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Large Carbonate Associated Sulfate isotopic variability between brachiopods, micrite, and other sedimentary components in Late Ordovician strata

Present, Theodore M. and Paris, Guillaume and Burke, Andrea and Fischer, Woodward W. and Adkins, Jess F. (2015) Large Carbonate Associated Sulfate isotopic variability between brachiopods, micrite, and other sedimentary components in Late Ordovician strata. Earth and Planetary Science Letters, 432 . pp. 187-198. ISSN 0012-821X. https://resolver.caltech.edu/CaltechAUTHORS:20151106-150649239

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Abstract

Carbonate Associated Sulfate (CAS) is trace sulfate incorporated into carbonate minerals during their precipitation. Its sulfur isotopic composition is often assumed to track that of seawater sulfate and inform global carbon and oxygen budgets through Earth's history. However, many CAS sulfur isotope records based on bulk-rock samples are noisy. To determine the source of bulk-rock CAS variability, we extracted CAS from different internal sedimentary components micro-drilled from well-preserved Late Ordovician and early Silurian-age limestones from Anticosti Island, Quebec, Canada. Mixtures of these components, whose sulfur isotopic compositions vary by nearly 25‰, can explain the bulk-rock CAS range. Large isotopic variability of sedimentary micrite CAS (^(34)S-depleted from seawater by up to 15‰) is consistent with pore fluid sulfide oxidation during early diagenesis. Specimens recrystallized during burial diagenesis have CAS ^(34)S-enriched by up to 9‰ from Hirnantian seawater, consistent with microbial sulfate reduction in a confined aquifer. In contrast to the other variable components, brachiopods with well-preserved secondary-layer fibrous calcite—a phase independently known to be the best-preserved sedimentary component in these strata—have a more homogeneous isotopic composition. These specimens indicate that seawater sulfate remained close to about 25‰ (V-CDT) through Hirnantian (end-Ordovician) events, including glaciation, mass extinction, carbon isotope excursion, and pyrite-sulfur isotope excursion. The textural relationships between our samples and their CAS isotope ratios highlight the role of diagenetic biogeochemical processes in setting the isotopic composition of CAS.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/j.epsl.2015.10.005DOIArticle
ORCID:
AuthorORCID
Present, Theodore M.0000-0002-4747-2174
Paris, Guillaume0000-0001-8368-1224
Burke, Andrea0000-0002-3754-1498
Fischer, Woodward W.0000-0002-8836-3054
Adkins, Jess F.0000-0002-3174-5190
Additional Information:© 2015 Elsevier B.V. Received 18 June 2015; Received in revised form 30 September 2015; Accepted 4 October 2015. Funding for this work was provided by the American Chemical Society Petroleum Research Fund New Directions grant #53994-ND2, NSF Division of Earth Sciences award EAR-1349858, and the Agouron Institute grant AI-GC17.09.3. We thank David Jones and Benjamin Gill for thoughtful reviews. We thank David Fike and Seth Finnegan for helpful input and field context for the Anticosti Island specimens. We thank Renata Cummins for instruction on how to prepare brachiopod secondary-layer fibrous calcite, and Lindsey Hedges, Fenfang Wu, and Nathan Dalleska for analytical support. We thank Joe Kirschvink for help interpreting rock magnetic data. Thank you to Kristin Bergmann for providing the T. transversa specimen, and Nivedita Thiagarajan for help preparing deep-sea coral samples. Ion chromatography was done at the Caltech Environmental Analysis Center.
Funders:
Funding AgencyGrant Number
American Chemical Society Petroleum Research Fund53994-ND2
NSFEAR-1349858
Agouron InstituteAI-GC17.09.3
Subject Keywords:multi-collector inductively coupled plasma mass spectrometry; MC-ICP-MS; sulfur isotopes; Hirnantian; Silurian; diagenesis
Record Number:CaltechAUTHORS:20151106-150649239
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20151106-150649239
Official Citation:Theodore M. Present, Guillaume Paris, Andrea Burke, Woodward W. Fischer, Jess F. Adkins, Large Carbonate Associated Sulfate isotopic variability between brachiopods, micrite, and other sedimentary components in Late Ordovician strata, Earth and Planetary Science Letters, Volume 432, 15 December 2015, Pages 187-198, ISSN 0012-821X, http://dx.doi.org/10.1016/j.epsl.2015.10.005.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:61968
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:06 Nov 2015 23:56
Last Modified:20 Oct 2020 21:05

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