扬子地区震旦纪—寒武纪转折期大陆风化研究进展与展望

Continental weathering of Yangtze area during Edicaran(Sinian)—Cambrian transition stage:Advances and prospects

通过调研扬子地区震旦纪(埃迪卡拉纪)—寒武纪(E—C)转折期大陆风化、海洋环境和有机质富集特征研究。结果显示,扬子地区E—C转折期遭受了较强烈的化学风化作用,且在这一时期区内兼具浅水碳酸盐台地和深水盆地环境。在台地相区,下寒武统牛蹄塘组黑色岩系不整合接触于震旦系灯影组白云岩之上,该不整合与E—C转折期全球“大不整合”具有紧密的关系,盆地区发育的完整的沉积地层记录了台地区被风化地层的痕迹。现有大陆风化的地球化学证据集中于n(^(87)Sr)/n(^(86)Sr)、δ^(13)C、CIA和ε_(Nd)(t)等,同时这些地球化学数据也局限在少数的剖面和层段,因此迫切需要更多的地球化学参数来反映该风化作用的影响范围和演化特征。准确认识扬子地区E—C转折期大陆风化作用与海洋环境演变间的耦合关系,是揭示古生物演化、有机质富集机制的重要环节。

The researches of continental weathering,paleo-marine environment,and organic matter enrichment during Edicaran(Sinian)—Cambrian(E—C)transition stage in the Yangtze area,were organized and summarized in the present study.The results show that,during this stage,the Yangtze area suffered a strong chemical weathering,where includes carbonate platform facies and deep basin facies.The Early Cambrian Niutitang black shale lies with an unconformity upon the Edicaran Dengying dolomite in carbonate platform region,and this unconformity closely connected with the“Great Unconformity”during E—C transition stage around the word.However,in deep basin region,the Niutitang black shale conformably overlies on the Edicaran siliceous rock,and the complete E—C sedimentary strata has preserved weathering record of platform region.The existing geochemical evidences of continental weathering focus on ^(87)Sr/^(86)Sr、δ^(13)C、CIA,andε_(Nd)(t),and these geochemical data are limited to a few geological sections.Thus,more new geochemical factors are urgently needed to indicate the influence and evolution of the continental weathering during E—C transition stage.Finally,we suggest that an accurate understanding of coupling relationship between continental weathering and marine environment is significant for recognizing the evolution of life,and the enrichment of organic matter.