TT. Gunn — Carboniferous Rocks of England 8f Scotland. 345 



Tuedian Beds by the late Mr. Tate, of Alnwick, on account of their 

 being characteristically developed along the Tweed, In 1856 Mr. Tate 

 described these beds as consisting of grey, greenish, and lilac shales, 

 sandstones, slaty sandstones sometimes calcareous, thin beds of 

 argillaceous limestone and chert, and a few buff magnesian lime- 

 stones. Siigmaria ficoides, Lepidodendron, coniferous trees, and 

 other plants occur in some parts of the group, but there are no 

 workable beds of coal. The fauna consists chiefly of fish-remains, 

 Modiolse, and Entomostraca. Generally fresh-water and lacustrine 

 conditions are indicated.^ The thickness of this series along the 

 Eiver Tweed from Carham to Berwick m.ust be between 2,000 and 

 3,000 feet, and there is no doubt that it is the equivalent of the lower 

 part of the Calciferous Sandstone of Scotland. Sedgwick seems 

 to have been the first to point out the true position of these rocks 

 in the Carboniferous formation in his address to the Geological 

 Society in 1831 ; and in notes supplied by him for the third 

 edition of De la Beche's Geological Manual he expresses the 

 opinion that the Carboniferous Eed Sandstone of the Tweed is 

 superior to the Old Eed Sandstone, and is about of the age 

 of the Great Scar Limestone of Yorkshire and Cross Fell.^ The 

 natural inference from this would be that the limestones above 

 the Scremerston Coals belong to the Yoredale Series, and it will 

 be seen that this is so far true that most of the marine limestones 

 belong to that series, viz. those from the Dryburn to the Oxford 

 inclusive. This set of beds is thinner altogether here than in 

 Wensleydale, but the diiference is principally in the limestones, 

 which in Wensleydale amount to about 300 feet, while in 

 Northumberland they are not much more than half that thickness. 



Among the sandstones and shales that come between the Oxford 

 and the Woodend Limestones, occurs a marked band of oil shale 

 which is very constant in North Northumberland. It contains 

 remains of fishes, plants, and Ostracoda, and will be met with again 

 in the Scottish section. 



In the Northumberland section, No. 1 Limestone is the Dryburn 

 Limestone of Lowick and the Ebb's Snook Limestone of Beadnell, 

 and is called further south in Northumberland the Ten-Yard Lime- 

 stone. It is the Main or Twelve-Fathom Limestone of Wensleydale 

 and Swaledale, the Great Limestone of Teesdale and Weardale, and 

 is the uppermost member of Phillips' Yoredale Series. 



No. 2 Limestone is called at Lowick the Low Dean, and at 

 Scremerston the Sandbanks Limestone, while generally in Mid- 

 Northumberland it receives the name of the Eight- Yard Limestone. 

 It is called in North- West Yorkshire the Underset Limestone, and 

 in Teesdale and Weardale the Four-Fathom. 



No. 3 Limestone is the Acre Limestone of Lowick, where it is 

 also sometimes called the Dunstone (which name must not, however, 

 be confounded with the Dun Limestone, the lowest of the marine 



^ Proc. Berwickshire Nat. Field Club, vol. iv, p. 151. 

 2 De la Beche, Geological Manual, 1833, pp. 391, 392. 



