Enhanced calcareous nannoplankton productivity during the middle Miocene transition in the eastern Equatorial Pacific

Author(s): LeVay, Leah J.; Bralower, Timothy J.; Fox, Lyndsey; Holbourn, Ann; Kump, Lee R.; Romero, Oscar E.; Wade, Bridget S.
Author Affiliation(s): Primary:
Texas A&M University, International Ocean Discovery Program, College Station, TX, United States
Pennsylvania State University, United States
University of Leeds, United Kingdom
Christian-Albrechts-Universität, Germany
University of Bremen, Germany
University College London, United Kingdom
Volume Title: Geological Society of America, 2014 annual meeting & exposition
Source: Abstracts with Programs - Geological Society of America, 46(6), p.276; Geological Society of America, 2014 annual meeting & exposition, Vancouver, BC, Canada, Oct. 19-22, 2014. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0016-7592 CODEN: GAAPBC
Note: In English
Summary: The middle Miocene climate transition (MMT) is the final shift from a greenhouse climate into a modern-day-like ocean-atmospheric system with cold high latitudes and a strong meridional temperature gradient. The event is marked by the major expansion of the East Antarctic ice sheet (Mi-3; ∼13.8 Ma) as indicated by a 1 ppm increase in benthic foraminiferal δ18O values. The MMT is tied to enhanced bottom water formation and the cooling of high latitude regions; however, little is known about its effect on low latitude climate and oceanography. To determine how low latitudes were affected and if high latitude cooling/Antarctic ice sheet expansion influenced equatorial upwelling and surface productivity, we examined the calcareous nannoplankton assemblage, opal weight %, and grain size of sediments from IODP Site U1338 in the eastern equatorial Pacific. These records are compared to the benthic and planktonic foraminiferal stable isotope records, XRF element data, and surface temperature proxies to reconstruct upwelling conditions, vertical stratification, and biological pumping efficiency. Our results show a distinct shift in the nannoplankton assemblage associated with the MMT and Mi-3. At the MMT, warmer-water, oligotrophic taxa decrease in abundance and are replaced by cooler-water taxa. During the interval that is coincident with the maximum in Antarctic glaciation, there is a significant increase in small Dictyococcites species (< 3 µm). The dominance of this species has a bloom-like appearance, which in the modern ocean is indicative of high nannoplankton productivity. In addition, sedimentation rates increase during the first half of the glacial interval. This evidence suggests that equatorial productivity increased during the glaciation. Environmental changes also led to the rapid response of diatoms. These results can help us to better understand the linkage between high latitude forcing and equatorial upwelling dynamics.
Year of Publication: 2014
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Algae; Assemblages; Atlantic Ocean; Cenozoic; Expedition 339; Foraminifera; IODP Site U1388; Integrated Ocean Drilling Program; Invertebrata; Isotope ratios; Isotopes; Marine environment; Microfossils; Middle Miocene; Miocene; Nannofossils; Neogene; North Atlantic; O-18/O-16; Oxygen; Paleo-oceanography; Paleoclimatology; Paleoecology; Paleoenvironment; Plantae; Productivity; Protista; Stable isotopes; Tertiary
Coordinates: N361608 N361609 W0064739 W0064740
Record ID: 2015031524
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States