Geochemical data from sedimentary rocks are the primary source of information regarding Earth's surface evolution through time, including its air and water envelopes and interactions with life and deep Earth processes. The Sedimentary Geochemistry and Paleoenvironments Project (SGP) is a scientific consortium centered around open data and community-driven development of cyberinfrastructure tools and resources for sedimentary geochemistry and Earth history. Here we describe the SGP Phase 2 data release, which focused on incorporating Paleoproterozoic and Mesoproterozoic (2500–1000 million years ago) data and better accommodating carbonate data. This data release was built through the involvement of >200 researchers worldwide in academia, government, and industry, and provides the largest available public data resource for our user community in the academic fields of geochemistry, sedimentology, tectonics, paleontology, Earth history, and paleoclimate, as well as the petroleum and minerals industries. The dataset now encompasses 126,006 samples and 4,132,371 geochemical analyses. In addition to direct entry by SGP Team Members, we have ingested and incorporated datasets from the Geoscience Australia OZCHEM database, the Alberta Geological Survey, and the Deep-Time Marine Sedimentary Element Database (DM-SED) compilation. This paper details sampling in the Phase 2 dataset with respect to age, geography, lithology, and other geological characteristics, documents access via our search website and API, discusses possible issues and/or biases in the dataset that could impact analyses, describes plans for governance and stewardship of data from Indigenous lands, and serves as the citable reference paper for the data release.

The end-Triassic mass extinction was among the most severe biotic crises of the Phanerozoic. It has been linked with the global expansion of marine anoxia, and the prolongation of these conditions within epeiric seas has been proposed as a cause for the suppression of biodiversity during the early Jurassic Hettangian Stage. Testing this interpretation is complicated by spatially heterogeneous patterns of local marine redox conditions within the western Tethys European Epicontinental Shelf. In this study, we assess the redox state within this region by focusing on two carbonate successions in Italy, a peritidal platform at Mount Sparagio, Sicily, and an offshore ramp deposit at Val Adrara in the Southern Alps. Based on previously published I/Ca ratios, these locations record distinct local background redox conditions, with Val Adrara showing a notably lower pre-extinction oxygen saturation state than Mount Sparagio. Here, we measure S13C and S18O at Mount Sparagio and S44Ca and trace element ratios at both sites to identify the roles of mineralogical and diagenetic effects on the preservation of primary redox signals. A numerical framework of multiple elemental (Sr, Mg, Mn, I) and isotopic (S13C, S18O, S44Ca, S238U, and S34SCAS) ratios was constructed to recognize modes of carbonate diagenesis and source-mixing in the data. While diagenesis is impossible to completely rule out, our state-of-the-art approach provides robust evidence against common forms of diagenetic alteration as the main drivers of the overall paleoredox proxy trends. Where the redox signals are largely preserved, we interpret differences in pre-extinction I/Ca between the two sites to reflect distinct local oxygenation states. Drawing from published Community Earth System Model simulations, we propose that ocean circulation and hydrological regime could have been important drivers of spatial heterogeneity in paleo-redox conditions across the European Epicontinental Shelf.

Ecosystem function and its evolution depend on the number of taxa and the amount of biomass. For the oceans, spatial and temporal trends in diversity are well known, and spatial variation in biomass within the modern ocean is increasingly documented. Temporal variation in biomass, by contrast, remains undocumented, leaving a crucial gap in our understanding of how the marine biosphere evolved over geologic time. Here, we compiled compositional data from 7,749 marine limestone samples spanning the past 541 million years that document the proportion of sediment comprising the shells of animals, algae, and protists. The data capture temporal variation in skeletal content that is consistent across geologic settings, water depths, and latitudes. The variation largely parallels long-term trends in taxonomic diversity during intervals of diversification and across the three major mass extinctions with high-resolution compositional data, pointing toward a macroevolutionary coupling between marine biodiversity and biomass.

This study used systematic coring, hyperspectral scans, carbonate/siliciclastic analysis, and stable isotope measurements to evaluate environmental controls on large microbial buildup evolution. Buildups initiated on a discontinuous transgressive lag of flat-pebble conglomerate, controlling their spatial distribution and flat-based geometry. The consistent three-phase buildup architecture indicates allogenic forcing by fluctuations in sea level and siliciclastic influx. The initiation of each phase began in a pure carbonate system, with high-energy skeletal-oolitic grainstone interbuildup deposition. Depositional moats formed in the grainstone adjacent to buildups during phases 1 and 2. Buildups developed up to 5.7 m of synoptic relief during phases 1 and 3 prior to being onlapped by siliciclastic sediment. Phase 2 of the buildups intertongued with heterolithic interbuildup sediment, developing only 30 cm of synoptic relief. Lateral variability in phase 2 architecture indicates autogenic controls causing localized differences in microbialite growth rates versus interbuildup accumulation. Phases 1 and 3 display a dense calcitic calcimicrobial rind that surrounds and encloses the top of the buildups. The interior of buildups is composed of decimeter-scale stromatolitic columns, each encased by a calcimicrite rind and exhibiting mottled internal texture due to bioturbation and dolomitization. Interiors of buildups entrapped more carbonate sediment, creating greater porosity, and thus were destructively dolomitized. In contrast, the calcimicrite rinds of columns and the thick rinds surrounding buildups formed as biochemical carbonate precipitates, with minimal porosity, and, therefore, escaped dolomitization. The δ18O and δ13C values of the column and buildup rinds are consistent with late Cambrian seawater, supporting an origin as a precipitate and age as Sunwaptan.

During the Permo-Triassic time, an extensive epeiric carbonate platform (Khuff Formation) developed on the Arabian Plate. Besides becoming one of the world’s most prolific hydrocarbon reservoirs, the Khuff carbonates also recorded major shifts in physiochemical, biological, and environmental conditions associated with the Permo-Triassic mass extinction. However, recognition and expression of this catastrophic event in the Arabian Plate were unresolved due to ambiguous geochemical signals. Pervasive diagenesis has been interpreted as one of the major causes of creating such mixed geochemical signals, yet the origin and timing of diagenetic processes remain enigmatic. In this study, we used measurements of elemental concentrations and isotope ratios to help distinguish the geochemical signatures of Permo-Triassic environmental change from diagenetic influences related to dolomitization and dissolution-cementation. The geochemical results suggest that most of the primary signals have been altered by meteoric-driven diagenesis as shown from the REE pattern. Dolomitization occurred early, under near-surface conditions, driven primarily by modified Lower Triassic seawater. The δ18OVPDB and δ13CVPDB values fall within the expected range of Triassic seawater, 0.5 to -2.8‰ and 1.6 to 3.1‰, respectively. This interpretation is corroborated by the calculated clumped isotope (Δ47) temperature of around 34oC. The formation of oomoldic porosity and blocky cement in the Khuff carbonates, occurred later, during shallow burial (up to 1 km) and involving evolved and heated meteoric fluids as indicated by negative Eu anomalies, more negative δ18O (up to -8.2‰) and δ13C (up to -2.1‰) isotopes, depleted Sr concentrations and elevated Fe and Mn concentrations. The Δ47-derived temperature of the blocky cement further supports this argument, with values indicating precipitation at ~50oC. Thus, dissolution occurred in burial environments through cryptic dissolution that drove the cementation by increasing the saturation state of the formation waters. Furthermore, a model of fluid-rock interactions shows that meteoric fluids alone cannot explain the observed patterns, and a moderate to high degree of mixing between meteoric fluids and subsurface brines is required. These new constraints on the diagenesis of the Khuff Formation are critical for understanding and predicting the formation of porosity and the relative timing of hydrocarbon charge and migration in the subsurface. The integrated approach should also be applicable to other petroliferous carbonate provinces elsewhere.

The end-Triassic mass extinction was among the most severe biotic crises of the Phanerozoic. It has been linked with the global expansion of marine anoxia, and the prolongation of these conditions within epeiric seas has been proposed as a cause for the suppression of biodiversity during the Hettangian. Testing this interpretation is complicated by spatially heterogenous patterns of local marine redox conditions within the western Tethys European Epicontinental Shelf. In this study we assess the redox state within this region by focusing on two carbonate successions in Italy. Based on I/Ca ratios, these locations record distinct local background redox conditions, with Val Adrara showing notably lower pre-extinction oxygen saturation state compared to Mount Sparagio. To better explain these differences, δ44Ca and trace element analyses were used to identify the roles of mineralogical and diagenetic effects on the preservation of primary redox signals. A framework of multiple elemental (Sr, Mg, Mn, I) and isotopic (δ13C, δ18O, δ44Ca, δ238U and δ34SCAS) ratios was developed to identify factors that could influence carbonate geochemistry. Both sites probably retain some primary variation in δ238U, δ34SCAS and I/Ca, but they are likely also shaped by changing mineralogy and early diagenetic conditions which complicates interpretations of the seawater composition. Where the redox signals are largely preserved, we interpret differences in pre-extinction I/Ca between the two sites to reflect distinct local oxygenation states. Model simulations show that ocean circulation and hydrological regime could have been important drivers of spatial heterogeneity in paleo-redox conditions across the European Epicontinental Shelf.

A central question in the study of mass extinction is whether these events simply intensify background extinction processes and patterns versus change the driving mechanisms and associated patterns of selectivity. Over the past two decades, aided by the development of new fossil occurrence databases, selectivity patterns associated with mass extinction have become increasingly well quantified and their differences from background patterns established. In general, differences in geographic range matter less during mass extinction than during background intervals, while differences in respiratory and circulatory anatomy that may correlate with tolerance to rapid change in oxygen availability, temperature, and pH show greater evidence of selectivity during mass extinction. The recent expansion of physiological experiments on living representatives of diverse clades and the development of simple, quantitative theories linking temperature and oxygen availability to the extent of viable habitat in the oceans have enabled the use of Earth system models to link geochemical proxy constraints on environmental change with quantitative predictions of the amount and biogeography of habitat loss. Early indications are that the interaction between physiological traits and environmental change can explain substantial proportions of observed extinction selectivity for at least some mass extinction events. A remaining challenge is quantifying the effects of primary extinction resulting from the limits of physiological tolerance versus secondary extinction resulting from the loss of taxa on which a given species depended ecologically. The calibration of physiology-based models to past extinction events will enhance their value in prediction and mitigation efforts related to the current biodiversity crisis.

The end-Triassic biodiversity crisis was one of the most severe mass extinctions in the history of animal life. However, the extent to which the loss of taxonomic diversity was coupled with a reduction in organismal abundance remains to be quantified. Further, the temporal relationship between organismal abundance and local marine redox conditions is lacking in carbonate sections. To address these questions, we measured skeletal grain abundance in shallow-marine limestones by point counting 293 thin sections from four stratigraphic sections across the Triassic/Jurassic boundary in the Lombardy Basin and Apennine Platform of western Tethys. Skeletal abundance decreased abruptly across the Triassic/Jurassic boundary in all stratigraphic sections. The abundance of skeletal organisms remained low throughout the lower-middle Hettangian strata and began to rebound during the late Hettangian and early Sinemurian. A two-way ANOVA indicates that sample age (p < .01, η2  = 0.30) explains more of the variation in skeletal abundance than the depositional environment or paleobathymetry (p < .01, η2  = 0.15). Measured I/Ca ratios, a proxy for local shallow-marine redox conditions, show this same pattern with the lowest I/Ca ratios occurring in the early Hettangian. The close correspondence between oceanic water column oxygen levels and skeletal abundance indicates a connection between redox conditions and benthic organismal abundance across the Triassic/Jurassic boundary. These findings indicate that the end-Triassic mass extinction reduced not only the biodiversity but also the carrying capacity for skeletal organisms in early Hettangian ecosystems, adding to evidence that mass extinction of species generally leads to mass rarity among survivors.

Chondrodonta is an opportunistic, oyster‐like bivalve, common in shallow‐water carbonates of the Cretaceous Tethyan Realm. Despite its high abundance and widespread geographic distribution, the precise relationship between the early Aptian proliferation and environmental perturbations resulting from the Oceanic Anoxic Event 1a (OAE1a), has not been investigated. Stratigraphic and geochemical analyses of the lower Aptian Chondrodonta bedsets within the inner platform limestones of the Apulia Carbonate Platform (Gargano Promontory, southern Italy) are conducted to assess the environmental controls on the Chondrodonta proliferation and its timing and causal relationship to OAE1a. Chondrodonta occurs with sparse to common individuals within requieniid rudist floatstone–rudstones, forms monospecific biostromes during the early phase of stressed environmental conditions and then rapidly disappears at the peak of OAE1a. It proliferates in dysoxic seawater with relatively increased trophic sources, which correlate to increasing nutrient levels in the nearby pelagic realm. Chondrodonta‐rich beds are associated worldwide with the onset of OAE1a and occur in a transitional context between a stable and a strongly stressed environment, where the opportunistic behaviour of Chondrodonta is rather efficient. Increasing nutrient load and unstable environmental conditions right below the peak of OAE1a created an environmental ‘window’ favourable for Chondrodonta to proliferate, outplaying the less tolerant benthos (for example, rudists). The occurrence, duration and position of the environmental window were controlled by local palaeogeographic and hydrodynamic settings (i.e. low energy, decreased seawater oxygenation and circulation). Further increase in inhospitable conditions, leading to OAE1a, constituted an upper threshold for Chondrodonta and allowed mesotrophic taxa like Bacinella–Lithocodium and orbitolinids to dominate the benthic communities. The present study suggests that the proliferation of Chondrodonta in shallow‐water platform carbonates can be used as proxy for the initial phase of ecological stress related to OAE1a.

A key challenge regarding development of carbonate platforms is predicting the temporal pattern of platform-margin progradation, aggradation, retrogradation, and drowning. Numerical forward models of carbonate sedimentation have been widely applied to this problem, shedding substantial light on the roles of sediment production, transport, tectonic subsidence, and eustasy on the evolution of carbonate platforms. however, forward models are typically complex and computationally expensive, preventing comprehensive exploration of parameter space. In addition, the interactions among parameters are often nonlinear, preventing the development of simple expressions relating the position of the platform margin to the governing parameters of the model. To complement the considerable insights derived from numerical forward models, this study presents analytical expressions for the temporal evolution of the position of platform margins using the simplest possible assumptions regarding sediment production and transport. These expressions provide useful null models, deviations from which can be used to identify the particular effects of biology or seawater chemistry on carbonate factories in influencing the development of these important sedimentary deposits. Application of the model to synthetic and outcrop examples demonstrates that these simple equations are useful for parameter estimation that can then be used to guide more detailed, process-based numerical forward models.

Although Late Cambrian microbial build‐ups were recognized in the Point Peak Member of the Wilberns Formation in Central Texas (USA) nearly 70 years ago, only a few studies focused specifically on the build‐ups themselves. This study focuses on the interpretation of the regional (15 measured sections described in literature representing an area of 8000 km2) and local (field and drone photogrammetry studies in a 25 km2 area from within south Mason County) microbial build‐up occurrence, describes their growth phases and details their interactions with the surrounding inter‐build‐up sediments. The study establishes the occurrence of microbial build‐ups in the lower and upper Point Peak members (the Point Peak Member is informally broken up into the lower Point Peak and the upper Point Peak members separated by Plectotrophia zone). The lower Point Peak Member consists of three <1 m thick microbial bioherms and biostrome units, in addition to heterolithic and skeletal/ooid grainstone and packstone beds. One, up to 14 m thick, microbial unit associated with inter‐build‐up skeletal and ooid grainstone and packstone beds, intercalated with mixed siliciclastic–carbonate silt beds, characterizes the upper Point Peak member. The microbial unit in the upper Point Peak member displays a three‐phase growth evolution, from an initial colonization phase on flat based, rip‐up clast lenses, to a second aggradation and lateral expansion phase, into a third well‐defined capping phase. The ultimate demise of the microbial build‐ups is interpreted to have been triggered by an increase of water turbidity caused by a sudden influx of fine siliciclastics. The lower Point Peak member represents inner ramp shallow subtidal and intertidal facies and the upper Point Peak member corresponds to mid‐outer ramp subtidal facies. Understanding the morphological architecture and depositional context of these features is of importance for identifying signatures of early life on Earth.