REINTERPRETING THE SWEAT HYPOTHESIS FROM THE PERSPECTIVE OF EDIACARAN CYCLOMEDUSOIDS: THE BASK CONNECTION (BALTICA-ALASKA-SIBERIA-KLAMATH

Fossil cyclomedusoids from the Antelope Mountain Quartzite (AMQ) of the eastern Klamath Yreka terrane (Yt) in California include Ediacaria sp. and Beltanella sp., typical of the latest Neoproterozoic-Vendian Ediacaran fossil assemblage (640-575 Ma).  They are most similar to northern hemisphere cyclomedusoids of Baltica (B) and NW Laurentia, placing them in Ben Waggoner's Australian biogeographic province along with Siberia (S).  The AMQ was derived from a continental source other than Laurentia, and contains detrital zircons of Archean to Mesoproterozoic age (3200-1300 Ma).  Paleolatitudes of 579-556 Ma rocks in the nearby Trinity terrane (Tt), which shed ophiolitic detritus into the Yt during early to middle Paleozoic, suggest locations of 7° ± 3° N or S in the Vendian, and 31° ± 5° N or S in the Middle Devonian as determined by paleomagnetism.  Biogeographic affinities for Paleozoic Yt fossils (e.g., brachiopods, gastropods, trilobites, sphinctozoan sponges) show repeated links to B, S, and Alaskan-Uralian terranes, as well as the Canadian Arctic.  Species of Cambrian-Devonian corals, sponges, and shelly faunas endemic to Yt and Alaskan accreted terranes, and Uralian terranes, suggest increasing isolation and limited exchange with the microcontinents of B, S, and NW Laurentia through the Paleozoic.  This evidence suggests that the AMQ formed on a Vendian continental shelf between Australia, Baltica, Siberia, and Laurentia as Rodinia broke apart.  The AMQ was incorporated into Yt along an active intraoceanic convergent margin, which continued developing through the Middle Devonian as one or more interconnected island chains which allowed exchange of faunal elements between Baltica, Alaska, Siberia, and the Klamaths – the BASK connection.