PLIOCENE CHRYSOPHYCEAN STOMATOCYSTS FROM THE SONOMA VOLCANICS, NAPA-COUNTY, CALIFORNIA

We use International Statospore Working Group (ISWG) guidelines to tax onomically describe the chrysophycean cyst flora from a deposit (ca. 2 .5-4 m.y.) in the Sonoma Volcanics from Napa County, California. Cyst preservation was very good. We observed a total of 21 different cysts (19 with SEM, 2 with LM only), nine of which are described here for th e first time. This represents a relatively low diversity flora when co mpared to cyst assemblages in Holocene sediments. Dominant cyst morpho types that have previously been described in the literature indicate t hat the environment of deposition was probably shallow (littoral) and alkaline. We believe that this study is the first to describe pre-Holo cene cysts using ISWG guidelines. At this time, it is unclear whether newly described morphotypes represent extinct or extant species.