关键词: 泥盆系, 同位素, 碳酸盐岩

Abstract: The carbon isotopic composition in carbonates at Guangxi and adjacent areas shows an isotopic increasing from Lower Devonian to upper Devonian and Carboniferous. The range of δ¹⁸C values vary from a low of -1‰～-4‰ in the Emsian to a high of +0.5‰～+2.5‰ in the Famennian and Toumaisian (C₁). The δ¹⁸O trend for Devonian carbonates reveals a variety with geologic time, showing a W shape as two negative shifts in the Eifelian (D₂) and the Frasnian (D₃), and three positive shifts in the Emsian(D₁), Giverian (D₂), and Famennian and Toumaisian, respectively. The carbon isotopic trend in the Devonian carbonates of south China reflect that the great vicissitude of biosphere and then the atmosphere and sediments happened during the Devonian. Both trends of δ¹³C and δ¹⁸O values in carbonates at Guangxi and adjacent areas are similar to that of trends originally preserved in the low-Mg calcite brachiopoda shells from same latitude, the tropical sea of North America during Devonian. Therefore, both carbon and oxygen isotope compositions in the Devonian carbonates of south China are originally preserved either and could be a potential tool for stratigraphic correlation.

Key words: Devonian, stable isotope, carbonate