An official website of the United States government
The latest Triassic was an interval of prolonged biotic extinction culminated by the end-Triassic Extinction, which is associated with a pronounced perturbation of the global carbon cycle that can be connected to extensive volcanism of the Central Atlantic Magmatic Province (CAMP). Earlier chaotic perturbations of the global carbon cycle can also be tied to the onset of declining latest Triassic diversity, which reached its maximum across the Norian-Rhaetian boundary (NRB). These perturbations are global across the Panthalassa Ocean to both sides of the Pangean supercontinent in both the Northern and Southern Hemispheres. The NRB witnessed the severe global extinctions of significant marine fossil groups, such as ammonoids, bivalves, conodonts and radiolarians. The onset of the stepwise Late Triassic extinctions coincided with the NRB carbon perturbation (d13Corg), indicating that the combined climate and environmental changes impacted the global biota. The trigger of this event is attributed to a volcanic event pre-dating the NRB, an alternative source of volcanogenic gas emissions, and/or a meteorite impact.
more »
« less
Biotic extinction at the Norian/Rhaetian boundary (Upper Triassic): geochemical and isotope evidence of a previously unrecognised global event
turnovers culminating in the so-called End-Triassic Extinction. We attribute onset of this interval of declining diversity to unusually high volcanic activity at the Norian/Rhaetian boundary (NRB) that may have initiated the stepwise extinctions of the Late Triassic [1]. We correlate the initiation of a rapid decline in 87Sr/86Sr and 187Os/188Os seawater values [2, 3] to a negative organic carbon isotope shift, which we attribute to volcanogenic CO2 outgassing to the ocean-atmosphere system by the Angayucham large igneous province (LIP). By studying the geochemical and isotope composition of bulk rocks from different sections located at different latitudes, sides of the Pangea continent and Hemispheres, we documented an accelerated chemical weathering due to global warming by elevated CO2, which enhanced nutrient discharge to the oceans and thus greatly increased biological productivity; higher export production and oxidation of organic matter led to oceanic dysoxia to anoxia at the NRB. Biotic consequences of these climatic and environmental changes include severe extinctions of several fossil groups, such as ammonoids, bivalves and radiolarians, as has been documented worldwide [1].
more »
« less
- Award ID(s):
- 1654088
- PAR ID:
- 10430883
- Date Published:
- Journal Name:
- Goldschmidt 2022 Abstract
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
null (Ed.)The Earth has been beset by many crises during its history, and yet comparing the ecological impacts of these mass extinctions has been difficult. Key questions concern the kinds of species that go extinct and survive, how communities rebuild in the post-extinction recovery phase, and especially how the scaling of events affects these processes. Here, we explore ecological impacts of terrestrial and freshwater ecosystems in three mass extinctions through the mid-Phanerozoic, a span of 121 million years (295–174 Ma). This critical duration encompasses the largest mass extinction of all time, the Permian–Triassic (P–Tr) and is flanked by two smaller crises, the Guadalupian–Lopingian (G–L) and Triassic–Jurassic (T–J) mass extinctions. Palaeocommunity dynamics modelling of 14 terrestrial and freshwater communities through a long sedimentary succession from the lower Permian to the lower Jurassic in northern Xinjiang, northwest China, shows that the P–Tr mass extinction differed from the other two in two ways: (i) ecological recovery from this extinction was prolonged and the three post-extinction communities in the Early Triassic showed low stability and highly variable and unpredictable responses to perturbation primarily following the huge losses of species, guilds and trophic space; and (ii) the G–L and T–J extinctions were each preceded by low-stability communities, but post-extinction recovery was rapid. Our results confirm the uniqueness of the P–Tr mass extinction and shed light on the trophic structure and ecological dynamics of terrestrial and freshwater ecosystems across the three mid-Phanerozoic extinctions, and how complex communities respond to environmental stress and how communities recovered after the crisis. Comparisons with the coeval communities from the Karoo Basin, South Africa show that geographically and compositionally different communities of terrestrial ecosystems were affected in much the same way by the P–Tr extinction.more » « less
-
We used spatial data from previously mapped preferential groundwater discharges throughout the Farmington River watershed in Connecticut and Massachusetts (https://doi.org/10.5066/P915E8JY) to guide water sample collection at known locations of groundwater discharging to surface water. In 2017 and 2019 - 2021, samples were collected during general river baseflow conditions (July ? November, less than 30.9 cms mean daily discharge (USGS gage 01189995, statistics 2010-2022) when the riverbank discharge points were exposed. We collected a suite of dissolved constituents and stable isotopes of water directly in the shallow saturated sediments of active points of discharge, and coincident stream chemical samples were also collected adjacent to locations of groundwater discharge. Data collected includes nutrients (NO3, NH4, Cl, SO4, PO4, dissolved organic carbon (DOC), and total nitrogen (TN)), greenhouse gases (CO2, CH4, and N2O), dissolved gases (N2, dissolved oxygen (DO)), conductivity, sediment characteristics, temperature, and spatial information. This dataset includes 2 main files: 1) Farmington_Chemistry_2017_2021.csv contains attribute information for each biogeochemical constituent collected at preferential groundwater discharges along the Farmington River network. 2)Farmington_Temporal_Cl_Rn_Iso_2020.csv contain attribute information for source characteristic data (Chloride, Radon, Isotope) collected at locations of repeat sampling at 5 groundwater seep faces along the Farmington River (Alsop and Rainbow Island).more » « less
-
Sections of the Gabbs Formation exposed near New York Canyon, Nevada, have long been recognized as important sites for Late Triassic and Early Jurassic stratigraphy, and the Norian-Rhaetian parts of these sections continue to be important for defining this boundary (NRB). The two candidate sections for the base of the Rhaetian are in Tethys; both sections utilize the first occurrence of the conodont species Misikella posthernsteini as a proxy for the boundary. Although not a candidate section, data from New York Canyon will help to determine the most suitable position for the NRB, especially in Panthalassa. Previous reports of conodonts from New York Canyon recognized a fauna with Mockina englandi, Mo. bidentata and morphotypes of Mo. mosheri in the Nun Mine Member, below isolated occurrences of Zieglericonus rhaeticum and Mi. posthernsteini in the Mount Hyatt and Muller Canyon members. The first occurrence of Mi. posthernsteini in the section occurs well above the first occurrence of Rhaetian ammonoids (Paracochloceras amoenum) and together with late Rhaetian radiolarians. It is also above excursions in Sr- and C-isotopes, both of which correlate with Tethyan NRB excursions. Therefore, the NRB has previously been placed much lower in North America than Tethys, at the first occurrences of the radiolarian Proparvicingula moniliformis and the conodont Mo. mosheri morphotype C. To help reconcile the biochronological and geochemical data from New York Canyon, new conodont samples have been collected from the Nun Mine and Mt Hyatt members at the New York Canyon Road and Luning Draw sections. These samples contain: Mo. englandi, Mo. bidentata, and Mo. mosheri morphotypes B and C, all previously reported from New York Canyon, although this is the first record of Mo. mosheri morphotype C from the Nun Mine Member; Parvigondolella spp. B and C, from much lower in the Nun Mine Member than previously reported; and Pa. andrusovi, which has not previously been recorded from North America. Overall, this fauna represents the Mo. bidentata and Mo. mosheri zones of North America, equivalent to the Sevatian Mo. bidentata and Pa. andrusovi zones of Tethys. This would be consistent with a higher placement of the NRB at New York Canyon; however, if the NRB is to be recognized at the first occurrence of Mo. mosheri morphotype C, then the boundary must be lower than previously thought, within the Nun Mine Member.more » « less
-
Catalano, Jeffrey; Passey, Benjamin H (Ed.)The geochemical characterization of phytoplankton-derived organic compounds found in marine sediments has been widely used to reconstruct atmospheric pCO2 thoughout the Cenozoic. This is possible owing to a well-established relationship between the carbon isotope ratios of phytoplankton biomass and CO2 concentration in the ambient seawater. An ideal molecular target for such proxy reconstructions would be degradation resistant on geologic timescales and unambiguously associated with known, experimentally tractable, organisms, so that species-specific models can be developed, calibrated, and applied to appropriate material. However, existing organic matter targets do not quite meet these criteria, primarily owing to ambiguity in the source species of recalcitrant compounds in deep time. Here we explore the potential of a novel organic carbon target for isotopic analysis: acidic polysaccharides extracted from the calcite plates (coccoliths) that are produced by all calcifying haptophytes. Carbohydrates are usually rapidly remineralized in sediments, but coccolith-associated polysaccharides (CAPs) are mechanically protected from diagenesis within the coccolith calcite lattice. Coccoliths can be taxonomically separated by size and identified, often to species level, prior to CAP extraction, providing a species-specific record. Coccolith morphology and composition are important additional sources of information, which are then unambiguously associated with the extracted CAPs. We find that carbon isotope ratios of CAPs changed in response to the environmental changes associated with a glacial cycle, which we attribute to temperature-driven changes in average growth rate. Once the underlying biosynthetic processes and the associated isotope effects are better understood, this archive of pristine organic matter has the potential to provide insight into phytoplankton growth rates and atmospheric pCO2 far beyond the Cenozoic, to when the first coccolithophores inhabited the surface ocean over 200 million years ago.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.46427/gold2022.11474
