Interpreting Phanerozoic δ13C patterns as periodic glacio-eustatic sequences

Al-Husseini, Moujahed; Ruebsam, Wolfgang

Abstract

The deterministic Orbital Scale of glacio-eustasy is calibrated with 405-kyr time-rock units named stratons. It predicts polar ice volumes (global sea level) varied throughout the Phanerozoic according to a periodic template that repeats every 14.58 myr. The scale represents the interval between 1.586 and 541.046 Ma with 37 orbitons, each lasting 14.58 myr and consisting of three dozons (4.86 myr, 12 stratons) and 36 stratons. In times older than c. 8.0 Ma the predicted ages of glacial maxima closely correlate to those of positive δ13C plateaus as estimated by radiometric and other dating techniques. This study illustrates the application of the scale in nine examples from the early Cambrian, late Ordovician and early Silurian, Carboniferous and Cretaceous. Each example compares the predicted glacio-eustatic signal to δ13C patterns (plateaus, valleys, rising and falling limbs) and cites supporting stratigraphic evidence for the interpretation (e.g., transgression, regression, erosional unconformity, sequence boundary, cold snap, flooding interval).

The examples also review empirical age estimates of stage boundaries and where inconsistent they are calibrated by the Orbital Scale. The results indicate several stage boundaries are defined in major δ13C plateaus that pass to glacio-eustatic unconformities and hiatuses. The 4.86-myr dozon stands out in the examples as the easiest-to-recognize stratigraphic unit because it is bounded by two significant δ13C plateaus or excursions that pass to unconformities. Dating δ13C plateaus according to the Orbital Scale may therefore provide key anchors that better constrain the geologic time scale.

Citation

Al-Husseini, M., & Ruebsam, W. (2020). Interpreting Phanerozoic δ13C patterns as periodic glacio-eustatic sequences. In M. Montenari (Ed.), Stratigraphy & Timescales (41-105). Elsevier. https://doi.org/10.1016/bs.sats.2020.08.005

• Online Publication Date: Oct 12, 2020
• Publication Date: 2020
• Deposit Date: Jun 6, 2023
• Publisher: Elsevier
• Pages: 41-105
• Series Title: Carbon Isotope Stratigraphy
• Series ISSN: 2468-5178
• Book Title: Stratigraphy & Timescales
• Chapter Number: 2
• ISBN: 978-0-12-820991-2
• DOI: https://doi.org/10.1016/bs.sats.2020.08.005