The North Sea Basin
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The North Sea Basin |
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| Fig 5.2.1 Map of the North Sea |
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| The North se is located between
Scotland and Norway.The North sea has a very long and complicated
history of subsidence. Deposition of sediment is particurly rapid during
the Permian and Mesozoic time periods creating layers many kilometers
thick.The figure above shows the major feateures of the north sea.The
Humber group is dominated by marine mudstones and clays.These have been
deposited after a large amount of subsidence.The Cromer Knoll group is
dominated by calcareous mudstones and thin limestones.The chalk group
dominates the Upper cretaceous and lowermost Paleocene ages.The late
Palaeocene is dominated by sandy turbidites which represent large
deposits from a submarine fan system.The Witch Ground Graben were formed
in the late Jurassic due to a large rifting event causing alot of
extension.Considerable amounts of thermal subsidence occured after this
which continue to the present day.This rapid subsidence was interupted
by an uplift due to the opening of the North Atlantic. |
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| Fig
5.2.2 Stratigraphic column taken from the North Sea. This column
illustrates the deposition history of the basin. |
| SUBSIDENCE |
| From the figure below we can see
that there are two periods of rapid susidence followed by two periods of
declining subsidence rates.On the figure curve 1 represents
backstripped subsidence curve with a constant water depth.Curve 2 is a
water loaded subsidence curve.Curve 3 is a theoretical water loaded
subsidence curve.Curve 4 represents the water depth profile while curve
5 is the net subsidence curve.There is very rapid subsidence in the
first twenty years of the basins history.This is due to the fact that
rifting lasted from 150 Ma to 130Ma.During the late cretaceous there is
a rapid increase in the amount of chalk deposition this leads to a rapid
increase in subsidence.During the palaeocene there is another rapid
increase in sediment input leading to further subsidence. |
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| Fig
5.2.3. Subsidence curves for Location C in the North Sea. |
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