For over 50 years, cores recovered from ocean basins have generated fossil, lithologic, and chemical archives that have revolutionized fields within the earth sciences. Although scientific ocean ...drilling (SOD) data are openly available following each expedition, the formats for these data are heterogeneous. Furthermore, lithological, chronological, and paleobiological data are typically separated into different repositories, limiting researchers' abilities to discover and analyze integrated SOD data sets. Emphasis within Earth Sciences on Findable, Accessible, Interoperable, and Reusable (FAIR) Data Principles and the establishment of community‐led databases provide a pathway to unite SOD data and further harness the scientific potential of the investments made in offshore drilling. Here, we describe a workflow for compiling, cleaning, and standardizing key SOD records, and importing them into the Paleobiology Database and Macrostrat, systems with versatile, open data distribution mechanisms. These efforts are being carried out by the extending Ocean Drilling Pursuits (eODP) project. eODP has processed all of the lithological, chronological, and paleobiological data from one SOD repository, along with numerous other data sets that were never deposited in a database; these were manually transcribed from original reports. This compiled data set contains over 79,899 lithological units from 1,125 drilling holes from 422 sites. Over 26,000 fossil‐bearing samples, with 5,378 taxonomic entries from 13 biological groups, are placed within this lithologic spatiotemporal framework. All information is available via GitHub and Macrostrat's application programming interface, which renders data retrievable by a variety of parameters, including age, site, and lithology.
Key Points
Scientific ocean drilling has produced vast amounts of data; however, they are not archived in a way that meets the Findable, Accessible, Interoperable, and Reusable data principles
The extending Ocean Drilling Pursuits project standardizes lithology, paleontology, and age data across decades of drilling programs
This project has migrated data sets to existing, open‐access, searchable databases to enable scientific research
The geological record is a three‐dimensional mosaic of gap‐bound rock bodies that, at any given scale of temporal resolution, were emplaced more or less continuously. At any geographic location, the ...irregular alternation of processes responsible for the formation and destruction of rock bodies results in the preservation of hiatus‐bound rock packages that have a distinct time of first occurrence (base, or oldest portion), a time of last occurrence (top, or youngest portion), and a suite of defining characters (e.g., lithologies, thickness, fossils, etc.). Many important aspects of the geologic record can be quantified by compiling the stratigraphic ranges of such gap‐bound rock packages. These include the quantity and spatial and temporal distribution of preserved rock, rates of rock formation, sequence stratigraphic architecture, and area‐weighted rates of expansion and contraction/erosional truncation of rock emplacement settings. This approach to characterizing the rock record is scalable, permitting application to records encompassing entire continents and hundreds of millions of years as well as individual basins and geologically short time intervals. To illustrate the utility of this approach and to provide a new high‐resolution analysis of the temporal structure of the geologic record, gap‐bound rock packages in the continental United States and southern Alaska were compiled directly from the American Association of Petroleum Geologists Correlation of Stratigraphic Units of North America (COSUNA) charts. The COSUNA charts were assembled at a temporal resolution of approximately 1–3 million years (m.yr.) in the Phanerozoic and contain 4173 gap‐bound rock packages. Many important aspects of the North American geologic record are revealed by the temporal distribution of gap‐bound rock packages, including rock quantity, long‐term rates of sediment accumulation, and basin turnover. The durations of gap‐bound sedimentary successions are approximately exponentially distributed, with a mean duration of 25.2 m.yr. and a median duration of 16.9 m.yr. The probability of initiation and truncation among sedimentary packages does not increase or decrease substantially during the Phanerozoic, but these parameters do vary on shorter timescales in response to tectonically and glacioeustatically driven changes in sea level. The largest increase in the rate of sediment truncation occurs at the end‐Permian, which marks a clear and fundamental temporal discontinuity in the sedimentary record of North America. Smaller discontinuities occur at the end‐Ordovician, the end‐Triassic, and the end‐Cretaceous. Lithologically, Cambrian‐Mississippian sedimentary successions are dominated by carbonates, and post‐Paleozoic successions are dominated by terrigenous clastics. The quantity of preserved rock, the carbonate/siliciclastic ratio, and the dominant lithology comprising terrigenous clastics all vary substantially from interval to interval during the Phanerozoic, indicating that processes governing the formation and destruction of sedimentary rocks vary on timescales of <5 m.yr.
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Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NMLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Macrostrat is a platform for deep‐time geoscientific research that integrates stratigraphic columns and geologic maps into a digital description of the crust. The database and supporting software ...track crustal evolution and provide location‐based geological information to geoscience end users. Macrostrat houses multiple scales of mapping and stratigraphic data, from continent‐ and basin level summaries to single quadrangles and measured sections. Currently, Macrostrat's primary data holdings consist of regional stratigraphic columns with a spatial footprint weighted heavily to North America. While the data are of sufficient scale and resolution to generate insights about Earth evolution, increasing resolution and expanding spatial coverage will allow a new generation of scientific and interpretive uses. The next phase of Macrostrat's development will increase the detail and complexity of Macrostrat's multiscale data holdings, largely by engaging a wider range of geoscientists in entering stratigraphic data. To support broad collaboration, we are building new web‐based software to assemble and visualize regional stratigraphic sequences, refine multiple working age models, and compose regional records from measured stratigraphic sections. These tools will allow Macrostrat to draw on the expertise of a wide range of geoscience workers and grow a dataset with global relevance and a variety of end uses. New capabilities will pave the way to processes for submission, review, coordination, and assimilation of community‐contributed stratigraphic datasets. Digital compilation of geological maps and columns requires substantial effort, and well‐designed systems for distributing this work in the geoscience community will allow Macrostrat to build more adaptable and scientifically relevant products.
We describe a new phase of Macrostrat's development that centres on building collaborative infrastructure to store, represent, and use digital stratigraphic datasets across scales. User‐friendly column visualization and editing tools will allow geoscientists to build comprehensive and locally meaningful column datasets that contribute to a community‐maintained model of the Earth's crust.
Geographic range is a good indicator of extinction susceptibility in fossil marine species and higher taxa. The widely-recognized positive correlation between geographic range and taxonomic duration ...is typically attributed to either accumulating geographic range with age or an extinction buffering effect, whereby cosmopolitan taxa persist longer because they are reintroduced by dispersal from remote source populations after local extinction. The former hypothesis predicts that all taxa within a region should have equal probabilities of extinction regardless of global distributions while the latter predicts that cosmopolitan genera will have greater survivorship within a region than endemics within the same region. Here we test the assumption that all taxa within a region have equal likelihoods of extinction.
We use North American and European occurrences of marine genera from the Paleobiology Database and the areal extent of marine sedimentary cover in North America to show that endemic and cosmopolitan fossil marine genera have significantly different range-duration relationships and that broad geographic range and longevity are both predicted by regional environmental breadth. Specifically, genera that occur outside of the focal region are significantly longer lived and have larger geographic ranges and environmental breadths within the focal region than do their endemic counterparts, even after controlling for differences in sampling intensity. Analyses of the number of paleoenvironmental zones occupied by endemic and cosmopolitan genera suggest that the number of paleoenvironmental zones occupied is a key factor of geographic range that promotes genus survivorship.
Wide environmental tolerances within a single region predict both broad geographic range and increased longevity in marine genera over evolutionary time. This result provides a specific driving mechanism for the spatial and temporal distributions of marine genera at regional and global scales and is consistent with the niche-breadth hypothesis operating on macroevolutionary timescales.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
•First in-situ SIMS δ13C - δ18O values of the ‘Shuram’ excursion from South Australia.•We argue for a water column origin for very low δ13C values (down to -12 permil).•We also document very early ...diagenetic dolomite with δ13C up to +5 permil.•Large range (10-12 permil) in δ18O values indicate very low water/rock ratios.•Large δ13C heterogeneity implies large δ13C gradients in Ediacaran oceans.
Ediacaran-aged (635–541 million years ago) marine sediments contain a large negative carbon isotope (δ13C) excursion, in which carbonate δ13C values reach −12‰ (VPDB). Known as the ‘Shuram’ excursion, many workers have interpreted this δ13C record as an unprecedented perturbation to the global carbon cycle, leading to speculation about a causal connection to the broadly contemporaneous rise of animal life. Others have interpreted the δ13C signal as a product of diagenesis, thereby minimizing its relevance for understanding the evolution of metazoans. Here, we present SEM imaging and in-situ δ13C and δ18O values measured by secondary ion mass spectrometry (SIMS) to assess these competing hypotheses in the Wonoka Formation of South Australia. Our results from the minimum of the excursion show that rounded sedimentary grains of calcite have δ13C values between −12.8 to −10.6‰ and δ18O values between −17.8 to −15.5‰ (VPDB). Euhedral dolomite that appears to have grown unimpeded in open sedimentary pore spaces also is present. These early-stage dolomites are interpreted as early authigenic in origin and have δ13C values that reach +5‰, requiring a formation fluid with a substantially different δ13C composition from basin waters or bulk sediment. Together, these results provide little evidence for the hypothesis that a late diagenetic overprint has generated the ‘Shuram’ excursion in the Wonoka. Instead, they suggest the presence of a large carbon isotopic gradient in the surface environment, with shallow waters capable of precipitating carbonates with very low δ13C (down to −12‰) and deeper shelf and/or marine pore waters generating carbonates with positive carbon isotope values (up to +5‰). Because negative isotope excursions of similar magnitude are found in widely dispersed Ediacaran basins, it is likely that this gradient was characteristic of shelf environments of this period and that a still-unknown global process led to the ‘Shuram’ excursion in shallow water carbonates.
Short-term variations in rates of taxonomic extinction and origination in the fossil record may be the result of true changes in rates of turnover, variable rates of fossil preservation, or some ...combination of the two. Here, positive extinction and origination rate excursions among Phanerozoic marine animal genera are reexpressed in terms of the amount of normal, background time they represent. In addition to providing a background-adjusted calibration of rate intensities, this reexpression determines the durations of sampling gaps that would be required to explain entirely all observed rate excursions as sampling artifacts. This possibility is explored by analyzing a new compilation of the timing and duration of sedimentary hiatuses in North America. Hiatuses spanning more than approximately one million years (Myr) in the marine sedimentary rock record have a mean duration of 73 Myr. There are two major hiatus types—those that form in response to long-duration tectonic cycles and that bound the major Sloss-scale sequences (mean duration 200 Myr), and those that form in response to shorter-duration changes in sediment accommodation space and that occur within major Sloss-scale sequences (mean duration less than 23 Myr). The latter are approximately exponentially distributed and have a mean duration that is comparable to the mean duration of intervening sedimentary rock packages. Although sedimentary hiatuses are generally long enough in duration to accommodate the hypothesis that short-term variations in rates of genus origination and extinction are artifacts of sampling failures at major unconformities (“Unconformity Bias” hypothesis), the observed evolutionary rates are not correlated with hiatus durations. Moreover, hiatuses that follow the major mass extinctions are not long in comparison to most other non–mass extinction intervals. These results do not support the hypothesis that hiatuses at major unconformities alone have artificially clustered genus first and last occurrences, thereby causing many of the documented statistical similarities between the temporal structure of the sedimentary rock record and macroevolutionary patterns. Instead, environmental changes related to the expansion and contraction of marine environments may have been the primary forcers of both biological turnover and the spatio-temporal pattern of sediment accumulation. Fully testing this “Common Cause” hypothesis requires quantifying and overcoming lingering taxonomic, biostratigraphic, facies, and numerous other biases that are both inherent in geologic data and imposed by imperfect knowledge of the fossil record.
It has previously been thought that there was a steep Cretaceous and Cenozoic radiation of marine invertebrates. This pattern can be replicated with a new data set of fossil occurrences representing ...3.5 million specimens, but only when older analytical protocols are used. Moreover, analyses that employ sampling standardization and more robust counting methods show a modest rise in diversity with no clear trend after the mid-Cretaceous. Globally, locally, and at both high and low latitudes, diversity was less than twice as high in the Neogene as in the mid-Paleozoic. The ratio of global to local richness has changed little, and a latitudinal diversity gradient was present in the early Paleozoic.
Late Devonian (Famennian) marine successions globally are typified by organic‐rich black shales deposited in anoxic and euxinic waters and the cessation of shelf carbonate sedimentation. This global ...‘carbonate crisis’, known as the Hangenberg Event, coincides with a major extinction of reef‐building metazoans and perturbations to the global carbon cycle, evidenced by positive carbon‐isotope excursions of up to 4‰. It has been suggested that authigenic carbonate, formed as cements in sedimentary pore spaces during early burial diagenesis, is a significant mass fraction of the total global carbon burial flux, particularly during periods of low oxygen concentration. Because some authigenic carbonate could have originated from remineralization of organic carbon in sediments, it is possible for this reservoir to be isotopically depleted and thereby drive changes in the carbon isotopic composition of seawater. This study presents bulk isotopic and elemental analyses from fine‐grained siliciclastics of the Late Devonian–Early Mississippian Bakken Formation (Williston Basin, USA) to assess the volume and isotopic composition of carbonates in these sediments. Carbonate in the Bakken black shales occurs primarily as microscopic disseminated dolomite rhombs and calcite cements that, together, comprise a significant mass‐fraction (ca 9%). The elemental composition of the shales is indicative of a dynamic anoxic to sulphidic palaeoenvironment, likely supported by a fluctuating chemocline. Despite forming in an environment favourable to remineralization of organic matter and the precipitation of isotopically depleted authigenic carbonates, the majority of carbon isotope measurements of disseminated carbonate fall between −3‰ and +3‰, with systematically more depleted carbonates in the deeper‐water portions of the basin. Thus, although there is evidence for a significant total mass‐fraction of carbonate with contribution from remineralized organic matter, Bakken authigenic carbonates suggest that Famennian black shales are unlikely to be sufficiently 13C‐depleted relative to water column dissolved inorganic carbon to serve as a major lever on seawater isotopic composition.
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