The Quarterly journal of the Geological Society of London (13071211583)

MOOEE — ABNORMAL SECO."DART DEPOSITS.

521

8. Section at Brocastle. — On taking the road from Bridgend to

Cowbridge, numerous small Liassic sections are passed, in which Ain-

monites Sauzianus and other remains show that they represent the

higher members of the Bridgend section. After passing these quar-

ries and finding them all of the same general character, it was my

intention to proceed direct to Cowbridge ; but when midway, at

Brocastle, at the mouth of the Liassic inlet previously indicated, I

observed a limekiln some way up an arable field, on the right of the

roadway, and thinking the beds there might occupy a difi'erent horizon

I determined to give them an examination. Instead of a Liassic, it

proved to be a Carboniferous Limestone quarry, very full of encri-

nital and other remains of that age. A shallow cartway from the

field led into the northern face of the limestone. On leaving the

quarry, a thin deposit of conglomerate, resting on the limestone

immediately under the soil, attracted my attention, and was at once

seen to contain many beautifal corals and univalves, the age of which

could not then be recognized, but the Liassic character of which sub-

sequent examinations revealed.

The section itself, given below, rendered at first but little assist-

ance in determining the age of the deposit.

Fig. 6. — Section at Brocastle.

a. Lower Lias.

b. Conglomerate.

c. Carboniferous Limestone.

d. Lead-vein.

d. A vertical fissure about 3 feet wide, formerly sunk about 50 feet in depth

for lead-ore.

c. Eastern face of nearly horizontal Carboniferous Limestone, 12 feet thick,

leading in from the field to the quarry.

b. Capping of Liassic conglomerate, accommodating itself to the edges of

the beds or to the surface of the Carboniferous Limestone when it formed the

base of the Liassic sea, averaging about 1 foot in thickness.

a. Dense irregularly bedded Pentacrinital Liassic limestones with Rhyncho-

nella variabilis and corals, exposed for about 5 feet in height, but the thickness

of which is unknown, dipping slightly towards the centre of the Bx'idgend basin,

abutting against and gradually passing into the conglomerate.

The very interesting fossiliferous deposit, No. 3, is in part com-

posed of angular blocks of Carboniferous Limestone, united by a very

dense variegated yellow, grey, or bluish Liassic limestone, and en-

closing also small pockets of Carboniferous Limestone sand, with

organic remains of that age, and into which colonies of Liassic Litho-

domi have penetrated.

The bivalves of this deposit are usually so surrounded by its dense

matrix as to be difficult of extraction, and for this reason are as yet

but imperfectly represented in my collection. Some of the corals,

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1867

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