“There’s wine in this dirt...”

Sonoma Mountain – Ancient Marine Sediments over Franciscan Complex

Sonoma Mountain exemplifies the diversity of Northern California geology.  It is a very early and uplifted formation, and roughly as old as the Mayacamas Range that separates Napa and Sonoma.  The Franciscan complex is interwoven with deposits of volcanic and sedimentary origin.  On the Northwest side, it is characterized by clay-loam deposits above an ancient landslide with rocky shale and basalt below the surface.