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1. A Tale of Two LIP- (Large-Igneous Province) Induced Hyperthermals: The end-Triassic extinction (ETE) and Toarcian OAE (T-OAE)

   Whiteside, J ; Yager, J ; Tackett, L ; Schaller, M ; Olsen, P ( December 2019 , American Geophysical Union Annual Conference)

   Although many sources of atmospheric CO2 have been identified, the major sinks are best understood in a deep-time context. Here, we focus on two Large Igneous Provinces (LIPs), the Central Atlantic Magmatic Province (CAMP) situated in the low latitude humid zone ~201.6 Ma and the Karoo-Ferrar located at high southern latitudes ~183 Ma. We use soil carbonate, lithologic, δD of n-alkanes, Sr data, and modeling to examine how these eruptions, hydrological cycling, and weathering impacted global atmospheric CO2, carbon cycling, and biotic extinction at the ETE and T-OAE hyperthermals. CAMP largely erupted in the tropics, doubled atmospheric CO2 from ~2,500 – 5,000 ppm at the ETE (observed in soil carbonates with an onset <1000 and a duration of <~20 ky) and rapidly sequestered CO2 (< 2,500 ppm) as recorded in Newark Supergroup basins (eastern US). These same strata preserve variations in the lake level expression of the climatic precession cycle based on lithology and δD. High cyclicity variance tracked high pCO2 (>~4000 ppm) and drove insolation-paced increases in precipitation. Leaf wax δD shows significant variability, reflecting an enhanced hydrological cycle at the ETE with repeated sudden shifts in relative evaporation for ~1 Myr. In marine strata, 87Sr/86Sr and 187Os/188Os values track changes in pCO2, suggesting a terrestrial/marine linkage through continental weathering, CO2, and runoff. Despite the northward movement of these basins into the arid belt, our data suggest lower evaporation relative to precipitation driven by lower temperatures, consistent with lower pCO2 due to CAMP weathering, which modeling estimates to have increased 6 to 10-fold for >1.6 Myr after the eruptive phase. Release of CO2 from the Karoo-Ferrar LIP similarly enhanced the hydrological cycle as evidenced from sedimentary observations (e.g., fine-scale turbidites and debris flow deposits) in Yorkshire (UK). The onset of the carbon isotope excursion at the T-OAE lasts 0.5 Myr with a 1.5 Myr duration modulated by astronomical pacing. Our leaf wax δD from the same strata show a transient enhancement in the hydrological cycle. Although the Karoo-Ferrar has a limited drawdown potential when compared with CAMP‐type basalts because of its higher latitude location, Toarcian weathering rates may have increased 2 to 5-fold, acting as a net sink 1–2 Myr after eruptions ceased. 

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2. Phosphate Scavenging During Lava‐Seawater Interaction Offshore of Kīlauea Volcano, Hawaii

   https://doi.org/10.1029/2021GC009754  

   Foreman, Rhea K. ; Björkman, Karin M. ; Funkey, Carolina P. ; Hawco, Nicholas J. ; Wilson, Samuel T. ; Rohrer, Tully ; White, Angelicque E. ; John, Seth G. ; Karl, David M. ( July 2021 , Geochemistry, Geophysics, Geosystems)

   The 2018, subaerial eruption of Kīlauea volcano, Hawaii, resulted in a 5‐km‐long stretch of coastline that actively drained lava into the ocean. Nutrients were added to the surrounding ocean through the dissolution of basaltic rock and thermal upwelling of deep water, thereby fueling a large phytoplankton bloom. Lava‐impacted, surface seawater had high suspended particle loads, and concentrations of chlorophyll, silicic acid, phosphate (P_i), nitrate, and iron that were elevated up to 12, 36, 5, 960, and 1,400 times, respectively, above the background oligotrophic levels. Widespread precipitation of iron oxyhydroxides (Fe_ox) led to extensive scavenging of the dissolved P_ipool, similar to what occurs along mid‐ocean ridge hydrothermal systems. This scavenging transformed a “fertilization” event into a P_isink near the coast of the ocean entry; however, nutrient data from outside the bloom suggest that P_icould also desorb from the Fe_oxas it is dispersed into the open ocean. From lava quench experiments, we estimate that the hydration state of the Fe_oxprecipitate (H₂O/Fe) was 5.2–5.7, and that the equilibrium partition coefficient of P_iinto Fe_ox(solid/liquid) was 10⁶. In addition,³³P_iradiotracer incubations were used to differentiate between biotic and abiotic uptake of P_iat Kīlauea's ocean entry. These findings are important for understanding modern‐day volcanic fertilization events, modeling nutrient dynamics during major events in Earth history (such as oxygenation of the atmosphere and the formation of large igneous provinces), and predicting the marine response to greater continental weathering in a warming climate.

    

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3. Biotic extinction at the Norian/Rhaetian boundary (Upper Triassic): geochemical and isotope evidence of a previously unrecognised global event

   https://doi.org/10.46427/gold2022.11474  

   Rigo, Manuel ; Onoue, Tetsuji ; Sato, Honami ; Tomimatsu, Yuki ; Soda, Katsuhito ; Godfrey, Linda ; Katz, Miriam ; Campbell, Hamish ; Tackett, Lydia ; Golding, Martyn ; et al ( October 2022 , Goldschmidt 2022 Abstract)

   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]. 

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4. The predominant control of hydroclimatic conditions on carbon and weathering fluxes at the hillslope scale

   Wen, Hang ; Sullivan, Pamela ; Billings, Sharon ; Ajami, Hoori ; Cueva, Alejandro ; Flores, Alejandro ; Hirmas, Daniel ; Koop, Aaron ; Murenbeeld, Kathryn ; Zhang, Xi ; et al ( December 2021 , American Geophysical Union annual conference)

   Soil biota generate CO2 that can vertically export to the atmosphere, and dissolved organic and inorganic carbon (DOC and DIC) that can laterally export to streams and accelerate weathering. These processes are regulated by external hydroclimate forcing and internal structures (permeability distribution), the relative influences of which are rarely studied. Understanding these interactions is essential a hydrological extremes intensify in the future. Here we explore the question: How and to what extent do hydrological and permeability distribution conditions regulate soil carbon transformations and chemical weathering? We address the questions using a hillslope reactive transport model constrained by data from the Fitch Forest (Kansas, United States). Numerical experiments were used to mimic hydrological extremes and variable shallow-versus-deep permeability contrasts. Results demonstrate that under dry conditions (0.08 mm/day), long water transit times led to more mineralization of organic carbon (OC) into inorganic carbon (IC) form (>98\%). Of the IC produced, ~ 75\% was emitted upward as CO2 gas and ~ 25\% was exported laterally as DIC into the stream. Wet conditions (8.0 mm/day) resulted in less mineralization (~88\%), more DOC production (~12\%), and more lateral fluxes of IC (~50\% of produced IC). Carbonate precipitated under dry conditions and dissolved under wet conditions as the fast flow rapidly droves the reaction to disequilibrium. The results depict a conceptual hillslope model that prompts four hypotheses for our community to test. H1: Droughts enhance carbon mineralization and vertical upward carbon fluxes, whereas large hydrological events such as storms and flooding enhance subsurface vertical connectivity, reduce transit times, and promote lateral export. H2: The role of weathering as a net carbon sink or source to the atmosphere depends on the interaction between hydrologic flows and lithology: transition from droughts to storms can shift carbonate from a carbon sink (mineral precipitation) to carbon source (dissolution). H3: Permeability contrasts regulate the lateral flow partitioning via shallow flow paths versus deeper groundwater though this alter reaction rates negligibly. H4: Stream chemistry reflect flow paths and can potentially quantify water transit times: solutes enriched in shallow soils have a younger water signature; solutes abundant at depth carry older water signature. 

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5. Data from: The role of Southeast Asian island topography on Indo-Pacific climate and silicate weathering

   https://doi.org/10.6078/D1271P  

   Chiang, John ; Maffre, Pierre ( January 2023 , Dryad)

   The modern configuration of the South East Asian Islands (SEAI) evolved over the last fifteen million years, as a result of subduction, arc magmatism, and arc-continent collisions, contributing to both increased land area and high topography.  The presence of the additional land area has been postulated to enhance convective rainfall, facilitating both increased silicate weathering and the development of the modern-day Walker circulation.  Using an Earth System Model in conjunction with a climate-silicate weathering model, we argue instead for a significant role of SEAI topography for both effects.  This dataset archives model output used in this investigation, including simulations using the Community Earth System Model version 1.2, and the climate-silicate weathering model GEOCLIM. All data are in Netcdf format, and were generated either by the Community Earth System Model 1.2 (Hurrell et al. 2013) or the climate-silicate weathering model GEOCLIM (Park et al. 2020).  Model output is organized into 4 tar files: 1) B1850C5.tar Contains model output for the fully coupled CESM1.2 runs, for 2D fields and for 3D pressure vertical velocity (W) between 10S-10N.  Monthly mean data for years 41-110 of the simulations.   Naming convention is No SEAI topography: B1850C5_noSEAItopo_y41-110.nc and B1850C5_noSEAItopo_W_y41-110.nc 50% SEAI topography: B1850C5_0.5SEAItopo_y41-110.nc and B1850C5_0.5SEAItopo_W_y41-110.nc 100% SEAI topography: B1850C5_y41-110.nc and B1850C5_W_y41-110.nc 150% SEAO topogaphy: B1850C5_1.5SEAItopo_y41-110.nc and B1850C5_1.5SEAItopo_W_y41-110.nc 2) E1850C5.tar Contains model output for the slab ocean CESM1.2 runs, for 2D fields and for 3D pressure vertical velocity (W) between 10S-10N.  Monthly mean data for years 21-50 of the simulations.  Naming convention is No SEAI topography: E1850C5_noSEAItopo_y21-50.nc and E1850C5_noSEAItopo_W_y21-50.nc 50% SEAI topography: E1850C5_0.5SEAItopo_y21-50.nc and E1850C5_0.5SEAItopo_W_y21-50.nc 100% SEAI topography: E1850C5_y21-50.nc and E1850C5_W_y21-50.nc 150% SEAO topogaphy:  E1850C5_1.5SEAItopo_y21-50.nc and E1850C5_1.5SEAItopo_W_y21-50.nc 3) GEOCLIM.tar Contains model output from the climate-silicate weathering model GEOCLIM.  Data is provided for all 573 parameter combinations.  All values are climatological annual means. All files contain these variables: GMST: global mean surface temperature (in K) atm_CO2_level: atmospheric pCO2 (in ppm) degassing: globally-integrated CO2 flux (in mol/yr) The files ending with 1xCO2.nc also contain these spatial fields: lithology fraction: fraction of land covered by a lithology class erosion: Regolith erosion rate (m/yr) weathering: Ca-Mg weathering rate (mol/m^2/yr) E1850C5_1xCO2.nc - GEOCLIM output using the Modern SEAI simulation as input, and for CO2 fixed to 286.7ppm.  E1850C5_noSEAI_1xCO2.nc - GEOCLIM output using the no SEAI simulation as input, and for CO2 fixed to 286.7ppm.  E1850C5_noSEAItopo_1xCO2.nc - GEOCLIM output using the flat SEAI simulation as input, and for CO2 fixed to 286.7ppm.  E1850C5_noSEAI_equil.nc - GEOCLIM output using the no SEAI simulation as input, and CO2 adjusted so that system is in carbon flux equilibrium.   E1850C5_noSEAItopo_flatSEAIslope_equil.nc - GEOCLIM output using the flat SEAI simulation as input, and CO2 adjusted so that system is in carbon flux equilibrium.   4) Surface.tar Contains land fraction and surface geopotential fields for the modern SEAI (Landfrac.nc) and no SEAI (Landfrac_noSEAI.nc) simulations References Hurrell, J.W., Holland, M.M., Gent, P.R., Ghan, S., Kay, J.E., Kushner, P.J., Lamarque, J.F., Large, W.G., Lawrence, D., Lindsay, K. and Lipscomb, W.H., 2013. The community earth system model: a framework for collaborative research. Bulletin of the American Meteorological Society, 94(9), pp.1339-1360. Park, Y., Maffre, P., Goddéris, Y., Macdonald, F.A., Anttila, E.S. and Swanson-Hysell, N.L., 2020. Emergence of the Southeast Asian islands as a driver for Neogene cooling. Proceedings of the National Academy of Sciences, 117(41), pp.25319-25326. 

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