21-11 High-resolution Neogene Planktonic Foraminiferal Richness and Weak Correlation with Physical Forcing Factors

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

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The set of abiotic/biotic mechanisms and events thought to be responsible for biodiversity changes has long intrigued the paleontological community.  Neogene planktonic foraminifera experienced a major evolutionary turnover in the Middle Miocene relating to rapid radiation of the family Globorotalidae. During this interval, multiple long- and short-term environmental and biotic events occurred. The extent to which this species richness pattern was influenced, or driven, by external, physical events can be tested by comparing species-richness patterns to fluctuations in physical event proxy data. To address this issue, we compiled the high-resolution species-richness history for planktonic foraminifera through the Neogene world ocean based on ODP and IODP core records (252 cores). This composite richness history was then time-calibrated according to planktonic foraminifera and nanoplankton events in IODP Core 152-926B (equatorial Atlantic), achieving an average temporal resolution of 53.4 kyr per sampling level. Contrary to some previous reports, Neogene planktonic foraminiferal richness history showed no statistically significant variation corresponding to any documented long or short-term external physical oceanographic event. Likewise, onset of the rapid, Neogene Globorotaliids radiation exhibited no obvious relation to any physical environmental event or perturbation. Factor analysis of the species richness count showed four potential evolutionary faunas that contained taxa from different major groups. While the overall species richness showed significant but weak correlations with global δ¹⁸O (r = 0.31, ρ < 0.001) and δ¹³C (r = -0.27, ρ = 0.004) isotope data, only the Trilobatus/Globigerinoides/Orbulina/Globorotaloides fauna showed statistically significant correlations with the two isotopic proxies. Our investigation illustrates that Neogene planktonic foraminifera have complex association with the physical forcing factors and alternative explanations are needed to account for the long-term, macroevolutionary interaction between the globigerinid and globorotalid clades. Over and above these foraminiferal results, our discovery of this lack of coherence between the biodiversity patterns and the physical forcing factors suggests external forces may not always cause, dominate, or account for macroevolutionary histories, especially under detailed inspection.

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

doi: 10.1130/abs/2025AM-8499

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