Paleogene floras from the Gulf of Alaska region

Numerous collections of fossil plants from the Gulf of Alaska region were obtained from rocks that are well dated by marine mollusks. The mollusks indicate that the oldest possible age for the lowest plant assemblage is middle Eocene (Domengine) and that the youngest possible age for the highest Paleogene plant assemblage is middle Oligocene (Lincoln). Paleobotanical correlations indicate that the lowest plant assemblage is of late middle Eocene (early Ravenian) age, and the highest plant assemblage is of early Oligocene (Kummerian) age. A new provincial stage the Angoonian is proposed, based on assemblages from rocks in southeastern Alaska. The Angoonian is thought to be of late Oligocene (early Blakeley) age. Only one stratigraphically isolated assemblage from the Gulf of Alaska region has been recognized as of Angoonian age. The biostratigraphy of the Gulf of Alaska region and of other regions in Alaska indicates that the Seldovian, Homerian, and Clamgulchian Stages are probably entirely of Neogene age. The early Ravenian assemblages represent Paratropical Rain forest (that is, similar to vegetation of a region bordering the Tropical Rain forest); this conclusion is based on the physiognomic analysis of foliage. The most diverse families represented are Menispermaceae and Icacinaceae, which are accompanied by palms, Annonaceae, Myristicaceae, Dipterocarpaceae, Barringtoniaceae, and Myrtaceae. A minor element is represented by broad-leaved deciduous plants. Middle Ravenian assemblage was somewhat cooler (subtropical), as indicated by foliar physiognomy, the fewer Tropical Rain forest elements, and the diversity of Lauraceae. The late Ravenian assemblage represents a temperate forest. The Kummerian assemblages were again dominated by Lauraceae, and the physiognomic characters of the foliage indicate that a subtropical forest was again represented.