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首页> 外文期刊>Cretaceous Research >Carbon isotope stratigraphy and depositional oxia through Cenomanian/Turonian boundary sequences (Upper Cretaceous) in New Zealand
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Carbon isotope stratigraphy and depositional oxia through Cenomanian/Turonian boundary sequences (Upper Cretaceous) in New Zealand

机译：通过新西兰的Cenomanian / Turonian边界序列（上白垩统）的碳同位素地层学和沉积氧

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摘要

Stratigraphic sections across the Cenomanian/Turonian boundary (C/T boundary) are identified in New Zealand and were deposited in southern high latitudes of the palaeo-Pacific. Lithological evidence for Cretaceous Oceanic Anoxic Event 2 (OAE2), which preceded and spanned the C/T boundary, is lacking in these sections. The correlative interval is identified, however, from a positive 2‰ carbon isotope excursion (CIE) and from clustered highest occurrences of Cenomanian-restricted dinoflagellate taxa together with the lowest occurrence of Turonian Heterosphaeridium difficile. A zone lacking benthic macrofossils encompasses the CIE. In some sections, this interval is also characterized by distinctive red mudstone beds; the thickest such red bed (6-18. m thick) may overlap or just overlie the main part of the CIE interval. Shelly macrobenthos, notably inoceramid bivalves, disappeared >500. kyr prior to the CIE. This suggests that environmental deterioration associated with OAE2 may have preceded the inferred volcanic trigger that has been identified from other regions. Strong intermediate water depth oxia during OAE2, which contrasts with oceanic anoxic conditions that occurred elsewhere on the globe, apparently prevailed during the later phase of OAE2 in the southernmost Pacific. New data from New Zealand indicate that causal mechanism(s) of OAE2 may be complex.
机译：在新西兰确定了跨越西诺曼尼亚/突尼斯边界（C / T边界）的地层剖面，并沉积在古太平洋的南部高纬度地区。在这些部分中，缺少在C / T边界之前并跨越C / T边界的白垩纪海洋缺氧事件2（OAE2）的岩性证据。但是，可以从正的2‰碳同位素偏移（CIE）和成簇的西诺马尼亚限制型鞭毛鞭毛类生物的最高发生率与最低的艰难梭菌Heterosphaeridium发生率来确定相关区间。缺少底栖大型化石的区域涵盖了CIE。在某些地区，该层段还以独特的红色泥岩床为特征。最厚的这种红色层（6-18。m厚）可能重叠或恰好覆盖CIE间隔的主要部分。有壳的大型底栖动物，尤其是卵形双壳虫，消失了> 500。 CIE之前的Kyr。这表明与OAE2相关的环境恶化可能早于从其他地区识别出的推断火山爆发。与地球其他地方发生的海洋缺氧条件相反，OAE2期间有较强的中间水深缺氧，显然在最南端的太平洋的OAE2后期盛行。来自新西兰的新数据表明，OAE2的因果机制可能很复杂。

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