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North America contains abundant Cretaceous continental strata that hosts potential archives of paleoclimate records. While detailed work has been done in Late Cretaceous strata which not only contains archives for stable isotope proxies, but also leaf physiognomic work, less study has occurred in the Early Cretaceous which lack angiosperm-dominated floras. Here we present new paleotemperature estimates from multiple stable isotope proxies including d18O of pedogenic carbonates, clumped isotope paleothermometry, and paired stable isotopes of aquatic and semi-aquatic taxa. The southern-most data originate from the Hensel Formation of South Texas. Clumped isotope paleothermometry of pedogenic carbonates result in temperature estimates between 35°C and 42°C. Clumped isotope paleothermometry of lake and palustrine carbonates from the Cedar Mountain Formation range from 15°C and 31°C for lake carbonates and 20°C to 44°C for palustrine carbonates. Farther north in Wyoming, we utilize the oxygen isotope value of semi aquatic taxa such as crocodilians and turtles to provide a proxy for water and utilize the oxygen isotope value of fish scales and teeth to estimate temperature at 26°C though with significant error. Preliminary clumped isotope paleothermometry provides a temperature of 25°C. The farthest north locality, the Kootenai Formation contains lacustrine, palustrine, and pedogenic carbonates. Utilizing a previous empirically-derived latitudinal gradient of meteoric water, carbonate d18O values were used to estimate a temperature range for the Kootenai between 13°C and 28°C. These values provide a temperature gradient for the Aptian-Albian over the mid latitudes of North America of ~-1°C/degree of latitude.
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This content will become publicly available on May 13, 2026
Ecohydrology and paleoenvironment of the Cretaceous (Albian) Cloverly Formation: insights from multi-taxon oxygen isotope analysis of vertebrate phosphates
The Cloverly Formation of Montana and Wyoming preserves abundant nonmarine vertebrate fossils from the mid-Cretaceous, yet its paleoenvironment and faunal niche structure remain poorly understood. We analyzed δ18Οphosphatein over 100 fossil individuals from multiple vertebrate taxa collected from a single microfossil bonebed in Carbon County, Montana.To infer habitat preferences and water-use strategies, we compared δ18Οphosphatevalues within and across taxa. We reconstructed δ18Osurface_waterfrom semi-aquatic reptile values using regressions calibrated with data from modern environments and extant taxa. Using a multi-taxon framework, we estimated warm-season water temperatures from δ18Osurface_waterand δ18Οphosphateof lepisosteid (gar) scales, then converted these to air temperatures using a modern climate transfer function. δ18Οphosphatevalues ranged from 9.5‰ to 23.2‰ (VSMOW) and varied across taxa. Aquatic and semi-aquatic groups exhibited lower values than dinosaurian taxa. Our reconstructed mean δ18Osurface_waterwas −7.9‰ (95% CI: −10.1 to 5.5‰), yielding a warm-season water temperature of 26°C and an air temperature of 24°C. Intertaxon differences reflect niche partitioning and suggest primary isotopic signals are preserved. Unexpectedly high values in Bernissartiid-like neosuchian teeth may indicate greater ecohydrological diversity than previously recognized. Our δ18Osurface_waterestimate aligns with other Aptian-Albian proxies but exceeds model-based predictions, likely due to outdated assumptions underlying the model. The MAWSAT estimate falls within the upper range of model-data assimilation outputs. These results provide new context for ecological structure in the Cloverly fauna and offer the first quantitative temperature estimate for the Formation, helping to define baseline conditions between the Aptian-Albian Cold Snap and the Cretaceous Thermal Maximum.
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- Award ID(s):
- 1925942
- PAR ID:
- 10598873
- Publisher / Repository:
- Frontiers
- Date Published:
- Journal Name:
- Frontiers in Earth Science
- Volume:
- 13
- ISSN:
- 2296-6463
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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