PALEOCLIMATE ESTIMATES FOR THE CLARKIA P-40 SITE, NORTHERN IDAHO

16 million years ago, ancient Lake Clarkia formed when the Columbia River Flood Basalts dammed the St. Maries River near Clarkia, Idaho. The world-famous Clarkia Fossil Beds contain exceptionally preserved fish, plants, and palynomorph fossils that record the high temperatures of the Mid-Miocene Climatic Optimum. While the P-33 and P-37 localities of Lake Clarkia have been extensively studied, little has been done with the P-40 locality due to poor access to the site.

This study uses physiognomic characteristics of the fossil flora to determine paleoclimate estimates for the P-40 locality of the Clarkia Fossil Beds. Climate-Leaf Analysis Multivariate Program (CLAMP), leaf area analysis, and leaf margin analysis were used to look at mean annual temperatures (MAT), mean annual precipitation (MAP), growing season length, and other climate proxies. Preliminary estimates suggest the P-40 locality had 8-9˚C MAT and MAP of 70-80 cm a year. These estimates are in line with other Clarkia fossil localities during the Mid-Miocene Climatic Optimum. Micro- and macrofossil assemblages corroborate these estimates using nearest living relative techniques. Each of these localities provide insight into paleoclimate variability during the warmest time in the past 30 million years.