THE GEOLOGICAL STRUCTURE OF THE CANONBIE COALFIELD. 871 



the Cheviots occupied by the Lower Old Red Sandstone volcanic rocks, the Fell sand- 

 stones extend from Tweedmouth, by Carter Fell and across Dumfriesshire, to the mouth 

 of the Nith. In like manner the group of Scremerston coals has been traced from the 

 shore to the Old Red volcanic platform of the Cheviots, and reappears at Lewisburn in 

 the basin of the Rede Water, Northumberland, where, as Mr Clough* has shown, they 

 overlie the mass of the sandstones of Peel Fell, and come beneath the coal-seams of the 

 Plashetts. The Lewisburn coals cross over into the upper part of the Kershope Water 

 and into the head of Tweeden Burn, and appear in Scotland as the Muirburn and 

 Lawston Linn coals. 



It is obvious, therefore, that the Calcareous division of Northumberland, with its 

 dominant bands of marine limestone, are the equivalents of the Calcareous series which 

 in Liddisdale and Eskdale overlie the Lawston Linn and the Muir Bum coals. We may 

 reasonably proceed one step further and suggest that the massive marine limestones at 

 Lowick, Northumberland, including the Dryburn, Low Dean, Acre and Eelwell bands, 

 may be wholly or partly represented by the limestones of Penton Linns, Harelaw Hill 

 and Gilnockie in Liddisdale. But while there is doubtless a striking general resemblance 

 in lithological and palfeontological characters in the Lower Carboniferous rocks of these 

 two areas, pointing to similar terrestrial movements along the margin of the old 

 Silurian tableland, yet there are some specific distinctions worthy of note. It has been 

 shown that even below the Fell sandstones, in the upper part of the Cementstone group 

 in Liddisdale, marine limestones appear charged with crinoids, corals, brachiopods, gastero- 

 pods and other organisms which have not been found in the same group in Berwick- 

 shire nor in Northumberland — a fauna, indeed, which is characteristic of the 

 Carboniferous Limestone series. It further appears that the Scremerston coals, which 

 comprise several workable seams south of the Tweed, gradually diminish in number 

 and dwindle in importance when traced south-westwards into Dumfriesshire. The same 

 observation applies to the Lickar coals. 



Proceeding now to the consideration of the Carboniferous subdivisions in the 

 Lothians and Fife, we meet with certain marked divergencies from the types of 

 sedimentation in the border territory. Nevertheless it is possible to correlate the main 

 divisions. A glance at the vertical sections of the Carboniferous system in Edinburgh 

 and Fife shows how the sequence varies according to the special districts in which they 

 are taken. For our present purpose it will be sufficient if we indicate the general 

 characters of these divisions, and their equivalents in the border territory. 



In central Scotland the Lower Carboniferous rocks are grouped in two divisions : 

 (l) The Calciferous Sandstone series, overlain by (2) the Carboniferous Limestone series. 

 The former is subdivided into (a) the Cementstone group, consisting of green, gray and 

 red shales and clays, sandstones of various tints with pale argillaceous limestones or 

 cementstones, which, like their equivalents in Berwickshire and Dumfriesshire, are 

 singularly barren of organic remains, save on certain horizons; and (b) the oil shale 



* Mem, Ueol. Sur., " The Geology of Plashetts and Kielder," p. 36. 



