Cilwrgi Quarry
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Geology & landscape
Mining / Industrial: Quarry · Geological Period: Silurian · Rock Type: Limestone
Description
Description The geological interest of this site in technical terms may be defined as follows: A problematic site exposing the so called Usk Limestone, a unit variously assigned to Wenlock Limestone or the basal Ludlow Series. Traditionally regarded as forming part of the late Wenlock carbonate build up in the Usk area, the unit has more recently been described as an a typical limestone developement within the argillite dominated Ludlow. A bioherm within the limestone has a varied fauna; of particular interest are the abundant bryzoans. An important site for the stratigraphic debate on the supposed sunchronous sea level rise at the Welock-Ludlow Series boundary, and the position of this boundary in the southern Welsh borders. In layman's terms, the interest of this site may be expressed more simply, and such a statement is provided below. This should not be taken as definitive and further information as to details of the interest can be obtained from the Countryside Council for Wales. Cilwrgi Quarry exposes an important section through the Usk Limestone which has been of great value in helping to reconstruct the sequence of events which occurred during the middle to late Silurian, some 420 million years ago. The traditional view was that around this time much of the South Wales area was covered by a shallow sea which gradually became deeper as time passed. The limestones exposed at Cilwrgi were thought to represent the shallow marine conditions, but more recent work suggests that these deposits were in fact an atypical limestone developement within the later deepwater episode. The debate as to what these sediments represent is unresolved, and Cilwrgi Quarry is thus of great importance in the interpretation of the geological developement of the South Wales and Welsh Border area during middle to late Silurian times.