Origins and Alteration of Ediacaran Carbonates Recording the Shuram Excursion in Oman

Creators: Bergmann, Kristin D.¹; Osburn, Magdalena R.²; Anderson, Noah T.^{1, 3}; Hayhow, Claire¹; Wilcots, Julia^{1, 4}; Cantine, Marjorie D.^{1, 5}; Fischer, Woodward⁶; Bonifacie, Magali^{7, 8}

1. Massachusetts Institute of Technology
2. Northwestern University
3. Now at Cascade Climate, Somerville, MA, USA
4. Princeton University
5. University of Washington
6. California Institute of Technology
7. University of Paris
8. Institut de Physique du Globe de Paris

Abstract

The Shuram excursion is the largest known negative carbon isotope excursion in Earth's history. Recognized globally, it follows the Ediacaran Gaskiers glaciation and precedes a marked increase in the diversity and complexity of the earliest macroscopic multicellular organisms in the fossil record. A key question is whether this excursion reflects a primary perturbation to the carbon cycle, which would provide crucial insights into the environmental conditions shaping the earliest animals, or whether it is largely an artifact of later diagenetic alteration. To evaluate the extent of diagenesis in these rocks and constrain how much of the excursion reflects a primary signal, we investigate the sedimentology and geochemistry of carbonate strata in Oman using a variety of techniques spanning multiple spatial and temporal scales. Our multi‐faceted analysis identifies and characterizes four modes of diagenetic alteration, with sediment‐buffered conditions and authigenic carbonate precipitation as the dominant processes. However, the degree of alteration is insufficient to account for the range of marine sedimentologic and geochemical trends across the carbon isotope excursion. This suggests that, even with evidence of diagenesis, the rocks preserve a measurable record of changing conditions in both terrestrial and marine environments, offering unique insights into Earth's systems during a pivotal time in early animal evolution.

Copyright and License

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Acknowledgement

A.B. Jost, S. Kahn, M. Gonzalez, J. Melara-Valle, N. Chatterjee, C. Ma, J. Hurowitz, and Y. Guan provided additional assistance with instrument maintenance, analytical measurements, and sample preparation. Portions of this research were carried out at the Stanford Synchrotron Radiation Lightsource, a Directorate of SLAC National Accelerator Laboratory and an Office of Science User Facility operated for the US Department of Energy Office of Science by Stanford University. S. Webb and J. Johnson helped with the XANES measurements at SLAC and provided standard data. We thank Petroleum Development Oman employees for helpful discussions, particularly I. Gómez-Pérez, B. Al Balushi, S. Al Baloushi, Z. Al Rawahi, H. Al Rawahi, J. Amthor, E. Adams, G. Lopes Cardozo, and G. Forbes. We thank the Ministry of Energy and Minerals of the Sultanate of Oman and Petroleum Development Oman for permission to publish this manuscript and for fieldwork support. Specific thanks to the Shuram Group drivers and cooks for their work in the field, particularly Younis Saleh Aldouyani. We thank A. Pearson, R. Summons, F. Macdonald, D. Johnston, D. Rothman, A. Knoll, J. Eiler, and J. Grotzinger for conversations and comments as well as D. Fike, E. Sperling, L. Derry, T. Wong Hearing, and five anonymous reviewers for detailed and helpful feedback on versions of the manuscript. P. Bokulich provided valuable assistance editing the manuscript. K.D.B. acknowledges funding from the Packard Foundation and NASA Exobiology Grant 80NSSC19K0464. M.D.C. was supported by a National Defense Science and Engineering Graduate Fellowship. Open Access funding enabled and organized by MIT gold 2025.

Data Availability

The data supporting the conclusions of this study are openly available on Github and a Zenodo data repository (Bergmann et al., 2025). The repository includes:

Code: Python code used to generate figures and analysis presented in this paper, in.py format. Data: Raw and processed data within the following subfolders: GPS coordinates: GPS locations in Excel format. Stratigraphic Columns: A composite stratigraphic column and individual digitized columns in Excel format. Detailed drawn stratigraphic columns in PDF format. XRD (X-ray Diffraction): Raw and processed diffraction data for Shuram samples, in Word and XRML. ICP-OES (Inductively Coupled Plasma Analysis): Data on trace metal analysis, following strong and acidic leachates, in Excel format. SEM (Scanning Electron Microscopy): Microstructural and BSE images from various samples, including cryo-fracturing experiments, in TIFF format. EBSD (Electron Backscatter Diffraction): Processed EBSD data and associated raw images for calcite and dolomite samples, in PDF and JPG formats. EPMA (Electron Microprobe Analysis): Quantitative point data sets of elemental analysis of calcite and dolomite samples accompanied by images with labeled point locations, in CSV and PDF formats. Also includes EPMA maps of element counts in TXT format. XAS (X-ray Absorption Spectroscopy): Analysis of Mn and Fe standards, as well as processed Shuram data from SSRL, in Excel format. Carbon and Oxygen Isotope Data: Data set from Oman samples in CSV format. Clumped Isotope Data: Processed and raw data sets of clumped isotope measurements from Oman samples collected at MIT. Includes raw voltage data for each analysis and processed outputs from ClumpyCrunch and BLIMP, as well as plots summarizing standards and results, in CSV, HTML, and PNG formats. Burial History Data: Burial history models for three wells (A, B, C), in CSV format. SIMS Data: Raw and processed isotopic measurements as well as labeled SEM images of each analyzed point, in CSV, XLS, ASC, and PDF formats. Figures: All figures included in the study, in PDF format. ReadMe file.

Supplemental Material

Supporting Information S1 (PDF)

Additional Information

Inclusion in Global Research Statement:

Field studies were conducted in the Sultanate of Oman with permits, approval, and the support of Petroleum Development Oman and the Ministry of Energy and Minerals. Shuram Group provided all field logistical support.

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