Sr isotope variations in Oligocene–Miocene and modern biogenic carbonate formations of Koko Guyot (Emperor Seamount Chain, Pacific Ocean)
Authors/Creators
- 1. Vernadsky Institute of Geochemistry and Analytical Chemistry, RAS, 119334 Moscow, 19 Kosygina str., Russia
- 2. Nagoya University, Department of Earth and Planetary Sciences, 464-8601 Nagoya, Japan
- 3. Institute of Geology and Paleontology, Graduate School of Science, Tohoku University, Aramaki-aza-aoba 6-3, Aoba-ku, Sendai 980-8578, Japan
- 4. Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Ferrara, Via Saragat 1, I-44122, Ferrara, Italy
- 5. Zavaritsky Institute of Geology and Geochemistry, UB RAS, 620016 Ekaterinburg, 15 Akademika Vonsovskogo str., Russia
- 6. Sobolev Institute of Geology and Mineralogy, SB RAS, 630090 Novosibirsk, 3 Akademika Koptyuga ave., Russia
- 7. Far East Geological Institute, Far East Branch of Russian Academy of Sciences (FEGI FEB RAS), Prospekt 100-letiya, 159, 690022 Vladivostok, Russia
Description
Tables for manuscript "Sr isotope variations in Oligocene–Miocene and modern biogenic carbonate formations of Koko Guyot (Emperor Seamount Chain, Pacific Ocean)" by Irina A. Vishnevskaya, Marc Humblet, Yasufumi Iryu, Davide Bassi, Tatiana G. Okuneva, Daria V. Kiseleva, Andrey V. Vishnevskiy, Natalia G. Soloshenko, Pavel E. Mikhailik.
Abstract: The Hawaiian-Emperor Seamount Chain, a major topographic feature of the Pacific Ocean floor, is composed of seamounts capped with fossil coral reef deposits formed originally close to sea level but lying today hundreds of meters in water depth due to prolonged subsidence. These fossil reef deposits are important archives of paleoenvironmental changes and yield information on the subsidence history of the seamounts. We studied Sr isotope composition of Oligocene–Miocene coral reef limestone from Koko Guyot in the southern part of the Emperor Seamount Chain in order to assess the subsidence dynamics. The age of the studied samples with coral fragments established by Sr isotope stratigraphy varies from 26.3 to 20.1 Ma, while the youngest samples deposited at water depth of > 120 m, barren in corals and composed exclusively of bryozoans and coralline algae, are 15.3 Ma in age. The subsidence rate of the Koko Guyot volcanic structure was not uniform. Combining data of previous studies and those obtained in this study, the assessed subsidence rate was 0.046 ± 0.005 mm/yr during the first 25–30 Myr (from about 49–44 Ma ago). During this period of time, Koko Guyot was in bathymetric interval favourable for coral reef development and its subsidence was compensated by rapid vertical reef growth. Successively, the subsidence rate decreased to an average value of 0.019 ± 0.003 mm/yr from 20 to 15 Ma. The decrease in bottom subsidence coincided with unfavourable environmental conditions for coral reef development, leading to the disappearance of corals. The subsidence rate reached a value of 0.015 ± 0.002 mm/yr in the last 15 Ma, comparable to the present-day subsidence rate. The change in the sedimentary setting is also confirmed by the study of δ88/86Sr.