Calcareous nannoplankton assemblages across the Pliocene-Pleistocene transition in the southwestern Indian Ocean, IODP Site U1475

Author(s): Cares, Zoe; Farr, Clinton Layne; LeVay, L.; Tangunan, Deborah; Brentegani, Luna
Author Affiliation(s): Primary:
Texas A&M University, College Station, TX, United States
University of Bremen, Department of Geosciences, Bremen, Germany
Queensland University of Technology, Earth and Environmental Sciences, Brisbane, Queensl., Australia
Volume Title: AGU 2017 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2017; American Geophysical Union 2017 fall meeting, New Orleans, LA, Dec. 11-15, 2017. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: International Ocean Discovery Program (IODP) Expedition 361 cored six sites along the greater Agulhas Current System to track its intensity through time and to better understand its role in global oceanic circulation and climate. One of the main scientific objectives of this expedition was to determine the dynamics of the Indian-Atlantic Ocean Gateway circulation during Pliocene-Pleistocene climate changes in association with changing wind fields and migrating ocean fronts. The Indian-Atlantic Ocean Gateway contains a pronounced oceanic frontal system, the position of which has the potential to influence global climate on millennial scales. Owing to the physical differences between the frontal zones, this region has complex biogeochemistry, changes in phytoplankton distribution, and variations in primary productivity. Site U1475 was cored on the Agulhas Plateau in the Southwestern Indian Ocean and recovered a complete sequence of calcareous ooze spanning the last ≈7 Ma. Previous studies at this locality have shown latitudinal migrations of the frontal zones over the past ≈350 kyr that resulted in prominent millennial shifts in primary production, biological pump efficiency, and microfossil assemblages that coincide with Antarctic climate variability. Here we present initial results comprised of calcareous nannoplankton assemblages in order to test if similar latitudinal frontal migrations occurred during the Pliocene-Pleistocene transition (PPT; ≈2.7 Ma). The calcareous nannoplankton assemblage shows an abundance increase of taxa associated with cooler water and higher primary production across the PPT interval. In addition to a change in species abundance, the Shannon diversity index drops notably across the transition, which is typical of nannoplankton communities in more productive regions. These data suggest that a long-term change in sea surface temperature and nutrient availability took place across the PPT, potentially linked to the northward migration of frontal zones.
Year of Publication: 2017
Research Program: IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Cenozoic; Expedition 361; IODP Site U1475; Indian Ocean; International Ocean Discovery Program; Nannoplankton; Neogene; Paleoecology; Plankton; Pleistocene; Pliocene; Quaternary; Tertiary
Coordinates: S412537 S412536 E0251540 E0251538
Record ID: 2018074778
Copyright Information: GeoRef, Copyright 2018 American Geosciences Institute. Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union, Washington, DC, United States