184 MR. C. T. TRECHMANN ON A MASS OF ANHYDRITE [June I913, 



11. On a Mass of Anhydrite in ilie Magnesian Limestone at 

 Hartlepool, and on the Permian of South-Eastern Durham. 

 By Charles Taylor Trechmann, B.Sc. (Communicated by 

 Prof. E. J. Garwood, M.A., V.P.G.S. Bead January 8th, 



1913.) 



[Plate XXII— Map.] 



Contents. 



Page 



I. Introduction 184 



II. The Mass of Anhydrite in the Magnesian Limestone at Hartlepool. 185 



III. Borings in the Magnesian Limestone where it is protected by Bed 



Beds 193 



IV. The .Former Presence of Soluble Constituents in the Magnesian 



Limestone 195 



V. Nature of the Shell-Limestone and the Associated Strata 199 



VI. Typical Sections and Exposures in the Hartlepool Area 203 



(1) Hartlepool Foreshore. (5) Castle-Eden Dene. 



(2) West Hartlepool. (6) Hardwick Dene. 



(3) Blackball Bocks and (7) Hart Quarries. 



the coast-section to (8) Blackhall-Colliery Sinking 



the north and south. (1909-13). 



(4) Hesleden Dene. 



VII. Notes on the Palaeontology of the Hartlepool Area 214 



VIII. Summary of Conclusions 217 



I. Introduction. 



The exposures of Magnesian Limestone in the area under dis- 

 cussion in the present communication are indicated on the 1-inch 

 Geological Survey [Drift] Map, Sheet 103 N.E. (New Series, 

 Sheet 27), with the exception of the fine continuous sections of 

 Castle-Eden, Hardwick, and Hesleden Denes : these are only 

 indicated in part, and seem to have been overlooked b}' the sur- 

 veyors. JSTo attempt is made to distinguish the divisions of the 

 Magnesian Limestone. Otherwise I know of no paper dealing 

 with the district as a whole, though scattered references to the 

 exposures of the coast-section and Castle-Eden Dene occur in 

 various publications. 



The isolated outcrops of Upper Magnesian Limestone with their 

 associated anhydrite-mass, on which the two towns of Hartlepool 

 and West Hartlepool are built, are bounded on the west and north- 

 west by a valley filled with Glacial and superficial debris, probably 

 connected with the watershed of the pre-Glacial Tees Valley. The 

 nearest outcrops of Magnesian Limestone occur nearly 2 miles 

 away to the west, and nearly 3 miles away to the north-west along 

 the coast. 



The area is bounded on the south-east by the fault, everywhere 

 hidden and therefore largely problematical, which brings the Red 

 Beds down against the Magnesian Limestone, and is marked on the 



