TRANSACTIONS OF SECTION C. 673 



5. On the Stratigrapliical Position of the Salt Measures of South Burhajti. 

 By Professor G. A. Lebour, M.A., F.G.S. 



The beds above the main mass of the magnesian limestone in Durham are 

 seldom exposed at the surface, as the south of the country is covered by a thick 

 spread of drift. The presence of salt deposits havinfr, however, been proved some 

 years ago in the adjoining part of Yorkshire near Middlesbrough, several borings 

 for working them in the form of brine were soon put down in the flat country 

 between the Tees and the coast south of Seaton Carew. There are now altogether 

 some fifteen or sixteen such borings, most of which have reached beds of salt at 

 depths varying from 600 feet to over 1,200 feet. These have thrown much light 

 upon the rocks, hitherto scarcely known in this part of England, which lie between 

 the Rhsetic and the great Permian magnesian limestone of Durham. The author 

 exhibited sections of these beds, and gave reasons for suggesting that much of the 

 salt-measures of this district is probably the representative of the Upper or Rauch- 

 toacke Permian of Germany. 



The following table summarises fairly the classification tentatively suggested 

 by the author : — 



Avicula contorta beds (proved in Eston shaft and -rji ,• 



boring) 



7. Red and green marls, with gypsum (known onlyi 



south of the Tees) I Upper Trias. 



6. Red sandstone j 



Unconformity (?) 



5. Red sandstones and marls (? Lower) Trias. 



Unconformity (?) 



4. Red marly sandstones, marls, with lenticular beds of ] yy p n "an 



anhydrite, gypsum, and salt, and foetid limestone in r Vtj u «i q\ 

 •' 1 1 1 'j .^ J ii -L I ( xxaucnwacKe ). 



variable bands towards the base . . . . ) ^ ' 



3. Main magnesian limestone I Middle Permian. 



2. Marl slate with nsh-bed i 



1. Yellow sands Lower Permian. 



Unconfwmity . 



Carboniferous eocks. 



6. On the Carboniferov^ Limestone of the North of Flintshire.^ 

 By G. H. Morton, F.G.S. 



In the year 1870 I described before the Association the subdivisions into which 

 the carboniferous limestone of North Wales is naturally divided by clear lithological 

 characters, and in 1877 more fully described the subdivisions of the formation aa 

 they occur in the Eglwyseg ridge, near Llangollen. Since then the whole of Flint- 

 shire has been examined, and the original classification found to extend to the sea- 

 coast at the north of the county. Although the subdivisions are not piled up, one 

 over the other, in a precipitous outcrop, the succession is as clearly shown between 

 Prestatyn and Meliden as at Llanymynech and Llangollen, and the uniform 

 character of each subdivision along the intervening forty-four miles of country 

 is remarkable. 



The following four subdivisions of the carboniferous limestone are all well 

 exposed in a fine mural section three and a-quarter miles in length, from Castell 

 Prestatyn on the north to the end of Moel Hiraddug on the south, and occur in the 

 following descending order : — 



Upper Black Limestone. — A black, fine-grained, thin-bedded limestone, contain- 

 ing very few fossils, but including Posidomya Becheri and the remains of many 

 plants. Thickness, 200 feet. 



Upper Grey Limestone. — A dark-grey thin-bedded limestone with thin seams 



' Published in exteiiso in the Proceedings of the Liverpool Geological Society, 

 vol. v. p. 175. 



1886. X X 



