在新元古代，从十三里台期向马家屯期，胶辽徐淮地区的叠层石面貌发生根本改变，稳定展布的生物层礁为各种形态的丘状生物岩礁所替代，同时叠层石微构造发生突变，以半球状放射纤维组构为特征的微构造突然在不同类型的叠层石中同时出现。与此同时，伴随着碳氧同位素的负偏移，可能代表全球性海洋化学条件的变化，具有基本等时的特点。半球形放射纤维状组构可能是一类颇为特殊的初期钙化蓝藻构造，代表一个重要的生物事件。暂时性海洋分层现象及大洋底部缺氧海水的上涌可能是导致蓝藻钙化及碳氧同位素负偏移的根源，而850—800Ma左右海洋中由大量新生陆壳的形成及超大陆的裂谷化作用所引起的高热流异常是海洋分层及蓝绿藻钙化作用增强的原动力。

A sharp reduce in both the diversity and abundance of the stromatolites occurred at the boundary of the Neoproterozoic Shisanlitai and Majiatun Formations in southern Liaoning, as well as Weiji and Shijia Formations in northern Anhui and Jiangsu respectively. The abrupt change of stromatolitic microstructure accompanied with a distinct negative shift of carbon isotope values of carbonate carbon, is the key marker of an oceanographic chemical change, and consequently is of an isochoronic event. More evidences include the near synchronous occurrence of tussocky microstructure in the Pre Sinian strata, and its correlated shift of carbon isotope values in Majiatun and Shijia Formations, as well as formation I 6 of the Upper Riphean Atar Group in Mauritania. The tussocky microstructure is thought to be a special calcified blue alga, and temporal oceanic stratification and upwelling of the anoxia deep water afterwards may be the provenances of its calcification and the corresponding negative shift of carbon isotope values. The anomaly high hydrothemal flux in a time span from 850 Ma to 800 Ma indicated by the strontium isotopic ratios coincides with production of large amount of juvenile crust and rifting of a super continent, and gave rise to the transient oceanic stratification and enhancement of calcification of blue algae.

P534.3

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