79-10 Flora response to climate change through the Miocene Climate Optimum

Abstract:

Evidence of ancient climate change provides unique insights into not only past environmental interactions but also in understanding how current climate trends can impact plant physiology and ecosystems functioning. Future climate projections are similar to those of the Miocene Climatic Optimum (MCO), ~17-14 million years ago. Here we utilize paleobotanical climate proxies—Leaf Margin Analysis (LMA), Leaf Area Analysis (LAA), Climate Leaf Multivariate Program (CLAMP) and Bioclimatic Analysis (BA)— to derive quantitative paleoclimate estimates from eight different fossil sites in northern Idaho syn- and post-MCO. These sites, which are included in or are related to the Clarkia Fossil Beds (sites P35, P41, P42, P47), Oviatt Creek localities (sites P40, P38, P34), and Jungle Point (P36), span between 12.5 to 15.6 Ma. Reconstructed mean annual temperatures for Clarkia sites are between 10.2 °C and 14.3 °C and Oviatt and Jungle point sites are between 11.0 °C and 14.3 °C. Reconstructed mean annual precipitation for Clarkia sites is between 100 and 133 cm/yr while Oviatt and Jungle Point sites is between 104.7 and 166 cm/yr. These estimates indicate that sites younger than 15 Ma (P35, P41, P42, P47) may have sustained higher temperatures similarly occurring in the Miocene Climatic Optimum leading into the Middle Miocene Climatic Transition (MMCT) than originally thought. However, mean annual precipitation measurements show a much drier Miocene after 15 Ma. Investigating floral diversity changes may elucidate the regional response and why these younger, more transitional localities would stay relatively warm post-MMCO. 

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