. The Quarterly journal of the Geological Society of London . henorth-east of England, beyond those discovered in borings atNorthampton, and to the north-east of those exposed at Charnwood. 436 T. M. READE ON THE DATE OF THE LAST 35. The Date of the last Change of Level in Lancashire. ByT. Mellard Reale, Esq., , , (ReadApril 6, 1881.) In estimating geological time the difficulty always lies in getting areliable unit to measure with. Having surveyed and mapped out,on a scale of 6 inches to the mile, the whole series of Postglacialdeposits between Liverpool and the mouth of
. The Quarterly journal of the Geological Society of London . henorth-east of England, beyond those discovered in borings atNorthampton, and to the north-east of those exposed at Charnwood. 436 T. M. READE ON THE DATE OF THE LAST 35. The Date of the last Change of Level in Lancashire. ByT. Mellard Reale, Esq., , , (ReadApril 6, 1881.) In estimating geological time the difficulty always lies in getting areliable unit to measure with. Having surveyed and mapped out,on a scale of 6 inches to the mile, the whole series of Postglacialdeposits between Liverpool and the mouth of the river Douglas, Ihave often asked myself, Can the age of any of these deposits betranslated from mere sequence into years ? Observation has led meto believe that an approximation may be made in the case of theblown sand; and this, as I will presently show, bears upon the titleof my paper. A reference to the map (1 inch to the mile) and section, figs. 1 & 2, Fig. 1.—Sketch Map of the Coast at Blundellsands, near Liverpool.(Scale 1 inch to the mile.). CHANGE OF LEVEL IN LANCASHIRE. 437 and to those accompanying my paper on the Post-Glacial Geologyof Lancashire and Cheshire, in the Proceedings of the LiverpoolGeological Society, 1871-2, will explain the order and sequence ofthe deposits; and it will be seen that the last movement of the land inLancashire was downwards*. Submarine forests at the Alt mouth,the Eimrose brook, the Liverpool and Garston docks show that sub-sidence has taken place; and (which is perhaps quite as good evidence)sections of stream gullies, cut in the Boulder-clay and filled withrecent silt, at levels far below high water, are frequently met within dock-excavations. Upon the superior peat- and forest-bed, which is an extensioninland of the submarine forests, rests, as on a platform, some 22square miles of blown sand, in some cases rising 75 feet aboveOrdnance datum, and estimated by me to be at least 12 feet inaverage depth. This deposit is shown in my
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