Stable isotope analyses of belemnites from the Kachchh Basin, western India: paleoclimatic implications for the Middle to Late Jurassic transition
Stable isotope analyses of belemnites from the Kachchh Basin, western India: paleoclimatic implications for the Middle to Late Jurassic transition
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DOI：
10.1007/s10347-011-0278-9
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发表时间：
2012-04-01
期刊：
影响因子：
1.8
通讯作者：
Ramkumar, Mu.
中科院分区：
文献类型：
--
作者：
Alberti, Matthias;Fuersich, Franz T.;Ramkumar, Mu.
稳定同位素分析61成岩未改变的箭石喙从中晚侏罗世的印度西部的Kachchh盆地表明稳定的古温度跨越Callovian-Oxfordian边界（类似于14 A摄氏度）。只有在牛津中期结束时，水温下降超过3A摄氏度，然后在基默里纪再次达到更高的值（类似于12.3A摄氏度）。这些数据不支持中晚侏罗世过渡期的极地冰川作用，这必然会导致全球温度和海平面在边界处达到最低水平。卡奇盆地的卡洛夫至牛津岩石表明，相对海平面略有下降，导致了逐渐变浅。然而，这种回归的幅度相对较小，海平面最低值是在早期牛津晚期达到的，而不是接近边界。因此，从Kachchh盆地的结果，意味着几乎稳定的气候条件在中晚侏罗世过渡，并没有显示任何证据的极地冰川。
Stable isotope analyses of 61 diagenetically unaltered belemnite rostra from the Middle to Late Jurassic of the Kachchh Basin of western India suggest stable paleotemperatures across the Callovian-Oxfordian boundary (similar to 14A degrees C). Only at the end of the Middle Oxfordian water temperatures drop for more than 3A degrees C before reaching again higher values during the Kimmeridgian (similar to 12.3A degrees C). The data do not support polar glaciations proposed for the Middle to Late Jurassic transition, which necessarily would have led to a global temperature and sea-level minimum at the boundary. Callovian to Oxfordian rocks in the Kachchh Basin point to a gradual shallowing corresponding to a slight fall in relative sea level. However, the magnitude of this regression is comparatively small, and the sea-level minimum is reached in the late Early Oxfordian and not close to the boundary. Results from the Kachchh Basin therefore, imply almost stable climatic conditions during the Middle to Late Jurassic transition and do not show any evidence for polar glaciations.