169 



NOTES AND COMMENTS. 



UNCOXFORMITY IN THE NORTHUMBERLAND COAL- 

 MEASURES. 



At a recent meeting" of the London Geological Society, Prof. 

 Lebour and Dr. J. A. Smyth described an interesting case of 

 Unconformity and Thrust in the Coal-measures of Northumber- 

 land. The sections described occur on the coast north of the 

 Tyne, near Whitley sands. The base of the ' Table-Rocks 

 Sandstone ' is found to rest unconformably upon a series of 

 alternating shales and sandstones, among which is a well- 

 marked band of clay-ironstone crowded with Carbonicola anitn, 

 one of those ' mussel-beds ' which are found to be perhaps the 

 most remarkably-persistent strata in the North-of-England Car- 

 boniferous rocks. The entire junction, so far as it can be seen 

 at the base of the cliffs and on the foreshore, many parts of 

 which are only swept clear during exceptional weather, has 

 been studied as opportunity offered during a series of years. 

 The unconformity is shown by discordance in dip, by overlap of 

 the Table-Rocks Sandstone, and by the existence of a pebble- 

 bed, containing fragments of the mussel-band and other parts 

 of the underlying series, in the lower part of this sandstone. 

 But the upper, more massive, beds in the section have been 

 thrust in a northerly direction over the lower and more yielding 

 beds, the plane of g-liding corresponding accurately along parts 

 of the section with the plane of erosion. Towards the north of 

 the section the beds of the upper series are weakened by 

 intercalated bands of shale, and then differential action has been 

 set up. The result is that the thrust-plane is no long-er a 

 simple one coinciding- with the unconformity, but extends some 

 way above it. The effects of the thrust are seen in the 

 ploughing-up, folding, and faulting of the lower series, in the 

 penetration of tongues of sandstone from the upper series into 

 the lower, in the curling-up and shattering of the pebble-bed, in 

 the puckering and hardening of the shale, and in the blending- 

 of fragments of the various rocks subjected to its influence 



GEOLOGICAL SURVEY MAPS OF EAST YORKSHIRE. 

 The geologists of Yorkshire, and those who visit the county 

 to study its splendid development of Jurassic and Cretaceous 

 rocks will rejoice to learn that a new edition of the official maps 

 is being undertaken, and the more so as it has been decided to 

 produce them by colour-printing. The advantages of this 

 method are many ; not only will the price be reduced from 3s. a 



1906 June I. 



M 



