Previous stable oxygen isotope records of calcitic fossils (δ¹⁸O_shell) from Europe have been interpreted to reflect strong climatic perturbations throughout the Jurassic, but it is unknown whether they reflect global trends because data from other regions are sparse. Here, we use bivalve and brachiopod shells from western Asia and northern Africa to examine seawater temperatures at low latitudes as well as latitudinal temperature gradients in the Middle Jurassic. Our results include the first absolute temperature estimates for most of the study areas and this time interval. Furthermore, we acknowledge a latitudinal gradient in δ¹⁸O values of seawater (δ¹⁸O_sea) that leads to more realistic temperature reconstructions of tropical water temperatures, which were underestimated by earlier methods. Following this approach, δ¹⁸O_shell values translate into average equatorial water temperatures during the Middle Jurassic several degrees higher than today (as high as 34–35 °C). Such high temperatures cause environmental stress, probably explaining previously documented low diversities of low-latitudinal ecosystems (e.g., coral reefs) during this time interval. A comparison with literature data raises doubts over whether previously published European temperature curves are truly representative of global patterns. Instead, they might reflect the complex paleogeography of European basins influenced by regional and/or short-term changes in δ¹⁸O_sea values.

中文翻译：

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热带地区有压力吗？纬度海水δ18 O梯度对低纬中侏罗纪温度重建的影响

钙质化石（δ以前的稳定氧同位素记录¹⁸ Ø_外壳欧洲）已经被解释为在整个侏罗纪反映强烈的气候扰动，但目前还不清楚他们是否反映了全球趋势，因为来自其他区域的数据是稀疏。在这里，我们使用来自西亚和北非的双壳类和腕足类动物壳来检查低纬度的海水温度以及侏罗纪中部的纬度温度梯度。我们的结果包括大部分研究区域和该时间间隔的首次绝对温度估计。此外，我们承认一个纬度梯度δ ^18个海水中的O值（δ ¹⁸ Ø_海）导致热带水温的更现实的温度重建，而早期方法却低估了这一温度。按照该方法，δ ¹⁸ ö_壳值期间中侏罗纪几度转化为平均赤道水温度高于今日（高达34-35℃）。如此高的温度会引起环境压力，这可能解释了先前记录的低纬度生态系统（例如珊瑚礁）在此时间间隔内的低多样性。与文献数据的比较引起了人们对先前发布的欧洲温度曲线是否真正代表全球格局的怀疑。相反，它们可能反映了受δ区域和/或短期变化影响的欧洲盆地复杂的古地理¹⁸ O_海值。