GEOLOGY OF PART OF SOUTH DURHAM. 



161 



Fig. 3. 



In the George Pit, Etherley, irregular beds and patches of 

 sandstone occasionally appear in the Brockwell coal, where the 

 roof is formed of that rock. Sometimes one or more thin beds 

 of sandstone (often mixed with carbonaceous matter) come into 

 the seam for a few yards, accompanied probably with many sand- 

 stone roots of Stigmaria. At other times thick masses of the 

 same rock descend from the roof for two or three feet, fig. 3 re- 

 presenting one of them as seen in section. 



These latter cases appear as if the sandstone was interstra- 

 tified with the coal and hence contemporaneous ; while in the 

 former instance (fig. 2) the sandstone has evidently not been 

 put down until after the deposition of the coal and overlying 

 shale, as well as subsequent to their denudation. 



A little to the north of Brussleton Folly there is a sandstone 

 showing some peculiarities, which may be here noticed. The 

 sandstone, which is well exposed in a quarry, is massively bed- 

 ded, brown or yellowish, and coarse grained. It dips sharply 

 to the N.N.E., and is seen for nearly fifty feet in depth. A few 

 hundred yards to the east of the quarry what is apparently the 

 same sandstone is seen dipping in a similar direction at an angle 

 of 45°, evidently indicating the contiguity of a downthrow fault 

 to the south. 



The shaft of an abandoned pit is seen not far off, in which the 

 Brockwell coal is said to have been worked many years ago. 



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