On the Geology of the Old Radnor District, with special reference to an Algal Development in the Woolhope Limestone

Abstract

I. Introduction. The district which forms the subject of this communication has received but scanty attention in geological literature since the time of Murchison. Only one edition of the 1-inch Geological Survey map has been issued, namely, that published in 1840, and no explanatory memoir has yet appeared. Two of the horizontal sections published by the Geological Survey, however pass through the district, and these throw some light on the views adopted by the officers of the Survey regarding its general structure at the time when the district was mapped. They regarded the rocks of Old Radnor Hill as altered May Hill Sandstone, and the surrounding limestone, together with that which occurs at Nash Scar 3 miles away to the north-east, as altered Woolhope Limestone. Murchison, as shown by his description in ‘Siluria,’ considered the district to be one of especial interest. He draws attention to the differences exhibited by the limestone at Nash Scar and Old Radnor, when compared with the normal Woolhope Limestone and Shale at Corton and Haxwell, and remarks, ‘between these two …. lies the large and loftier rock of Nash Scar, in which the same limestones, whether thick-bedded or nodular, have been run together into one amorphous mass, in which the stratified character has been destroyed, and the shale driven off. …. In tracing the strata southwards along this axis, other masses of limestone, more or less amorphous, are seen near Old Radnor, which, in proportion as they approach the eruptive masses of Stanner and

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