Late-Holocene changes in sea level and environment on eastern Cape Breton Island, Nova Scotia, Canada

Abstract

The late-Holocene history of a coastal basin in Otter Harbour on the Great Bras D'Or of Cape Breton Island, Nova Scotia was reconstructed using micro- and macrofossils. The pollen stratigraphy shows a decrease in oak and pine pollen percentages around 4000 BP, while Tsuga pollen reaches a maximum. Over the last 1000 years, genera of the mixed hardwood forest have declined while boreal genera have increased, suggesting climatic cooling in the region. Human influence from 400 BP to the present is evidenced by increased pteridophyte spores and pollen of Rumex, Gramineae, and Ambrosia. Siliceous microfossils indicate that sea level in the Great Bras D'Or rose over the last 4000 years to 1.5 m below present level at 950 BP. This rate of sea-level rise, 16 cm per century, falls within the regional range of relative sea-level rise in the Maritimes of 10-30 cm per century for the last several thousand years. However, this long-term rate in the Maritimes is less than the rate of 30-35 cm per century determined from local tide gauges over the last hundred years. The discrepancy between these two rates can probably be attributed to recent changes in the eustatic or tectonic components of sea- level rise in this region.