Abstract
Whereas changes in pore water chemistry are known to impact carbonate sediment geochemistry, little is known about the impact of long unconformities on carbonate alteration. IODP Site 378-U1553 on the southern Campbell Plateau, with a 26-million-year, erosional unconformity, provides a key location for examining the impact of long-term unconformities on sub-surface chemistry and carbonate archives. This study examined 76 interstitial water samples for sulfate sulfur and oxygen isotopes, as well as 28 bulk carbonate samples for carbonate associated sulfate (CAS) sulfur isotopes, to quantify the effects of this unconformity on the sub-surface redox chemistry of the Site. The current state of the system suggests limited influence of redox processes on the CAS archive. Manganese reduction reaches 30 mbsf, with a decrease in manganese reduction between 20 and 30 mbsf. Below 30 mbsf, the system transitions to iron reduction to a depth of approximately 140 mbsf where sulfate reduction begins. Dissolved sulfate sulfur and oxygen isotope values suggest repeated oxygenation of sulfides. The CAS record from the Site deviates from previously published seawater values. However, the lack of a relationship between the dissolved sulfate and CAS records suggests most of the alteration of the CAS record likely occurred before the unconformity when the carbonate sediments were more reactive. This further supports the CAS record as a relatively robust archive, withstanding most post-depositional mechanisms of carbonate alteration.
| Original language | English |
|---|---|
| Article number | e2022PA004561 |
| Journal | Paleoceanography and Paleoclimatology |
| Volume | 38 |
| Issue number | 7 |
| DOIs | |
| State | Published - Jul 2023 |
Bibliographical note
Publisher Copyright:© 2023. American Geophysical Union. All Rights Reserved.
Funding
This research utilized samples provided by the International Ocean Discovery Program (IODP). IODP is funded by the US National Science Foundation and the member countries under the management of the Joint Oceanographic Institutions, Inc. We would like to thank the IODP Expedition 378 science party, crew, and science staff of the JOIDES Resolution, without whom this work would not be possible. We would also like to thank the staff at the IODP Gulf Coast Repository for their assistance with sampling. A. Reis received support from a post expedition award through the United States Science Support Program and Columbia University. The authors wanted to thank the associate editors at Paleoceanography and Paleoclimatology, Dr. Jerry Dickens, and an anonymous reviewer for their detailed feedback. This research utilized samples provided by the International Ocean Discovery Program (IODP). IODP is funded by the US National Science Foundation and the member countries under the management of the Joint Oceanographic Institutions, Inc. We would like to thank the IODP Expedition 378 science party, crew, and science staff of the , without whom this work would not be possible. We would also like to thank the staff at the IODP Gulf Coast Repository for their assistance with sampling. A. Reis received support from a post expedition award through the United States Science Support Program and Columbia University. The authors wanted to thank the associate editors at Paleoceanography and Paleoclimatology, Dr. Jerry Dickens, and an anonymous reviewer for their detailed feedback. JOIDES Resolution
| Funders | Funder number |
|---|---|
| International Ocean Discovery Program | |
| National Science Foundation (NSF) | |
| Univ. of Northern British Columbia |
Keywords
- carbonate associated sulfate
- carbonate diagenesis
- interstitial water sulfate
- redox chemistry
- sulfur isotopes
ASJC Scopus subject areas
- Oceanography
- Atmospheric Science
- Paleontology