Chapter 4 The Geology and Structure of the Celtic Sea

Abstract

Publisher Summary This chapter discusses the geology and structure of the Celtic Sea. The surface geology of the land areas fringing the Celtic Sea is almost exclusively concerned with Precambrian and Paleozoic rocks. In the south-west of Ireland, Devonian and Carboniferous sandstones, siltstones, and slates occur in alternating narrow outcrops extended E–W. In the south–east of Ireland, near Carnsore, granite of 430 Ma age intrudes Precambrian gneisses of the Rosslare Complex, to the north of which lie Cambrian and Ordovician slates. From Dungarvon to Dingle Bay lies the “Variscan Front” marked by faults with downthrow to the north or by upthrusting from the south. Further east, the “Variscan Front” can be traced in South Wales, where in southern Pembrokeshire, Precambrian and Lower Paleozoic rocks are thrust over Carboniferous. South of the line, folds are dominantly of E–W (Armorican) trend and affect Devonian and Carboniferous rocks much as in south–west Ireland whereas, to the north, strongly disturbed Precambrian and Lower Paleozoic rocks are structurally aligned along NE–SW Caledonian trends.