Pleistocene Deep Weathering

Abstract

THE recent communication by Sir Edward Bailey1, describing the brecciation of rocks beneath boulder clay, is most interesting, and his opinion that this phenomenon is unlikely to be due to ice-movement agrees with nay own observations. Examples can be seen in many places, and a particularly striking one was observed by me recently near Bury St. Edmunds, where chalk was seen to be shattered for a depth of 15 ft. below boulder clay. The glacial deposit at this section consisted largely of rounded pellets in a matrix of powdered chalk and sand, with many flints and occasional fragments of Jurassic septaria, Bunter quartzites and rare pebbles of Old Red Sandstone porphyrites. The state of the chalk under this boulder clay contrasted with that in the glacial deposit, as it was broken into angular pieces, but no rock fragments foreign to the chalk were found. Occasional rafts of this chalk-breccia had been thrust up into the boulder clay.