN BOUNDARY, THE KERMAN PROVINCE SOUTHEASTERN, CENTRAL IRAN

About 35 samples were collected from lower and upper parts of the proposed Frasnian-Famennian boundary in three sections of Upper Devonian marine sediments of the Kerman province. The biostratigraphical and geochemical studies indicate that about 45% extinction of brachiopods probably caused by the Frasnian-Famennian bioevents, which is slightly higher than thr rate of Devonian-Carboniferous extinction elsewhere. The results of isotopic carbon and oxygen isotope analysis (δ 13C%0 VPDB and δ 10O %VPDB) show a sudden decrease at the proposed Frasnian-Famennian extinction boundary which is followed by positive values above this horizon. The negative excursion may indicate a biomass extinction due to either a meteorite impact or decay of organic matter. The isotopic variations are correlated with those of faunal changes and their extinctions in the area.