3-D Structural Evolution and Analysis of
Complex Mesozoic Grabens in Guinevere Field
UK Southern
North
Sea
The Guinevere field
in the UK Southern
North
Sea
is
characterized by the presence of complex Mesozoic grabens trending in the
NW-SE. A prominent feature of these grabens is the presence of a Lower Triassic
Separation Zone (LTSZ), which is characterized by the absence of the Lower
Triassic Bunter Group (Bunter Shale and Sandstone Formations). These grabens
are bounded by basinward and landward listric growth faults which detach on the
Permian Zechstein and Triassic Haisborough Groups.
Graben1 shows crestal collapse structure containing
series of synthetic and antithetic faults, which probably developed as a result
of accommodating extension on the listric growth faults. Graben2 on the other
hand developed from an asymmetric half graben to a full graben with no crestal
collapse structures. An array of domino style faults with an oblique
extensional direction (ENE) relative to the graben bounding faults (NW-SE)
detaching on the Triassic Haisborough Group developed during the Jurassic
extension. The change in direction of these domino faults is attributed to a
reorientation of the stress field
.
A 3D structural evolution model is proposed for the formation of these grabens, the suggested mechanisms are salt tectonics and extensional faulting utilizing multiple detachment layers of the Permian Zechstein and Triassic Haisborough Group in two different phases of extension. Listric extensional faults cut and caused the rotation of the hanging wall units within the Upper Triassic sequences and detached on the Upper Permian Zechstein. The subsequent development of an antithetic listric fault detaching on the inclined Haisborough Group causes the separation zone to form during the Lower Jurassic.
AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California