300 STRATIGRAPHICAL GEOLOGY 



2. Cumberland and Northumberland Area 



In the north of England there are two coalfields which, though 

 now far apart, were originally parts of one continuous sheet of 

 Coal-measures which spread over the whole of the Lake District 

 and across the broad Pennine Hills. These are the Newcastle 

 coalfield, occupying parts of Durham and Northumberland, and 

 the Whitehaven coalfield in Cumberland. Remnants of the con- 

 necting strata have been preserved in the small Canonbie coalfield 

 on the border of Dumfries, in a faulted tract south of Haltwhistle 

 in Northumberland, another at Argill near Brough in Westmoreland, 

 and in patches of Millstone Grit on the west side of the Eden 

 Valley. 



The Newcastle coalfield is the largest of these tracts ; it extends 

 from the northern side of the Tees valley west of Darlington to the 

 mouth of the river Coquet, a distance of about 60 miles. It is 

 limited on the south by an anticlinal flexure which runs from 

 Barnard Castle to the mouth of the Tees, and the Millstone grit 

 runs into the sea near Alnmouth, so that the eastern part of the 

 coalfield passes beneath the floor of the North Sea. 



Millstone Grit. This division is of small thickness, and it is 

 doubtful what beds should be assigned to it. In Yorkshire the 

 Millstone grits thin rapidly as they are followed northward, and in 

 the North Riding are not more than 600 feet thick. Some of the 

 grits, however, are believed to come in again between Teesdale and 

 Tynedale, and have been mapped as forming broad plateaus on the 

 high fells of West Durham, but in this area they lose their coarse 

 gritty character and become indistinguishable from the sandstones 

 and flagstones of the Gannister measures. 



Lower Coal-measures. These beds likewise become much 

 thinner in a northerly direction, so that in Northumberland the 

 whole thickness between the Felltop limestone and the Brockwell 

 coal, which is the lowest workable seam, is only about 350 feet. 

 Of this Mr. Lebour assigns 150 feet to the Gannister measures, 

 and in this thickness there are two seams of coal. A few marine 

 fossils such as Aviculopecten papyraceus and stems of crinoids have 

 been found in these beds. 



The Middle Coal-measures maintain their thickness, which 

 in Durham is estimated at 2000 feet, and they contain some twenty 

 good seams of coal, including the Brockwell seam at the base and 

 the High Main seam, which is the highest known seam in the 

 series. Besides these there are many minor or less valuable seams, 

 bringing the total number to over sixty. Some of the shales con- 

 tain nodules and bands of ironstone which have occasionally been 



