High-resolution
sea-level change
This work
appears in publication B26. At Amherst Point, Nova Scotia, a
radiocarbon chronology for plant macrofossils in exposed salt-marsh
sediments 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/century.
Four phases of rapid aggradation (900 - 600 BC, 100 BC - 200 AD, 700 -
1100 AD, and 1600 AD - present) were interspersed with three phases of
slower aggradation (600 - 100 BC, 200 - 700 AD, and [tentatively] 1100
- 1600 AD). 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.
Increasing high water level at Amherst Point,
Nova Scotia.
Postglacial
sea-level changes in Newfoundland
Relative sea level has varied through space and
time in Newfoundland. In most areas of the island, relative sea level
(RSL) started to fall rapidly as soon as the coastal areas became free
of glacier ice. RSL dropped below modern sea level across much of the
island. In many fiords, sea level reached a minimum level and formed
deltas. These were then submerged as sea level rose in the middle and
late Holocene. The history of the northern Peninsula is different: RSL
fell through the entire postglacial period. Sea-level changes on the
island are described in publications B14, B17 and B21.
The seismic section at left shows a submerged delta (-30 m) in La Poile
Bay, near Port aux Basques, Newfoundland. It
formed c. 9.5 ka radiocarbon years BP. Changing
geography as a result of sea-level changes.
The effects of
changing sea levels in Atlantic Canada, since 13 000 radiocarbon years
BP, are described at the CoastWeb site.
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