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  • 1
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    Assessing Volcanic Controls on Miocene Climate Change (2022)
    Details
    Publication Date: 2022-03-25
    Description: The Miocene period saw substantially warmer Earth surface temperatures than today, particularly during a period of global warming called the Mid Miocene Climatic Optimum (MMCO; ∼17–15 Ma). However, the long‐term drivers of Miocene climate remain poorly understood. By using a new continuous climate‐biogeochemical model (SCION), we can investigate the interaction between volcanism, climate and biogeochemical cycles through the Miocene. We identify high tectonic CO2 degassing rates and further emissions associated with the emplacement of the Columbia River Basalt Group as the primary driver of the background warmth and the MMCO respectively. We also find that enhanced weathering of the basaltic terrane and input of explosive volcanic ash to the oceans are not sufficient to drive the immediate cooling following the MMCO and suggest that another mechanism, perhaps the change in ocean chemistry due to massive evaporite deposition, was responsible.
    Description: Plain Language Summary: The Miocene period was much warmer than today, with the Mid Miocene Climatic Optimum (MMCO, roughly 17–15 million years ago) especially warm. Due to the high surface temperatures, comparisons to projected climatic conditions as a result of anthropogenic climate change have been drawn. However, the drivers of climate during the Miocene are not well understood. By using a new type of climate model, we investigate the impact volcanic eruptions had on the period, and link the extreme warmth of the MMCO with greenhouse gas release from the eruption of the Columbia River Basalts Group (CRBG). We find weathering of the CRBG does not explain the cooling at the end of the MMCO, and so discuss other potential explanations such as evaporite deposition.
    Description: Key Points: A new climate‐biogeochemical model allows investigation of drivers of climate change in the Miocene. Columbia River Basalt Group (CRBG) degassing is sufficient to have caused the Mid Miocene Climatic Optimum (MMCO). Weathering of CRBG insufficient to drive cooling after the MMCO. This may be linked to evaporite deposition and changes to marine chemistry.
    Description: UK Natural Environment Research Council
    Description: French Research Agency (ANR)
    Keywords: ddc:551
    Language: English
    Type: doc-type:article
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    CITATION GEO-LEO
  • 2
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    Tephra Deposition and Bonding With Reactive Oxides Enhances Burial of Organic Carbon in the Bering Sea (2021)
    Details
    Publication Date: 2022-03-24
    Description: Preservation of organic carbon (OC) in marine sediments exerts a major control on the cycling of carbon in the Earth system. In these marine environments, OC preservation may be enhanced by diagenetic reactions in locations where deposition of fragmental volcanic material called tephra occurs. While the mechanisms by which this process occurs are well understood, site‐specific studies of this process are limited. Here, we report a study of sediments from the Bering Sea (IODP Site U1339D) to investigate the effects of marine tephra deposition on carbon cycling during the Pleistocene and Holocene. Our results suggest that tephra layers are loci of OC burial with distinct δ13C values, and that this process is primarily linked to bonding of OC with reactive metals, accounting for ∼80% of all OC within tephra layers. In addition, distribution of reactive metals from the tephra into non‐volcanic sediments above and below the tephra layers enhances OC preservation in these sediments, with ∼33% of OC bound to reactive phases. Importantly, OC‐Fe coupling is evident in sediments 〉700,000 years old. Thus, these interactions may help explain the observed preservation of OC in ancient marine sediments.
    Description: Plain Language Summary: The burial of organic carbon (OC) in marine sediments is one of the major carbon sinks on Earth, meaning that it removes carbon dioxide from the ocean‐atmosphere system. However, the speed at which burial occurs varies across the globe, and is dependent on a range of factors, from the amount of nutrients in the water column, to the type of sediment. Despite evidence suggesting that when tephra is deposited to the seafloor carbon burial is enhanced, very little work has been done to investigate this process. We have therefore analyzed sediments from the Bering Sea, where volcanoes from the Aleutian Islands and Kamchatka regularly deposit tephra in the ocean. We found that OC burial is indeed associated with ash deposition, and importantly, that OC is preserved in the ash layers themselves. We show here that this carbon is preserved effectively because of chemical reactions between the OC and reactive iron, which is released by the ash, creating conditions which preserve carbon for hundreds of thousands of years.
    Description: Key Points: Tephra layers are loci of marine organic carbon (OC) burial with distinct carbon isotopic compositions. Preservation primarily linked to association of OC with reactive iron phases, accounting for ∼80% of all OC in tephra layers. OC‐reactive Fe coupling is observed in sediments 〉700,000 years old, indicating long‐term persistence of these complexes.
    Description: NERC
    Keywords: ddc:551.9
    Language: English
    Type: doc-type:article
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    CITATION GEO-LEO
  • 3
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    Viability of greenhouse gas removal via artificial addition of volcanic ash to the ocean (2020)
    Elsevier
    In:  Anthropocene, 32 . Art.Nr. 100264.
    Details
    Publication Date: 2021-01-08
    Description: Mitigating human contributions to climate change is a highly debated topic, as it becomes evident that many nations do not adhere to optional reductions in global emission. Substantial research is taking place into negative carbon technologies that actively reduce the amount of atmospheric carbon dioxide (CO2) via greenhouse gas removal (GGR). Various GGR methods have been proposed, from reforestation to ocean fertilisation. This article discusses advantages of an approach based on enhanced input of tephra to the ocean, to increase the drawdown of atmospheric CO2. Natural addition of tephra to the ocean results in preservation of enhanced organic matter in sediment. Hence, augmenting its delivery should raise the level of sequestration. Calculations indicate that offshore tephra addition could sequester 2750 tonnes of CO2 per 50,000 tonnes of ash delivered (a typical bulk carrier’s capacity). The cost is estimated as ∼$55 per tonne of CO2 sequestered and is an order of magnitude cheaper than many proposed GGR technologies. Further advantages include: tephra addition is simply an augmentation of a natural Earth process, it is a low technology approach that requires few developments, and it may sequester carbon for thousands of years. Hence, offshore tephra addition warrants further investigation to assess its viability.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.ancene.2020.100264
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Shallow-water hydrothermal venting linked to the Palaeocene–Eocene Thermal Maximum (2023)
    Nature Research
    Details
    Publication Date: 2024-02-07
    Description: The Palaeocene–Eocene Thermal Maximum (PETM) was a global warming event of 5–6 °C around 56 million years ago caused by input of carbon into the ocean and atmosphere. Hydrothermal venting of greenhouse gases produced in contact aureoles surrounding magmatic intrusions in the North Atlantic Igneous Province have been proposed to play a key role in the PETM carbon-cycle perturbation, but the precise timing, magnitude and climatic impact of such venting remains uncertain. Here we present seismic data and the results of a five-borehole transect sampling the crater of a hydrothermal vent complex in the Northeast Atlantic. Stable carbon isotope stratigraphy and dinoflagellate cyst biostratigraphy reveal a negative carbon isotope excursion coincident with the appearance of the index taxon Apectodinium augustum in the vent crater, firmly tying the infill to the PETM. The shape of the crater and stratified sediments suggests large-scale explosive gas release during the initial phase of vent formation followed by rapid, but largely undisturbed, diatomite-rich infill. Moreover, we show that these vents erupted in very shallow water across the North Atlantic Igneous Province, such that volatile emissions would have entered the atmosphere almost directly without oxidation to CO 2 and at the onset of the PETM.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    The impact of volcanic ash deposition and the Storegga Slide on organic carbon preservation processes in marine sediments near Iceland (2023)
    Elsevier
    Details
    Publication Date: 2024-02-27
    Description: The burial of organic carbon (OC) in marine sediments is a considerable sink for carbon, removing OC from the active ocean-atmosphere system. Both the total OC buried, and the proportion of OC retained in sediments after burial, varies by location, with some areas of the ocean floor known to be 'hotspots' of OC sequestration. Two potential such hotspots may be sediments containing high proportions of tephra (the unconsolidated products of explosive volcanism), and locations of turbidite deposition, but knowledge of specific burial regimes in such locations remains poorly constrained. To fully investigate these processes, we performed a holistic (organic and inorganic) geochemical analysis of samples from the Aegir Ridge, which contain both tephra layers and material from the Storegga Slide, a large turbidite. We show sediments found between the Storegga Slide and the tephra are a location of high OC preservation, linked to reducing conditions caused by the rapidly deposited slide layer sealing the sediments from overlying water column O2. We see little evidence for tephra positively affecting OC preservation at our site, but this is likely a feature of specific burial conditions, with the responsible mechanisms depending highly on the nature of the tephra. Our findings demonstrate how even in locations proposed as OC burial hotpots, the processes controlling this burial are highly complex, and that levels of sedimentary OC burial must be assessed on a case-by-case basis.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Evidence for Low-Pressure Crustal Anatexis During the Northeast Atlantic Break-up (2023)
    Details
    Publication Date: 2024-03-25
    Description: While basaltic volcanism is dominate during rifting and continental breakup, felsic magmatism may also comprise important components of some rift margins. During International Ocean Discovery Program (IODP) Expedition 396 on the continental margin of Norway, a graphite-garnet-cordierite bearing dacitic, pyroclastic unit was recovered within early Eocene sediments on Mimir High (Site U1570), a marginal high on the Vøring transform margin. Here, we present a comprehensive textural, mineralogical, and petrological study of the dacite in order to assess its melting origin and emplacement. The major mineral phases (garnet, cordierite, quartz, plagioclase, alkali feldspar) are hosted in a fresh rhyolitic, highly vesicular, glassy matrix, locally mingled with sediments. The xenocrystic major element chemistry of garnet and cordierite, the presence of zircon inclusions with inherited cores, and thermobarometric calculations all support a crustal metapelite origin. While most magma-rich margin models favor crustal anatexis in the lower crust, thermobarometric calculations performed here show that the dacite was produced at upper-crustal depths (〈 5 kbar) and high temperature (750–800 °C) with up to 3 wt% water content. In situ U-Pb analyses on zircon inclusions give a magmatic age of 54.6 ± 1.1 Ma, revealing the emplacement of the dacite post-dates the Paleocene-Eocene Thermal Maximum (PETM). Our results suggest that the opening of the North Atlantic was associated with a phase of low-pressure, high-temperature crustal melting at the onset of the main phase of magmatism.
    Type: Article , NonPeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - without review
  • 7
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    (Figure 3) Dust flux determined from peat core MOHOS in the Eastern Carpathians, Romania (2017)
    PANGAEA
    Details
    Publication Date: 2023-02-07
    Keywords: Calendar age; COMPCORE; Composite Core; Core; DEPTH, sediment/rock; Dust, flux; MOHOS; Mohos, Romania; see reference(s)
    Type: Dataset
    Format: text/tab-separated-values, 312 data points
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    DATA PANGAEA
  • 8
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    Age determination and dust flux of peat core MOHOS (2017)
    PANGAEA
    In:  Supplement to: Longman, Jack; Veres, Daniel; Ersek, Vasile; Salzmann, Ulrich; Hubay, Katalin; Borman, Marc; Wennrich, Volker; Schäbitz, Frank (2017): Periodic input of dust over the Eastern Carpathians during the Holocene linked with Saharan desertification and human impact. Climate of the Past, 13(7), 897-917, https://doi.org/10.5194/cp-13-897-2017
    Details
    Publication Date: 2023-02-23
    Description: Reconstructions of dust flux have been used to produce valuable global records of changes in atmospheric circulation and aridity. These studies have highlighted the importance of atmospheric dust in marine and terrestrial biogeochemistry and nutrient cycling. By investigating a 10800-year-long paleoclimate archive from the Eastern Carpathians (Romania) we present the first peat record of changing dust deposition over the Holocene for the Carpathian-Balkan region. Using qualitative (X-ray fluorescence (XRF) core scanning) and quantitative inductively coupled plasma optical emission spectrometer(ICP-OES) measurements of lithogenic (K, Si, Ti) elements, we identify 10 periods of major dust deposition between 9500-9200, 8400-8100, 7720-7250, 6350-5950, 5450-5050, 4130-3770, 3450-2850, 2000-1450, 800-620, and 60 cal yr BP to present. In addition, we used testate amoeba assemblages preserved within the peat to infer local palaeohydroclimatic conditions. Our record highlights several discrepancies between eastern and western European dust depositional records and the impact of highly complex hydrological regimes in the Carpathian region. Since 6100 cal yr BP, we find that the geochemical indicators of dust flux have become uncoupled from the local hydrology. This coincides with the appearance of millennial-scale cycles in the dust input and changes in geochemical composition of dust. We suggest that this is indicative of a shift in dust provenance from local-regional (likely loess-related) to distal (Saharan) sources, which coincide with the end of the African Humid Period and the onset of Saharan desertification.
    Type: Dataset
    Format: application/zip, 2 datasets
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    DATA PANGAEA
  • 9
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    (Table 1) Age determination of peat core MOHOS in the Eastern Carpathians, Romania (2017)
    PANGAEA
    Details
    Publication Date: 2023-02-23
    Keywords: Age, 14C AMS; Age, 14C calibrated, IntCal13 (Reimer et al., 2013); Age, dated; Age, dated material; Age, dated standard deviation; Calendar age, maximum/old; Calendar age, minimum/young; COMPCORE; Composite Core; DEPTH, sediment/rock; MOHOS; Mohos, Romania; Sample, optional label/labor no
    Type: Dataset
    Format: text/tab-separated-values, 96 data points
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    DATA PANGAEA
  • 10
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    Geochemical results for 〈5 µm size fraction sediments of core PS75/056-1 (2022)
    PANGAEA
    Details
    Publication Date: 2023-08-22
    Description: This dataset contains the geochemical results for the dust fraction (〈5 µm size fraction) of sediment core PS75/056-1 from the South Pacific Subantarctic Zone (55.16°S, 114.78°W; 3581 m water depth) collected during R/V Polarstern expedition ANT-XXVI/2 (PS75 BIPOMAC) in 11/2009-01/2010 (Gersonde, 2011, doi:10.2312/BzPM_0632_2011). The original lithogenic dust provenance signal was extracted from a total of 108 samples (incl. 13 full replicates) between 0.03 and 9.93 m core depth covering the period from ~8,000 to ~260,000 years before present. The age model is from van der Does et al. (2021, doi:10.1016/j.quascirev.2021.106978). All samples were analyzed for their trace element content using a ThermoFinnigan Element II ICP-MS and their radiogenic isotope composition (Nd, Pb, Sr) was analyzed with a ThermoScientific Neptune Plus MC-ICP-MS at the ICBM in Oldenburg, Germany
    Keywords: Adopted from van der Does et al. (2021); AGE; ANT-XXVI/2; Barium; Calculated, PAAS-normalized (Taylor and McLennan, 1985); Cerium; Depth, bottom/max; DEPTH, sediment/rock; Depth, top/min; Dust provenance; Dysprosium; Erbium; Europium; Europium anomaly; Gadolinium; Gravity corer (Kiel type); Holmium; ICP-MS, Thermo Finnigan, Element 2; Iron fluxes; Laboratory code/label; Lanthanum; Lanthanum/Ytterbium ratio; Lead; Lead-206/Lead-204 ratio; Lead-206/Lead-204 ratio, standard deviation; Lead-206/Lead-204 ratio, standard error; Lead-207/Lead-204 ratio; Lead-207/Lead-204 ratio, standard deviation; Lead-207/Lead-204 ratio, standard error; Lead-207/Lead-206 ratio; Lead-207/Lead-206 ratio, standard deviation; Lead-207/Lead-206 ratio, standard error; Lead-208/Lead-204 ratio; Lead-208/Lead-204 ratio, standard deviation; Lead-208/Lead-204 ratio, standard error; Lead-208/Lead-206 ratio; Lead-208/Lead-206 ratio, standard deviation; Lead-208/Lead-206 ratio, standard error; Lutetium; Multi-collector ICP-MS (MC-ICP-MS), Neptune Plus, Thermo; Neodymium; Neodymium-143/Neodymium-144 ratio; Neodymium-143/Neodymium-144 ratio, standard error; Polarstern; Praseodymium; PS75/056-1; PS75 BIPOMAC; Radiogenic isotopes; Rare earth elemets; Samarium; Sample comment; SL; Southern Hemisphere Westerly Winds; Southern Ocean; South Pacific Ocean; Strontium; Strontium-87/Strontium-86 ratio; Strontium-87/Strontium-86 ratio, standard deviation; Strontium-87/Strontium-86 ratio, standard error; Terbium; Thulium; Ytterbium; Zirconium; ε-Neodymium; ε-Neodymium, standard deviation; ε-Neodymium, standard error
    Type: Dataset
    Format: text/tab-separated-values, 5019 data points
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    DATA PANGAEA
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