Calibration of chron C29r: New high-precision geochronologic and paleomagnetic constraints from the Hell Creek region, Montana

Research Article| May 02, 2018 Calibration of chron C29r: New high-precision geochronologic and paleomagnetic constraints from the Hell Creek region, Montana Courtney J. Sprain; Courtney J. Sprain † 1Department of Earth and Planetary Science, University of California, Berkeley, California 94720, USA †Present address: Geomagnetism Laboratory, Department of Earth, Ocean and Ecological Sciences, University of Liverpool, Liverpool L69 7ZE, UK; c.sprain@liverpool.ac.uk. Search for other works by this author on: GSW Google Scholar Paul R. Renne; Paul R. Renne 1Department of Earth and Planetary Science, University of California, Berkeley, California 94720, USA2Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, California 94709, USA Search for other works by this author on: GSW Google Scholar William A. Clemens; William A. Clemens 3Department of Integrative Biology, University of California, Berkeley, California 94720, USA4Museum of Paleontology, University of California, Berkeley, California 94720, USA Search for other works by this author on: GSW Google Scholar Gregory P. Wilson Gregory P. Wilson 5Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, Washington 98195, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2018) 130 (9-10): 1615–1644. https://doi.org/10.1130/B31890.1 Article history received: 20 Jul 2017 rev-recd: 12 Jan 2018 accepted: 16 Mar 2018 first online: 02 May 2018 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Courtney J. Sprain, Paul R. Renne, William A. Clemens, Gregory P. Wilson; Calibration of chron C29r: New high-precision geochronologic and paleomagnetic constraints from the Hell Creek region, Montana. GSA Bulletin 2018;; 130 (9-10): 1615–1644. doi: https://doi.org/10.1130/B31890.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The mass extinction at the Cretaceous-Paleogene boundary marks one of the most important biotic turnover events in Earth history. Yet, despite decades of study, the causes of the Cretaceous-Paleogene boundary crises remain under debate. An important tool that has the capacity to greatly improve our understanding of the events around the Cretaceous-Paleogene boundary is the geomagnetic polarity time scale (GPTS). The GPTS is used for age control in numerous Cretaceous-Paleogene boundary studies, including the timing of Deccan Traps volcanism, a majority of studies in marine sections, and studies on climate and ecological change across the Cretaceous-Paleogene boundary. The current calibration of the GPTS for circum–Cretaceous-Paleogene boundary polarity chrons (C30n–C28n) from the Geologic Time Scale draws heavily on astronomical tuning and uses a 40Ar/39Ar age for the Cretaceous-Paleogene boundary as a tie point that has since been shown to be 200 ka too old. Furthermore, complex sedimentation has been recorded in marine sections immediately following the Cretaceous-Paleogene boundary, which can possibly obscure orbital signals and complicate cyclostratigraphic interpretation. An independent test of the cyclostratigraphy for this time period is imperative for confidence in the astronomical time scale. Further, polarity reversal ages given in the GPTS do not include uncertainty estimates, making them unsuitable for quantitative chronometry. Recent calibrations have been attempted using U/Pb geochronology on zircons; however, U/Pb zircon dates may be biased by pre-eruptive zircon residence times of tens to hundreds of thousands of years.In this study, we provide constraints on the timing and duration of the most important circum–Cretaceous-Paleogene boundary chron, chron C29r, using high-precision 40Ar/39Ar geochronology and magnetostratigraphy on fluvial sediments from the Hell Creek region, Montana. Here, we show results for 14 new magnetostratigraphic sections, and 18 new high-precision 40Ar/39Ar dates, which together provide six independent constraints on the age of the C29r/C29n reversal and two constraints on the C30n/C29r reversal. Together, these results show that the duration of C29r was 587 ± 53 ka, consistent with the most recent Geologic Time Scale calibration and previous U-Pb age models. We further present new geochronologic data for the Cretaceous-Paleogene boundary that provide the most precise date yet, of 66.052 ± 0.008/0.043 Ma. Integration of our results into the extensive paleontological framework for this region further provides important constraints on rates of terrestrial faunal change across the Cretaceous-Paleogene boundary. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.