The Precambrian (Archæan) Rocks of Shropshire. Part II

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Abstract
Summary of Results: 1. On a south-south-west line running between Pontesbury and Linley Hall are seven distinct elevations, composed wholly or in part of Archæan rocks. 2. This line corresponds with a great fault, on the east side of which Longmynd rocks dip easterly, and on the west Tremadoc shales dip westerly. 3. The prevailing rock-types are purple rhyolites at the north end of the chain, purple hornstone (or hälleflinta) in the middle, and purple and green hornstone (or hälleflinta), with some indurated grits, partly derived from a gneissic series, at the south. 4. The Precambrian age of these rocks is proved by their close lithological affinities with known Salopian types, and by the almost universal occurrence of fragments of the purple rhyolites in the Longmynd series. The strike, also, is usually more or less transverse to the strike of the Cambrian deposits. 5. The rocks of this axis belong exclusively to the younger of the two Salopian Archæan groups, no traces of granitoid or gneissic rocks, except as included fragments, having been detected.

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