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Reynolds, R. W., Jerrett, R., Marca, A. 
ORCID: https://orcid.org/0000-0002-7751-5446, Davies, M., Bernasconi, S. M., Paxton, R. B., Nowell, G., Dennis, P. ORCID: https://orcid.org/0000-0002-0307-4406, Balthasar, U. and Price, G. D.
(2026)
A Tropically Hot Late Jurassic North American Sundance Sea: Evidence for the Oxfordian Warm Interval.
Paleoceanography and Paleoclimatology, 41 (7).
ISSN 2572-4525
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Abstract
The Late Jurassic greenhouse climate was characterized by elevated atmospheric CO 2 (pCO 2) at 600–1,000 ppm and sea-surface temperatures substantially warmer than today. These conditions peaked during the Oxfordian, when extensive epicontinental seaways, including the North American Sundance Sea, dominated mid-latitude paleoceanography. We present clumped isotope (Δ 47) and 87Sr/ 86Sr analyses of Oxfordian belemnite and Gryphaea fossils from the Sundance Sea to reconstruct paleotemperatures (tΔ 47) and assess the balance between open ocean and terrestrial inputs. The data reveal (a) a mean tΔ 47 of 30.6°C (±1.6 1SE), or 27.6°C (±1.6 1SE) if subjected to maximum bond reordering, reflecting unusually high mid-latitude sea-surface temperatures; (b) δ 18O seawater values ranging from −2.3‰ (±1.5 1SE) to −0.1‰ (±0.7 1SE) within the Sundance Sea; and, (c) evidence of a slight radiogenic enrichment in 87Sr/ 86Sr (0.706850, offset by 2.0 × 10 −5 to 3.0 × 10 −5) relative to the reconstructed global seawater curve for the early-mid Oxfordian, indicating a limited connectivity between the Sundance Sea and Panthalassic Ocean. When integrated with existing Jurassic Δ 47 records, these findings provide evidence for an Oxfordian Warm Interval and locally elevated sea-surface temperatures in the Sundance Sea relative to the coeval open ocean, owing to its marginal or semi-enclosed hydrography. This furthermore demonstrates the capacity of the Δ 47 proxy to resolve the upper thermal bounds of Jurassic greenhouse climates.
| Item Type: | Article |
|---|---|
| Additional Information: | Availability Statement: All data and supporting information is available at Reynolds et al. (2026). |
| Uncontrolled Keywords: | jurassic,oxfordian warm interval,sundance sea,clumped isotopes,paleoclimate,oceanography,atmospheric science,palaeontology ,/dk/atira/pure/subjectarea/asjc/1900/1910 |
| Faculty \ School: | Faculty of Science Faculty of Science > School of Environmental Sciences |
| UEA Research Groups: | Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences Faculty of Science > Research Groups > Geosciences |
| Related URLs: | |
| Depositing User: | LivePure Connector |
| Date Deposited: | 13 Aug 2026 11:51 |
| Last Modified: | 14 Aug 2026 13:57 |
| URI: | https://ueaeprints.uea.ac.uk/id/eprint/104114 |
| DOI: | 10.1029/2025PA005364 |
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