424" DfiRWENTHAUGH LAND IN DERWENT GUT. 



5. Sand, average i-ft. 3-in., maximum 2-ft., and minimum 



6-in, 



6. Boulder Clay, average 13-ft., maximum 23-ft., and 



minimum 3-ft. 



It is important to notice the differences between these 

 maxima and minima. 



■ The roclv-bed is mostly in grey Carboniferous shale resting 

 on white " post," as sandstones are locally called. 



Carboniferous post forms the bed in holes 10 and 12, shale 

 in all the others. When the ancient undisturbed Carboni- 

 ferous strata are penetrated to any considerable distance there 

 is evidence of a much more venerable denudation than this 

 under consideration, in the presence in No. 2 hole of gravel 

 mixed with grey shale below the ordinary grey shale, and 

 over hard post and grey shale with post girdles. 



Immediately above this shale and post lies a bed of hard 

 boulder clay with an average thickness of 13-ft. In No. 12 

 hole an empty space of 6-in. was passed through, near the 

 middle of this boulder clay. This open space is significant, 

 as' it may indicate the existence of life forms even in that- 

 inclement period. ■ ■ . 



Above the boulder, clay rests generally brown clay with 

 saiid partings, mostly dry, but sometimes wet, and in No. 3 

 hole, with a. whinstone (basalt) boulder i-ft. thick. In 

 No. ID hole this brown clay rests on a 2-ft. bed of sand, 

 and in No. i hole on 6-in. of sand mixed with coal. This 

 clay deposit has the -great average thickness of 65-ft. 6-in., 

 and seems identical with the Teme Valley or Birtley clay*. 

 Geologists appreciate the presence of the whinstone boulder 

 more than the sinker did. 



The absence of this betl of sand in 10 out of the 12 holes 

 is very significant, for it clearly indicates a very considerable 



* The brown clay appears in holes Nos. 10 and 11 not only below but also above 

 the gravel and sand. This may mean that the quiet conditions were intcmiptcd 

 towards the close of that period and again resumed, or it may be that the gravel and 

 sand of these. t\yo holes i^ on a different horizon to the gravel and sand of all the 

 other holes. In either case considerable denudation is indicated, a^id the evidence 

 1)ccomes valuable. 



