U-shaped Burrows Near Blea Wyke

Extract. (Published by permission of the Trustees of the British Museum.) The matrix is a sandstone, consisting mainly of somewhat angular quartz grains of fairly uniform size; their average diameter (according to Mr. Campbell Smith, who, by permission of Dr. Prior, has kindly examined the rock with the microscope) is about 0.1 mm. Many of them are stained with yellow oxide of iron. There are also a few grains of felspar and an occasional zircon. There is no trace of calcareous substance in the specimens examined. Small flakes of mica are sparsely disseminated through the rock; it is laminated but not fissile, and the laminæ are sometimes marked by carbonaceous fragments. These last, in conjunction with the false-bedding seen in the field, indicate the estuarine nature of the deposit, as generally recognised. The freshly broken rock is porous, not particularly hard, and of a pale yellow colour due to iron. The weathering agents, in which sea-spray is included, produce a very hard outer layer, often with a still harder crust stained reddish-brown by the dissolved and redeposited iron. It is the combination of the hardening process with the erosive action of the weather that leads to the etching out of lines of weakness, which would otherwise have been undetected. The structures thus revealed are, in the main, the following.