130 
PROCEEDINGS COTTESWOLD CLUB 
I ot6 
INTRODUCTION. 
The Usk Inlier lies a few miles to the North of Newport, 
and just to the East of the South Wales Coalfield. It is about 
midway between the Tortworth Silurian Inlier described by 
Dr. F. R. C. Reed and Prof. S. H. Reynolds' and the P>uilth 
area described by Miss Wood.^ 
The first description of the Inlier seems to be that by 
Murchison in his “ Silurian System, and there are man}’ 
references to it in his “ Siluria.’' In the Survey Memoirs 
of 1846 De la Beche published a table of the Usk formations, 
and referred them to the Ludlow, Wenlock, Caradoc and Upper 
Llandeilo ages T but Phillips, in the Memoir of 1848, ^ was 
the first to describe the Silurian beds of Usk in detail. From 
the fossil evidence he included the beds which had been called 
Caradoc and Llandeilo in the Wenlock series. He regarded the 
Old Red Sandstone beds as conformable to the Ludlow rocks. 
In 1909 an account of the area appeared in the Survey 
Memoir which dealt with the country round Newport.^ In 
this Phillips’ conclusion as to the ages of the rocks was con- 
firmed, but very few additional details about the Silurian beds 
were given. The fossil evidence referred to is scanty, and 
plenty of scope is left for further investigation in the district. 
The important conclusion is arrived at in this memoir, 
that the beds at the base of the Old Red Sandstone, which are 
seen 40 miles further West, are not represented in the Usk 
district, so that the junction between the Old Red Sandstom' 
and the Ludlow beds may be here an unconformable one. 
Very little detailed work seems to have been done in 
recent years on the Silurian beds of South Wales. Prof. Sollas, 
in 1879, described the Silurian district near Cardiff,^ which 
lies about 20 miles to the S.W. of Usk, where he found Ludlow 
and Wenlock beds of a total thickness of 950 feet. Miss Wood 
has described the Silurians near Builth, some 40 miles to the 
North-West, and these, with their graptolitic beds, show no 
analogy to the type of Silurian beds seen at Usk. The Tort- 
worth area, some 20 miles to the East, shows about 625 feet 
1 Quart. Jour. Geol. Soc., Vol. l.Kiv. (1908), p. 512. 
2 Quart. Jour. Geol. Soc., Vol. Ivi. (1900), p. 413. 
3 “ Silurian System ” (1839), pp. 438-441. 
4 Mem. Geol. Surv. (1846), Vol. i., p. 22. 
5 Mem. Geol. Surv. (1848), Vol. ii., pp. 196-208. 
6 ‘‘ Geology of the South \Vales Coalfield,” pt. i, “ Country round Newport ” (1909). 
7 Quart. Jour. Geol. Soc., vol. xxxv. (1879), pp. 475 * 507 . 
