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A HISTORY OF LANCASHIRE MESOZOIC PERIOD

The formation of the red sandstones and marls which we have considered under the name of Permian brought to a close that period of geological time known as Palæozoic, and was in turn succeeded by the Mesozoic, in which higher orders of animals and plants appeared, and in which the rocks were less mechanical in origin, and owed more to accumulation in quiet waters and the aggregation of the remains of various life forms. The rocks of this period have also suffered much less by earth movement and change than the older rocks. The distinction between Palæozoic and Mesozoic rocks is a purely arbitrary one, retained for convenience, but possessing no actual justification, as in many places no satisfactory line can be drawn between the Permian and the Trias, the one apparently passing gradually into the other.

TRIAS

The various members of the Triassic System which are represented in Lancashire are the following:—

The Triassic rocks occupy a large extent of the flat country forming the Lancashire sea-board from Liverpool to Morecambe Bay, which it encircles as far as Walney Island and the south part of the Furness district. The greatest breadth of this lowland plain is in the neighbourhood of Preston, where it is about 20 miles across. The Triassic beds have been brought against the edges of the older rocks by a great fault system in post-Triassic time, with a western downthrow.

BUNTER

The Bunter Sandstone and Pebble Beds are well developed in the neighbourhood of Liverpool, where they have received considerable attention from local geologists. The Bunter Sandstone usually lies deep, but could formerly be seen at Eastham and Ince before the making of the Manchester Ship Canal. It is also seen at Eccleston Hall, near St. Helens. The beds are famous for the amount of water they contain, and many borings have been put down into them, from which a huge supply is obtained. The Pebble Beds are well exposed near Liverpool, and in quarries at Wavertree, the section at Olive Mount being especially good. By the late G. H. Morton they were divided in the Liverpool area into Lower and Upper Pebble Beds, the latter containing few pebbles.

The Upper Red Sandstone is exposed in nearly all the railway cuttings on the north, east, and south of Liverpool, and it lies in massive beds often of a bright red colour, streaked with grey. At Liverpool it is usually too soft to use as a building stone, but at Frodsham, Runcorn, and Ormskirk it is very hard, although it weathers badly.

KEUPER

The Keuper Sandstones and Marls which form the Upper Trias lie at the surface to the west of the Bunter series, the two running side by side from Liverpool northwards, the Keuper Series forming a goodly portion of the coastline, though occasionally obscured under a heavy load of Glacial drift, or Blown sand. At one time the Keuper Sandstone was extensively quarried at Liverpool, the lower beds forming a good building stone. That obtained from Runcorn is even more durable. Just outside the county boundary at Storeton in the Wirral peninsula, extensive quarries are opened in the Keuper Sandstone, and have yielded sandstone slabs showing a most interesting series of footprints, ripple markings, and rain pittings. The footprints, which are of large size and five-toed, are believed to have been made by an amphibian closely allied to, if not identical with, the Labyrinthodon. To the animal which made them the name of Cheirotherium has been given. To smaller footprints of a different type the name of Rhynchosaurus has been given. Remains of the latter have also been found in Warwickshire.

The Keuper Red Marls consist of red and grey marls and shales, with bands of sandstone. The thin flaggy sandstones are often ripple-marked, and their surfaces are at times studded by beautiful pseudomorphous crystals of common salt. A large area of the Red Marls stretches from Formby to Southport, having been proved by borings, but it is all deeply covered by drift. At Runcorn the Marls are seen on the banks of the Weaver. Near Fleetwood, at Preesall, a boring put down in the 24