A HISTORY OF NORTHAMPTONSHIRE 



an extensive coral reef, which rises above the general surface of the 

 deposits now constituting the ironstone beds under part of North- 

 ampton. 



The Lower Estuarine Beds consist, usually, of white or light 

 purplish sands, with some argillaceous matter, but the latter may 

 preponderate. A striking characteristic of these beds is the almost 

 universal presence in them of vertical black streaks or even carbonized 

 stems of plants of contemporaneous growth. Two distinct periods of 

 plant growth may be traced over many square miles,' and at places 

 [e.g. Corby), horizontally bedded carbonaceous matter may be detected 

 between the plant beds, indicating contemporaneous denudation in the 

 neighbourhood. 



The sand as such is used for various purposes ; where more 

 indurated as a building stone (at Kingsthorpe for example), though very 

 little at the present day ; the clay beds for brickmaking (Dene and else- 

 where), and terra-cotta* manufacture (Stamford). 



Notwithstanding the often very distinctive characters of these beds, 

 it is impossible to regard them otherwise than as the upper part of one 

 series, the Northampton Sand. 



The Northampton Sand then embraces the three sets of beds just 

 described, and these may quickly pass from one into the other. For in- 

 stance, at Duston, two miles west of Northampton, the ironstone beds are 

 fully 30 feet thick ; at Berry Wood, three-quarters of a mile to the north- 

 west, in the entire thickness of 68 feet of Northampton Sand there is 

 no true ironstone, but only ferruginous rock ; in another three-quarters 

 of a mile in the same direction the whole exposure, some 30 feet, is 

 white, or only slightly ruddy sand ; at New Duston, one and a half miles 

 nearly north of the ironstone workings, under about 4 feet of white 

 sand, are 42 feet of either ruddy building stone, or calcareous rock 

 and slaty beds, with fossiliferous limestones near the base. In a southerly 

 direction the white sands rest directly upon Upper Lias Clay (Grafton 

 Regis and Paulerspury) ; and in a south-easterly direction the series 

 apparently dies out very rapidly and is not to be detected at and beyond 

 Preston Deanery, which latter place is only four and a half miles from 

 Duston. On passing the Ise brook in a north-easterly direction the 

 Northampton Sand maintains a much more equable facies over a con- 

 siderable area. 



The Estuarine origin of the deposits may be pretty confidently 

 affirmed, judging by their rapid variations in character, both vertically 

 and horizontally ; beds with corals and other marine fossils alternate with 



' Beeby Thompson, 'The Oolitic Rocks at Stowe-Nine-Churches,' Journ. North. Nat. 

 Hist. Soc, No. 48, vol. vi. p. 295 ; 'Excursion to Weldon, Dene, and Gretton,' Proc. Geo/. 

 Assoc, vol. xvi. p. 226 (Nov. 1899). 



* John W. Judd, ' The Geology of Rutland,' etc., Memoirs of the Geological Survey, 

 pp. 103, 104. 



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