Vol. 69.] IN THE MAGNESIAX LIMESTONE AT HARTLEPOOL. 



213 



(8) Blackhall-Colliery Sinking (1909-13). 



This sinking has been of great help in elucidating the structure 

 of the district, and shows that the normal Permian succession 

 exists beneath the Upper and the Upper Middle beds exposed 

 at the surface. 



It is situated almost midway between the typical exposures of 

 Upper Shell-Limestone of Blackball Eocks and Castle-Eden Dene, 

 and is probably the only sinking that pierces the whole thickness 

 of the Shell- Limestone, though it is situated not on the centre, but 

 near the eastern slope of the reef. 



Two shafts were sunk, the northern and the southern shaft, 

 165 feet apart. A drift to carry off the water was sunk between 

 these and the sea, 210 feet east of the shafts, to a depth of 246 feet. 



The following section is drawn up, both from data which I 

 obtained myself, and from examination of rock-samples taken from 

 authenticated levels, in the possession of the Horden Collieries 

 Company, Ltd. It represents the section in the southern shaft. 

 The thicknesses given for the Upper Limestones are not absolutely 

 certain. The total thickness of the Permian strata is 688 feet, and. 

 the depth of the base of the sand-bed from the surface is 756 feet. 



Highest 

 Limestone 



CoNCKETIONARY 



Limestones. 



Uppek 



Shell- 

 Limestone. 



Main 

 Shell- 

 Limestone. 



Lowek 



Limestones. 



Makl- 



Slate. 



Yellow 

 Sands. 



Thi 

 in 



Boulder Clay 



Broken limestone, similar to a ~\ 

 bed exposed in the railway- ' 

 cutting near by. It has a roe- C 



stone in part J 



Limestones with well-developed ~) 

 concretionary structure \ 



ckness 



feet. Fauna. 



63 



19 No fossils seen. 



(?) 



No fossils seen. 



Shell - Limestones 

 character 



of 



variable 



I 



3 



Typical Shell-Limestones )- 



I 



Yellow, bedded, friable limestones. °\ 



155 j Highly fossiliferous, but 

 (. with a restricted fauna. 



fProfusely fossiliferous. 



180 -^ 



Fully developed fauna. 

 Masses of bryozoa at 



(^ several levels. 



Fragments of bryozoa and 

 drifted plant-remains. 



Brown friable limestone. 



White friable nodular limestone. 



Hard brown and white bedded J> 240 No fossils seen. 

 limestones. 



Very hard, brown, banded lime- 

 stones, with carbonaceous part- 

 ings 7 J 



Compact dark-grey and 

 shales .., 



black ^ 



3 



' Paltsoniscits, Plati/som 

 j *Pj/gopterus, etc. wi 



f Fa I a 01 

 J coprc 



Sand-bed, very compact in parts, ~) 

 resembling a dark-gre}' sand- I 

 stone-conglomerate. Enclosing f 

 pyrite in cracks and veins J 



coprolitic matter. AIso- 

 L 1 (f)Fosidonomya. 



26 No fossils 



