Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/536

 At a distance of three-quarters of a mile due W. of Hopping Hill, at u, is the very ancient and large " Old " Duston stone-pit, which presents a characteristic section of some 40 feet elevation.

At the top of the section, at the eastern extremity of the pit, is the white sand C, reaching a thickness in some places of 4 feet : this thins away, and is absent in the southern portion of the same section. At the base of this sand is the plant-bed, with vertical perforations, in what is here a slightly ferruginous and very friable sandstone. Beneath this are some 12 feet of the variable beds D, overlying 4 feet of coarse limestone and slaty beds ; and below, from 18 to 20 feet of the lower beds, E, of the Northampton Sand.

The following are the details of the section as recently exposed : —

Section of Old Duston Stone-pit, giving Quarrymen's Terms.

ft. in. ft. in.

1. White sand nil to 4 0

2. Brown soft sandstone, with vertical plant-markings (" root-perforations"?) nil to 1 6

3. " The Roylands " — a series of beds, each from 6 to 9 inches in thickness, very variable, sometimes hard, in which condition it is " best " building- stone, and sometimes " caly " or crumbling. These beds occur in two divisions, the building-stone of the upper being of a rich red-brown colour, and of the latter of a colder fawny-brown colour. Wood is frequently found, and I obtained from these beds a slab ripple-marked ; sandy zones also occur, in which the tests of shells are perfectly preserved 9 0 to 10 0

4. Orange sand, with rounded cores of arenaceous limestone, the remains probably of the original bed after being subjected to the action of water charged with carbonic acid 1 6 to 2 0

5. " White Pendle " — in two beds : —

a. Coarsely granulated limestone, made up sometimes of oolitic grains in a matrix of calcareous cement, sometimes of crystalline angular particles with comminuted shells, more or less arenaceous in places, and containing Belemnites, large Lima nov. sp., large Hinnites abjectus, &c 2 0 to 3 0

b. Arenaceous and calcareous slaty beds, very like to, and called by the pitmen, " Colleyweston slate " 2 0 to 3 0

6. " The Yellow " building-stone — consisting of six or seven beds of varying thickness, in two divisions, differing somewhat in tone of colour ; these beds contain " pot-lids " of ironstone, also Cardium cognatum &c 6 0 to 7 0

7. "Best Brown Hard" building-stone, in three or four beds — a coarser, stronger stone than that of the other beds, but of a rich red- brown colour : it contains few fossils 6 0

8. " Rough Rag " — a slightly calcareous sandstone, green-hearted, hard and durable, used for copings, gravestones, and building : it contains Ammonites Murchisonoe, A. opalinus, Nautilus, Ceromya bajociana, Pholadomya fidicula, Cardium cognatum, Caculloea, &c, and a characteristic zone of Astarte elegans 3 0

9. " Hard Blue " — a very hard blue-hearted stone, the surfaces of joints and bedding brown from oxidation : it contains the same fossils as the last bed, no. 8, excepting Ammonites Murchisonoe and the Astarte-elegans zone 3 0 to 4 0

10. The presence of water prevents the working of the stone in this pit to a lower depth ; but in an old unused pit in an adjoining field the beds for about three feet lower are exposed ; and these consist of cellular ironstone, having sometimes green arenaceous, and sometimes ochreous cores 3 0