Title:
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The structure and evolution of the Wessex Basin
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The subsidence form of many sedimentary basins consist of two
discrete phases of basin development: a rapid subsidence phase related to
riftinq of the crust and thinninq of the sub-crustal lithosphere followed
by a thermal or flexural subsidence phase. In marked contrast to this
simple models prediction, some basins exhibit a complicated subsidence
history consisting of one or more phases of extension and thermal
recovery (construction phase). These phases may in turn be followed by
phases of destruction (inversion) which could introduce an additional
drivinq subsidence.
The Wessex Basin is such an example. PolyPhase reactivation of
basement thrusts and wrench (or transfer) faults tended to
compartmentalize the basement, thereby leading to the initiation of
discrete (Permian-Cretaceous) pull-apart deoocentres openinq alonq
northwest-southeast faults. On the basis of structural and subsidence
data, the Wessex Basin has been interpreted as the result of thin
skinned crustal extension above an intracrustal late Variscan listric
detachment surface, with significantly reduced ~xtension of the subcrustal
lithosphere and is not the result of simple lithospheric
stretching as described previously. The same detachment surface
facilitated inversion and hence the destruction of the basin, beginning
in the late Cretaceous-early Tertiary.
The structural development of the Wessex Basin, both during
extension and compression, was ultimately controlled by the plate motion
of Africa relative to Europe. Such plate motions successfully predict
the observed northwest-southeast sinistral motion in the Stephanian-
Aptian, east-west sinistral motion durinq the Aptian-Cenomanian, and
northwest-southeast dextral motion and inversion from the Cenomanian -to
the Present day.
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