186-1 Paleoclimate reconstruction and floral response during and after the Miocene Climatic Optimum 16 million years ago: an analogue to future climate warming

Session: New Approaches to Old Fossil Collections (Posters)

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Abstract:

Understanding past global climate change and subsequent floral response is integral to approaching modern and future climatic shifts.  Plant architecture is deeply influenced by environmental conditions and fossil leaf morphology has the unique ability to store invaluable terrestrial climatic information of the past. The use of analogs has become instrumental in understanding future climate projections as well as global warming’s impact on plant physiology. In this study, we utilized foliar physiognomic (size and shape) measurements to derive quantitative paleoclimate estimates of a past climatic warming event, the Miocene Climatic Optimum from the Clarkia fossil beds in northern Idaho. Over 10,000 fossil specimens of the Clarkia Fossil Beds are now housed at the University of Idaho in the Department of Earth and Spatial Sciences. This extensive natural history collection of primarily leaf fossils holds an incredible opportunity to investigate the sites’ analog potential and changing diversity through major climatic shifts. This is compared to other fossil sites, Oviatt Creek and P40, near Clarkia, Idaho after the peak of the thermal optimal to understand the transitional period in the temperature and precipitation decline. Using physiognomic methods—Leaf Margin Analysis (LMA), Leaf Area Analysis (LAA), and Climate Leaf Analysis Multivariate Program (CLAMP)—preliminary results of the 15.7 million year old Clarkia Fossil Beds show mean annual temperatures 11.4° to 13.6 °C (52-56.5° F) and mean annual precipitation ~196 cm/yr. Locality P40 (estimated at 16-15.4 million years old) yielded mean annual temperatures from 12° to 13 °C (53°-55 °F) and mean annual precipitation values from 200 to 216 cm/yr. In contrast, the ~12.8 million year old Oviatt Creek fossil site estimates are expected to be cooler and drier. These results show a much warmer Idaho than modern mean annual temperatures of ~7° C (47° F) and ~80 cm/year for mean annual precipitation. This reconstruction shows floral response to the onset of the climatic optimum and its subsequent cooling.  

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

doi: 10.1130/abs/2025AM-5832

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