9 Quaternary and Tertiary Records of Past Environments, Pacific Northwest I: In Honor of Calvin Heusser

Saturday, 5 May 2007
8:00 AM - 12:00 PM

MUSKEG ARCHIVES OF VEGETATION, MIGRATION, AND CLIMATE HISTORY IN THE GULF OF ALASKAN ARC

Paper number: 9-10
Program: SYMPOSIA SESSIONS
Time: 10:45 AM – 11:05 AM

Authors

Abstract

New peatland sites ranging from the Bering Glacier foreland to the Kenai and Kodiak have been investigated for pollen and spores, macrofossils, LOI, and AMS C-14 dating. In south-central Alaska, a peat section located on the Kaliakh River in the lowlands between the eastern lobe of the Bering Glacier and Icy Bay, Alaska spans 16,000 calendar years. Herbaceous tundra and shrub species dominate the late-glacial. Open meadow herbs bridged the transition between tundra and an Alnus interval that persisted for nearly 10,000 years. A 4000-yr migration lag for Picea over 50 km from Icy Cape to Dark Bank supports the inferred retreat of the Bering Glacier during the early-mid Holocene. Wind-blown Picea pollen appears at Dark Bank for nearly three millennia before colonization around 3800 yr BP, followed by Tsuga heterophylla and T. mertensiana at 3000 yr BP.

Swanson Fen, a muskeg in the northern Kenai Lowlands provides a sensitive late-glacial to Holocene record that lies in an ecotone between interior boreal forest and maritime coastal forest today. Four distinct vegetation zones reveal changes from 14,000 years ago. The pioneer vegetation includes a dominance of herbaceous (Artemisia, Apiaceae, Asteroideae) and shrubby (Betula) species. The second zone marking the Holocene boundary shows a striking increase in Polypodiaceae(ferns) and Picea (spruce) and a decrease in shrubby species such as Betula. The third zone indicates a decline in Polypodiaceae and a reemergence of Betula, while the final most recent zone reveals a marked increase in Picea and Tsuga mertensiana.

A Holocene section from Phalarope Pond, Kodiak, reveals the early increase of Polypodiaceae at the Holocene boundary, followed by the dramatic declines in Betula and Artemisia until their resurgence in the late Holocene. The pattern of climate shift parallels the Kenai record, with increased temperature in the early Holocene followed by a cooler, moister Neoglacial interval up to present.