30. On some NEWLY EXPOSED SECTIONS of the "WOOLWICH AND READING BEDS" at READING, BERKS. By Prof. T. RUPERT JONES, F.R.S., F.G.S., and C. COOPER KING, Esq., R.M.A., F.G.S. (Read February 24, 1875.)

§ I. Introduction.-Coley Hill, in the south-western suburb of Reading, is composed of "Woolwich and Reading Beds," lying on Chalk. It is south of the similarly constituted Castle Hill, and divided from it by a small but deep valley, opening on the Kennet, which here runs from south to north at the eastern end of each of these little hills, and divides them from the high ground on which the Katesgrove Kiln is situated.

This last-mentioned locality was visited and described by Dr. Buckland in 1814 ("Catsgrove-Hill Brick-kilns," Trans. Geol. Soc. vol. v. p. 278), by Mr. Rolfe about 1833 (ibid. ser. 2, vol. v. p. 127), by Mr. Prestwich about 1852 (Quart. Journ. Geol. Soc. vol. x. p. 87), and in 1858 by the Geological Surveyors, who reported on it in 1861 and 1872 (Memoirs Geol. Survey, Explan. Sheet 13,' 1861, p. 29, and vol. iv. 1872, p. 188). At the same time they surveyed Castle and Coley Hills above mentioned (ibid. p. 39, and ib. p. 197). At none of these places in 1858 were exposures of the Lowest Reading Beds and the Chalk open to view.

*

Of late years, however, a greater local demand for lime has led to the excavation of Chalk at Coley Hill+; and since 1869 we have made repeated observations, as further sections of these Lowest Tertiary strata have been exposed at the pits on the north and south sides of the eastern end of the hill.

§ II. The Bottom Bed.-On the very even but perforated surface of the Chalk, noticed by Buckland, Rolfe, Prestwich, Whitaker, and others as occurring in Berks and Hertfordshire, the loamy and pebbly green sands§, constituting the "Bottom Bed" (Whitaker), were found to carry the usual abundance of Oyster-shells, with casts of

* 66 'David's Hill," Buckland, "St. David's Hill," Prestwich; opp. citt. We have been told that at the Castle-Kiln pit, now disused and partly built over, extensive underground excavations in the Chalk were formerly carried

on.

The north pit is worked by Mr. Collier, and the south pit by Mr. Wheeler. Some seams in this part of the formation consist of brown clay traversed vertically and obliquely by irregular subcylindrical lumps of green sand, as if a mud had been channelled by animals (lobster-holes for instance), or perforated by stems and masses of sea-weeds, and the cavities so produced subsequently filled up with sand.

other Bivalves, also many Sharks' teeth, not of large size, and one fragment of a palate of Myliobates (Wheeler's pit). Carbonized woody matter was also observed in small quantities. Besides the green-stained unworn Chalk-flints characterizing this deposit, pebbles also of flint occur, and many sharp fragments of flint, which have nothing but the glaze of their surface and their position in the series to indicate antiquity. Possibly they were split off on shore by frost in cold seasons of the period. One small pebble of siliceous schist, another of quartzite, and small angular pieces of Chalk were also met with.

At one spot in the northern pit of Coley Hill Oyster-shells were absent; at all events, in the small area (about 4 feet square) of the trial-pit, shown by the lower part of Section No. 3 (Pl.XXII., plan of the pit, figs. 3 & 4). In the adjacent large Chalk-pit (Section No. 4, fig. 4), 35 yards to the east, there was clear evidence of the Oyster-bed, and indeed of its forming two layers.

In Mr. Wheeler's pit (marked "Coley Kiln" on the Ordnance Map) on the southern side of the hill, about 120 yards distant, the Oysters abound at the same horizon, but are not distinctly in two layers.

The Ostrea are known to occur at Katesgrove, mile to the east, and at the railway-cutting,mile to the west, near the Bath Road; but they were not found by Mr. Whitaker at Castle Kiln, about 200 yards to the north (Mem. Geol. Survey, Explan. Sheet 13,' pp. 24 and 39).

We re

§ III. The Blue Clays in the Buff Sand.-As elsewhere, in neighbouring sections described by Prestwich and Whitaker, a blue shale occurs in Section No. 4, at about 12 feet above the Chalk. cognized it at Collier's, Wheeler's, and Poulton's (Katesgrove) Pits as a laminated, tough, silty clay, with frequent patches of decomposed vegetable matter, and with black (manganese?) infiltrations in its jointings.

In Section No. 4 a seam of lignitiferous bluish grey clay, 3 inches thick, traverses the yellow sand 3 feet 6 inches above the bluish shale above mentioned; and in Wheeler's pit, 118 yards distant, on the south side of the hill, there are three or more similar seams, curved, and varying in thickness and persistency, in a corresponding position among the false-bedded yellowish sands.

In Section No. 4 the lower band of shale has a full development of about 3 feet, with yellowish sand above and below; but at a distance of 35 yards to the W., and vertically above the spot where we noticed the absence of Oysters in the lowest beds, both this clay and the upper and thinner seam are wanting, yellow sands, 26 feet thick, intervening between the " Bottom Bed" and the Mottled Clay

*

* The leaf-bed, with which these blue shales correspond, has been found close by, on the north, at Castle Kiln (Whitaker, Geol. Surv. Mem.' vol. iv. p. 197), and half a mile to the west, at the railway-cutting near the Bath Road (Prestwich, Quart. Journ. Geol. Soc. vol. x. p. 88). It is also known to occur at Shaw Hill, near Newbury, 13 miles distant. Mr. Rickman found that some of the "Woolwich Beds near Dulwich abound with leaves (Mem. Geol. Surv. vol. iv. p. 131).

above. Nor was the blue clay noticed by Mr. Whitaker at the Castle Kiln above mentioned.

In the yellow sands of Sections Nos. 3 and 2 (Pl. XXII. fig. 4), however, on the same horizon as that of the plant-bearing clays in Section No. 4, some irregular thin seams of bluish tough clay with numerous scattered blue clay galls, at least one subangular green-coated flint, and some lines of broken lignite appear to take the place of the discontinued strata; and in another section (No. 1) 24 yards to the west of Section No. 2, and 69 yards W. of No. 4, there were still no indications of the missing clay-beds, except a thin seam of grey clay and clay-galls, with a pebble of black siliceous schist, or lydite, and some subangular grey Chalk-flints. This scam is similar in relative position and appearance to that in Section No. 2; but it is at a somewhat higher level, owing to its eastward dip of about 3°.

At Section No. 6, facing north, in a corner of the pit and 70 yards north of Section No. 1, some thin seams of clay and clay-galls come up in the sands (which are here lighter in colour) to within 5 feet of the surface, and, by their relative position and easterly dip, are evidently connected with the set of similar seams in Sections Nos. 1 and 2. In Section No. 6, however, the sands are disturbed by a fault, and some Mottled Clay is let down. The buff and grey sands come in again on the other side, Section No. 7, in fig. 4.

In Section No. 5 the Buff Sands lying below the Mottled Clay and on the grey shale have a local feature of considerable interest. Just where they happened to be attenuated by the slope of the valley, namely for the 25 yards between the disappearance of the Mottled Clay above and the exposure of the grey shale beneath, they contain numerous clay-galls of large size, some 18 inches in diameter. Some are mottled, and the majority are grey in colour; but many are ferruginous and hard from change, and somewhat septarian. Ferruginous nodules of a similar nature occur, in far less abundance, in the same sand (but greenish) in Wheeler's pit, on the south side of the hill*. In Collier's pit some of the galls above mentioned consist of grey sandy clay; others of tough, light-brown clay with some sand; and others of dense dark-brown clay. They often contain chalkflints, rolled and subangular, of various sizes, with flint, grit, and quartz sand. Some of the lowest of these nodules, nearest to the shale below, are much changed, consisting only of limonite crusts and ochreous cores. These nodules occur in large numbers in the excavations over the blue shale for at least 45 yards beyond the eastern margin of the pit; and one at least was found low down in the grey and buff sands of Section No. 6, on the same horizon, 100 yards distant to the west.

The false-bedded quartzose sands, in which both the above-mentioned regular shales and the derived clays and clay-galls occur, vary from white and grey to buff and ochreous in these sections, as elsewhere; and their surface has a slope of nearly 5° to the S.E. by E. (magnetic), almost reaching the top of the ground in Section No. 6,

* The ochreous nodules, yielding an excellent pigment, referred to by Mr. Rolfe, op. cit. p. 127, are probably the same as these.