Identification of neogene woods from Alaska-Yukon

Abstract

Woods collected from early Middle Miocene to Late Pliocene localities at high latitudes (more than 60° N) of Alaska and Canada were examined microscopically to determine taxonomic affinities. All were conifers and most are Pinaceae. Features useful in the identification of conifers are reviewed, including characteristics of growth rings, resin canals, cross-field pitting, ray tracheids, longitudinal and ray parenchyma, helical thickenings and cell sizes. Some of the problems in feature recognition in fossil conifer woods due to compression and fungal and microbial degradation are discussed. Although relatively few wood samples were examined, these samples provide information consistent with that derived from the pollen, leaf, and fruit and seed record obtained from the same deposits, and provide additional documentation for a cooling of climate and changes in the flora and vegetation from the early Middle Miocene to the Late Pliocene. In the early Middle Miocene samples from northeastern Alaska, there are woods of Taxodiaceae and soft pines ( Pinus spp.) with growth rings greater than 1 cm wide; in the Late Pliocene there are woods of spruce ( Picea) and larch ( Larix) with growth rings less than 1 mm wide.