SURFACE AND DEEP STRUCTURAL CONTROL OF THE NW CARBONIFEROUS BASIN OF IRELAND: SEISMIC PERSPECTIVES OF AEROMAGNETIC AND SURFACE GEOLOGICAL INTERPRETATION

Abstract

A detailed study of the magnetic and seismic data in and adjacent to the NW Carboniferous Basin of Ireland suggests that surface faults, mainly in the Carboniferous and Devonian rocks, are directly related to regional faults on older subjacent basement. These regional faults have controlled the tectonics of the area since the Late PreCambrian.The primary faults are associated with the steeply‐dipping fault zone whose presence is marked by the Fair Head‐Clew Bay magnetic linear (FCL). The FCL can be traced to the east where it becomes concident with the Highland Boundary Fault zone of Scotland. The Highland Boundary Fault maarks the southern limit of the Dalradian rocks. and was a plate margin beignning in Late Combrian‐ Early Ordovician (Grampian)times. In ireland, the FCL also marks this Lower Paleozoic plate boundary. Associated secondary magnetic linears (linears) indicate the presences of other basement fault caused by mkovement on the FCL, which were rejuvencated during the Upper Paleozoic.Large magnitude movement on these fault‐systems commenced druging the Early Paleozoic and continued through the Devonian, with lesser magnitude movement continuing until after the Carboniferous. The abrupt change from the more than 4,500 m of Paleozoic sediments present south of the FCL to approximately 1,500 m of sediments to the north is a result of complex wrench‐faulting, shown by flower structures in seismic profiles, Fold orientations and fold and fault deflections near the major sinistral fault are also consistent with formation within a sinistral strain field.