Osmium-isotope evidence for two pulses of increased continental weathering linked to Early Jurassic volcanism and climate change
Large Igneous Provinces (LIPs) are proposed to have caused a number of episodes of abrupt environmental change by increasing atmospheric CO2 levels, which were subsequently alleviated by drawdown of CO<sub>2</sub> via enhanced continental weathering and burial of organic matter. Here,...
| Main Authors: | , , , , , , , , , |
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| Format: | Journal article |
| Language: | English |
| Published: |
Geological Society of America
2016
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| _version_ | 1826278347064213504 |
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| author | Percival, L Cohen, A Davies, M Dickson, A Hesselbo, S Jenkyns, H Leng, M Mather, T Storm, M Xu, W |
| author_facet | Percival, L Cohen, A Davies, M Dickson, A Hesselbo, S Jenkyns, H Leng, M Mather, T Storm, M Xu, W |
| author_sort | Percival, L |
| collection | OXFORD |
| description | Large Igneous Provinces (LIPs) are proposed to have caused a number of episodes of abrupt environmental change by increasing atmospheric CO2 levels, which were subsequently alleviated by drawdown of CO<sub>2</sub> via enhanced continental weathering and burial of organic matter. Here, the sedimentary records of two such episodes of environmental change, the Toarcian Oceanic Anoxic Event (T-OAE) and preceding Pliensbachian–Toarcian (Pl–To) event (both potentially linked to the Karoo–Ferrar LIP), are investigated using a new suite of geochemical proxies that have not been previously compared. Stratigraphic variations in osmium-isotope ( <sup>187</sup>Os/<sup>188</sup>Os) records are compared with those of mercury (Hg) and carbon isotopes (δ<sup>13</sup>C) in samples from the Mochras Core, Llanbedr Farm, Cardigan Bay Basin, Wales. These sedimentary rocks are confirmed as recording an open-marine setting by analysis of molybdenum/uranium enrichment trends, indicating that the Os-isotope record in these samples reflects the isotopic composition of the global ocean. The Os-isotope data include the first results across the Pl–To boundary, when seawater <sup>187</sup>Os/<sup>188</sup>Os increased from ∼ 0.40 to ∼ 0.53, in addition to new data that show elevated <sup>187</sup>Os/<sup>188</sup>Os (from ∼ 0.42 to ∼ 0.68) during the T-OAE. Both increases in <sup>187</sup>Os/<sup>188</sup>Os correlate with negative carbon-isotope excursions and increased mercury concentrations, supporting an interplay between terrestrial volcanism, weathering, and climate that was instrumental in driving these distinct episodes of global environmental change. These observations also indicate that the environmental impact of the Karoo–Ferrar LIP was not limited solely to the T-OAE |
| first_indexed | 2024-03-06T23:42:34Z |
| format | Journal article |
| id | oxford-uuid:6fd1d013-b9ef-4079-acd9-e53a13c4946c |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T23:42:34Z |
| publishDate | 2016 |
| publisher | Geological Society of America |
| record_format | dspace |
| spelling | oxford-uuid:6fd1d013-b9ef-4079-acd9-e53a13c4946c2022-03-26T19:33:07ZOsmium-isotope evidence for two pulses of increased continental weathering linked to Early Jurassic volcanism and climate changeJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:6fd1d013-b9ef-4079-acd9-e53a13c4946cEnglishSymplectic Elements at OxfordGeological Society of America2016Percival, LCohen, ADavies, MDickson, AHesselbo, SJenkyns, HLeng, MMather, TStorm, MXu, WLarge Igneous Provinces (LIPs) are proposed to have caused a number of episodes of abrupt environmental change by increasing atmospheric CO2 levels, which were subsequently alleviated by drawdown of CO<sub>2</sub> via enhanced continental weathering and burial of organic matter. Here, the sedimentary records of two such episodes of environmental change, the Toarcian Oceanic Anoxic Event (T-OAE) and preceding Pliensbachian–Toarcian (Pl–To) event (both potentially linked to the Karoo–Ferrar LIP), are investigated using a new suite of geochemical proxies that have not been previously compared. Stratigraphic variations in osmium-isotope ( <sup>187</sup>Os/<sup>188</sup>Os) records are compared with those of mercury (Hg) and carbon isotopes (δ<sup>13</sup>C) in samples from the Mochras Core, Llanbedr Farm, Cardigan Bay Basin, Wales. These sedimentary rocks are confirmed as recording an open-marine setting by analysis of molybdenum/uranium enrichment trends, indicating that the Os-isotope record in these samples reflects the isotopic composition of the global ocean. The Os-isotope data include the first results across the Pl–To boundary, when seawater <sup>187</sup>Os/<sup>188</sup>Os increased from ∼ 0.40 to ∼ 0.53, in addition to new data that show elevated <sup>187</sup>Os/<sup>188</sup>Os (from ∼ 0.42 to ∼ 0.68) during the T-OAE. Both increases in <sup>187</sup>Os/<sup>188</sup>Os correlate with negative carbon-isotope excursions and increased mercury concentrations, supporting an interplay between terrestrial volcanism, weathering, and climate that was instrumental in driving these distinct episodes of global environmental change. These observations also indicate that the environmental impact of the Karoo–Ferrar LIP was not limited solely to the T-OAE |
| spellingShingle | Percival, L Cohen, A Davies, M Dickson, A Hesselbo, S Jenkyns, H Leng, M Mather, T Storm, M Xu, W Osmium-isotope evidence for two pulses of increased continental weathering linked to Early Jurassic volcanism and climate change |
| title | Osmium-isotope evidence for two pulses of increased continental weathering linked to Early Jurassic volcanism and climate change |
| title_full | Osmium-isotope evidence for two pulses of increased continental weathering linked to Early Jurassic volcanism and climate change |
| title_fullStr | Osmium-isotope evidence for two pulses of increased continental weathering linked to Early Jurassic volcanism and climate change |
| title_full_unstemmed | Osmium-isotope evidence for two pulses of increased continental weathering linked to Early Jurassic volcanism and climate change |
| title_short | Osmium-isotope evidence for two pulses of increased continental weathering linked to Early Jurassic volcanism and climate change |
| title_sort | osmium isotope evidence for two pulses of increased continental weathering linked to early jurassic volcanism and climate change |
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