MICROSCOPIC CHARACTERIZATION OF THE PALYNOMORPHS OF THE MIOCENE CLARKIA LAKE SEDIMENTS, CLARKIA, IDAHO

The Miocene Clarkia Lake beds near Clarkia, Idaho (upper St. Maries River Valley) display some of the finest plant fossils in the world. This site is characterized by excellent quality of preservation and large taxonomic diversity. Previous studies of these beds concentrated on macrofossil assemblages with limited microfossil studies. The goal of this study is to characterize the taxonomic diversity of the Clarkia Lake palynomorphs. Palynomorphs of the Clarkia Lake sediments are exquisitely preserved, and are excellent candidates for investigation by Scanning Electron (SEM) and Light Microscopy. Light microscope counts of the Clarkia palynomorphs indicate the density of flora in the area to be between 750 thousand and 1.5 million grains per cubic centimeter based on the Stockmarr (1972) method of introduced Lycopodium tracers. SEM imaging enhances palynomorph ornamentation leading to a more accurate taxonomic identification of the Clarkia flora that includes 48 families and 98 genera. Well-represented palynomorphs include: Taxodiaceae/Cuppressacae, Castanea/Lithocarpus, Quercus Pinus, Picea, Pterocarya, Salix, Ilex, Liquidambar, numerous fungal spores, diatoms, and dinoflagellates. Information obtained by SEM and Light Microscopy of the Clarkia Lake microfossil assemblage should prove useful for interpretation of paleobotanical and paleoclimate records.