Intercalibration of Radioisotopic and Astrochronologic Time Scales for the Cenomanian/Turonian Boundary Interval, Western Interior Basin, USA

Stephen R Meyers, S Seiwert, B Singer, B Sageman, D Condon, J Obradovich, B Jicha, D Sawyer

Research output: Contribution to journalArticlepeer-review

153 Scopus citations

Abstract

We develop an intercalibrated astrochronologic and radioisotopic time scale for the Cenomanian-Turonian boundary (CTB) interval near the Global Stratotype Section and Point in Colorado, USA, where orbitally influenced rhythmic strata host bentonites that contain sanidine and zircon suitable for 40Ar/39Ar and U-Pb dating. Paired 40Ar/39Ar and U-Pb ages are determined from four bentonites that span the Vascoceras diartianum to Pseudaspidoc- eras flexuosum ammonite biozones, utilizing both newly collected material and legacy sani- dine samples of J. Obradovich. Comparison of the 40Ar/39Ar and U-Pb results underscores the strengths and limitations of each system, and supports an astronomically calibrated Fish Can- yon sanidine standard age of 28.201 Ma. The radioisotopic data and published astrochronol- ogy are employed to develop a new CTB time scale, using two statistical approaches: (1) a sim- ple integration that yields a CTB age of 93.89 ± 0.14 Ma (2σ; total radioisotopic uncertainty), and (2) a Bayesian intercalibration that explicitly accounts for orbital time scale uncertainty, and yields a CTB age of 93.90 ± 0.15 Ma (95% credible interval; total radioisotopic and orbital time scale uncertainty). Both approaches firmly anchor the floating orbital time scale, and the Bayesian technique yields astronomically recalibrated radioisotopic ages for individual ben- tonites, with analytical uncertainties at the permil level of resolution, and total uncertainties below 2‰. Using our new results, the duration between the Cenomanian-Turonian and the Cretaceous-Paleogene boundaries is 27.94 ± 0.16 Ma, with an uncertainty of less than one-half of a long eccentricity cycle.
Original languageEnglish
Pages (from-to)7-10
JournalGeology
Volume40
DOIs
StatePublished - 2012

Fingerprint

Dive into the research topics of 'Intercalibration of Radioisotopic and Astrochronologic Time Scales for the Cenomanian/Turonian Boundary Interval, Western Interior Basin, USA'. Together they form a unique fingerprint.

Cite this