Sandstone-Plugged Pipes in the Lower Old Red Sandstone of Shropshire, England

Abstract

ABSTRACT Red sandstones and siltstones of the fluviatile Ditton Series (Lower Old Red Sandstone) are pierced at many localities in the Clee Hills by sandstone-plugged pipes lying nearly normal to the bedding. These cylinders are long and narrow and sharply cut depositional structures of the host beds. The cylinders often carry siltstone fragments and sometimes course horizontally for long distances beneath siltstone layers before rising into higher beds. The less steeply inclined plugged pipes are usually associated with lateral structures formed of alternate, arcuate bands of fine siltstone conglomerate and sandstone. At one locality the cylinders rise from a convolute bedded sandstone. The sandstone cylinders are thought to have resulted from the plugging of tubular ducts eroded by groundwater rising through unconsolidated deposits to reach the depositional surface. The lateral structures seem to indicate the migration of the loci of erosion. The Lower Old Red Sandstone plugged pipes belong to a class of structures which includes sand and mud volcanoes, spring pits, and certain cylindrical structures described from other sandstones.