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Published August 28, 2018 | Supplemental Material + Published
Journal Article Open

A 600-Million-Year Carbonate Clumped-Isotope Record from the Sultanate of Oman

Abstract

Carbonate clumped-isotope thermometry is a promising technique that has the potential to help decode the significance of the variability of both physical and geochemical compositions of ancient carbonate rocks. This study utilizes a 600-million-year record of marine carbonate rocks from the subsurface and surface of the Sultanate of Oman to explore how burial and exhumation affected the carbonate clumped-isotope thermometer. Samples span 6 km of burial depth, and include calcite and dolomite mineralogies and a range of carbonate rock textures. We find evidence for two broad patterns in the physical and geochemical behavior of carbonate rocks during burial. The first group of carbonates yield water δ^(18)O_(VSMOW) compositions slightly enriched or equal to an expected "ice-free" seawater composition of –1.2‰ and display good to fair textural preservation suggesting that cementation and lithification occurred within tens of meters of the sediment–water interface. Temperatures from the second group sit on the present-day geotherm, yield highly enriched water δ^(18)O_(VSMOW) compositions, and display fair to poor textural preservation. We find no evidence for solid-state reordering in paired analyses of calcites and dolomites. Our results contribute to a growing body of work that indicates that the seawater δ^(18)O_(VSMOW) composition has not changed significantly over 600 Myr and was not –6‰ in the Ediacaran.

Additional Information

© 2018 SEPM (Society for Sedimentary Geology). Received 12 November 2017; accepted 7 June 2018. We thank two anonymous reviewers, Bruce Wilkinson, and John Southard for providing helpful comments. We would like to thank the Ministry of Oil and Gas of the Sultanate of Oman for permission to access samples and for publication permission. Petroleum Development Oman contributed field logistical support, subsurface sample access, and borehole temperature data. We thank Gideon Lopes Cardozo, Zuwena Al Rawahi, Joachim Amthor, Irene Gomez-Perez, Gordon Forbes, and Aly Brandenburg from Petroleum Development Oman in particular for supporting many aspects of this project. We would like to thank Maggie Osburn and Jena Johnson for fieldwork assistance related to sampling the Nafun Group in the Huqf outcrop area. Outcrop samples from Qarn Alam salt dome were provided by Said Al Balushi and Monique Mettraux. We would also like to thank Nami Kitchen, Chi Ma, and Nick Boekelheide for analytical assistance. A National Science Foundation Graduate Research Fellowship was provided to K. Bergmann. The Agouron Institute and the MIT node of the NASA Astrobiology Institute contributed to analytical costs.

Attached Files

Published - i1527-1404-88-8-960.pdf

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Supplemental Material - Tables.xls

Supplemental Material - da_88_8_bergmann_captions.docx

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August 24, 2023
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