Ostracod response to late Pleistocene oceanographic changes in the tropical Indian Ocean

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Author(s): Alvarez Zarikian, C. A.; Nadiri, C.; Alonso-García, M.; Hernandez, P.; Marcantonio, F.; Kroon, D.; Kunkelova, T.; Betzler, C.; Rodrigues, T.; Lindhorst, S.
Author Affiliation(s): Primary:
International Ocean Discovery Program, College Station, TX, United States
Texas A&M University, College Station, TX, United States
Instituto Portugues do Mar e da Atmosfera (IPMA), Divisao de Geologia e Georecursos Marinhos, Lisbon, Portugal
University of Edinburgh, Edinburgh, United Kingdom
Universität Hamburg, Geologisch-Paläontologisches Institut, Hamburg, Germany
Volume Title: AGU 2018 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2018; American Geophysical Union 2018 fall meeting, Washington, DC, Dec. 10-14, 2018. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Sedimentary records from IODP Sites U1467 and U1471 uncovered a mostly unread sedimentary archive of oceanographic and climatic changes in the Maldives Inner Sea, located in the northern Indian Ocean, that are associated with intensity variations of the South Asian Monsoon (SAM). The SAM is an intense climatic phenomenon that provides ample precipitation to southern Asia, and is linked to a seasonal reversing wind pattern that controls the modern ocean circulation and productivity in the north and central Indian Ocean. Thus, deep-water ventilation and the development of the oxygen minimum zone (OMZ) in the water column are also closely related to the SAM. Well-preserved and abundant calcareous microfossils in the cored Pleistocene sequence at Site U1467 has enabled us to use benthic biota as indicators of past oceanographic conditions. In this study, we present ostracod assemblages combined with biogeochemical data from Sites U1467 and U1471 (X-ray fluorescence core scanning, biomarkers, sediment grain size, trace elements [Baxs, Uauth], and total organic carbon) to study the late Pleistocene history of bottom water ventilation and variability of the OMZ in the northern Indian Ocean. The new micropaleontological and geochemical records reveal oscillations in surface and bottom water conditions that are clearly associated with glacial/interglacial cyclicity and sea level variations. Interglacial ostracod faunas include taxa usually predominant in modern low-oxygen, organic-rich sediments, and their distribution points to periods of SAM intensification, high surface productivity, bottom water oxygenation minima, and expansion of the OMZ in the northern Indian Ocean during MIS 1, 5, 7, 9, 11 and 13. In contrast, glacial ostracod faunas predominantly consist of epifaunal species primarily found in well-oxygenated environments. This assemblage is interpreted to represent increased bottom water circulation and ventilation, lower bottom water temperature, and variable levels of food supply. In addition, the presence of common deep sea, cold water genera (e.g., Bradleya and Poseidonamicus) during times of lower sea level may point to the influence of Antarctic Intermediate Water in the Maldives Inner Sea and the northern Indian Ocean during glacial times.
Year of Publication: 2018
Research Program: IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
Key Words: 10 Paleontology, Invertebrate; Arthropoda; Cenozoic; Cores; Crustacea; Expedition 359; IODP Site U1467; IODP Site U1471; Indian Ocean; International Ocean Discovery Program; Mandibulata; Marine environment; Marine sediments; Microfossils; Ostracoda; Paleo-oceanography; Paleoenvironment; Pleistocene; Quaternary; Sediments; Upper Pleistocene
Coordinates: N045101 N045103 E0731702 E0731701
N044559 N044559 E0730808 E0730806
Record ID: 2019063578
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