PLANT FOSSILS FROM THE KANAKA CREEK BEDS, SOUTHWESTERN BRITISH COLUMBIA: PALEOCENE OR EOCENE?

Exposures of arkosic sandstones and mudstone along Kanaka Creek are mapped as the basal part of the Tertiary Huntingdon Formation, which correlates with similar rocks of the Chuckanut Formation in Washington State. The Chuckanut has been variously interpreted as latest Cretaceous to Eocene based on plant fossils, with recent evidence favoring an Eocene age based on fission track ages (55 Ma and younger), although the oldest rocks are not dated. In the absence of radiometric dates, the age of the Kanaka beds is more uncertain, with estimates between Paleocene and Oligocene at various times. The most recent palynological investigations suggest a late Paleocene age, based on indicator pollen such as Paraalnipollenites, Intratriporopollenites, Insulapollenites and other taxa. Other pollen and spores, however, are more typical of Eocene rocks of the younger Huntingdon Formation (Kitsilano Member)studied near Vancouver, such as Ilex, Ulmus, Osmunda, and Trilites solidus.

Plant megafossils consist of compressions and impressions of ferns, conifers, and angiosperms. Taxonomic resolution is hampered by the sandy matrix and carbonization which obscures higher order leaf venation. Nevertheless, a diverse assemblage has been identified, dominanted by mostly fertile fronds of Woodwardia spp., foliage of Glyptostrobus and other Taxodiaceae, and a variety of angiosperm leaves such as Macclintockia, Platanusspp., Macginitiea angustiloba, Joffrea, and many others. Particularly significant are the identifications of Platanus bella, Viburnum antiquum, cf. Celtis aspera (=Viburnum asperum), and two ovulate cones of cf. Fokienia ravenscragensis. These last four fossils are known elsewhere only from Paleocene rocks. The palynomorphs and megafossils collectively suggest that Paleocene rocks are present at Kanaka Creek, although occurences of Eocene taxa suggest the hypothesis that these exposures may straddle the Paleocene-Eocene boundary.