The Paleocene-Eocene Thermal Maximum (PETM; ~55.9 Ma) was a geologically rapid warming period associated with carbon release, which caused a marked increase in the hydrological cycle. Here, we use lithium (Li) isotopes to assess the global change in weathering regime, a critical carbon drawdown mechanism, across the PETM. We find a negative Li isotope excursion of ~3‰ in both global seawater (marine carbonates) and in local weathering inputs (detrital shales). This is consistent with a very large delivery of clays to the oceans or a shift in the weathering regime toward higher physical erosion rates and sediment fluxes. Our seawater records are best explained by increases in global erosion rates of ~2× to 3× over 100 ka, combined with model-derived weathering increases of 50 to 60% compared to prewarming values. Such increases in weathering and erosion would have supported enhanced carbon burial, as both carbonate and organic carbon, thereby stabilizing climate.

Abstract. Large-scale magmatic events like the emplacement of the North Atlantic Igneous Province (NAIP) are often coincident with periods of extreme climate change such as the Palaeocene–Eocene Thermal Maximum (PETM). One proxy for volcanism in the geological record that is receiving increased attention is the use of mercury (Hg) anomalies. Volcanic eruptions are among the dominant natural sources of Hg to the environment; thus, elevated Hg∕TOC values in the sedimentary rock record may reflect an increase in volcanic activity at the time of deposition. Here we focus on five continental shelf sections located around the NAIP in the Palaeogene. We measured Hg concentrations, total organic carbon (TOC) contents, and δ13C values to assess how Hg deposition fluctuated across the PETM carbon isotope excursion (CIE). We find a huge variation in Hg anomalies between sites. The Grane field in the North Sea, the most proximal locality to the NAIP analysed, shows Hg concentrations up to 90 100 ppb (Hg∕TOC = 95 700 ppb wt %−1) in the early Eocene. Significant Hg∕TOC anomalies are also present in Danish (up to 324 ppb wt %−1) and Svalbard (up to 257 ppb wt %−1) sections prior to the onset of the PETM and during the recovery period, while the Svalbard section also shows a continuous Hg∕TOC anomaly during the body of the CIE. The combination with other tracers of volcanism, such as tephra layers and unradiogenic Os isotopes, at these localities suggests that the Hg∕TOC anomalies reflect pulses of magmatic activity. In contrast, we do not observe clear Hg anomalies on the New Jersey shelf (Bass River) or the Arctic Ocean (Lomonosov Ridge). This large spatial variance could be due to more regional Hg deposition. One possibility is that phreatomagmatic eruptions and hydrothermal vent complexes formed during the emplacement of sills led to submarine Hg release, which is observed to result in limited distribution in the modern era. The Hg∕TOC anomalies in strata deposited prior to the CIE may suggest that magmatism linked to the emplacement of the NAIP contributed to the initiation of the PETM. However, evidence for considerable volcanism in the form of numerous tephra layers and Hg∕TOC anomalies post-PETM indicates a complicated relationship between LIP volcanism and climate. Factors such as climate system feedbacks, changes to the NAIP emplacement style, and/or varying magma production rates may be key to both the onset and cessation of hyperthermal conditions during the PETM. However, processes such as diagenesis and organic matter sourcing can have a marked impact on Hg∕TOC ratios and need to be better constrained before the relationship between Hg anomalies and volcanic activity can be considered irrefutable.

Abstract. Large-scale magmatic events like the emplacement of the North Atlantic Igneous Province (NAIP) are often coincident with periods of extreme climate change such as the Palaeocene–Eocene Thermal Maximum (PETM). One proxy for volcanism in the geological record that is receiving increased attention is the use of mercury (Hg) anomalies. Volcanic eruptions are among the dominant natural sources of Hg to the environment; thus, elevated Hg/TOC values in the sedimentary rock record may reflect an increase in volcanic activity at the time of deposition. Here we focus on five continental shelf sections located around the NAIP in the Paleogene. We measured Hg, total organic carbon (TOC) concentrations, and δ13C values to assess how Hg deposition fluctuated across the carbon isotope excursion (CIE). We find a huge variation in Hg anomalies between sites. The Grane field in the North Sea, the most proximal locality to the NAIP analyzed, shows Hg concentrations up to 90,100 ppb (Hg/TOC = 95,700 ppb/wt%) in the early Eocene. Significant Hg/TOC anomalies are also present in Danish (up to 324 ppb/wt%) and Svalbard (up to 257 ppb/wt%) sections prior to the onset of the PETM and during the recovery period, while the Svalbard section also shows a continuous Hg/TOC anomaly during the body of the CIE. The combination with other tracers of volcanism, tephra layers and unradiogenic Os isotopes, at these localities suggests that the Hg/TOC anomalies reflect pulses of magmatic activity. In contrast, we do not observe clear Hg anomalies on the New Jersey shelf (Bass River) or the Arctic Ocean (Lomonosov Ridge). This large spatial variance could be due to more regional Hg deposition. One possibility is that phreatomagmatic eruptions and hydrothermal vent complexes formed during the emplacement of sills led to submarine Hg release, which is observed to result in limited distribution in the modern. The Hg/TOC anomalies in strata deposited prior to the CIE may suggest that magmatism linked to the emplacement of the NAIP contributed to the initiation of the PETM. However, evidence for considerable volcanism in the form of numerous tephra layers and Hg/TOC anomalies post-PETM indicates a complicated relationship between LIP volcanism and climate. Factors such as climate system feedbacks, changes to the NAIP emplacement style, and/or varying magma production rates may be key to both the onset and cessation of hyperthermal conditions during the PETM.

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We present new structural, geochemical, and U-Pb zircon data from syn-to lateorogenic sedimentary-volcanic basins in the southwestern part of the Trondheim Nappe Complex (TNC), central Norwegian Caledonides. In this area, a succession of E-MORB type metabasalt, jasper, ribbon chert with associated sandstone and conglomerate, and green siltstone is interpreted to represent volcanism and sedimentation in a hitherto little known spreading-dominated tectonic environment. This environment is different from the suprasubduction zone ophiolite setting dominating the Iapetus rock record elsewhere in the Scandinavian Caledonides. This volcanic and sedimentary succession was overturned and isoclinally folded in a pre-427 Ma orogenic phase. Post-427 Ma cross-bedded sandstones were deposited on the eroded surface of the previously deformed rocks, representing a rare example of a late Silurian or younger sedimentary basin within the Scandinavian Caledonides. The crossbedded sandstones are intercalated and/or overlain by post-427 Ma intermediate volcanic/subvolcanic rocks of calc-alkaline composition, representing a hitherto unknown volcanic phase within the TNC and elsewhere within the Scandinavian Caledonides. Their particular geochemical signature could be the result of late-stage subduction zone volcanism just prior to the onset of continent-continent collision between Baltica and Laurentia, or much younger post-collisional extensional melting with inherited subduction signatures.