Upper Ordovician (Mohawkian) carbon isotope (δ13C) stratigraphy in eastern and central North America: Regional expression of a perturbation of the global carbon cycle
Upper Ordovician (Mohawkian) carbon isotope (δ13C) stratigraphy in eastern and central North America: Regional expression of a perturbation of the global carbon cycle
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DOI：
10.1016/j.palaeo.2005.03.008
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发表时间：
2005-06
期刊：
影响因子：
--
通讯作者：
Seth A. Young;M. Saltzman;S. M. Bergström
中科院分区：
文献类型：
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作者：
Seth A. Young;M. Saltzman;S. M. Bergström
北美东部记录的古滕贝格碳同位素漂移（GICE）表明，区域性、地球化学上不同的水团、上升流和海洋环流对碳酸盐台地碳同位素记录的影响。来自俄克拉荷马州、肯塔基州、弗吉尼亚州和西弗吉尼亚州的晚期Turinian-Chatfieldian碳酸盐记录了正碳同位素偏移（≥+3.0‰），即GICE偏移。GICE考察与已建立的生物地层学（始于北美大陆中部Phragmodus undatus牙形刺带，并继续通过Plectodina tenuis带）、层序和事件地层学有关。以前建立的碳酸盐岩平台上的正碳同位素位移模型已在GICE考察期间进行了测试，其中地球化学上不同的水团被定义为上奥陶统。在GICE之前，海平面的大幅度上升促进了开阔洋沃茨向劳伦西亚碳酸盐台地的交换;然而，在陆表海和邻近的伊阿佩托斯洋之间的水团之间的有限或缓慢的循环和交换仍然很明显。GICE考察中记录的当地变化与富营养同位素轻沃茨的上涌、初级生产力的增加以及随后的有机碳生产和埋藏直接相关。
The Guttenberg carbon isotope excursion (GICE) documented from eastern North America demonstrates the effects that regional, geochemically distinct water masses, upwelling, and ocean circulation have on the carbon isotope record from carbonate platforms. Late Turinian–Chatfieldian carbonates from Oklahoma, Kentucky, Virginia, and West Virginia record a positive carbon isotope excursion (≥+3.0‰), the GICE excursion. The GICE excursion has relations to established biostratigraphy (beginning in the North American Midcontinent Phragmodus undatus Conodont Zone and continuing through the Plectodina tenuis Zone), sequence, and event stratigraphy. Previously established models for positive carbon isotope shifts on carbonate platforms have been tested during the GICE excursion, where geochemically distinct water masses are defined for the Upper Ordovician. A major eustatic sea-level rise before the GICE promoted a greater exchange of open ocean waters onto the carbonate platform of Laurentia; however, restricted or sluggish circulation and exchange between water masses within the epeiric seas and the adjacent Iapetus Ocean were still apparent. Local variations documented in the GICE excursion are directly related to upwelling of nutrient rich isotopically light waters, increased primary productivity, and the subsequent organic carbon production and burial.