2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014)

Paper No. 43-24
Presentation Time: 2:45 PM


BAMBRICK BANKS, Jillian, Geology & Geophysics, Louisiana State University, Baton Rouge, LA 70803, BENTLEY, Samuel J., Department of Geology & Geophysics, Louisiana State University, Baton Rouge, LA 70803 and WARNY, Sophie, Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803

Recent global climate model simulations suggest a high potential for future warming of the subarctic northwest North Atlantic in response to rising anthropogenic greenhouse gas concentrations. Such warming could alter large scale ocean circulation by changing surface water density and ultimately slowing North Atlantic thermohaline circulation. Okak Bay, an embayment along the northeastern Labrador coast, is especially sensitive to such climate changes, as it receives water from the Labrador Sea (in the North Atlantic), and is near the present latitudinal tree line. The Bay is also adjacent to several long inhabited European and pre-contact archaeological sites. This seasonally anoxic fjord-like bay has preserved the fossil record dating back to nearly 9,000 calBP with a 0.5 to 2.6 mm/y sedimentation rate, based on a preliminary age model. As a result, this location contains a unique record of terrestrial and marine environmental change, as well as anthropogenic influence at the subarctic boundary throughout the Holocene.

This investigation sets out to determine how terrestrial and marine conditions have changed over the past several thousand years in the in Okak region, and to evaluate if anthropogenically induced environmental change is discernible in proxy records. To answer these questions, this study couples microfossil (pollen and dinoflagellates) and sedimentological (physical properties, sedimentation rates, and XRF) data extracted from several sediment gravity cores ranging from 80 to 214 cm in length and a piston core 430 cm long retrieved from Okak Bay. Preliminary data suggest a trend towards increasing terrestrial sediment input to the Bay throughout the latest Holocene, with fluctuations towards higher magnetic susceptibility values over the last 5000 years. Preliminary microfossil data indicate a possible vegetation shift in the region, as conifer genera are more prevalent at the top of the core, and Alnus sp. dominates at the base of the core. This higher influx of tree pollen may be indicative of late Holocene warming and more favorable conditions to support forest growth.