Evaluation of paleoclimatic conditions east and west of the southern Canadian Cordillera in the mid-late Paleocene using bulk organic δ13C records

摘要: Abstract Carbon isotope records from organic matter provide a key data set for constraining past fluctuations in the isotopic composition of atmospheric carbon dioxide (δ13Catm), hydrologic conditions, and plant community composition. Here we evaluate spatiotemporal shifts these three conditions using δ13C values bulk (δ13Cbulk) Paleocene strata northwest Washington, U.S.A. west-central Alberta, Canada. Our contains 352 analyses Chuckanut Paskapoo formations. Mean δ13Cbulk two areas are statistically indistinguishable (− 24.5‰ − 24.4‰ (VPDB), respectively), exhibit wide range (~ 5–7‰). In both sequential vertical samples show large values, on average ~ 1.0‰ ± 1.0 (1σ). There no distinct up-section trends or structured excursions ~ 850 meter stratigraphic section Formation nor ~ 125 meter Formation. Furthermore, independent weight percent (%C) lithology sample. The lack systematic relationship correlation between %C indicates fractionation during post-mortem processes, such as microbial respiration, exerted minimal influence patterns. independence suggests variability is unrelated to local spatial gradients vegetation water availability across paleo-landscape. However, similar stochastic intra-site within modern settings. absence structured, secular variation CO2, rainfall, Moreover, that previous excursion ascribed Paleocene–Eocene Thermal Maximum actually result aliasing related sampling density. Finally, mean regions imply similarly wet humid climatic when combined with sedimentologic paleobotanical data. support early Paleogene circulation models strong orographic precipitation patterns Pacific Northwest associated incipient extensional tectonics region enhanced transport moisture-laden polar air masses southward into Canadian continental interior.