GEOLOGY 



It may be seen from this table that Northamptonshire is built up 

 chiefly of Jurassic rocks (Lias and Oolite), upon a foundation of Upper 

 Palaeozoic ones. It is partially and irregularly roofed over by Quater- 

 nary deposits. The sculpturing of the county into hills and valleys as 

 we now see it, was begun before, continued with interruptions during, 

 and completed after the Pleistocene period. 



THE FOUNDATIONS OF NORTHAMPTONSHIRE 



The Mesozoic rocks of Northamptonshire rest upon an old, irregular 

 land surface of Palaeozoic or older rocks, which may be regarded as the 

 foundation of the county. This Old Land Surface has been found, and 

 the rocks composing it penetrated to a small depth, at a few places in 

 the county, by deep borings, and we propose in this section to give a 

 summary of the interesting information thus obtained. 



Archaean. The Volcanic Period 



The oldest rocks known in Britain have been named ' Archaean,' 

 and, since the existence of life on the earth at the time of their formation 

 has not been satisfactorily demonstrated, the term ' Azoic ' has been 

 applied to the era of their formation. 



During late Archsean times Orton in Northamptonshire was the 

 site of a volcano, possibly one of a string of volcanoes extending from 

 Charnwood Forest in Leicestershire, in a south-easterly direction, as far 

 as Cambridgeshire. The Orton volcano poured forth a lava rich in 

 silica, which, could it have been seen in a less altered condition than 

 that in which it is now found, would probably have been called a 

 ' dacite.' As the lava gradually cooled it became devitrified, losing its 

 glassy nature by the development of crystals, and then, or afterwards, 

 was crushed, and took on the form it now has, to which the names 

 quartz-felsite or (perhaps more suitably) quartz-porphyry have been 

 given. 



The above remarks embody opinions that have been expressed by 

 Prof. T. G. Bonney and others in various papers, and have been arrived 

 at from a comparison of some volcanic rocks found in a deep boring at 

 Orton with the volcanic rocks of Charnwood Forest in Leicestershire, 

 some 25 miles to the north-north-west, and of High Sharpley in particu- 

 lar, and also of both with the old volcanic rocks of the Wrekin and 

 Wales.^ 



The Orton boring was a trial one for coal, made in Harrington 

 Dale, in 1883-84, by Mr. J. Fleming of Newcastle, and although un- 



* Henry John Eunson, 'The Range of the Palaeozoic Rocks beneath Northampton,' 

 Quart.Journ. Geol. Saf. (Aug. 1884), vol. xl. p. 492 ; 'Deep Boring at Orton, near Kettering, 

 Northamptonshire,' Journ. North. Nat. Hist. Soc, vol. iv. pp. S7-68 ; Hill and Bonney, 'The 

 Pre-carboniferous Rocks of Charnwood Forest,' Quart. 'Journ. Geol. Soc, vol. xxxvi. p. 342 ; 

 T. G. Bonney, ' On the Archaean Rocks of Great Britain,' Report of the Brit. Aisoc, 

 Montreal (1884), p. 537 ; 'Presidential Address to the Geological Society,' Quart. "Journ. Geol, 

 Soc, vol. xli., pt. 2, p. 48. 



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