Lough Neagh : the site of a Cenozoic pull-apart basin

The Lough Neagh Basin in Northern Ireland is the site of a Cenozoic depocentre defined by
gravity measurements and a thick succession of Paleocene basaltic lavas and Upper Oligocene
clays. Much of the Cenozoic outcrop is concealed by Lough Neagh, but the rhombic outline
of the lough provides some indication of the underlying structural control of the depocentre.
Several authors have inferred that a Cenozoic pull-apart basin lies within the Lough Neagh
area and suggest it is one of a number of transtensional basins, including the Bovey and
Petrockstow basins in SW England, associated with NW to NNW-trending strike-slip fault
zones. Solid geology maps and gravity data show that the structure of the Lough Neagh Basin
is dominated by a segmented, orthogonal pattern of offset NNW and NE-trending faults. It is
proposed that pull-apart basin formation took place in the Mid-Paleocene by dextral
movement on these offset faults. The potential link between strike-slip tectonics and Cenozoic
volcanism in the north of Ireland is briefly considered.