Earliest Triassic microbialites in the South China block and other areas: controls on their growth and distribution
Earliest Triassic microbialites in the South China block and other areas: controls on their growth and distribution
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DOI：
10.1007/s10347-007-0105-5
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发表时间：
2007-08-01
期刊：
影响因子：
1.8
通讯作者：
Guo, Li
中科院分区：
文献类型：
--
作者：
Kershaw, Steve;Li, Yue;Guo, Li
最早的三叠纪微生物岩（ETM）和无机碳酸盐晶体扇形成后，二叠纪末大规模灭绝（约。251.4Ma）。ETM与更稀有且更具区域性的后续三叠纪微生物岩不同。华南陆块北方和南方ETM的巨大差异表明了地理上的省，并且ETM在整个赤道特提斯洋最丰富，具有进一步的地理变化。ETM产于超缺氧成层海洋的浅海陆棚中，形成了唯一广泛分布的古生代微生物岩，其结构类似于寒武-奥陶纪，并短暂地发生在最新的奥陶纪、晚志留世和晚泥盆世沉积之后。早在三叠纪中期生物复苏之前，ETM就消失了，但如果将其解释为灾难类群，原因尚不清楚。一般而言，ETM的发生表明微生物介导的钙化发生在上涌的富碳酸盐缺氧沃茨与温暖的充气表面沃茨混合的地方，形成区域缺氧，因此极端碳酸盐过饱和和缺氧条件都是其生长所必需的。长期的海洋和大气变化可能是ETM形成的触发因素。在赤道西盘古大陆，最早的微生物岩是早三叠世晚期，但如果在未来的工作中发现保存完好的早三叠世相，则可能在西盘古大陆存在ETM。
Earliest Triassic microbialites (ETMs) and inorganic carbonate crystal fans formed after the end-Permian mass extinction (ca. 251.4 Ma) within the basal Triassic Hindeodus parvus conodont zone. ETMs are distinguished from rarer, and more regional, subsequent Triassic microbialites. Large differences in ETMs between northern and southern areas of the South China block suggest geographic provinces, and ETMs are most abundant throughout the equatorial Tethys Ocean with further geographic variation. ETMs occur in shallow-marine shelves in a superanoxic stratified ocean and form the only widespread Phanerozoic microbialites with structures similar to those of the Cambro-Ordovician, and briefly after the latest Ordovician, Late Silurian and Late Devonian extinctions. ETMs disappeared long before the mid-Triassic biotic recovery, but it is not clear why, if they are interpreted as disaster taxa. In general, ETM occurrence suggests that microbially mediated calcification occurred where upwelled carbonate-rich anoxic waters mixed with warm aerated surface waters, forming regional dysoxia, so that extreme carbonate supersaturation and dysoxic conditions were both required for their growth. Long-term oceanic and atmospheric changes may have contributed to a trigger for ETM formation. In equatorial western Pangea, the earliest microbialites are late Early Triassic, but it is possible that ETMs could exist in western Pangea, if well-preserved earliest Triassic facies are discovered in future work.