Journal of Petroleum Geology, vol. 22(3), July 1999, pp.
287-304
TECTONIC EVOLUTION OF THE SOUTHERN -
CENTRAL IRISH SEA BASIN
S. Maingarm+, C. Izatt*, R. J.
Whittington+ and W. R. Fitches+#
Interpretation of 2D
seismic refection data combined with correlation of five wells in the southern part of the Central Irish Sea Basin show a
NE-SW trending graben, whose bounding faults are considered to be reactivated lineaments
of Precambrian age. The basin fill comprises mainly Carboniferous and Triassic
successions, with localised and thin occurrences of Lower Jurassic and Tertiary rocks, all
of which are unconformably overlain by Quaternary sediments. Due to poor data quality, the
structural evolution of the area during the Late Palaeozoic is poorly understood. During
the Triassic, the basin was subjected to thermal subsidence with a phase of minor uplift
in the Anisian. The major phase of extension in the basin took place during the ?Middle -
Late Jurassic and had a NW-SE orientation. Subsequent Late Jurassic sinistral shear along
the NE-SW trending basin bounding fault is suggested to have taken place, giving rise to a
series of north-south intra-basinal faults. The present-day structure of the basin is a
broad anticline, inherited from a Cretaceous - Early Tertiary compressional phase. During
the Palaeocene the area was subjected to regional uplift, followed by minor extension
along the NW boundary fault during the Eocene - Oligocene. A Late Tertiary phase of
transpression is postulated to have occurred, which inverted north-south trending faults
and folded the base-Tertiary unconformity.