High latitude meteoric δ18O compositions from the Cenomanian Bastion Ridge Formation, Axel Heiberg Island, Canadian Arctic Archipelago: a palaeoclimate proxy from the Sverdrup Basin
Published:April 14, 2020
Jeffrey B. Ross, G. A. Ludvigson, C. J. Schröder-Adams, M. B. Suarez, 2020. "High latitude meteoric δ18O compositions from the Cenomanian Bastion Ridge Formation, Axel Heiberg Island, Canadian Arctic Archipelago: a palaeoclimate proxy from the Sverdrup Basin", Cretaceous Climate Events and Short-Term Sea-Level Changes, M. Wagreich, M. Hart, B. Sames, I. O. Yilmaz
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Stable isotope analyses of a siderite-cemented siltstone from the Cenomanian Bastion Ridge Formation, Axel Heiberg Island, Canada, produce a range of δ18O values from −21.9 to −18.4‰ Vienna Pee Dee Belemnite (VPDB), and δ13C values ranging from 2.0 to 4.4‰ VPDB. A meteoric siderite line of −18.95 ± 0.33‰ VPDB is calculated from siderite cements of the authigenic component. At estimated palaeolatitude of 68–72° N and palaeotemperature range from 12.6 to 13.7°C, the calculated δ18O range of palaeoprecipitation is −23.3 to −23.0‰ Vienna Standard Mean Ocean Water (VSMOW). This result is compatible with other published meteoric water δ18O datasets from Cretaceous Arctic studies, but is near the lower end of the range of estimated δ18O values. The modern δ18O empirical relationship of Dansgaard and Earth System models simulating meteoric δ18O values does not yield results for palaeopolar regions that match proxy δ18O datasets. Orographic effects of contemporaneous mountain belts and seasonal biases in groundwater recharge have been proposed to explain this paradox regarding depleted meteoric water δ18O values from proxy data in greenhouse worlds. Evidence for local to regional orographic effects and alpine snowmelt biasing groundwater recharge is lacking for the Sverdrup Basin deposits, further indicating that the Dansgaard relationship does not apply to ancient greenhouse worlds.
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Cretaceous Climate Events and Short-Term Sea-Level Changes
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Sea-level constitutes a critical planetary boundary for both geological processes and human life. Sea-level fluctuations during major greenhouse phases are still enigmatic and widely discussed in terms of changing climate systems. The geological record of the Cretaceous greenhouse period provides a deep-time view on greenhouse-phase Earth system processes that facilitates a much better understanding of the causes and consequences of global, geologically short-term, sea-level changes. In particular, Cretaceous hothouse periods can serve as a laboratory to better understand a near-future greenhouse Earth. This volume presents high-resolution sea-level records from globally distributed sedimentary archives of the Cretaceous involving a large group of scientists from the International Geoscience Programme IGCP 609. Marine to non-marine sedimentary successions were analysed for revised age constraints, the correlation of global palaeoclimate shifts and sea-level changes, tested for climate-driven cyclicities, and correlated within a high-resolution stratigraphic framework of the Geological Timescale. For hothouse periods, the hypothesis of significant global groundwater-related sea-level change, i.e. aquifer-eustasy as a major process, is reviewed and substantiated.