1897.] NEW YORK ACADEMY OF SCIENCES. 2-39 



Should this ever be the case and the Middle Coal Measures be 

 reached, another 80 feet of coal, spread over nearly 4 square 

 miles, will be added to the coal resources of Lancashire. 



Post Carboniferous Changes. 



The causes which have operated in altering the character of 

 the Lancashire Coal Measures since their deposition are of three 

 kinds, viz : flexures or folding, denudation and faulting. 



Formation of Synclines and Anticlines. 



\. Careful mapping has shown that the whole of the Carbon 

 iferous system of Lancashire has been thrown into a number of 

 anticlines and synclines along a line running west of north and 

 east of south, the axes of the folds being north of east and 

 south of west. This folding caused the separation of the Burn- 

 ley coal field from that of south Lancashire, the crest of the in- 

 tervening arch, "the Rossendale Anticlinal,'" being afterwards 

 denuded down to the Millstone Grit Series. The former field 

 owes its preservation to the formation at this time of the Pendle 

 Hill Range, in which the lower beds are brought up again to the 

 north of the coal field in a line parallel to the Rossendale anti- 

 clinal. 



The approximate age of this S3'stem of folds is indicated by 

 the occurrence of Permian deposits in the Pendle range, lying 

 upon the upturned and denuded edges of the Coal Measures and 

 even overlapping on to the Millstone Grit.* 



This evidence shows that the development was post-Carbon- 

 iferous and Pre-Permian, and that denudation of the Coal Meas- 

 ures preceded the deposition of the Permian. 



2. The high ground on the east of the Lancashire coal field 

 in which the Millstone Grit Series outcrop owes its origin to a 

 simple fold formed subsequent to those we have considered, and 

 developed along a north and south line. The folds, as a whole, 

 gave origin to the Pennine chain of hills now forming the main 

 axis of elevation in the north of England. 



This huge fold cuts off the Lancashire coal field on the west 

 from that of Yorkshire on the east. That the two were formerly 

 continuous is abundantly proved by the close correlation which 

 can be established between them, and the regularity of succes- 

 sion upon each side of the axis of upheaval. 



The age of this north and south flexure is not by any means 

 clearly determinable. That it was formed before the deposition 



* Hull, " Observations on the Relative Ages of the Leading Physical Features and 

 Lines of Elevation of the Carboniferous District of Lancashire and Yorkshire. Quart- 

 erly Journal Geol. Soc, vol. 24. 1868. 



