Colloquium: Dr. Maria Rose Petrizzo - How can microfossils help to decipher environments, climates, and Earth’s History over the last 140 Ma?

Dr. Maria Rose Petrizzo - 2025 GSA Distinguished International Lectureship
University of Milan

Topic: How can microfossils help to decipher environments, climates, and Earth’s History over the last 140 Ma?

Academic Host: Pam Stephens

Abstract: Planktonic foraminifera are heterotrophic, unicellular protists that secrete calcite shells typically less than a millimeter in diameter and inhabit the upper water column of the open ocean. Owing to their rapid evolutionary rates, widespread distribution, high preservation potential, and abundance in pelagic and hemipelagic sediments, they represent one of the most powerful microfossil groups for biostratigraphy, biochronology, paleoceanography, and paleoenvironmental reconstruction since the Cretaceous (~143 Ma). Planktonic foraminifera first appeared in the Early Jurassic within the Tethyan Bioprovince and diversified markedly from the Early Cretaceous onward. Biogeographic provinces broadly comparable to those of the modern oceans can be recognized in the Cretaceous, although their spatial organization reflects changing paleogeography, land–sea configurations, and latitudinal climatic belts. Correlation across latitudinal provinces remains a key challenge and requires improved understanding of species diachroneity, endemism, and provincialism as taxa evolved, spread through oceanic gyres and boundary currents. Examples from low- and high-latitude sedimentary records illustrate how paleoecological controls shaped planktonic foraminiferal abundance, diversity, and biogeographic distributions throughout the Cretaceous and Cenozoic. Temporal changes in species composition reveal evolutionary and extinction patterns that document biological responses to short- and long-term environmental change and provide insights relevant to modern assessments of ecosystem resilience. Finally, the fundamental role of planktonic foraminifera in the construction of geological timescales is highlighted.