Redox conditions and ecological resilience during Oceanic Anoxic Event 2 in the Western Interior Seaway
Robinson, L. J.; George, K. S.; Fox, C. P.; Marshall, J. E.A.; Harding, I. C.; Bown, P. R.; Lively, J. R.; Marroquín, S.; Leckie, R. M.; Dameron, S.; Gröcke, D. R.; Papadomanolaki, N. M.; van Helmond, N. A.G.M.; Whiteside, J. H.
(2023) Palaeogeography, Palaeoclimatology, Palaeoecology, volume 618, pp. 1 - 18
(Article)
Abstract
Oceanic Anoxic Events (OAEs) are important geological events that may be analogues to future climate-driven deoxygenation of our oceans. Much of the global ocean experienced anoxic conditions during the Cenomanian–Turonian OAE (OAE2; ∼94 Ma), whereas the Western Interior Seaway (WIS) experienced oxygenation at this time. Here, organic geochemical and palynological
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data generated from Cenomanian–Turonian age sediments from five sites in the WIS are used to investigate changing redox and ecological conditions across differing palaeoenvironments and palaeolatitudes. Heterogeneity across the sites is apparent, but important relationships and trends among oceanographic variables are recognised: 1) Increasing total organic carbon (TOC) and CaCO3 percentages indicate the onset of a sea-level maximum towards the end of OAE2; 2) C28 sterane is shown to be a useful marker for prasinophyte abundance, and concurrent increases in this marker and overall sterane abundance indicate prasinophyte-driven increase in algal productivity in a stratified water column; and 3) sterane ratios can be a more reliable geochemical proxy than redox proxies for assessing the Benthic Oxic Zone. Our redox data do not always follow established trends for the WIS overall, particularly for proximal settings. We therefore surmise that local effects, such as nutrient-driven expansion of the oxygen minimum zone and/or sedimentation-driven anoxia just below the sediment-water interface, have overprinted regional trends.
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Keywords: Cretaceous, Organic geochemistry, Prasinophytes, Steranes, Taverne, Oceanography, Ecology, Evolution, Behavior and Systematics, Earth-Surface Processes, Palaeontology
ISSN: 0031-0182
Publisher: Elsevier Saunders
Note: Funding Information: LJR acknowledges support from the Natural Environmental Research Council UK (NE/L002531/1), AAPG Foundation Grant-in-Aid (Marta S. Weeks Named Grant) and Geological Society of London Research Grant (William George Fearnsides fund). Samples were generously donated by Mark Leckie (Lohali Point and Billings Landfill), Guy Plint (Pratts Landing) and the USGS Core Research Centre (Rebecca Bounds). Samples from Lohali Point originate from Navajo and Hopi ancestral lands. We thank the Bureau of Land Management for access to Gunnison Gorge NCA, with work conducted under BLM permit to JRL. Marjean Cone assisted in sample acquisition from Gunnison Gorge, and David Noe provided important guidance on the stratigraphy of the area. We thank Richard Twitchett (Natural History Museum) for insightful conversations. CPF acknowledges CIRA grant CIRA-2019-066. Funding Information: LJR acknowledges support from the Natural Environmental Research Council UK ( NE/L002531/1 ), AAPG Foundation Grant-in-Aid (Marta S. Weeks Named Grant) and Geological Society of London Research Grant (William George Fearnsides fund). Samples were generously donated by Mark Leckie (Lohali Point and Billings Landfill), Guy Plint (Pratts Landing) and the USGS Core Research Centre (Rebecca Bounds). Samples from Lohali Point originate from Navajo and Hopi ancestral lands. We thank the Bureau of Land Management for access to Gunnison Gorge NCA, with work conducted under BLM permit to JRL. Marjean Cone assisted in sample acquisition from Gunnison Gorge, and David Noe provided important guidance on the stratigraphy of the area. We thank Richard Twitchett (Natural History Museum) for insightful conversations. CPF acknowledges CIRA grant CIRA-2019-066. Publisher Copyright: © 2023
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