On the Llandovery and Associated Rocks of Conway (North Wales)

Abstract

I. Introduction, and Description of Area . The Geological Survey Map (Sheet 78 N.E.) of the district lying immediately south of the town of Conway reveals an outcrop of Tarannon Shales, which is curious as regards its relation to the associated formations, since the Tarannon Shales are represented as being both underlain and overlain by rocks of Wenlock age. This circumstance led us to examine this special area; and our attention having already been directed to the occurrence of graptolitic shales below the Tarannons in other parts of Wales, we thought it' possible that they might also be present in the Conway district. Our observations in that district have extended over a fairly wide region, including the greater part of the valley of the Afon Gyflin between Conway and Y–Ro; but the only area which we have mapped in anything like detail lies immediately south of the town of Conway itself, and occupies the hill opposite Conway Castle and the railway. This area is bounded on the east by the River Conway, and on the west by a fault (‘ boundary–fault,‚ as we term it in the following pages) which brings a calcareous grit of Bala age against Silurian beds.The northern limit of the area is formed by the Afon Gyffn, a‚ tributary stream of the River Conway, which it joins just below the Castle. The southern limit has been taken, for convenience, at the beginning of the dense woods belonging to Benarth Asylum. In other places higher up the valley,