Carbon isotopes and sequence stratigraphy
Carbon isotopes and sequence stratigraphy
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碳同位素和层序地层学
DOI：
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发表时间：
1996
期刊：
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通讯作者：
A. Gale
中科院分区：
文献类型：
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作者：
S. Mitchell;C. Paul;A. Gale
摘要 介绍了下塞诺曼阶晚期至下土兰阶早期的三个剖面（盎格鲁-巴黎盆地的 Folkestone、下萨克森盆地的 Wünstorf 和克利夫兰盆地的 Speeton）的碳同位素（δ13C）地层。这些同位素曲线之间的相似性表明它们是由同步的全局过程控制的，并且可用于高分辨率关联。此外，该层段的层序地层分析表明，每个同位素偏移都与层序边界和/或重叠表面相关。斯皮顿路段的整个塞诺曼尼亚也证明了这一点。我们表明，大多数（如果不是全部）δ13C 偏移在当前地层分辨率的限制内是同步的。我们将背景 δ13C 值的增加解释为白垩纪中期海平面上升导致可埋藏海洋有机碳的洋底（特别是大陆架）面积增加。因此，背景 δ13C 值可以提供一种独立的方法来估计过去的海平面升降。我们将 δ13C 的急剧偏移解释为反映了碳循环的更快速变化，特别是在海平面快速变化时沉积物中有机碳的埋藏率和/或深层和中层水团中的储存率。当其他标准模糊或缺乏时，碳偏移可能有助于定位层序边界。
Abstract The carbon isotope (δ13C) stratigraphy of the late Lower Cenomanian to early Lower Turonian is presented for three sections (Folkestone in the Anglo-Paris Basin, Wünstorf in the Lower Saxony Basin and Speeton in the Cleveland Basin). The similarity between these isotope curves suggests that they were controlled by synchronous, global processes and can be used for high resolution correlation. Furthermore, sequence stratigraphic analysis of this interval reveals that each isotope excursion is associated with a sequence boundary and/or onlap surface. This is also demonstrated for the whole of the Cenomanian for the section at Speeton. We show that most (if not all) δ13C excursions are synchronous within the limits of current stratigraphic resolution. We interpret the increase in background δ13C values as representing an increase in the area of ocean floor (specifically continental shelf) available for burial of marine organic carbon caused by the mid-Cretaceous rise in eustatic sea-level. Thus background δ13C values may provide an independent method for estimating past eustatic sea-levels. We interpret the sharp δ13C excursions as reflecting more rapid changes in the carbon cycle particularly the rate of burial of organic carbon within sediments, and/or of storage in deep and intermediate water masses, at times of rapidly changing sea-level. Carbon excursions may be useful in locating sequence boundaries when other criteria are obscure or lacking.