Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/531

1870.] SHARP NORTHAMPTONSHIRE OOLITES. 365 Fig. 3. — Section of double Fault in Northampton.

ft.

a. Surface-soil 1

b. Limestone in thin broken layers, sometimes full of shells, chiefly Ostrea, and crystalline from the presence of carbonate of lime, having an irregular incline to the S.E. ; at the bottom a softer zone, containing Ostrea Sowerbyi and large Rhynchonella concinna 3

c. Soft cream-coloured sand and clay-bed, full of Ostrea Sowerbyi 2

d. Blue clay, with ferruginous band (e) 2 to 3 B

f. White and grey sand with an admixture of clay, stratified, and ferruginous in places up to 8 C

The presence here of the lower zone of limestone with Rhynchonella concinna and Ostrea Sowerbyi, and the blue clay with a well-marked ferruginous band at base, irregularly overlying the white and grey sand, completely identify this section with that at Kingsthorpe, notwithstanding that the blue clay (B) has thinned down from 14 feet to 3 feet.

About half a mile to the N.E. of this section, on the Kettering road, and close to the stand of the race-course, is a large pit (k), quarried for clay, sand, and building-stone. At the top of this section appears a cream-coloured clay, which I think may possibly be of Drift origin, and composed of the material of the denuded limestone. I am induced to suggest this by the fact of the very irregular surface (attributable to erosion) of the Blue Clay beneath (B) ; which varies in thickness from 1 to 3 feet, and appears somewhat disturbed in places. The ferruginous band, which elsewhere characteristically bases this clay, is observable also in this section.

The Sand (C) is here of the full thickness of 12 feet. It is much stratified and variegated in places, and upon the whole it is more ferruginous than I have found it in other sections. Some beds are hardened nearly into stone. The plant-bed occurs several feet above the bottom of the sand.

Beneath this sand, separated by a well-defined line, is a ferruginous sandstone, about 12 feet in thickness, disposed in five beds, the lower one of which is more ferruginous than those above it. These are upper beds of the series D ; and, as in the case of the ferruginous sandstone basing the section of the sand-pit (f) at Kingsthorpe, they yield no fossils. I obtained, however, from this pit a ripple-marked slab of the ferruginous sandstone, upon the upper face of which is a film of the white sand. Evidently it is a fragment of the surface-material of the upper bed of this sandstone, and indicates a littoral or an estuarine condition of the area at the period represented by this junction.

About a quarter of a mile N. of this point is Mr. Bass's pit (l). The lower part of the last is represented, I think, in the upper beds of this section. The pit is excavated quite through the ferruginous beds, down to the Upper Lias.