Deccan Traps flood basalt volcanism affected ecosystems spanning the end‐Cretaceous mass extinction, with the most significant environmental effects hypothesized to be a consequence of the largest eruptions. The Rajahmundry Traps are the farthest exposures (~1,000 km) of Deccan basalt from the putative eruptive centers in the Western Ghats and hence represent some of the largest volume Deccan eruptions. Although the three subaerial Rajahmundry lava flows have been geochemically correlated to the Wai Subgroup of the Deccan Traps, poor precision associated with previous radioisotopic age constraints has prevented detailed comparison with potential climate effects. In this study, we use new ⁴⁰Ar/³⁹Ar dates, paleomagnetic and volcanological analyses, and biostratigraphic constraints for the Rajahmundry lava flows to ascertain the timing and style of their emplacement. We find that the lower and middle flows (65.92 ± 0.25 and 65.67 ± 0.08 Ma, ±1σ systematic uncertainty) were erupted within magnetochron C29r and were a part of the Ambenali Formation of the Deccan Traps. By contrast, the uppermost flow (65.27 ± 0.08 Ma) was erupted in C29n as part of the Mahabaleshwar Formation. Given these age constraints, the Rajahmundry flows were not involved in the end‐Cretaceous extinction as previously hypothesized. To determine whether the emplacement of the Rajahmundry flows could have affected global climate, we estimated their eruptive CO₂ release and corresponding climate change using scalings from the LOSCAR carbon cycle model. We find that the eruptive gas emissions of these flows were insufficient to directly cause multi‐degree warming; hence, a causal relationship with significant climate warming requires additional Earth system feedbacks.

中文翻译：

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裸露的拉贾蒙德陷阱中没有白垩纪-古近界：40Ar / 39Ar年代最长的Deccan熔岩流的精细年代学，磁力地层学和生物地层学

Deccan Traps洪水玄武岩火山活动影响了整个白垩纪末期生物灭绝的生态系统，最严重的环境影响被认为是最大喷发的结果。Rajahmundry圈套是西高止山脉假定的喷发中心距离Deccan玄武岩最远（〜1,000 km），因此是Deccan喷发量最大的部分。尽管三个航空Rajahmundry熔岩流在地球化学上与Deccan Trap的Wai亚组相关，但与以前的放射性同位素年龄限制相关的精度差，无法与潜在的气候影响进行详细的比较。在这项研究中，我们使用新的⁴⁰ Ar / ³⁹Ar年代，古磁和火山学分析以及Rajahmundry熔岩流的生物地层学约束条件确定了它们的沉积时间和样式。我们发现，较低和中间流（65.92±0.25和65.67±0.08马，±1个σ系统的不确定性）的magnetochron C29r内爆发并分别德干陷阱的Ambenali形成的一部分。相比之下，作为马哈巴列什瓦尔组的一部分，C29n喷出了最高流量（65.27±0.08 Ma）。考虑到这些年龄限制，Rajahmundry血流并未像先前所假设的那样参与白垩纪末期的灭绝。为了确定Rajahmundry流的进驻是否会影响全球气候，我们估计了它们的爆发性CO ₂使用LOSCAR碳循环模型的标度来释放和相应的气候变化。我们发现这些流的爆发性气体排放不足以直接导致多度变暖。因此，与显着气候变暖的因果关系需要额外的地球系统反馈。