410 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 23,
tougher, and more marly part of the Upper Boulder-clay. The stone
facing or "hulking" of the sloping shore from the New Pier to the
Gynn, conceals this clay on the coast; but in the gully close to the
Gynn Inn a fine coast-section of it commences. It reaches a thickness
of at least 30 feet, and may be distinctly seen overlying the
middle sand and gravel for a distance of about two miles in a northerly
direction, and irregularly attenuating until it is lost under blown
sand. In its upper part it is generally of a dull red colour and
somewhat incoherent; in its lower part it is compact, and often of a
grey or blue colour. Generally speaking, though not always, stones are
rather sparingly distributed through it, and they are seldom large.
A kind of grey siliceous sandstone, occasionally with quartz veins,
is perhaps the most prevalent; but greenish grey porphyry is very
common, and granite not unfrequent. A large boulder may here and
there be seen. The upper part of this deposit is used as a brick-clay
and the lower as a marl*. It is apparently devoid of stratification,
though, I believe, the action of spades in brick-pits and of
rain on sea-cliffs is capable of effacing all traces of bedding in either
of the Boulder-clays (see Lower Boulder-clay between Bardsea and
Baycliff). The Rev. Mr. Thornber informed me that he found a
lump of haematitic iron-ore from the Furness district in this clay.
b. Middle Sand and Gravel.—Beneath the Upper Boulder-clay a very fine section of sand and gravel may be seen exposed in the cliff north of Blackpool. It would appear to thin out in a southerly direction before reaching Blackpool, or under some part of the town, as no trace of it can be detected on the coast south of the New Pier, where the lower clay comes nearly to the surface, and is directly overlain by Scotch slutch or (a little further inland) by the upper clay. I have not seen it exposed further south than the Gynn gully. It cannot be cut off by a fault in the gully, as the lower clay underneath preserves a nearly uniform level all along the shore. It probably wedges out between the two clays a short distance to the south of the Gynn. In the Gynn gully, about 30 feet in thickness of the sand may be seen capped with the upper clay. Here the edges of the laminae have to a certain depth been cut off by denudation on the landward side. To the north of the Gynn the deposit of sand and gravel is well known; and many sea-shells (Cardium, Tellina, &c.) have been found in it by Mr. Binney, Mr. Darbishire, and others. It consists of successive beds of fine and coarse sand displaying many varieties of oblique lamination and false bedding, alternating with layers of well-rounded pebbles likewise more or less false-bedded. The sand comes nearly to the surface immediately to the north of Uncle Tom's Cabin, but again becomes covered with the upper clay. Northwards, nearly a mile beyond Uncle Tom's Cabin, the middle drift consists almost entirely of arenaceous beds (capped with clay) which dip towards the north at a small angle, the surface of the ground above nearly conforming to the dip, until in the direction of Rossall these beds are lost under blown sand.
- The existence of marl-pits in this part of the country may almost be regarded
as an indication of Upper Boulder-clay.
