Abstract The magnitude of temperature changes in the Early Jurassic are not well known. Clumped isotope measurements can potentially be used to provide better constrains, but unfortunately many of the well-studied sedimentary successions that preserve Lower Jurassic fossils experienced burial temperatures above the limits of preservation of Δ47, which for geological timescales is thought to be between 80–120 °C. Samples from these basins are expected to be partially reordered and yield apparent clumped isotope temperatures that are warmer than original values. Here, we explore whether useful paleoclimate information can be recovered from these samples. We test the hypothesis that relative temperature differences are preserved in partially reordered samples when they experience a common burial history. This was done with the use of reordering models and Δ47 measurements of early Jurassic belemnites from the Aubach section of the SW German Basin, a basin that has a relatively well constrained burial history with maximum burial temperatures above 90 °C. We find that even though partial reordering progressively erases the Δ47 difference between samples, the majority (>50%) of the signal is preserved when samples are buried at temperatures as high of 150 °C for up to 200 Ma. Moreover, the models demonstrate that – regardless of burial conditions – partially reordered samples always preserve minimum records of temperature change across climate events. These inferences are supported by the belemnite Δ47 data that show partially reordered compositions and warming/cooling patterns across the Early Jurassic that closely mimic observations from independent proxies. Model observations are used to interpret a 13 ± 4 °C (95% ci) temperature increase that is observed in the belemnite data across the Early Toarcian. The large magnitude of the temperature excursion is explained as a combination of warming and a change in belemnite habitat before and after the Toarcian Ocean Anoxic Event. Our results demonstrate the usefulness of partially reordered samples and further open the use of this proxy in deep time settings.

中文翻译：

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使用重新排列的箭石块状同位素组成重建早托阿尔世（侏罗纪）变暖的幅度

摘要 早侏罗世的温度变化幅度尚不清楚。成簇同位素测量可潜在地用于提供更好的约束，但不幸的是，许多经过充分研究的保存下侏罗纪化石的沉积序列经历了高于 Δ47 保存极限的埋藏温度，对于地质时间尺度，该值被认为在 80-120 之间℃。预计来自这些盆地的样本将被部分重新排序，并产生比原始值更高的表观聚集同位素温度。在这里，我们探索是否可以从这些样本中恢复有用的古气候信息。我们检验了这样一个假设，即当它们经历共同的埋葬历史时，在部分重新排序的样本中保留了相对温度差异。这是通过使用重新排序模型和来自德国西南盆地 Aubach 剖面的早期侏罗纪箭石的 Δ47 测量值来完成的，该盆地具有相对较好的埋藏历史，最大埋藏温度高于 90 °C。我们发现，即使部分重新排序逐渐消除了样本之间的 Δ47 差异，但当样本在高达 150 °C 的温度下埋藏长达 200 Ma 时，大部分（> 50%）信号仍会保留。此外，这些模型表明，无论埋葬条件如何，部分重新排序的样本始终保留了气候事件中温度变化的最低记录。这些推论得到了箭石 Δ47 数据的支持，这些数据显示了整个早侏罗世的部分重新排列的成分和变暖/变冷模式，这些数据与独立代理的观察结果非常相似。模型观测值用于解释 13 ± 4 °C (95% ci) 的温度升高，该温度升高在整个早托阿尔阶的箭石数据中观察到。大幅度的温度漂移被解释为托亚西洋缺氧事件前后变暖和箭石栖息地变化的结合。我们的结果证明了部分重新排序的样本的有用性，并进一步开放了该代理在深度时间设置中的使用。大幅度的温度漂移被解释为托亚西洋缺氧事件前后变暖和箭石栖息地变化的结合。我们的结果证明了部分重新排序的样本的有用性，并进一步开放了该代理在深度时间设置中的使用。大幅度的温度漂移被解释为托亚西洋缺氧事件前后变暖和箭石栖息地变化的结合。我们的结果证明了部分重新排序的样本的有用性，并进一步开放了该代理在深度时间设置中的使用。