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Continental flood basalt provinces (CFBs) are cataclysmic magmatic events, whose brief "main-phases" (durations ∼1 Ma;

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.

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Abstract. The element mercury (Hg) is a key pollutant, and much insight has been gained by studying the present-day Hg cycle. However, many important processes within this cycle operate on timescales responsive to centennial to millennial-scale environmental variability, highlighting the importance of also investigating the longer-term Hg records in sedimentary archives. To this end, we here explore the timing, magnitude, and expression of Hg signals retained in sediments over the past ~90 ka from two lakes, linked by a subterranean karst system: Lake Prespa (Greece/North Macedonia/Albania) and Lake Ohrid (North Macedonia/Albania). Results suggest that Hg fluctuates largely independent of variability in common host phases in each lake, and the recorded sedimentary Hg signals show distinct differences first during the late Pleistocene (Marine Isotope Stages 2–5). The Hg signals in Lake Prespa sediments highlights an abrupt, short-lived, peak in Hg accumulation coinciding with local deglaciation. In contrast, Lake Ohrid shows a broader interval with enhanced Hg accumulation, and, superimposed, a series of low-amplitude oscillations in Hg concentration peaking during the Last Glacial Maximum, that may result from elevated clastic inputs. Divergent Hg signals are also recorded during the early and middle Holocene (Marine Isotope Stage 1). Here, Lake Prespa sediments show a series of large Hg peaks; while Lake Ohrid sediments show a progression to lower Hg values. Around 3 ka, anthropogenic influences overwhelm local fluxes in both lakes. The lack of coherence in Hg accumulation between the two lakes suggests that, in the absence of an exceptional perturbation, local differences in sediment composition, lake structure, and water balance all influence the local Hg cycle, and determine the extent to which Hg signals reflect local or global-scale environmental changes.

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