The Date of the last Change of Level in Lancashire

Abstract

In estimating geological time the difficulty always lies in getting a reliable unit to measure with. Having surveyed and mapped out, on a scale of 6 inches to the mile, the whole series of Postglacial deposits between Liverpool and the mouth of the river Douglas, I have often asked myself, Can the age of any of these deposits be translated from mere sequence into years? Observation has led me to believe that an approximation may be made in the case of the blown sand; and this, as I will presently show, bears upon the title of my paper. A reference to the map (1 inch to the mile) and section, figs. 1 & 2, and to those accompanying my paper on the Post-Glacial Geology of Lancashire and Cheshire, in the ‘Proceedings of the Liverpool Geological Society’ 1871–2, will explain the order and sequence of the deposits; and it will be seen that the last movement of the land in Lancashire was downwards. Submarine forests at the Alt mouth, the Rimrose brook, the Liverpool and Garston docks show that subsidence has taken place; and (which is perhaps quite as good evidence) sections of stream gullies, cut in the Boulder-clay and filled with recent silt, at levels far below high water, are frequently met with in dock-excavations. Upon the superior peat-and forest-bed, which is an extension inland of the submarine forests, rests, as on a platform, some 22 square miles of blown sand, in some cases rising 75 feet above Ordnance datum