Highest Coal-measures of Durham. 203 



schist to a slate is due to exceptionally severe pressure having locally 

 converted the slate into a phyllite and so far crushed the schist that 

 it is hardly distinguishable from the latter rock. This may be seen, 

 for instance, in the Tyrol on the ascent from Mittersill to Kitzbiihel 

 (29), and in the cliffs south of Torcross in Devon (30). 

 (To be continued.) 



IX. — On the Highest Coal-measures ok "Zone" of Anthracomya 



PlULLirSI IN THE DURHAM COALFIELD. 



By C. T. Trechmann, D.Sc, F.G.S., and D. Woolacott, D.Sc, F.G.S. 



(PLATE V.) 



IT has been known for some considerable time that the highest beds 

 of the Northumberland and Durham Coalfield lie approximately 

 beneath the town of Sunderland. 1 The great syncline of the Coal- 

 measures of this area is distinctly accentuated in North-East Durham, 

 so that a secondary basin-like depression is formed, in the centre of 

 which these high beds occur. 2 Beneath Sunderland, where the top 

 layers also exist, the Carboniferous rocks are concealed by the 

 overlying Permian strata, but at a place called Claxheugh on the 

 "Wear, about two miles west of Sunderland, the Coal-measures are 

 exposed for a short distance on both the north and south banks of 

 the river. 



These beds represent the horizon known as the zone of Anihracomya 

 Phillipsi. It is not generally known among British geologists that 

 these specially high beds occur in the northern coalfield, so that we 

 consider it desirable to put this fact definitely on record, and to add 

 some details on the stratigraphy and palaeontology of the beds in 

 question, the result of several visits to the locality. The sectiou 

 described is exposed on the north bank of the Wear, and is the one 

 that is specially fossiliferous. The shale, with the bands of clay 

 ironstone from which most of the fossils are obtained, does not occur 

 in the section on the opposite side. The small section of Coal-measures, 

 about 90 yards long and about 15 feet high, is cut off by a fault on the 

 west which throws down the Permian Yellow Sands. This is the same 

 displacement that brings down the Permian rocks, which are so well 

 exposed in the Claxheugh escarpment. 3 The Carboniferous rocks 

 consist of argillaceous sandstones at the base, a layer of dark fissile 

 shale, 3 feet thick, with two or three irregular nodular bands of clay 

 ironstone, and beds of grey sandy micaceous shale. The sequence 

 is shown in the section, Pig. 1. During one of our visits to the 

 locality, Dr. Woolacott observed that the exposure, besides the four 



1 J. W. Kirkby, " On the Occurrence of Fossils in the Highest Beds of the 

 Durham Coal-measures": Trans. Tyneside Nat. Field Club, vol. vi, pt. ii, 

 pp. 220-5, 1864. 



2 D. Woolacott, " Stratigraphy and Tectonics of the Permian of Durham 

 (Northern Area) " : Proc. Univ. Durham Phil. Soc, vol. iv, pt. v, p. 246, 

 1911-12. 



3 D. Woolacott, "On Sections in the Lower Permian Bocks at Claxheugh 

 and Down Hill, Co. Durham": Trans. Nat. Hist. Soc. Northumberland, 

 Durham, and Newcastle-upon-Tyne, N.S., vol. v, pt. i, p. 155. 



