PROSPECTS, PITFALLS, AND PRATFALLS OF HIGH LATITUDE PALEOENVIRONMENTAL RECONSTRUCTION FROM THE POST-ERUPTIVE SEDIMENTARY FILL OF KIMBERLITE PIPES IN NORTHERN CANADA (Invited Presentation)

Several kimberlite pipes in subarctic Canada host thick accumulations of Early Cenozoic lake sediment and peat that accumulated in maar basins. Extensive diamond exploration drilling has provided a valuable window into this unique sedimentary archive of paleoenvironments during the sustained “greenhouse” interval prior to the onset of global cooling ~45 million years ago, in a high-latitude region otherwise devoid of sediment cover. Multidisciplinary studies of the “Giraffe” and “Wombat” kimberlite pipes highlight the potential of this sedimentary record, but also underscore the challenges of early Cenozoic terrestrial paleoenvironmental reconstruction, particularly with respect to geochronology. We present substantial revisions to the geochronological frameworks for both kimberlite pipes based on tephra glass-fission-track, tephra zircon U-Pb, and pollen biostratigraphy techniques. These new geochronological frameworks underpin revisions to the Middle Eocene paleo-CO₂ record from the ~48 Ma “Giraffe” kimberlite pipe and development of biomarker-based paleoclimate proxy records from well-preserved lacustrine facies. The revised “Wombat” pipe geochronology is less secure, but new and ongoing research on its post-eruptive fill gives insight into latest Cretaceous paleoclimate, paleogeography, paleoecology, and biogeochemical cycling.