148-11 Foraminifera Assemblages Across the Mid-Pleistocene Transition in the Ross Sea, Antarctica

Session: Insights from Microfossils and Their Modern Analogs: From Traditional to Emerging Approaches (Posters)

Poster Booth No.: 198

Presenting Author:

Adam Elkin

Authors:

Elkin, Adam Matthew¹, Leckie, Robert Mark², Kim, Erin³, Prunella, Catherine⁴, Seidenstein, Julia⁵, Shevenell, Amelia E.⁶

(1) Department of Earth, Geographic, and Climate Sciences, University of Massachusetts Amherst, Amherst, MA, USA, (2) Department of Earth, Geographic, and Climate Sciences, University of Massachusetts Amherst, Amherst, MA, USA, (3) Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA, (4) New York Sea Grant, Bronx, NY, USA, (5) Florence Bascom Geoscience Center, United States Geological Survey, Reston, VA, USA, (6) College of Marine Sciences, University of South Florida, St. Petersburg, FL, USA,

Abstract:

Approximately 1.25 to 0.75 Ma, Earth’s climate shifted from 41 kyr to 100 kyr glacial-interglacial cyclicity, during the mid-Pleistocene Transition (MPT). Although this shift in global climatic cycles is well-documented in the geological record, the associated forcings and feedbacks remain unknown. Foraminiferal assemblage data are useful for understanding past shifts in climate, ocean dynamics, and marine ecology. Here we present foraminiferal assemblage data across the MPT from the Ross Sea of Antarctica. These data enable assessment of foraminifera biodiversity and ocean circulation changes across a major climate transition. We generated benthic and planktic foraminifera assemblages in early to middle Pleistocene sediments (~1.6 to 0.7 Ma) recovered from the shelf edge of the Ross Sea of Antarctica International Ocean Discovery Program (IODP) Expedition 374 Hole U1523A (74° 9.02’ S, 176° 47.70’ W) at a water depth of 828 m. This site is influenced by the Antarctic Slope Current (ASC), which regulates the presence of warm Circumpolar Deep Water on the Ross Sea shelf. We observe a marked reduction in foraminiferal abundances during glacial intervals after MIS 31 (~1 Ma), while abundant foraminifera exist and assemblages are dominated by planktic species during interglacials. We also observe an increase in the abundance of benthic species Trifarina earlandi during the middle Pleistocene. These trends, coupled with lithologic variations and stable oxygen and carbon isotope data from T. earlandi and planktic species Neogloboquadrina pachyderma suggest glacial-interglacial changes in the strength of the ASC across the MPT, with important implications for heat and nutrient delivery to the continental shelf.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7569

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