Geological Society, 681 



a slioll-bank in the Middle Magiicsian-Limestono sea), aud their 

 sudden disappearance in tlio Up[)er Limestone. No corals, 

 cchinoderms, polyzoa, brachiopods, or cephalopods have ever 

 been found above the top of tlie Middle Fossiliferous division : 

 only a few fishes, gastroj)ods, lamellibrauchs, entomostraca, and 

 foraminifera occurring in the Upper beds. The Lower and Middle 

 Fossiliferous Limestones are marked by the ]>rcsencc of Productus 

 horridus Sow. Fish-remains occur at tw o horizons : namely, the 

 Marl Slate and the Flexible Limestone, aud the beds above these 

 deposits. 



The Brecciated Beds, which occur at various horizons, chiefly 

 however in the two Middle divisions, constitute the most marked 

 tectonic feature of the Magnesian Limestone of the area. They have 

 been produced by thrusting, which brought about a decrease in the 

 lateral extension of the Permian. Associated with the breccias 

 are other proofs of thrusting : (I) Thrust or shear-planes ; (2) (Jis- 

 turbod and displaced masses of Lower Limestone ; (3) intruded 

 breccias ; (4) slickensidod and grooved, horizontal and vertical 

 surfaces ; (5) cleavage ; (6) folding, both on a local and on a general 

 scale ; (7) buckling, tliickening, aud s(iueezing-out of beds ; (8) pha- 

 coidal and other structures ; and (9) Assuring. The main thrust 

 at ilarsden appears to have acted from a few degrees south of oast 

 to a few degrees north of west ; there are, however, distinct evi- 

 dences of movement from other directions in different parts of the 

 district. Experiments made on the compressive strength of the 

 rocks aficcted by the thrust at Marsden, indicate that the thrusting 

 reached a maximum of about 300 tons per square foot. Observations 

 made by Mr. S. 11. Haselhurst, M.Sc, in the Cullercoats area seem 

 to prove that the thrusting occurred later than the post-Permian 

 movement of the Ninety-Fathom Dyke — some faulting in the area 

 is, however, later than the thrusting — , and it appears evident that 

 the shattering of the strata was produced prior to the pre-Glacial 

 era of denudation. It may have been connected with the Miocene 

 movements that produced such marked changes in the physiography 

 of Britain. 



May 10th, 1911.— Prof. W. W, Watts, Sc.D., M.Sc, F.R.S., 

 President, in the Chair. 



The following communications were read : — 



1. ' The Lower Carboniferous Succession in the North-West of 

 England.' By Prof. E. J. Garwood, M.A., Sec.G.S. 



The area dealt with includes the whole of Westmorland north and 

 west of the Dent Fault, together with North Lancashire to the 

 north of the Lune Yalloy ;* and the extreme northern corner of 

 Yorkshire, to the west of Middleton-in-Teesdale, is also included. 



The following general succession has been established : — 



A7in. & Mag. N. Uist. Ser. 8. Vol. viii. 45 



