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THE GEOLOGICAL SOCIETY OF LONDON
HOLMES ARTHUR The PreCambrian and Associated Rocks
The district which forms the subject of this communication
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abundant acid ammonites anhydrite apertural appears associated bands basic become beds biotite Buckman Capricorn cent character close collected colour composition conglomerate considerable consist containing crystalline crystals deposits described diameter direction district dykes east evidence exposed fault feet felspar fossils frequently Geol Geological give gneisses granite greater green grey grits gypsum Hill igneous important inches increase indicate interest intrusions irregular later less limestone localities lower magma marked marl mass material miles minerals nearly occasionally occur Old Radnor Oolite origin orthoclase parallel pegmatites period pink places portion Pre-Cambrian present probably Prof pyrites Quarry quartz recorded regard represented result rocks rounded Sandstone secondary sediments seen separated shales side similar sometimes species specimens structure suggested surface thick thin trace upper usually Valley whole whorl