25-8 Milankovitch forcing and Cambrian climate dynamics: Integrated stratigraphy of the Miaolingian Epoch in Baltica

Session: Refining the Cambrian—Biotas, Multiproxy Correlations, Workable Global Divisions, and Paleogeography: Discussions in Honor of Fred Sundberg

Presenting Author:

Valentin Jamart

Authors:

Jamart, Valentin¹, Pas, Damien², Hinnov, Linda A.³, Spangenberg, Jorge E.⁴, Adatte, Thierry⁵, Nielsen, Arne T.⁶, Schovsbo, Niels H.⁷, Thibault, Nicolas R.⁸, Arts, Michiel⁹, Daley, Allison C.¹⁰

Abstract:

The remarkably continuous and well-preserved Alum Shale Formation has been intensively studied in northwestern Europe as a proven source rock for petroleum and for its biostratigraphic importance.

The identification of Milankovitch-driven climate cycles in cyclostratigraphy performed on the Miaolingian part of the Alum Shale Formation, coupled with updated bio- and chemostratigraphic frameworks, has the potential to significantly improve the Cambrian time scale. High-resolution XRF core scanning data of the sedimentary series from the well-preserved Albjära-1 drill core from Scania, southern Sweden reveals prominent cycles corresponding with theoretical Cambrian Milankovitch periodicities. The most prominent peak, identified as a potentially stable 173-kyr obliquity modulation (“inclination metronome”), was used to build an astronomically calibrated time scale (ATS) for the Miaolingian Series that faithfully restitutes the expression of precession, obliquity and eccentricity. This calibration results in duration estimates for the Miaolingian Series, Guzhangian, Drumian and Wuliuan (part) stages, the Paradoxides forchhammeri, Goniagnostus nathrosti, Ptychagnostus punctuosus, Ptychagnostus atavus, and Ptychagnostus gibbus (part) agnostoids biozones, and the Drumian carbon isotope excursion (DICE). The durations of the stages and biozones provide critical constraints for a global Cambrian time scale. Stratigraphic continuity with the ATS previously published by Zhao et al. (2022)  was ensured by incorporating and anchoring these results to the Cambrian-Ordovician boundary U-Pb numerical age (486.78 ± 0.53 Ma) located in the uppermost part of the core.

In addition to refining the chronostratigraphy of the Cambrian in Baltica, we have developed a paleoclimatic model for Cambrian outer shelf settings that explains the links between predominant obliquity and eccentricity forcings and fluctuations in sea-level and aeolian dust fluxes as major drivers of sedimentation.

REFERENCES

Zhao, Z. F., Thibault, N. R., Dahl, T. W., Schovsbo, N. H., Sorensen, A. L., Rasmussen, C. M. O., & Nielsen, A. T. (2022). Synchronizing rock clocks in the late Cambrian. Nature Communications, 13(1). https://doi.org/10.1038/s41467-022-29651-4

 

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8632

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.