CGRG Bibliography of Canadian Geomorphology
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Author : Graf, M.-T.; Shaw, J.; and Chmura, G.L.
Date : 2007.
Title : Reassessing proposed rates of recent eustatic sea level rise in Atlantic Canada.
Publication : CANQUA Ottawa 2007. Canadian Quaternary Association Conference, June 4-8, 2007. Carleton University, Ottawa, Ontario, Canada.
Issue :
Page(s) :
Abstract
Previous work at Amherst Point in the Cumberland Basin of the Bay of Fundy used salt marsh deposits to reconstruct sea level variation and tidal expansion in Atlantic Canada for the last 3000 years. Organic horizons in the salt marsh sedimentary sequence were interpreted as representing periods of slower sea level rise when marshes aggraded at lower rates, while periods of rapid marsh aggradation were thought to represent periods of accelerated sea level rise. The Amherst Point data suggested four periods of accelerated sea level rise at 900-600 BC, 100 BC-AD 200, AD 700-1100, and AD 1600 to present. Recent work in adjacent John Lusby Marsh suggests that the most recent episode of accelerated sea level rise was due to the influence of anthropogenic land use changes, specifically loss of diking infrastructure established by Acadian settlers in the late 1600s and early 1700s. We have reanalyzed pollen assemblages from Amherst Point using modern pollen and fungal spore assemblages from four different grassland land uses in the area: salt marsh, farmed dikeland with grazing/manuring, farmed dikeland without grazing/manuring, and abandoned dikeland. Our analysis reveals that the sediments dated 315 ±60 yrs BP and interpreted to represent a period of very slow marsh aggradation, contain a pollen signature indicative of dikeland land use. Analysis of historical air photos supports the theory that the Amherst Point core site was located on a former dikeland surface and that the period of very low marsh aggradation followed by sudden and rapid marsh aggradation actually represents an extended period of dikeland land use terminated by a sudden dike breach in the 1940s. In the 50-odd years since breach, approximately 1 m of sediment has accumulated on the restored marshes, indicating that upper Bay of Fundy salt marshes are able to quickly adjust to rapid and dramatic rises in sea level.
Bibliography of Canadian Geomorphology