GEOLOGY cene deposits are distinguished from those of later age by their freedom from cretaceous rock debris. Mr. Deeley divides them into three epochs, viz. the Older Pleistocene, the Middle Pleistocene and the Newer Pleistocene. The Boulder Clays of the lower series, or older epoch, are tough bluish or reddish clays chiefly made up of the subjacent rocks or of those immediately to the north or west and contain fragments of all the Pennine rocks. The boulders in them are such as would be brought down by glaciers descending the valleys of the Derwent and Wye and crossing the valley of the Trent. The clays of the middle and newer epochs contain large quantities of flint and chalk and, except in the west, not so large a proportion of boulders from the Pennine Chain. The beds associated with the Boulder Clays consist of widespread deposits of sand or gravel formed during times of submergence, or of fluviatile gravels occupying terraces bordering the main watercourses. Not only does the development of each deposit vary largely in different localities, but there is an indication of an almost continuous series of changes from early glacial times down to the present day. The following is Mr. Deeley's classification of the Pleistocene de- posits in this district : NEWER PLEISTOCENE EPOCH Later Pennine Boulder Clay. Interglacial River Gravel. MIDDLE PLEISTOCENE EPOCH Chalky Gravel. Great Chalky Boulder Clay. Melton Sand. OLDER PLEISTOCENE EPOCH Middle Pennine Boulder Clay. Quartzose Sand. Early Pennine Boulder Clay. Interbedded with the Boulder Clays of the Older Pleistocene are deposits of fine light yellowish or reddish false bedded sand and gravel. A fine section of this sand occurs at Blackwall near Kirk Ireton. It is about 25 feet thick and consists of coarse sand or grit, derived apparently from the breaking up of the Yoredale Sandstone, which forms the ridge upon which it rests. The sand contains numerous pebbles of quartzite, quartz, sandstone, and is obliquely laminated. It is only slightly con- solidated, and at a short distance looks not unlike Bunter pebble beds. Mr. Deeley considers that the Middle Pennine Boulder Clay was formed in the path of the glaciers which came down the valleys of the Derwent, Wye and Dove and crossed the partly submerged valley of the Trent in the direction of the Charnwood Hills. The presence of erratics at Burton-on-Trent foreign to the district point to the deflection of the Scotch and Cumbrian glaciers into the western portion of the Trent basin. Several masses of this Boulder Clay have been found in the southern part of Derbyshire. At the village of Spondon east of Derby is a 29
