Provenance and Paleoflora of the Cretaceous Caribou Pass Formation, South-Central Alaska: Development of a Collisional Foreland in the Final Stages of Island Arc Accretion
Preliminary collections of a leaf megafossil impression flora reveal the occurrence of ferns (Cladophlebis), conifers (Metasequoia), and dicots (including Dicotylophyllum, at least one member of the Menispermaceae, platanoid forms, and others). These remains may indicate temperate climate conditions in mid- to high-latitude regions of Alaska during the Cretaceous and provide a biostratigraphic link to similar paleofloras that have been documented from Upper Cretaceous nonmarine strata elsewhere in southern Alaska.
The Caribou Pass formation and age-equivalent strata throughout the Alaska Range suture zone record the first occurrence of nonmarine sedimentation associated with the final stages of island arc accretion. These strata may represent exhumation of primarily Mesozoic source areas of the Wrangellia composite terrane in a collisional foreland basin setting. Further study is needed to compare trends in provenance and paleoflora occurrences from nonmarine Cretaceous strata throughout the Alaska Range suture zone.