Abstract
Abstract. To explore cause and consequences of past climate change, very accurate age models such as those provided by the astronomical timescale (ATS) are needed. Beyond 40 million years the accuracy of the ATS critically depends on the correctness of orbital models and radioisotopic dating techniques. Discrepancies in the age dating of sedimentary successions and the lack of suitable records spanning the middle Eocene have prevented development of a continuous astronomically calibrated geological timescale for the entire Cenozoic Era. We now solve this problem by constructing an independent astrochronological stratigraphy based on Earth's stable 405 kyr eccentricity cycle between 41 and 48 million years ago (Ma) with new data from deep-sea sedimentary sequences in the South Atlantic Ocean. This new link completes the Paleogene astronomical timescale and confirms the intercalibration of radioisotopic and astronomical dating methods back through the Paleocene–Eocene Thermal Maximum (PETM, 55.930 Ma) and the Cretaceous–Paleogene boundary (66.022 Ma). Coupling of the Paleogene 405 kyr cyclostratigraphic frameworks across the middle Eocene further paves the way for extending the ATS into the Mesozoic.
Highlights
Accurate absolute age determinations are essential for the geologic study of Earth history
A major change had to be made around 120 rmcd, which was reported as problematic during shipboard analysis (Shipboard Scientific Party, 2004)
Derived absolute ages for the Paleocene–Eocene Thermal Maximum (PETM) and K-Pg boundary are consistent with the intercalibration of radioisotopic and astronomical dating methods
Summary
Accurate absolute age determinations are essential for the geologic study of Earth history. Development of cyclostratigraphic records and the application of astronomical tuning (Hinnov, 2013) have evolved into powerful chronostratigraphic tools for highly accurate calibration of the Neogene timescale (Lourens et al, 2004), as well as synchronizing the widely used radioisotopic 40Ar / 39Ar and U / Pb absolute dating methods (Kuiper et al, 2008). Beyond the 50 Ma limit for short eccentricity multimillionyear-long geological records (Hinnov and Hilgen, 2012) with a 405 kyr eccentricity cyclostratigraphic framework have to be anchored in absolute time (Kuiper et al, 2008) by very precise radioisotopic ages from ash layers
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