Vol. 52.] LLANDOVERY and associated rocks OF CONWAY. 273 



14. On the Llandovery and Associated Rocks of Conway (North 

 Wales). By Miss G. L. Elles and Miss E. M. R. Wood, 

 Bathurst Students, Newnham College, Cambridge. (Com- 

 municated by J. E. Mare, Esq., M.A., E.R.S., Sec. G.S. 

 Read January 8th, 1896.) 



Contents. 



Page 

 I. Introduction, and Description of Area 273 



II. Literature 275 



III. General Sequence 276 



IV. Detailed Description of the Beds 277 



1. The Llandovery Rocks. 



2. The Tarannon Shales. 



3. The Wenlock Shales. 



4. The Denbighshire Grits and Flags. 



V. Correlation with other Areas 284 



1. The Llandovery Rocks. 



2. The Tarannon Shales. 



3. The Wenlock Shales. 



4. The Denbighshire Grits and Flags. 



VI. General Conclusions 288 



Geological Map of District south of Conway 274 



I. Introduction, and Description oe Area. 



The Geological Survey Map (Sheet 78 jN\E.) of the district lying 

 immediately south of the town of Conway reveals an outcrop of 

 Tarannon Shales, which is curious as regards its relntion 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 Gymn 

 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 

 ConAvay, 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 Gyffin, 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, where we hoped to find a similar 

 succession, the ground was low-lying and all rock-exposures were 

 concealed beneath a tract of alluvium. 



