188-7 Quantifying the Early Miocene Conundrum: Insights from biotic and geologic systems

Session: Linking Biodiversity Loss to Environmental Stressors Through Integrated Approaches (Posters)

Poster Booth No.: 85

Presenting Author:

Elizabeth Sibert

Authors:

Sibert, Elizabeth C.¹, Antell, Gawain T.², Auderset, Alexandra³, Browne, Imogen M.⁴, Farmer, Jesse R.⁵, Hess, Anya V. ⁶, Kasbohm, Jennifer⁷, Lam, Adriane R.⁸, Matsuzaki, Kenji⁹, Smith, Jansen A.¹⁰, Swain, Anshuman¹¹, Woodhouse, Adam¹²

(1) Geology & Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, USA, (2) Department of Geography, University of California, Los Angeles, Los Angeles, CA, USA, (3) School of Ocean and Earth Science, University of Southampton, Southampton, United Kingdom, (4) Department of Earth Sciences, Binghamton University, Binghamton, NY, USA; Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN, USA, (5) School for the Environment, University of Massachusetts Boston, Boston, MA, USA, (6) Atmospheric Oceanic and Environmental Science, George Mason University, Fairfax, VA, USA, (7) Earth & Planets Laboratory, Carnegie Science, Washington, DC, USA, (8) Department of Earth Sciences, Binghamton University, Binghamton, NY, USA, (9) Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba, Japan, (10) Department of Earth and Environmental Sciences, University of Minnesota Duluth, Duluth, MN, USA, (11) Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, USA; Museum of Paleontology, University of Michigan, Ann Arbor, MI, USA, (12) School of Earth and Environmental Sciences, Cardiff University, Cardiff, United Kingdom,

Abstract:

The early Miocene is emerging as a potentially transformative time in marine ecosystem history. Though the differences between Late Oligocene and Middle Miocene biota are considerable - enough to warrant a boundary between the Paleogene to Neogene Periods - a dearth of sampling in the early Miocene, along with relative stability in the genus-level richness of traditionally studied marine fossils (e.g. shallow water hard-shelled invertebrates), has led to an assumption that the transition between Oligocene and Middle Miocene fauna was gradual and uneventful. This assumption of relative stasis has been bolstered by the relative stability in traditional climate proxies such as benthic foraminifera-derived carbon and oxygen isotopes throughout the interval. However, recent high-resolution marine microfossil, phylogenetic, and geochemical records have revealed that the early Miocene was far from stable, but rather was a time of significant ecological upheaval that led to permanent changes in marine ecosystem structure and function at a scale not observed since the Cretaceous-Paleogene Mass Extinction, 66 million years ago. The early Miocene biotic changes spanned trophic levels from primary producers to top predators, impacting diatoms, foraminifera, reef fish, and whales, among other marine taxa. For example, open ocean sharks were particularly impacted, suffering the largest extinction event known in their 400 million year history, which corresponds with a global disruptive event in planktic foraminifera community composition. Though a clear environmental driver for these ecological changes is not yet known, the upheaval observed in the marine biota corresponds with an abrupt shift in foraminiferal-bound nitrogen isotopes, which may signal a change in deep ocean oxygenation or nutrient cycling. Together these records suggest that the rapid changes in biodiversity and marine community structure during the Early Miocene were profound, and set the stage for the ocean ecosystem structure observed from the later Miocene to present day. Here we explore the biotic range and environmental correlates to this critical and understudied interval in Earth’s history, using a multidisciplinary scoping literature review to collate disparate studies that include, but may not discuss early Miocene data, to synthesize early Miocene biotic, climatic, and environmental records and evaluate the links between environmental change and this biotic transformation. 

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

doi: 10.1130/abs/2025AM-10237

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