“Short” or “long” Rhaetian ? Astronomical calibration of Austrian key sections

Research output: Contribution to journalArticle

Abstract

The establishment of the Late Triassic time scale has given rise to considerable controversy, particularly regarding the Rhaetian duration and the inferred absolute age models. In this respect the astronomical polarity time scale (APTS) established from the continental successions of the Newark Basin (eastern North America) is considered as a reference record, although its completeness is questioned. Numerous magnetostratigraphic correlation schemes have been proposed between the APTS and biostratigraphically well-constrained Tethyan marine sections. This has led to two main contrasting options: a “short” Rhaetian duration (about 4–5 myr), and a “long” one (about 8–9 myr). Astronomical calibration of the Tethyan Rhaetian and estimate of its duration is necessary to help advance this debate. We have undertaken a cyclostratigraphic analysis of a Rhaetian composite record built from four overlapping Austrian reference sections. Magnetic susceptibility variations of the 131.5 m thick record are astronomically paced by the precession and 405-kyr orbital eccentricity cycles. 405-kyr orbital tuning allows to establish a floating time scale, and thus to suggest a minimum duration of 6.69 myr of the Rhaetian stage. Given the well-established radioisotopic age of the Rhaetian-Hettangian boundary of 201.36 Ma, an age no younger than 208.05 Ma for the Norian-Rhaetian boundary can be proposed. This result will contribute to the refinement of the Late Triassic time scale, but it does not solve the long-standing debate on bio-magnetostratigraphic correlations between the continental Newark APTS and the Tethyan marine sections, nor the question of the completeness of the Rhaetian Newark Basin.

Details

Authors
  • Bruno Galbrun
  • Slah Boulila
  • Leopold Krystyn
  • Sylvain Richoz
  • Silvia Gardin
  • Annachiara Bartolini
  • Martin Maslo
Organisations
External organisations
  • Pierre and Marie Curie University
  • University of Vienna
  • Karl-Franzens-University of Graz
  • Muséum National d'Histoire Naturelle (Sorbonne Universités)
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Geology

Keywords

  • 405 kyr eccentricity tuning, Cyclostratigraphy, Late Triassic time scale, Magnetic susceptibility, Northern Calcareous Alps, Rhaetian
Original languageEnglish
Article number103253
JournalGlobal and Planetary Change
Volume192
Publication statusPublished - 2020
Publication categoryResearch
Peer-reviewedYes