Abstract The Late Triassic time interval witnessed several important biological turnovers, extinctions and onset of new life forms. Therefore, it is crucial to better constrain the tectonic, climatic and oceanographic framework at this time. The radiogenic strontium isotopic composition (87Sr/86Sr) of seawater, recorded in marine carbonates is sensitive to variations in continental weathering and oceanic spreading rates. This makes it a powerful proxy for palaeo-environmental reconstructions and an excellent global stratigraphic correlation tool of marine sediment records. In this study, we present a new and extended 87Sr/86Sr dataset across the late Norian - Hettangian interval, established from carbonate successions in Austria and Turkey. The well-established biostratigraphy and high sampling resolution allow evaluating changes in the 87Sr/86Sr record with a better time constraint than in previous studies. An exceptionally sharp trend towards unradiogenic values has been observed in the latest Norian and in the early Rhaetian from 0.70800 to 0.70779. Considering Late Triassic climate change, updated tectonic models and actual dating of magmatic events, possible explanations for the observed trend in the 87Sr/86Sr record are: (i) enhanced dissolution of pre-Norian carbonates, (ii) dissolution of widespread Late Triassic evaporites and (iii) tectonic reorganization of sedimentary basins due to the break-up of the supercontinent Pangea. At the very end of the Choristoceras marshi Zone, in the late Rhaetian, the unradiogenic 87Sr/86Sr trend is reversed. This is likely related to environmental changes due to the continental emplacement of the Central Atlantic Magmatic Province.

中文翻译：

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上三叠统海水87Sr/86Sr演化的新约束

摘要 晚三叠世时期见证了几次重要的生物更替、灭绝和新生命形式的出现。因此，此时更好地约束构造、气候和海洋框架至关重要。在海洋碳酸盐中记录的海水放射性锶同位素组成 (87Sr/86Sr) 对大陆风化和海洋扩散率的变化很敏感。这使其成为古环境重建的有力代表和海洋沉积物记录的优秀全球地层相关工具。在这项研究中，我们提出了一个新的扩展的 87Sr/86Sr 数据集，该数据集是从奥地利和土耳其的碳酸盐岩层序建立的，跨越晚诺里安期 - 赫唐阶期。完善的生物地层学和高采样分辨率允许以比以前的研究更好的时间限制评估 87Sr/86Sr 记录的变化。从 0.70800 到 0.70779，在最新的诺里安和早期的雷蒂安中观察到非放射性值的异常急剧趋势。考虑到晚三叠世气候变化、更新的构造模型和岩浆事件的实际测年，对 87Sr/86Sr 记录中观察到的趋势的可能解释是：(i) 前诺里阶碳酸盐岩的溶解增强，(ii) 广泛的晚三叠世蒸发岩的溶解(iii) 由于盘古超大陆的分裂，沉积盆地的构造重组。在 Choristoceras marshi 区的最末端，在 Rhaetian 晚期，非放射性 87Sr/86Sr 趋势发生逆转。