292-4 A Composite δ13C Profile of the Early Cretaceous (Valanginian) Weissert Event in Utah Correlates in Detail with the Published Record in Japan

Abstract:

We have produced a detailed, age-constrained δ¹³C (organic) profile revealing the Valanginian carbon-isotope excursion (CIE) or “Weissert Event” (WE) from an ~11 m-thick composite section of the alluvial and palustrine Yellow Cat Member (YCM) of the Cedar Mountain Formation. The YCM in our study area (Poison Strip, Grand County, Utah) contains pervasive evidence for long intervals of pedogenesis. Our profile is amply constrained by two cryptotephra CA-ID-TIMS U-Pb ages (Joeckel et al. Geosciences, https://doi.org/10.3390/geosciences13020032). The structure of the WE in our YCM composite δ¹³C (organic) profile from the salt-tectonic Yellow Cat basin correlates remarkably well with one produced from ~200 m of Panthalassan marine strata in northeastern Japan reported by T. Tomaru et al. 2025, (Newsletters in Stratigraphy, https://doi.org/10.1127/nos/2025/0868). They identified multiple constituent minor CIEs of the WE, naming those segments of their profile as NP2, PP4, NP3, NP4, PP5, NP5, and PP6, in ascending stratigraphic order. All seven of these features are readily identified in our profile as well, despite an eighteen-fold difference in stratigraphic thickness. This remarkable correspondence in the detailed structure of the first major CIE during the Cretaceous Period leads us to conclude that, at least in this case, the chemostratigraphic record “compensates” for a highly incomplete sedimentary record in conferring a means of correlation between stratal packages of vastly different scale in the terrestrial and marine realms. Accordingly, we encourage a significant paradigm shift in how disparate stratigraphic, and chemostratigraphic records are interpreted, compared, and correlated.

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