GEOLOGY 



p. 2) — representing a period of time during which deposits of the aggre- 

 gate thickness of some 20,000 feet were formed in other localities — and 

 it be asked what was happening here, the answer is clearly this, that 

 the denudation which did not finish till late in Triassic times com- 

 menced a great deal later than the Lower Carboniferous period, or there 

 could otherwise have been none of the Carboniferous Limestone left. 

 In other words, there must have been a very considerable thickness of 

 rocks for denuding agents to act upon, over the Carboniferous Limestone 

 now found, and these may well have included the Coal Measures. 



The Permian and Trias. The Mountainous Period 



A termination to the long Carboniferous period appears to have 

 been brought about by extensive earth movements in the part of the 

 world embracing what is now England, by which great arches (anticlinal 

 axes) and corresponding troughs (synclinal axes) were formed, having 

 directions approximating more nearly to east and west than to the other 

 cardinal points. In the troughs the Permian rocks were deposited, and 

 any Coal Measures below preserved for the time being, whilst the ridges 

 were exposed to denudation, and the coal originally on them swept away. 



At the close of the Permian period a new series of earth movements 

 resulted in the formation of other ridges along approximately north and 

 south lines.* It was this later series which completed the Pennine chain, 

 the great central ridge of the north of England. The two sets of inter- 

 secting ridges divided the coal formations into groups of depressions, 

 commonly called basins, and in the partially land-locked hollows so 

 produced the Trias beds were deposited, whilst the newly-formed ridges 

 were being denuded of both Permian and Coal Measures. 



Northamptonshire shared in one or both of these earth movements, 

 and throughout the greater part of the Trias, if not also the Permian 

 period, was largely a land surface, subject to denudation, and during the 

 later stages at least, as the Carboniferous Limestone and other older rocks 

 got exposed, acquired an appearance comparable to that of the moun- 

 tainous parts of Derbyshire now. Still, it may be pointed out, the problem 

 of finding coal in Northamptonshire remains unsolved. 



The conclusion of the Paleozoic period in geological history, and 

 the slightly later closing of the long land period over Northamptonshire, 

 left then a very uneven surface, mostly of limestone, as a foundation upon 

 which the main mass of the well known stratified rocks of the county were 

 afterwards piled almost uninterruptedly through some millions of years. 



THE BUILDING UP OF NORTHAMPTONSHIRE 



To appreciate properly the character and proportions of the Jurassic 

 architecture of Northamptonshire, it is necessary to take a glance at 

 conditions over a larger area. We have spoken of earth movements 

 resulting in folds of the rocks ; these were merely wrinkles in a vast 



' Edw. Hull, Tht Coal Fields of Great Britain. 

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