NEW INSIGHTS FROM A CYCADOPHYTE-DOMINATED PALEOFLORA IN THE EARLY JURASSIC TALKEETNA VOLCANIC FORMATION, TALKEETNA MOUNTAINS, ALASKA

Early Jurassic plant remains are preserved in volcaniclastic siltstones, sandstones, and moderately-developed paleosols of the Talkeetna Volcanic Formation (Peninsular Terrane) in south-central Alaska. New collections from East Boulder Creek and Hicks Creek in the southern Talkeetna Mountains north of the Matanuska Valley yield cycadophyte, pteridosperm, and conifer foliage, as well as reproductive organs and wood, from the upper third of the ~5-7 km thick formation. Their presence in beds that lack marine faunal elements indicates occasional subaerial exposure and sedimentation in what is a mostly marine oceanic arc sequence. Foliage including Cladophlebis, Otozamites, Sagenopteris, and Pagiophyllum is preserved as compressions and impressions in fluvial facies. Coalified and charcoalified wood occurs within and on top of paleosol horizons as fallen trunks up to ~78 cm in diameter but remains unidentifiable. Interbedded with paleobotanically fossiliferous beds are airfall tephra deposits with volcanic bombs and bivalve-containing beds of possible freshwater deposition. This revised list of floral elements from the Talkeetna Volcanic Formation is placed into phytogeographic context with northern continental floras and plate configurations in the Early Jurassic to test recently published models of Alaskan terrane accretion.