Newly recognized fossil cyclomedusoids from the Yreka terrane include Ediacaria sp. and Beltanella sp. They are typical of the Ediacaran fossil assemblage, range from 640 to 575 Ma, and thus are latest Neoproterozoic (Vendian) in age. The Yreka terrane structurally overlies the Trinity terrane, which also includes Vendian rocks. The Yreka terrane is a polygenetic stack of sedimentary and metasedimentary thrust sheets consisting of the Vendian Antelope Mountain Quartzite, Siluro-Devonian turbidites (trench fill), lower Paleozoic mélanges (accretionary complexes), and the Lower Devonian Gazelle Formation (trench-slope basin deposits). The Trinity terrane is a polygenetic mafic-ultramafic complex consisting of multiple mantle tectonite...