James S. Eldrett

The American Geophysical Union (AGU) announces the new living collection “Impactful Datasets in Earth, Space, and Environmental Sciences” which recognizes the creation and curation of datasets enabling research, analysis, and decision making beyond what is captured by traditional academic impact metrics. The collection highlights datasets through the dimensions of People, Planet, and Prosperity, and includes a curated set of nominated datasets and accompanying special collection of data papers. Developed with the Earth Science Information Partners (ESIP) community, the nomination and review process initially invites contributors from across research, operations, and public service, to nominate datasets important to their work, and then submit a data paper that expands upon the nomination text for inclusion in the special collection. This commentary highlights the rationale for the living collection, and the process of nomination. The collection serves as a living reference that strengthens data culture, supports reproducible geoscience, and provides enduring access to critical information for science and society.

The Cenomanian–Turonian Greenhouse-Hothouse interval, encompassing Oceanic Anoxic Event 2 (OAE-2), represents one of the most intensively studied episodes of global environmental change in Earth History. However, despite extensive research, nitrogen isotope records from this interval remain geographically limited with a recent compilation highlighting that some continental margins were under-represented (e.g. one location and/or limited stratigraphic coverage per margin). This prevents a comprehensive understanding of the local and regional variability in nitrogen cycling in these Greenhouse to Hothouse conditions. This study provides new nitrogen isotope data, integrated with an extensive multidisciplinary dataset from multiple cores and outcrops across a single margin to provide new insights into the spatial and temporal variability in marine nitrogen cycling and marine primary producer community response. This study demonstrates that nitrogen isotope depletion in the Cretaceous Western Interior Seaway began in the Early Cenomanian (approx 97-98 Ma) , significantly earlier than previously recognized. The occurrence of δ15N-depleted organic matter, coupled with biomarker and palynological evidence for abundant (cyano-) bacteria, indicates enhanced diazotrophy in oxygen-deficient surface waters resulting in ammonium as the dominant form of fixed nitrogen in the photic zone. These conditions favoured low diversity eukaryote communities dominated by blooms in Prasinophyceae and Peridiniales (Dinophaceae), likely due to their ability to more efficiently assimilate ammonium through alternative nitrogenases enzymes. However, the observed δ15N values, even under broadly similar environmental conditions impacted by periodic volcanic events, can vary significantly over relatively short distances suggesting that, despite large-scale controls, local physiographic conditions significantly influenced the nitrogen cycle and related biological responses. This highlights the need to integrate data from multiple stratigraphic sections across a basin to fully capture the complexity of nitrogen cycle dynamics and associated ecological feedback during extreme climate events.

Oxidative weathering of organic carbon in sedimentary rocks is a major source of CO₂ to the atmosphere over geological timescales, but the size of this emission pathway in Earth's past has not been directly quantified due to a lack of available proxy approaches. We have measured the rhenium isotope composition of organic‐rich rocks sampled from unweathered drill cores and weathered outcrops in south Texas, whose stratigraphic successions can be tightly correlated. Oxidative weathering of more than 90% of the organic carbon and ∼85% of the rhenium is accompanied by a shift to lower rhenium isotope compositions in the weathered outcrops. The calculated isotope composition of rhenium weathered from the initial bedrock for individual samples varies systematically by ∼0.7‰ with different fractions of rhenium loss. This variation can be empirically modeled with isotope fractionation factors of α = 1.0002–1.0008. Our results indicate that the isotope composition of rhenium delivered to the oceans can be altered by weathering intensity of rock organic matter and that the rhenium isotope composition of seawater is sensitive to past oxidative weathering and associated CO₂ emissions.

This study documents the detailed palynology of the Bridge Creek Member, Greenhorn Limestone Formation, at the Rock Canyon anticline outcrop, west of Pueblo, Colorado, USA. The section is the formally ratified Global Boundary Stratotype Section and Point (GSSP) for the base of Turonian Stage and corresponding Lower Turonian Substage, and the only proposed GSSP for the base of the Middle Turonian Substage. The authors’ previously published palynological data from the underlying Cenomanian strata in the nearby US Geological Survey (USGS) Portland-1 core, and from cores and an outcrop of Cenomanian, Turonian and earliest Coniacian age in SW Texas, are reviewed for biostratigraphy. Dinoflagellate cyst ranges and events in both areas are calibrated against other published bio- and chemostratigraphical (carbon isotope) data and an astronomical age model. A regional dinoflagellate cyst zonation is proposed, adapted from a Central and Northern European scheme, comprising three zones and four subzones. Comparison with vintage published palynological data from other states, including Arizona, Kansas, Utah, Wyoming and Montana, indicates that the zonation is probably applicable to marine sections throughout the Cretaceous Western Interior Seaway of the USA. The new palynological data from around the Lower–Middle Turonian boundary at Pueblo support its proposal as a GSSP.

The Late Cretaceous Epoch was characterized by major global perturbations in the carbon cycle, the most prominent occurring near the Cenomanian–Turonian (CT) transition marked by Oceanic Anoxic Event 2 (OAE-2) at 94.9–93.7 Ma. The Cretaceous Western Interior Seaway (KWIS) was one of several epicontinental seas in which a complex water-mass evolution was recorded in widespread sedimentary successions. This contribution integrates new data on the main components of organic matter, geochemistry, and stable isotopes along a north–south transect from the KWIS to the equatorial western Atlantic and Southern Ocean. In particular, cored sedimentary rocks from the Eagle Ford Group of west Texas (∼ 90–98 Ma) demonstrate subtle temporal and spatial variations in palaeoenvironmental conditions and provide an important geographic constraint for interpreting water-mass evolution. High-latitude (boreal–austral), equatorial Atlantic Tethyan and locally sourced Western Interior Seaway water masses are distinguished by distinct palynological assemblages and geochemical signatures. The northward migration of an equatorial Atlantic Tethyan water mass into the KWIS occurred during the early–middle Cenomanian (98–95 Ma) followed by a major re-organization during the latest Cenomanian–Turonian (95–94 Ma) as a full connection with a northerly boreal water mass was established during peak transgression. This oceanographic change promoted de-stratification of the water column and improved oxygenation throughout the KWIS and as far south as the Demerara Rise off Suriname. In addition, the recorded decline in redox-sensitive trace metals during the onset of OAE-2 likely reflects a genuine oxygenation event related to open water-mass exchange and may have been complicated by variable contribution of organic matter from different sources (e.g. refractory/terrigenous material), requiring further investigation.

The Late Cretaceous Epoch was characterized major global perturbations in the carbon cycle, the most prominent occurring near the Cenomanian-Turonian (CT) transition marked by Oceanic Anoxic Event/OAE-2 at 94.9–93.7 Ma. The Cretaceous Western Interior Seaway (KWIS) was one of several epicontinental seas in which a complex water-mass evolution was recorded in widespread sedimentary successions. This contribution integrates new data on the main components of organic matter, geochemistry, and stable isotopes along a North-South transect from the KWIS to the equatorial western Atlantic and Southern Ocean. In particular, cored sedimentary rocks from the Eagle Ford Group of West Texas (~ 90–98 Ma) demonstrate subtle temporal and spatial variations in paleoenvironmental conditions and provide an important geographic constraint for interpreting water-mass evolution. High latitude (boreal-austral), equatorial tethyan and locally sourced Western Interior Seaway water-masses are distinguished by distinct palynological assemblages and geochemical signatures. The northward migration of a tethyan water-mass into the KWIS occurred during the early-middle Cenomanian (98–95 Ma) followed by a major re-organization during the latest Cenomanian-Turonian (95–94 Ma) as a full connection with a northerly- boreal water-mass was established during peak transgression. This oceanographic change promoted de-stratification of the water column and improved oxygenation throughout the KWIS and as far south as the Demerara Rise off Suriname. In addition the recorded decline in redox-sensitive trace metals during the onset of OAE-2 likely reflects a genuine oxygenation event related to open water-mass exchange and may have been complicated by variable contribution of organic matter from different sources (e.g. refractory/terrigenous material), requiring further investigation.