A Tropically Hot Late Jurassic North American Sundance Sea: Evidence for the Oxfordian Warm Interval
ORCID
- U. Balthasar: 0000-0001-5293-2430
- G. D. Price: 0000-0002-2461-7465
Abstract
The Late Jurassic greenhouse climate was characterized by elevated atmospheric CO2 (pCO2) 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 (Δ47) and 87Sr/86Sr analyses of Oxfordian belemnite and Gryphaea fossils from the Sundance Sea to reconstruct paleotemperatures (tΔ47) and assess the balance between open ocean and terrestrial inputs. The data reveal (a) a mean tΔ47 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) δ18O 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 Δ47 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 Δ47 proxy to resolve the upper thermal bounds of Jurassic greenhouse climates.
DOI Link
Publication Date
2026-07-27
Publication Title
Paleoceanography and Paleoclimatology
Volume
41
Issue
7
ISSN
2572-4517
Acceptance Date
2026-07-20
Deposit Date
2026-08-10
Funding
Natural Environment Research Council. Grant Number: NE/S007334/1
Additional Links
Keywords
clumped isotopes, Jurassic, Oxfordian warm interval, paleoclimate, Sundance Sea
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Reynolds, R., Jerrett, R., Marca, A., Davies, M., Bernasconi, S., Paxton, R., Nowell, G., Dennis, P., Balthasar, U., & Price, G. (2026) 'A Tropically Hot Late Jurassic North American Sundance Sea: Evidence for the Oxfordian Warm Interval', Paleoceanography and Paleoclimatology, 41(7). Available at: 10.1029/2025PA005364
