Search for: All records

Calcite is known to incorporate a range of non-constituent ions during its precipitation from aqueous solutions. Their concentrations (measured as E/Ca ratios, where E denotes the elemental forms of non-constituent ions) in calcite formed in seawater can serve as useful tools for paleoceanographic studies. But this requires concrete understanding of the incorporation patterns and their dependence to environmental factors at the time of mineral precipitation. Here, we present Na/Ca, K/Ca, S/Ca, and B/Ca ratios of inorganic calcite samples generated in laboratory experiments using Mg-free artificial seawater with systematic manipulations of pH, [DIC], and [Ca2+]. The three parameters were varied both individually (the pH, DIC, and Ca experimental series) and in tandem (the pH-Ca and DIC-Ca series) to form calcites under variable versus near-constant precipitation rates (denoted as R). All measured E/Ca ratios showed a robust positive linear dependence to changes in [Ca2+] in the Ca, pH-Ca, and DIC-Ca series, irrespective of changes in R. While K/Ca and S/Ca ratios changed almost exclusively with [Ca2+], Na/Ca and B/Ca ratios showed an additionally strong increase with increasing pH and a more moderate increase with rising [DIC], when R changed accordingly in the pH and DIC series. While R-driven kinetic effects and/or formation of certain cation–anion pairs may be important for the elemental uptake in calcite under some circumstances, these mechanisms or processes cannot fully account for the observed trends in every experimental series for all E/Ca ratios considered here. We propose that the observed E/Ca trends can be comprehensively explained by simultaneously considering the nonequivalent influence of changes in solution [Ca2+] and [CO32−] on step-specific kink formation dynamics and the size difference between the respective non-constituent ions (K+, Na+, SO42−, and B(OH)4− and B(OH)3) relative to Ca2+ and CO32− that constitute the calcite lattice. 

New major and trace element data on samples collected during the IODP (International Ocean Discovery Program) Expedition 396, ODP (Ocean Drilling Program) Leg 104, and DSDP (Deep Sea Drilling Project) Leg 38 on the Vøring margin, including 209 whole rocks analyses on hard rock samples (basalt, granite, andesite, dacite and rhyolite), 13 whole rock data on ash layers, and 381 in situ pXRF analyses on basaltic rocks. The DIGIS geochemical data repository is a research data repository in the Earth Sciences domain with a specific focus on geochemical data. The repository archives, publishes and makes accessible user-contributed, peer-reviewed research data in standardised form (EarthChem Team, 2022, https://doi.org/10.26022/IEDA/112263) that fall within the scope of the GEOROC database (https://georoc.eu). All submissions of new data will be considered for inclusion in the GEOROC database. It is hosted at GFZ Data Services through a collaboration between the Digital Geochemical Data Infrastructure (DIGIS) for GEOROC 2.0 (https://digis.geo.uni-goettingen.de) and the GFZ Helmholtz Centre for Geosciences. 

The late Paleocene and early Eocene (LPEE) are characterized by long-term (million years, Myr) global warming and by transient, abrupt (kiloyears, kyr) warming events, termed hyperthermals. Although both have been attributed to greenhouse (CO₂) forcing, the longer-term trend in climate was likely influenced by additional forcing factors (i.e., tectonics) and the extent to which warming was driven by atmospheric CO₂remains unclear. Here, we use a suite of new and existing observations from planktic foraminifera collected at Pacific Ocean Drilling Program Sites 1209 and 1210 and inversion of a multiproxy Bayesian hierarchical model to quantify sea surface temperature (SST) and atmospheric CO₂over a 6-Myr interval. Our reconstructions span the initiation of long-term LPEE warming (~58 Ma), and the two largest Paleogene hyperthermals, the Paleocene–Eocene Thermal Maximum (PETM, ~56 Ma) and Eocene Thermal Maximum 2 (ETM-2, ~54 Ma). Our results show strong coupling between CO₂and temperature over the long- (LPEE) and short-term (PETM and ETM-2) but differing Pacific climate sensitivities over the two timescales. Combined CO₂and carbon isotope trends imply the carbon source driving CO₂increase was likely methanogenic, organic, or mixed for the PETM and organic for ETM-2, whereas a source with higher δ¹³C values (e.g., volcanic degassing) is associated with the long-term LPEE. Reconstructed emissions for the PETM (5,800 Gt C) and ETM-2 (3,800 Gt C) are comparable in mass to future emission scenarios, reinforcing the value of these events as analogs of anthropogenic change. 

Abstract The Paleocene‐Eocene Thermal Maximum (PETM, ∼56 million years ago) is among the best‐studied climatic warming events in Earth history and is often compared to projected anthropogenic climate change. The PETM is characterized by a rapid negative carbon isotope excursion and global temperature increase of 4–5°C, accompanied by changes in spatial patterns of evaporation and precipitation in the global hydrologic cycle. Recent climate model reconstructions suggest a regionally complex and non‐linear response of one important aspect of global hydrology: enhanced moisture flux from the low‐latitude ocean. In this study, we use the elemental and stable isotope geochemistry of surface‐dwelling planktic foraminifera from a low‐latitude Atlantic deep‐sea sedimentary record (IODP Site 1258) to quantify changes in sea‐surface temperature (SST) and salinity. Foraminiferal Mg/Ca and δ¹⁸O values are interpreted with a Bayesian forward proxy system model to reconstruct how SST and salinity changed over the PETM at this site. These temperature and salinity reconstructions are then compared to recent climate model simulations of Eocene warming. Our reconstructions indicate °C of warming, in excellent agreement with estimates from other tropical locations and modeled PETM warmth. The regional change in salinity is not as straightforward, demonstrating a slight decrease at extremepCO₂forcing (a reversal of the modeled sense of change under moderatepCO₂forcing) in both model and proxy reconstructions. The cause of this non‐linear response is unclear but may relate to increased South American continental runoff or shifts in the Inter‐Tropical Convergence Zone. 

The mid-Norwegian margin is one of the best studied volcanic rifted margin on Earth. Geophysical investigations have demonstrated the presence of well-developed seaward-dipping reflectors, landward-dipping reflectors, marginal highs, ash layers and sill complexes. These features have been proven to consist of magmatic rocks through the international Deep Sea Drilling Program (DSDP expedition 38, 1974), Ocean Drilling Program (ODP expedition 104, 1985), International Discovery Program (IODP expedition 396, 2021), and commercial drilling. A total of fifteen drill cores penetrated magmatic rocks that formed between 57 and 50 million-years ago. Here we provide a compilation of all new and published data for magmatic rocks in the fifteen drill cores (n= 563). This dataset represent a resource for examining the origin of magmatism associated with continental breakup and rifted margin formation, particularly the formation of excess magmatism compared to normal mid-oceanic spreading ridges, mantle-crust interaction, and the linkage of magmatism to global hyperthermal events on Earth’s surface. The DIGIS geochemical data repository is a research data repository in the Earth Sciences domain with a specific focus on geochemical data. It is hosted at GFZ Data Services through a collaboration between the Digital Geochemical Data Infrastructure (DIGIS) for GEOROC 2.0 (https://digis.geo.uni-goettingen.de) and the GFZ Helmholtz Centre for Geosciences. The repository archives, publishes and makes accessible user-contributed, peer-reviewed research data that fall within the scope of the GEOROC database. Compilations of previously published data are also made available on the GEOROC website (https://georoc.eu) as Expert Datasets. 

Abstract The mid‐Norwegian Margin, part of the North Atlantic Igneous Province (NAIP), is a well‐studied volcanic rifted margin formed during the breakup between Greenland and Eurasia ∼56 Ma, with the largest accumulation of magmatic material hosted by the Vøring Margin section. Despite extensive study in the area, the main controls on magmatic productivity during continental breakup remain debated. To constrain the drivers of breakup magmatism, we developed an inverse Monte Carlo statistical melting model that infers source mineralogy from basalt chemistry. When applied to basalts recently recovered on the Vøring Margin, our results reveal a clear shift in source mineralogy during rifting, with peak magmatism coinciding with clinopyroxene enrichment, despite mantle potential temperatures likely being capped below 1500°C. We also establish that, while the proto‐Iceland mantle plume played a role during the emplacement of the NAIP, the main driver for the continental breakup magmatism is lithospheric thinning as a consequence of continent breakup. This study provides new insights into the magmatic and geodynamic evolution of the mid‐Norwegian Margin, emphasizing the role of lithospheric refertilization in driving breakup magmatism. 

The geological record encodes the relationship between climate and atmospheric carbon dioxide (CO₂) over long and short timescales, as well as potential drivers of evolutionary transitions. However, reconstructing CO₂beyond direct measurements requires the use of paleoproxies and herein lies the challenge, as proxies differ in their assumptions, degree of understanding, and even reconstructed values. In this study, we critically evaluated, categorized, and integrated available proxies to create a high-fidelity and transparently constructed atmospheric CO₂record spanning the past 66 million years. This newly constructed record provides clearer evidence for higher Earth system sensitivity in the past and for the role of CO₂thresholds in biological and cryosphere evolution.