28. On the FOSSILIFEROUS SILURIAN ROCKS of the SOUTHERN HALF of the TORTWORTH INLIER. BY FREDERICK RICHARD COWPER REED, M.A., F.G.S., and Prof. SIDNEY HUGH REYNOLDS, M.A., F.G.S. (Read June 3rd, 1908.)

(b) The Avening-Green, Damery, Ironmill-Wood, and Tort

IV. Mutual Relations of the Rocks, and Earth-Movements affecting them

V. General Remarks on the Fossils

VI. Summary and Conclusions VII. Lists of Fossils

I. INTRODUCTION.

534

535

535

537

538

IN the Quarterly Journal of the Geological Society for 1901 (vol. lvii, pp. 267-84 & pls. x-xi) is a paper by one of us, in collaboration with Prof. C. Lloyd Morgan, dealing with the igneous rocks and the associated sedimentary deposits of the Tortworth Inlier. The present communication may be regarded as, to some extent, supplementary to the above. Full references to the earlier work on the district having been given in the paper just mentioned, they will not be repeated here.

The field-work has been carried out by one of us (S. H. R.); the identification of the fossils, involving the re-examination of the various public and private collections, by the other (F. R. C. R.).

The expense of the work, which has involved the digging of a number of trenches and the opening-up of a series of old quarries, has been lightened latterly by means of a grant from the British Association for the Advancement of Science. We are much indebted to the landlords, the Earl of Ducie, Earl Fitzhardinge, and Sir George Jenkinson, Bart., for their kindness in facilitating these excavations. We desire also to thank Mr. J. Harle, Lord Ducie's agent, and Mr. J. Peter, Lord Fitzhardinge's agent, for help and information.

II. DESCRIPTION OF THE EXPOSURES.

(1) The Llandovery Beds.

The Llandovery rocks crop out along an area generally from 1 to 2 miles wide, which follows the general trend of the Carboniferous Limestone rim of the Bristol Coalfield, and stretches in a north-westerly direction from Charfield Green to the neighbourhood of Woodford and Middlemill, and then, after an interval occupied

Fig. 1.—Geological map of the Tortworth Inlier and the immediate neighbourhood.

by Wenlock rocks, from Falfield to a point in Eastwood Park
south-east of the House. The continuity of the outcrop to the
north of Charfield Green is broken for a space by the overlap of
the Trias, and the exposures in the south-western part of the area
are exceptionally poor and scanty. The best exposures occur in

the northern and eastern portions; and it is only in them that the contemporaneous igneous rocks, which add a special interest to the Tortworth Llandovery series, are met with.

For purposes of description, the regions where Llandovery rocks are found may be classified as follows;—

(a) The Charfield-Green Area.

(b) The Avening-Green, Damery, Ironmill-Wood, and Tortworth Areas. (c) The Daniel's-Wood Area.

(d) The Middlemill and Woodford Areas.

(e) The Eastwood-Park Area.

(a) The Charfield-Green Area.

This patch of Silurian rocks, which has a maximum length of about a mile and a width of about half a mile, is surrounded on all sides by Keuper. In the Geological-Survey map it is shown as consisting (apart from the two trap-bands) entirely of Llandovery rocks, but the north-western part really consists of Wenlock strata.

In the paper already mentioned, the exposures immediately associated with the trap are described. The following additional exposures of Llandovery rocks may be enumerated :—

(1) By a little pond, a short distance north-west of Pool Farm.
(2) An old, greatly overgrown quarry, 150 yards east-north-east of Charfield
Station. Inspection of Buckland & Conybeare's map shows this to
be probably Long's Quarry, from which certain fossils in the Jermyn-
Street collection were obtained. Weaver mentions the occurrence of
strontium-sulphate in Long's Quarry.
(3) In the bed of the small stream which, flowing in a north-easterly
direction, joins the Little Avon near Ebury Hill. The lower trap-
band is well exposed, both in the stream and in the field to the south,
and overlying the trap is red micaceous sandstone.

The above-mentioned exposures are all east of the Midland Railway. West of the line, Llandovery sandstone dipping from 30° to 35° west-south-westwards occurs in the bed of a little stream, about midway between Vine Cottage and Hillhouse Farm; and a short distance farther north, at Fowler's-Court Farm, there is a considerable exposure of Llandovery rocks dipping at 10° W. 15° S.

At all these localities the Llandovery dips in a westerly or southwesterly direction, and possesses the same lithological character as in the better-exposed region in the neighbourhood of Damery. The prevalent fossils are-Colospira hemispherica, Atrypa reticularis, Chonetes striatella var., Phacops Weaveri, and Encrinurus punctatus.1

All the exposures as yet described are in rocks underlying the upper trap-band; but, in the previous communication already mentioned, an account is given on pp. 270 & 271 of a small section in Cullimore's Quarry, Charfield Green, where fossiliferous calcareous ash occurs overlying the upper trap-band. Recent cutting

1 The authors of names of fossils being cited in the general table appended to this paper (pp. 538-43), it has been thought unnecessary to repeat them throughout the paper.

back of the hedge has exposed a considerably larger and better section of ashy limestone and other material occupying a hollow in the trap (see fig. 2, below). The section is as follows:

(5) Surface-soil.

Thickness in feet inches

(4) Limestone, sometimes nearly pure, sometimes full of
minute ashy particles, occasionally with bigger lapilli
of vesicular basalt. Crowded with fossils, chiefly
brachiopods

(3) Band of compact grit, containing Stricklandinia lirata
and Spirifer plicatellus var. radiatus

(2) Band of gritty limestone, when unweathered containing
in places much finely-divided ashy material, but as
a rule considerably decalcified. Crowded with fossils,
chiefly corals

(1) Compact fine-grained material, resembling baked shale
and resting on the trap

A

[Scale: 1 inch = rather less than 1 foot.]

Patch of trap surrounded by sedimentary material.

B = Patch of sedimentary material enclosed in the trap.

1

The section above described appears to be the same as that recorded by Weaver, and illustrated by his pl. xxxix, fig. 2. The two fossiliferous bands seem to be those which he says are

composed of sandstone, slate-clay, carbonate of lime, oxide of iron, and traplike matter, intermixed

He mentions the occurrence of numerous corals, bivalves, and a trilobite in these bands. He represents, however, the strata as

1 Trans. Geol. Soc. ser. 2, vol. i, pt. ii (1824) p. 334.

partly interbedded with the trap, which is not in accordance with our observations.

Weaver draws special attention to the band of compact material ('grey hornstone') forming Band 1 in the foregoing section, and discusses the question as to whether it owes its hard character to alteration by the heat of the trap.

This section has yielded a large series of fossils, in addition to those mentioned on p. 271 of the previous paper; and the presence of Stricklandinia lirata, Phacops Weaveri, Strophomena compressa, Streptelasma elongatum, and Heliolites parasitica, although not affording conclusive evidence, indicates a Llandovery rather than a Wenlock age.

The following are the additional species met with1:

Lord Ducie's collection contains Modiolopsis mytilimeris and Grammysia sp., in greenish-grey sandstone unlike any rock now exposed.

At the time of publication of the previous paper in the Quarterly Journal no fossils had been found in the bed of grey sandstone, which is described (p. 271) as interbedded with shale above the calcareous ash at Cullimore's Quarry; from this we have now, however, obtained Atrypa reticularis, Cœlospira hemispherica, Streptis monilifera (?), Rhynchonella serrata," and Alveolites sp.2

(b) The Avening-Green, Damery, Ironmill-Wood, and Tortworth Areas.

These, the most fossiliferous localities for Silurian rocks in the district, are situated on a bed of sandy limestone or calcareous sandstone having a thickness of about 500 feet, and lying between

1 The sign in our fossil-lists indicates that the species is abundant; and ** that it is very abundant.

2 Found by Mr. F. J. Richards.