K. Lambeck, SEA-LEVEL CHANGE ALONG THE FRENCH ATLANTIC AND CHANNEL COASTS SINCE THE TIME OF THE LAST GLACIAL MAXIMUM, Palaeogeography, palaeoclimatology, palaeoecology, 129(1-2), 1997, pp. 1-22
Holocene sea-level change along the French Atlantic and English Channe
l coast is not uniform because of the response of the crust to the cha
nging ice and water loads in Late Pleistocene and Holocene time. The p
attern of the spatial variability is a north-south trend, of decreasin
g sea levels levels at any time. This results primarily from the isost
atic response to the melting of the Fennoscandian ice sheet. Superimpo
sed upon this is a mainly east-west trend resulting from the isostatic
response of the crust to the addition of the meltwater into the Atlan
tic ocean. The combined effect is that at any time sea levels vary spa
tially along this coastline by amounts that are predicted to reach 20
m from the time of the Last Glacial Maximum to about 10,000 radiocarbo
n yr ago, about 15 m at 8000 yr ago and about 10 m at 6000 yr ago. Thu
s observations of past sea levels should not be combined into a single
sea-level curve unless first corrected for the glacio-hydro-isostatic
factors. Alternatively, the data should only be used to construct reg
ional curves for relatively short sections of the coastline, such as P
as-de-Calais and Picardie, Normandie, Cotes-du-Nord, Finistere, or the
Vendee and Charente-Maritime region. Even within such constrained reg
ions the spatial variability may still be of the order of a few meters
. Analysis of the observational data by region indicates that major os
cillations in sea level are unlikely to have occurred, that levels at
no location exceeded the present mean sea level, and that there may ha
ve been a small (similar to 3 m) increase in eustatic sea level over t
he past 6000 yr. Palaeo-shorelines and palaeo-water depths for the Eng
lish Channel and the Atlantic coast shelf have been predicted using th
e isostatic and eustatic models and the results indicate that in-situ
marine deposits older than 6000-7000 yr are unlikely to be found along
many sections of the present coastline.