382 ME. G, H. jyiORTOX ox THE CAEBO^IFEROTTS [Aug. 1 898, 



29. The CAEBONifEEOTJs LiMESToiTE of the CoTTNTUY around Llaxdtjdxo 

 (North Wales). By G. H. Mortox, Esq., F.G.S. (Read May 

 4th, 1898.) 



I. Great Orxe's Head. 



The Carboniferous Limestone, and the subdivisions into which it 

 is divided in Xorth Wales, were described in papers read before 

 the British Association and the Liverpool Geological Society between 

 the years 1870 and 1898. The most recent paper on • The Carbo- 

 niferous Limestone of the Yale of Clwyd,' is in the Proc. L'pool 

 Geol. Soc. vol. viii, 1897-9S. It contains a description of the sub- 

 divisions of the Limestone, including the Purple Sandstone, which 

 consists of a series of sandstones and shales described by Mr. George 

 Maw in 1S65 as Permian,^ and more recently by Mr. Aubrey Strahan 

 in 1890 as Coal Measures.^ 



The following table shows the subdivisions that occur in the Yale 

 of Clwyd, aud in two other areas previousl}* described. The Purple 

 Sandstone is shown to be on the horizon of the highest subdivision of 

 the Carboniferous Limestone in Flintshire and Denbighshire : — 



Vale of Clwyd. Prestatyn and Holywell. Mold aiid Llangollen. 



Purple Sandstone. ITpper Black Limestone. Arenaceous Limestone. 



Upper Grey Limestone. Lpper Grej- Limestone. L^pper Grey Limestone, 



Middle White Limestone. Middle White Limestone. Middle White Limestone. 



Lower Brown Limestone. Lower Bi'own Limestone. Lower Brown Limestone. 



Ked Basement Beds. Red Basement Beds. E/ed Basement Beds. 



The Great Orme's Head is a prominent headland on the sea- 

 coast of Caernarvonshire. It is separated from the mainland by 

 an isthmus a mile in width and about 20 feet above Ordnance 

 datum, and must have formed an island in post-Glacial times. 

 Llandudno, the well-known watering-place, is situated on the south- 

 east, and principally on the alluvial land. The Head is 2 miles 

 in length from east to west, and 1 mile from north to south ; it is 

 bounded on the north and west by precipitous cliffs, which rise from 

 the sea-level to an elevation of 200 or 300 feet. Along the south- 

 eastern side there is a fringe of Boulder Clay, but the limestone 

 rises with a steep escarpment at 50 or 100 yards from the sea- 

 margin. On the terrace of drift are the ruins of Gogarth Abbey, 

 about 50 feet above the sea. The highest point is close to the 

 Telegraph, 679 feet above Ordnance datum ; St. Tudno's Church, 

 called after the patron saint of the Head, is near ihe northern cliff, 

 and is 3324 feet above sea-level. At the extreme north is the 

 Lighthouse, about 200 feet in elevatiou. A drive has been con- 

 structed aU round the Head, varying from 10(.) to 200 feet above 

 the sea along the face of the cliff'. The surface on the top of the 



^ Eep. Brit. Assoc. i^B'^ham) 18G5, p. 67 ; G.-ol. Ma/. 1865, pp. 380 & 523. 

 2 Mem. Geol. Surv. 18UU, 'Geol. of Fhnt, Mold, ^t Eutliin,' p.Jl. 



