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Groundwater-derived solute fluxes to the ocean have long been assumed static and subordinate to riverine fluxes, if not neglected entirely, in marine isotope budgets. Here we present concentration and isotope data for Li, Mg, Ca, Sr, and Ba in coastal groundwaters to constrain the importance of groundwater discharge in mediating the magnitude and isotopic composition of terrestrially derived solute fluxes to the ocean. Data were extrapolated globally using three independent volumetric estimates of groundwater discharge to coastal waters, from which we estimate that groundwater-derived solute fluxes represent, at a minimum, 5% of riverine fluxes for Li, Mg, Ca, Sr, and Ba. The isotopic compositions of the groundwater-derived Mg, Ca, and Sr fluxes are distinct from global riverine averages, while Li and Ba fluxes are isotopically indistinguishable from rivers. These differences reflect a strong dependence on coastal lithology that should be considered a priority for parameterization in Earth-system models.

Author(s): Valier Galy (corresponding author) [1]; Bernhard Peucker-Ehrenbrink [1]; Timothy Eglinton [1, 2] Riverine export of particulate organic carbon (POC) to the ocean affects the atmospheric carbon inventory over a [...]

The end-Permian mass extinction (251 Ma) was the largest in Earth's history, and the great extent of biospheric perturbation is recorded as dramatic shifts in carbon isotope ratios of sedimentary materials. Both terrestrial and extraterrestrial events are commonly invoked as causative mechanisms for the crisis, and the primary reason for the event remains the subject of controversy. Geochemical indicators sensitive to the influence of extraterrestrial material involve platinum group elements and osmium and helium isotope ratios. Analyses of extinction levels in two sections from Austria and Italy reveal no evidence of an extraterrestrial impact. The end-Permian crisis, it appears, was a homegrown catastrophe. Keywords: Permian-Triassic boundary, impacts, mass extinctions, Os isotopes, He isotopes.

Radiogenic Os from the continents dominates the late Cenozoic marine Os budget. A variety of proposed radiogenic sources includes organic-rich sediments, Precambrian shields, and Re-rich sulfides. Identifying the dominant sources of radiogenic Os to the oceans has a strong impact on past climate models because weathering of silicates acts as a net sink of CO(sub 2), whereas weathering of organic matter acts as a source. Here we investigate the effects of black shale weathering on the integrity of the Re-Os isotope system and release of Re and platinum group elements. Time-correlative pairs of fresh (drill core) and weathered (outcrop) black shales of Late Ordovician age (Utica Shale magnafacies, Quebec) were analyzed for Re, Os, Ir, Pt, and Pd, as well as total S, N, and C (as C(sub carb) and (sub org)). The results indicate that 25%-64% of the initial Re budget, 45%-90% of the Os budget, 14%-65% of the Ir budget, 60%-77% of the Pt budget, 69%-86% of the Pd budget, and 44%-96%of the C(sub org) budget are lost during weathering. We use positive correlations of Os, Pt, and Pd with C(sub org) and N to calculate the respective platinum group element concentrations in the unweathered organic matter end member as approximately 3 ng/g Os, approximately 9 ng/g Pt, and 11-24 ng/g Pd. Although black shales make up Keywords: black shale, weathering, osmium, platinum group elements, rhenium.

EarthCube Data Discovery Studio (DDStudio) is a crossdomain geoscience data discovery and exploration portal. It indexes over 1.65 million metadata records harvested from 40+ sources and utilizes a configurable metadata augmentation pipeline to enhance metadata content, using text analytics and an integrated geoscience ontology. Metadata enhancers add keywords with identifiers that map resources to science domains, geospatial features, measured variables, and other characteristics. The pipeline extracts spatial location and temporal references from metadata to generate structured spatial and temporal extents, maintaining provenance of each metadata enhancement, and allowing user validation. The semantically enhanced metadata records are accessible as standard ISO 19115/19139 XML documents via standard search interfaces. A search interface supports spatial, temporal, and text‐based search, as well as functionality for users to contribute, standardize, and update resource descriptions, and to organize search results into shareable collections. DDStudio bridges resource discovery and exploration by letting users launch Jupyter notebooks residing on several platforms for any discovered datasets or dataset collection. DDStudio demonstrates how linking search results from the catalog directly to software tools and environments reduces time to science in a series of examples from several geoscience domains. URL: datadiscoverystudio.org [ABSTRACT FROM AUTHOR]

The isotopic composition of osmium (Os) in continental surface waters and shallow ground waters has been determined by analyzing fresh-water Fe-Mn nodules and bog ores. The isotopic composition of the continental runoff from the Precambrian Baltic shield is much more radiogenic (187Os/186Os = 31.2-65.4) than the runoff from the Phanerozoic sedimentary platform to the south of the Baltic Sea (187Os/186Os = 8.6-11.0). Fe-Mn nodules from the Baltic Sea have intermediate values (187Os/186Os = 12.4-21.2), indicating mixture of North Sea water and continental fresh water. Isotope mass-balance calculations indicate that the concentration of Os in the continental runoff is similar to the Os concentration in seawater. Extrapolating these data to infer the global runoff yields [approximately]48 kg/yr, comparable with previous estimates. The residence time of Os in seawater relative to continental runoff is calculated at [approximately]32 ka. The oceanic residence time of Os relative to the bulk input to seawater is [approximately]16 ka, if the mean 187Os/186Os of the continental runoff is 16. The Os isotopic composition of the continental runoff is much more variable than previously suggested, 187Os/186Os values >30 being characteristic of Precambrian shields. Glaciation of old cratonic shields might therefore modulate riverine supply of this very radiogenic cratonic Os, linking accelerated increase in the marine Os isotope record to glaciations of Precambrian shields.