Radiocarbon-dated benthonic foraminiferal zones in three cores provide new information on the evolution of the deep and intermediate water masses off Gaspé Peninsula. The deglacial phase in the deep Laurentian Channel began before 14 000 BP and was characterized by low-salinity (<20‰) or alternating low-salinity and saline (~35‰) water. This was followed by a cold saline phase, which ended ca. 13 500 BP, and a salinity minimum (30–33.5‰), which began ca. 12 100 BP. Between 8700 and 7900 BP, the temperature and salinity of the deep water mass increased, resulting in the modern deep water mass (temperature 4–6 °C, salinity 34.5–34.9‰) at the end of the Goldthwait Sea episode. The salinity of the deep water was apparently controlled by the meltwater flux from the ice front during the deglacial phase. After the deglacial phase the characteristics of the deep water mass were determined by the composition of offshore water entering the Laurentian Channel. Runoff from the Lake Agassiz – Great Lakes system does not appear to have mixed with the deep water of the Goldthwait Sea. The deglacial phase in Chaleur Trough, which is within the intermediate water mass, began before 12 200 BP. The temperature of the intermediate water mass has remained close to 0 °C after deglaciation; however, the salinity has increased from 25–30‰ at 12 200 BP to about 33.5‰ by 5900 BP.
A radiocarbon 14 C chronology determined for plant macrofossils in exposed salt-marsh sediments at Amherst Point, Nova Scotia, Canada, shows that the edge of the high salt marsh aggraded 7.5 m since 900 bc, equivalent to a mean rate of 25.9 cm 100 yr −1 . Four phases of rapid aggradation (900-600 bc, 100 bcad 200, ad 700-1100, and ad 1600 to present) were interspersed with three phases of slower aggradation (600-100 bc, ad 200-700, and (tentatively) ad 1100-1600). The stepped pattern of marsh aggradation probably resulted from eustatic sea-level fluctuations superimposed on background signals of crustal subsidence and tidal-range expansion. Because the rate of high salt-marsh aggradation lagged or exceeded the rate of higher high water (HHW) increase at various times, the high salt-marsh aggradation trend only approximates the trend of HHW increase. The eustatic sea-level fluctuations are estimated to have a range of at least 0.8 m.
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