【摘要】 通过对贵州新元古代陡山沱期不同相区碳酸盐岩帽的岩石特征和地球化学特征的研究 ,发现不同相区具有不同的同位素和岩石组合。铜仁地区当时处于浅海 ,其“碳酸盐岩帽”下部相的薄层白云岩 ,变形构造发育 ,δ13 C表现出高的负异常可达 - 12 .4 8‰ ,而到上部相的厚层白云岩 ,δ13 C明显向正异常反向迁移 ,但还是处于 - 3.0‰～ - 1.0‰之间 ;当时为次深海的台江五河地区δ13 C明显偏负 ,在碳酸盐岩下部相底部为 - 8.2 78‰～ - 6 .6 5 1‰ ;清镇地区当时为泻湖 ,其中陡山沱组底部碳酸盐δ13 C值为 - 3.718‰～ - 0 .2 0 9‰ ,从下向上表现出Ca逐渐增加。可以看出 ,由于所处的环境不同导致其同位素数值有差异 ,但还是表现出全球都有分布的冰期后负异常的特点。岩石特征的研究发现虽然不同的沉积环境具有不同的岩石特征 ,但在 3个地区均发现冰川沉积与碳酸盐岩沉积之间具有过渡特点的沉积特征 ,说明二者间并非是突变关系。由此对“雪球地球”假说提出新的认识。更多还原

【Abstract】 As a mystery of Neoproterozoic,Cap Carbonates lying on the glacial diamictites with negative carbon isotopic anomalies have been found in many regions of the world. The authors studied the Cap Carbonate in three different depositional environments in Guizhou Province,where negative carbon isotopic anomalies were observed. The negative carbon isotopic anomalies are different in different depositional environments. The flat bedding at the lower part of the cap in Tongren and Qingzhen areas can not be explained by the “snow-ball” model. Furthermore,the crystal fans at the lower part of the cap in Tongren area exhibit soft sedimentary deformational structures that may be attributed to rebound-induced seismicity. The phenomena suggest the existence of a transitional stage after the Marinoan glacial period. Not conspicuous as it is,the transitional stage can also be found in the other two areas,which implies the rapid transition from the icehouse to the greenhouse in Snowball Earth. Calculation shows that the transition stage might have lasted for 280 000 years.更多还原