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

摘要： 广西及邻区下泥盆统至下石炭统稳定碳同位素组成逐渐增大，由埃姆斯阶（Ｄ_１）一１‰～一４‰增至法门阶，杜内阶的＋0.5‰～＋2.5‰。同时期δ¹⁸Ｏ呈“Ｗ”型分布，在艾菲尔阶（D¹₂）和弗拉斯阶（D¹₃）两个负向波动；在埃姆斯阶（D³_{1222311δ¹³Ｃ和δ¹⁸Ｏ的变化特征可与同时期、同纬度的北美大陆保存完好的低镁方解石质腕足动物壳中碳、氧同位素组成良好的对比。因此，华南碳酸盐中碳、氧同位素组成基本保存了泥盆纪古海洋中同位素的特征，是很有潜力的地层对比工具。}

关键词: 泥盆系, 同位素, 碳酸盐岩