【作者】 姜立君； 张卫华； 高慧； 杨瑞东；

【Author】 JIANG Lijun ZHANG Weihua GAO Hui YANG Ruidong (Guizhou university ofTeochnology, Guiyang, Guizhou, 550003)

【机构】 贵州工业大学；

【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,发现尽管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,δ¹³C表现出高的负异常可达-12.48‰,而到上部相厚层白云岩,δ¹³C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δ¹³C明显偏负,在碳酸盐岩下部相底部为-8278‰～-6.651‰;清镇地区当时为泻湖,其中陡山沱组底部碳酸盐δ¹³C值为-3.718‰～-0.209‰,从下向上表现出Ca逐渐增加。可以看出由于它们所处的环境不同导致它们的同位素数值有差异,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,但在三个地区均发现冰川沉积与碳酸盐岩沉积之间存在具有过渡特点的沉积特征,这说明两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 an enduring enigma of Neoproterozoic, the Cap Carbonate has been found in many regions of the world on lying on the glacial diamictites with negative carbon isotopic. There are many hypothesized explanations for this paleoclimatic dichotomy are high orbital obliquity, true polar wander, reduced solar luminosity, snowball albedo, CO2 drawdown, stagnant ocean overturn, and reinterpretation of diamictites as mega-impact ejecta.The authors studied the Cap Carbonate in three different depositional environments in Guizhou Province, where the negative carbon isotopic was observed. The negative carbon isotopic in different depositional environments is different.The flatbedding at the lower part of the cap in the Tongren and Qingzhen regions can not be explained by the "snow-ball" model. Furthermore, the crystal fans at lower part of the cap in the Tongren region exhibit soft-sediment deformational structures that may be attributed to rebound-induced seismicity. The phenomena indicate the transition stage after the Marinoan glacial. Unconspicuous as it is, the transition stage in the other two regions can also be found. As shows the rapid icehouse to greenhouse transition in Snowball Earth. The transition stage may last 280,000 years by calculating.更多还原