Holocene history of Bedford Basin, Nova Scotia: foraminifera, dinoflagellate, and pollen records

Publisher Website
Google Scholar
Abstract
Three piston cores from Bedford Basin, a silled coastal inlet, provide the basis for a micropaleontological study of postglacial to recent sediments. Fiver faunal units (4 foraminiferal, 1 arcellacean) are found in core 79-11: a surface assemblage, followed by deep estuarine, marginal marine, transition and freshwater (arcellacean) assemblages. The other cores contain only expanded marine sequences. The top of the transition zone in core 79-11 has a 14C age of 5830 .+-. 230 yr BP, indicating a rise in sea level of at least 20 m (the sill depth) during the Holocene. Four dinoflagellate assemblage zones are found in core 79-11. The first (Operculodinium centrocarpum-Bitectatodinium tepikiense) is typical of a silled basin with marine water of near-normal salinity; the second (Peridinium conicoides-cyst C) indicates a temperate marine environment with strong fluvial influence (marginal marine); the third (P. limbatum) in dominated by freshwater cysts and the fourth (Dinocyst sp. A) is dominated by subarctic brackish water cysts. Four pollen assemblage zones are found in core 79-11. Zones C1-C3 indicate mixed boreal-deciduous forest vegetation. Zone B indicates early Holocene park-woodland vegeation, the base of which has a 14C age of 7705 .+-. 550 BP. The palynozones in the marine sediment core are correlatable with 14C-dated stratigraphies from Nova Scotian lakes. Foraminifera and dinoflagellate assemblages in core 79-11 reflect the response of the microfauna and microflora to changes in water depth, salinity and temperature, which have accompanied changes in sea level and climate during the past 8000 yr. Major changes in the marine biota during the recent period of urban development may be due to increased sediment influx and effluent discharge. The effects of anthropogenic changes are small compared to those accompanying the Holocene marine transgression.