Northampton Sand Formation
The Northampton Sand Formation, sometimes called the Northamptonshire Sand, is a Middle Jurassic geological formation which is placed within the Inferior Oolite Group. It was formerly worked extensively in Northamptonshire for its ironstone.
The Northampton Sand Formation constitutes the lowest part of the Inferior Oolite Group and lies on the upper Lias clay. It attains a maximum thickness of up to to the north and west of Northampton where it lies in a subterranean basin. In the south, it fades out around Towcester. Northward from the edge of the basin in the upper Lias, under Northampton, it lies progressively lower beneath the Jurassic Lincolnshire limestones. A little to the north of Corby Glen it is at about from the surface. It fades out under north Lincolnshire as the strata rise towards the Market Weighton Axis.
Fossils found in it indicate that it dates from the early Bajocian and formed in an extensive, shallow sea on the northwestern margin of the London-Brabant Massif. Dinosaur remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus.There is a description of the twentieth century exploitation of the Northampton Sand for iron-smelting in the Wellingborough article.
