THE PERMIAN FORMATION. 07 



THE PERMIAN FORMATION IN THE NORTH-EAST 

 OF ENGLAND, 



WITH SPECIAL REFERENCE TO THE PHYSICAL CONDITIONS 

 UNDER WHICH THESE ROCKS WERE FORMED. 



BY E. WILSON, F.G.S. 



Our knowledge of the Permian rocks of the north-east of England 

 may be said to date from the publication of the now classical work of 

 the late Adam Sedgwick, on " The Geological Relations and Internal 

 Structure of the Magnesian Limeston ■." in the year 1829 (a. Since 

 that time many valuable memoirs have been written by Messrs. King, 

 Kirkby, Ramsay, Howse, Sorby, Ward, Green, Lucas, and others, on 

 the physical structure, geological classification, and palseontological 

 characteristics of this extremely interesting and important group of 

 rocks; so that, at the present day, comparatively little remains to be 

 learnt on these heads. When, however, geologists have come to 

 speculate as to the mode of formation of the magnesian limestone, a 

 considerable diversity of opinion is at once apparent among them. 

 Some authors, Prof. Ramsay and Dr. T. Sterry Hunt, for instance, 

 have suggested that these dolomitic limestones were chemically form 'd 

 originally, having been precipitated from concentrated solutions in 

 inland salt lakes, while others, of whom the most prominent is Dr. 

 Sorby, have come to the conclusion that the magnesian limestone 

 agrees with most other limestones in having had an organic origin, and 

 that the original structure has since been in great measure obliterated 

 by mineral infiltrations, and chemical decompositions and recrystallisa- 

 tions, or that, at any rate, it owes its origin partly (and largely) to 

 organic and partly to chemical processes. 



In the following essay my chief aim will be to put forward a feasible 

 hypothesis to account for the origination of the peculiar group of 

 deposits that constitute the Permian formation in the north-east of 

 England. In order, however, to supply the necessary basis of fact on 

 which I ground my theoretical conclusions, it will, in the first place, be 

 necessary to describe, in some detail, the mineral character and dis- 

 tribution, the thicknesses, and fossil contents of the various sub-divisions 

 of the Permian series in their range, through the counties of Durham. 

 Yorkshire, and Notts. 



For much of the information here given I am of necessity largely 

 indebted to the labours of others. At the same time I shall myself 

 contribute several new facts— the results of my work among these 

 rocks for many years past — that have a direct bearing. on the very 

 difficult problem of the mode of origin of these rocks. 



Geographical Distribution, etc. 

 The Permian rocks of the north-east of England, or rather the 

 narrow fringe of those rocks exposed at the surface along their western 



ta> Trans, of Geol. Soc, London. 2nd Ser., vol. iii., pt. 1., p. 37. 



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