460 TRANSACTIONS OF SECTION C. 
conclusion can be drawn, it is suggested that the breccia has in large measure 
resulted from erosion, which operated during the period of upheaval of this 
and neighbouring anticlinal ridges. 
3. The Silurian Inlier of Usk. By C. I. Garnixer, M.A., E.G.5. 
The Usk Inlier is roughly oval in shape, measuring about eight miles and a 
half from N. to S. and four miles from E. to W. It is crossed by an important 
E. and W. fault, which divides it into two nearly equal parts. The southern 
half is composed of two anticlines separated by a fault. The axes of these folds 
run roughly north and south, and dip southwards. The western anticline is the 
larger of the two, and shows Wenlock Shales and Limestone and Ludlow beds; 
these are all very fossiliferous. 
The anticline has been much broken by faulting, and the limestone is now in 
twelve separate parts. Careful observations of the dips prove faulting to be a 
satisfactory explanation of this separation. The Silurians are separated from 
the Old Red Sandstone to the west, from Littlemill to Trostra, by a fault, but 
from Trostra to Llandegveth and Graigwith the basement bed of the Old Red 
Sandstone, a yellow quartzose sandstone, rests with apparent conformity on the 
Ludlow beds. The eastern anticline is thinner than the western one. Its 
lowest bed seen is the Wenlock Limestone of Cwm Dowlais, this being covered 
by Ludlow beds, which run south through Llangibby Park. A fault line 
separates these Ludlows from the Old Red Sandstone to the east. The Wenlock 
Shale is a brown sandy shale where its lowest beds are seen in the railway 
cuttings near Bryn, and it becomes more sandy in its higher parts, a definite 
sandstone occurring close to its summit. The Wenlock Limestone has about 
twelve feet of massive limestone at its base, largely formed of crinoid fragments, 
and, above this, irregularly bedded limestone separated by thin shaly partings. 
Corals are scarce, brachiopods and trilobites common. The Ludlow beds are, for 
the most part, brown sandy shales, with calcareous nodules or thin calcareous 
layers, but towards their summit they pass up into sandstones. The northern 
half of the Inlier is far less simple than the southern in its structure, and is 
more concealed by drift. ‘Its western boundary is everywhere obscured, but 
Ludlow beds are seen here and there dipping towards the Old Red Sandstone not 
far off the boundary. The central part is composed of Wenlock Shale, and the 
eastern margin is composed of Ludlow beds dipping eastwards and faulted against 
the Old Red Sandstone. The Wenlock Limestone is not met with in this 
northern half of the Inlier. The simpest explanation of these facts is that the 
Wenlock Shale is faulted against the Ludlow beds on both sides. As the 
Aymestry Limestone is absent from the district, it seems impossible to separate 
the Ludlow beds into an upper and a lower division, but fossils have been care- 
fully collected in order to see if any horizons can be fixed. The main boundary 
faults are crossed at several spots by minor east and west faults, which cause 
small lateral displacements. 
4. Preliminary Nole on a Buried River Channel near Peterborough. 
By Rev. A. Irvine, D.Sc., B.A. 
_ Attention was drawn to the existence of a pre-glacial river channel (250 yards 
wide at Fletton). So far as the evidence has been investigated in the field 
the channel appears to have been buried under glacial deposits, across which 
the River Nene cuts its upper course. The general trend of the channel points 
to a possible connection (in pre-glacial times) with the upper part of the Trent 
basin in one direction, and with the Thames basin (through the buried valleys 
of the Cam and the Stort)’ in the other; and, so far as the examination has 
gone, this inference is borne out by the nature of the detritus which fills the 
ancient channel. The writer hopes to carry out a more complete examination 
of the ground during the next few weeks. Meanwhile the postulated capture 
of the Lower Trent by the Humber can be fairly referred to glacial damming 
co-operating with differential movements of the crust, the Boulder Clay having 
7 A. Irving, Brit. Assoc. Reports, Sheffield, 1910, p. 616. 
