WEXFORD GEOLOGY

Samuel Lewis

1837

The county, in its geological relations, forms part of the clay-slate tract, which stretches, on the eastern side of the granitic range, from the northern part of the county of Wicklow to the Atlantic. The strata in the southern portions are in some places considerably inflected, but in the northern parts of the county they maintain a tolerably uniform north-eastern and southwestern direction, with a dip to the south-east; and the clay-slate is here found immediately in contact with granite, which is the chief component of the Blackstairs and Mount Leinster ranges.

The Forth mountain consists almost entirely of quartz rock, with a tendency to the slaty structure from interposed laminae of clay-slate. The strata range 25° north of east and south of west, and dip 45° towards the north-west: they are occasionally traversed by fissures and by veins of quartz, and in these veins have appeared in some places indications of lead, copper, and iron. The lower grounds and eminences in the vicinity of Forth are composed of alternations of quartz rock and clay-slate: the former rock, which is sometimes iron-shot and of a deep reddish hue, ranges to the north of Wexford town, forming its foundation, and in its southern progress constituting the White Rocks near Kerlogue, extending still further south: clay-slate is visible on the south-eastern side of Forth, and to the north-west is distinctly seen at Carrigg bridge, and in several other parts around the inner haven of Wexford. It is traversed by contemporaneous veins of quartz, and probably contains several beds of greenstone, blocks and fragments of this rock being observable on the strand near Saunders Court, and smaller pieces in the fields above and towards the entrance of Edenvale.

The general components of the south-eastern quarter of this county are also quartz rock and clay-slate interstratified, disposed in the manner above described, and containing occasionally beds of greenstone. Towards Carnsore Point the land gradually rises, forming a low swell of ground, composed apparently of granite, as great blocks of that rock, with some few scattered masses of mica slate, occupy its entire surface. The approach to a granite soil is indicated even at Broadway village, a little north of the lake, where blocks of that rock and of mica slate begin to appear. The granite base breaks forth again in Carrigburn and Camorus hills, to the north-west of Forth; and blocks of granite are strewed over a part of the county extending towards Bannow on the south.

At Caim, near the eastern foot of the granitic chain, the clay-slate appears to contain several beds of greenstone; and the bridge over the Urrin stream is mostly built of it. Traces of the same rock occur also near Enniscorthy, on both sides of the Slaney: the clay-slate and quartz rock in the vicinity of this town are sometimes much intermingled. Vinegar hill and the craggy rocks stretching towards Solsborough are principally composed of the latter; so also is Carrigrua-more, to the north-east. But the principal ranges of elevated land, such as Slieve-buy, Bree hill, Slieve kelter, &c., are clay-slate; and quarries are opened in several parts of the line adjacent to the granitic chain, some of the best slates being raised in the neighbourhood of Newtown-Barry and towards Kilkevin to the north-east.

A black, slightly carbonated clay occurs near Enniscorthy, where it is mistaken for coal, and some trials were made in consequence: this rock generally contains finely disseminated iron pyrites, and exhibits also thinly interspersed galena. The eastern side of Waterford harbour, in this county, consists principally of clay-slate in strata nearly vertical, but it is surmounted by a cap of sandstone in Broomhill: a similar cap occurs more to the south, in Templetown hill, which gradually declines till it underlines the tongue of floetz limestone which extends to the extremity of Hook Point. This limestone is arranged in strata of only a few inches in thickness, dipping at an angle of from 4° to 8° towards the south, and contains numerous bivalves and corallites: its connection with the sandstone is most conspicuous on the eastern, coast, proceeding along which to the north the limestone becomes interstratified with slate clay, and this latter rock at length predominates, alternating with very thin beds of limestone and acquiring a much higher elevation.

At the point of junction with the red sandstone beneath it, at Houseland castle, the latter is of a fine grain and red cast. More to the north it acquires a coarser structure, thick beds of conglomerate being interstratified with fine-grained, red, perishable sandstone. These rocks form a bold coast of abrupt precipices, extending to Carnyven headland, eastward of Templetown hill and south of Bagenbon Head. Detached portions of the sandstone shew themselves in other places.

The inner haven of Wexford is partly lined with four isolated patches of this rock lying unconformably on the clay-slate: it is of a deep red colour, and is principally composed of fragments of quartz, with a few of clay-slate, cemented by iron-shot quartz. Park Point, on the south side of the haven, consists chiefly of this sandstone arranged in strata from one to two feet thick, which are sometimes separated by a thin seam of red soapy clay. On the western side of the northern extremity of the inner basin is another smaller patch of red conglomerate, situated to the west of the Castle bridge.

In a dell westward of Artramont castle is a similar small patch, and a fourth of larger extent occurs in Saunders Court demesne. At Duncormuck is another patch of sandstone, which comes in contact with floetz limestone; and it is found in the Saltee islands, where it is based on the clay-slate. At Ballyback, where Waterford harbour narrows to the north, are caps of sandstone conglomerate, reposing unconformably on clay-slate, and containing many pebbles of granite, but fragments of clay-slate are the predominating constituents.

The great body of the rugged and isolated hill of Taragh, east of Gorey, consists of porphyry, with a compact felspar base, that sometimes passes into horn-stone, containing inlaid crystals of glassy felspar; but greenstone also appears occasionally. Besides the limestone of Hook Point, there is a narrow slip at Drinagh, a mile south of Wexford, which follows the coast for four or five miles southward, consisting of a blueish grey kind, containing corallites and bivalves, and associated with a brownish grey, fine, granular magnesian limestone. A third small limestone district occurs at Duncormuck, and extends from the coast into the interior three or four miles; it is generally of a reddish brown cast, apparently derived from the sandstone conglomerate in its vicinity.

A lead mine was discovered at Caim and wrought for several years: the works are now about to be resumed. At Clonmines the remains of an ancient mine are still to be traced; and galena has been found here, partly adhering to quartz and rhomboidal ironstone, and partly thrown on shore after storms, by which portions of the cliff had been torn away. The old heaps in the neighbourhood are supposed to be the remains of the silver mines said to have been worked by the ancient Ostmen.

At Kerlogue, near Wexford, is a small vein of copper ore, of the malachite or carbonated green copper ore species. Specimens of plumbago were found, about three years since, at Greenfield, near Enniscorthy; and in quarrying for stone at Bloomfield, in the same neighbourhood, about a year ago, some fine specimens of asbestos were discovered, the only ones known to exist within the county.

The horns and bones of the moose deer have been found in the alluvial districts both on the east and south, where there is marl. About a year since, a perfect fossil skeleton of the Cervus Megaceros, or gigantic horned deer of Ireland, was found at Ballyhuskard, near the bog of Itty, exceeding in its dimensions the fossil deer in the Dublin museum.

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