Page:Transactions of the Natural History Society of Northumberland, Durham, and Newcastle-upon-Tyne (1867).djvu/34

18 extends westward from Cullercoats, the Coal Measures have been thrown down on the north side from 500 feet to 1000 feet. Probably, too, the effect of the Penine upheaval has extended further northward into Northumberland, though without producing any great break in the strata in the direct line of action; for the general direction of the strata is from north to south. There are many other smaller displacements of the Coal Measures, but the Mountain Limestone strata are even more disturbed by faults: one seen in the Shilbottle colliery, ranging from east to west, throws down the beds on the south side 120 feet; another great fault near to Annstead, going westward, throws the strata down on the north side about 1000 feet.

Of this formation only one member, the Magnesian Limestone, appears in our district. It was usual to group with it an irregular, loose, sandy deposit, and some red sandstones lying below it; but the discovery of several true Coal Measure plants, such as Pinites Brandlingi, Trigonocarpon Nöggerathi, Catamites approximatus, and Sigillaria reniformis, in these sandstones, at Tynemouth, and of Neuropteris giganica, Sphenopteris latifolia, &c., in the shales connected with them, shows that these red sandstones should be grouped with the Coal Measures, the place assigned to them by Dr. William Smith, the father of English geology. Mr. Howse, in 1857, proposed, that they should be considered as the uppermost members of the Carboniferous formation, with which they are seen to be conformable in the section on the coast at Tynemouth.

The Magnesian Limestone occurs in Northumberland in three small patches overlying the Coal Measures; one at Tynemouth forming the top of the cliff, and the others at Cullercoats and Whitley, where it has been preserved by the Ninety-fathom Dike, which has thrown down the strata on the north. It occupies in Durham a large space, somewhat triangular in shape, one side extending from South Shields along the coast to Hartlepool, the other having a wavy line from the same point to