174-2 Latitudinal Trends in Early Cretaceous North American Continental Palaeo-Ecosystems from the Western Interior Basin as Determined by Isotopic and Trace Element Ratios of Vertebrate Fossils

Session: Environmental Instability During Greenhouse Periods: Impact on Terrestrial and Marine Ecosystems

Presenting Author:

Authors:

Abstract:

Major global carbon cycle perturbations likely stemming from the suspected Kerguelen Large Igneous Province resulted in the positive carbon isotopic excursion known as Ocean Anoxic Event 2. This excursion coincided with one of the most intense global greenhouse conditions in Earth’s geologic history. The lead-up to this period also coincided with major, global hydrologic cycle changes from a relatively cool Aptian Age to the excessive heat of the Cenomanian Age. The hydrologic cycle of Western North America experienced an increase in storm strength and dominance of eddy diffusion fractionation over advection-based fractionation as evidenced by the preserved oxygen isotopes (δ18O) from meteoric water proxies originating from the North American continent. This pattern, called an isotopic landscape or isoscape, can be observed by the geostatistical interpolation of oxygen isotopic proxies. The resulting pattern shows a latitudinal effect (water movement from the equatorial regions moving poleward) has a dominant control over the dispersal pattern of δ18O. The preference of eddy diffusion over advection results in a shallow δ18O gradient from equator to the poles in opposition to previous interpretations but in conformity with General Circulation Models of the Albian-Cenomanian. We examine the effects of these latitudinal climatic conditions on continental ecosystems by using geochemical composition (C and O-isotopic composition and Ba/Ca vs Sr/Ca ratios) of vertebrates as a proxy for niche space. Albian-Cenomanian fossil localities include: the Dunvegan Formation from British Columbia, Canada; the Cloverly Formation from Montana/Wyoming, USA; the Wayan Formation from Idaho, USA; the Antlers Formation from Texas/Oklahoma, USA; and the Woodbine Formation from Texas/Oklahoma, USA. A comparison of the water δ18O from these sites is compared to the continental oxygen isoscape prediction for these sites. Carbon isotopic values as well as trace element ratios are also observed from each specimen in pursuit of dietary/migratory/diagenetic implications.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10354

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