TY - JOUR

T1 - Sr isotope variations in Oligocene–Miocene and modern biogenic carbonate formations of Koko Guyot (Emperor Seamount Chain, Pacific Ocean)

AU - Vishnevskaya, Irina A.

AU - Humblet, Marc

AU - Iryu, Yasufumi

AU - Bassi, Davide

AU - Okuneva, Tatiana G.

AU - Kiseleva, Daria V.

AU - Vishnevskiy, Andrey V.

AU - Soloshenko, Natalia G.

AU - Mikhailik, Pavel E.

N1 - Funding Information: The authors are grateful to Tatyana Nikolaevna Dautova (Head of the 86th voyage of the research vessel “Akademik M.A. Lavrentiev”) and to A.V. Zhirmunsky (National Scientific Centre of Marine Biology, Far Eastern Branch, Russian Academy of Sciences Vladivostok) for organizing the work; and to the members of the Deepwater Equipment Department of A.V. Zhirmunsky National Scientific Centre of Marine Biology, Far Eastern Branch, Russian Academy of Sciences (NSCMB FEB RAS) and Alexei Mikhailovich Asavin for their help with rock sampling. The authors thank Aleksey Kotov for his assistance with carbonate rock sample analyses. We thank Editor-in-Chief of Marine Geology Dr. Adina Paytan and anonymous reviewers for their valuable comments and suggestions, which improved the quality of the manuscript. Participation in the 86th voyage of the R/V “Akademik M.A. Lavrentiev” was made possible owing to a state assignment of the FEGI FEB RAS (state registration number AAAA-A17-117092750071-2). The reequipment and comprehensive development of the “Geoanalitik” shared research facilities of the IGG UB RAS was financially supported by a grant by the Ministry of Science and Higher Education of the Russian Federation for 2021–2023 (Agreement No. 075-15-2021-680). Chemical and isotopic investigations were conducted in the Geoanalitik Center for Collective Use of the IGG UB RAS as part of the state assignments of the GEOCHI RAS and IGG UB RAS (state registration number AAAA-A18-118053090045-8). Funding Information: Participation in the 86th voyage of the R/V “Akademik M.A. Lavrentiev” was made possible owing to a state assignment of the FEGI FEB RAS (state registration number AAAA-A17-117092750071-2). The reequipment and comprehensive development of the “Geoanalitik” shared research facilities of the IGG UB RAS was financially supported by a grant by the Ministry of Science and Higher Education of the Russian Federation for 2021–2023 (Agreement No. 075-15-2021-680). Chemical and isotopic investigations were conducted in the Geoanalitik Center for Collective Use of the IGG UB RAS as part of the state assignments of the GEOCHI RAS and IGG UB RAS (state registration number AAAA-A18-118053090045-8). Publisher Copyright: © 2022 Elsevier B.V.

PY - 2022/9

Y1 - 2022/9

N2 - The Hawaiian–Emperor Seamount Chain, a major topographic feature of the Pacific Ocean floor, is composed of seamounts capped with fossil coral reef deposits that originally formed close to sea level but are now covered by hundreds of meters of water owing to prolonged subsidence. These fossil reef deposits are important archives of paleoenvironmental change and yield information on the subsidence history of the seamounts. We studied the Sr isotope compositions of Oligocene–Miocene coral reef limestone from Koko Guyot in the southern Emperor Seamount Chain to assess the dynamics of the subsidence. The ages of the studied samples containing coral fragments established by Sr isotope stratigraphy vary from 26.3 to 20.1 Ma. In contrast, the youngest samples (15.3 Ma), which were deposited in water depths of >120 m, are barren of corals and are composed exclusively of bryozoans and coralline algae. The subsidence rate of the Koko Guyot volcanic structure was not constant over time. Integration of our new data with the results of previous studies reveals that the subsidence rate was 0.046 ± 0.005 mm/yr during the first 25–30 Myr (from 49–44 to 20 Ma). During this period, Koko Guyot was in a bathymetric interval favorable for coral reef development, and its subsidence was compensated by rapid vertical growth of the reef. Subsequently, the subsidence rate decreased to an average value of 0.019 ± 0.003 mm/yr from 20 to 15 Ma. The decrease in the rate of bottom subsidence coincided with unfavorable environmental conditions for coral reef development, leading to the disappearance of corals. The average subsidence rate has been 0.015 ± 0.002 mm/yr since 15 Ma, comparable to the present-day subsidence rate. We also analyzed the stable Sr isotope ratios (δ88/86Sr) of warm-water coral samples formed at 25–20 Ma (0.32‰ ± 0.1‰), as well as carbonate of large benthic foraminifera, coralline algae, and other non-coral species for the period 20–15 Ma (0.10‰ ± 0.09‰). We suggest that the large difference in carbonate δ88/86Sr between 25–20 and 20–15 Ma corresponds to a difference in the fractionation factor caused by environmental and benthic community change.

AB - The Hawaiian–Emperor Seamount Chain, a major topographic feature of the Pacific Ocean floor, is composed of seamounts capped with fossil coral reef deposits that originally formed close to sea level but are now covered by hundreds of meters of water owing to prolonged subsidence. These fossil reef deposits are important archives of paleoenvironmental change and yield information on the subsidence history of the seamounts. We studied the Sr isotope compositions of Oligocene–Miocene coral reef limestone from Koko Guyot in the southern Emperor Seamount Chain to assess the dynamics of the subsidence. The ages of the studied samples containing coral fragments established by Sr isotope stratigraphy vary from 26.3 to 20.1 Ma. In contrast, the youngest samples (15.3 Ma), which were deposited in water depths of >120 m, are barren of corals and are composed exclusively of bryozoans and coralline algae. The subsidence rate of the Koko Guyot volcanic structure was not constant over time. Integration of our new data with the results of previous studies reveals that the subsidence rate was 0.046 ± 0.005 mm/yr during the first 25–30 Myr (from 49–44 to 20 Ma). During this period, Koko Guyot was in a bathymetric interval favorable for coral reef development, and its subsidence was compensated by rapid vertical growth of the reef. Subsequently, the subsidence rate decreased to an average value of 0.019 ± 0.003 mm/yr from 20 to 15 Ma. The decrease in the rate of bottom subsidence coincided with unfavorable environmental conditions for coral reef development, leading to the disappearance of corals. The average subsidence rate has been 0.015 ± 0.002 mm/yr since 15 Ma, comparable to the present-day subsidence rate. We also analyzed the stable Sr isotope ratios (δ88/86Sr) of warm-water coral samples formed at 25–20 Ma (0.32‰ ± 0.1‰), as well as carbonate of large benthic foraminifera, coralline algae, and other non-coral species for the period 20–15 Ma (0.10‰ ± 0.09‰). We suggest that the large difference in carbonate δ88/86Sr between 25–20 and 20–15 Ma corresponds to a difference in the fractionation factor caused by environmental and benthic community change.

KW - Sr/Sr ratio

KW - Bryozoans

KW - Corals

KW - Hawaiian hotspot

KW - Hawaiian–Emperor Seamount Chain

KW - Larger foraminifera

KW - Subsidence

KW - δSr

UR - http://www.scopus.com/inward/record.url?scp=85135526713&partnerID=8YFLogxK

U2 - 10.1016/j.margeo.2022.106879

DO - 10.1016/j.margeo.2022.106879

M3 - Article

AN - SCOPUS:85135526713

VL - 451

JO - Marine Geology

JF - Marine Geology

SN - 0025-3227

M1 - 106879

ER -