Vol. 70.] LITHOLOGY OF DURHAM MAGNESIAS' LIMESTONES. 263 



C3 



O 



Lower Limestones. 

 Dolomitic. 



Yellow, friable, bedded, 



powdery 



Nodular portion in the above 

 Yellow, bedded, rather soft . . 

 White, bedded, compact 



Hard, grey, compact, bedded... 



Thinly-bedded, with plant- 

 remains 



Yellow, hard, bedded, porous... 



Brown, friable, well-bedded ... 



Soft, friable, oolitic 



Dark, bedded, compact, with 

 plants 



Lower Limestones. 

 Calcareous. 



Grey, compact, fossiliferous ... 67 

 Shell of Productus in the above 68 

 Grey, nodular, compact, fossi- 

 liferous I 70 



62 

 63 

 64 

 65 



66 



69 

 71 



72 

 73 



74 



Marl Slates. 



Dark, flaggy, hard 



Dark, soft, bituminous, with 

 fish-remains 



75 



76 



0*21 

 0-18 

 0-15 

 0-12 



4-15 

 2-00 

 0-69 

 0-23 



3'48 



0-63 

 nil 



1-68 



12-48 

 41-18 



O 



1-05 

 1-80 

 1-70 

 1-50 



1-01 1 4*52 



5'19 



5-19 



0-93 



13-39 



4-91 



94-17 

 97-02 



95-27 



10-19 

 1-65 



£ 

 o 



C 



'■" s b « 

 £ s E ts 



<5 



99-17 



98-68 

 98-09 

 98-97 



9277 



88-56 

 92-04 

 98-91 

 86-31 



90-92 



3-26 



2-48 



3-20 



0-08 

 003 



{ 



0-14 1 



0-15 

 tr. 



0-08 

 tr. 



tr. 



70-67 0-46 

 39-12 1-83 





Locality 



" 



> 



0-42 





0-13 





059 



r 



0-22 





FeO 





2-22 J 



1-93 

 1-23 



0-48 

 0-31 



Blackball Colliery 

 Sinking. 



Thick ley Quarry. 

 Sherbum Hill. 

 Piercebridge. 

 High Conisclifle. 



0-63 Middridse. 



. 30 I Thickly Quarry. 

 0'37 Garmundsway. 



°' 67 J Blackball Colliery 

 0-56 I) Sinking. 



In the third column S.C. and S.D. indicate the calcareous and powdery dolomitic portions of 

 segregated rocks. When not otherwise stated, the rock has suffered no greater visible alteration 

 than the leaching-out of soluble sulphates, and the more or less complete oxidation of ferrous com- 

 pounds common to all the Magnesian Limestones that are unprotected by a covering of anhydrite 

 or of Bed Beds. 



EXPLANATION OF PLATES XXX VT AND XXXVII. 



[All the sections, except PL XXXVI, fig. 4, have been treated with Lemberg's 

 solution. The staining is not easily distinguishable in the photographs, on 

 account of darkening due to carbonaceous impurities.] 



Plate XXXVI. 



Fig. 1. Gypsum and dolomite. Warren Cement- Works Boring, Hartlepool. 

 Analysis No. L. The gypsum is of secondary origin through 

 hydration of anhydrite, and the dolomite, otherwise occurring as 

 allotriomorphic aggregates, develops rhombic outlines where pro- 

 jecting into or lying in the gypsum. X 25. (See p. 243.) 

 2. Shell-Limestone. Claxheugh, near Sunderland. A bryozoonal and 

 crinoidal reef-deposit. The organisms are almost completely dolomi- 

 tized, and exhibit a cryptocrystalline structure. The circular object 

 is a crinoid ossicle X 5. (See p. 242.) 



Q. J. G. S. No. 278. t 



