The Quarterly Journal of the Geological Society of London, Volumen 88

abundant acid albite apatite augite basalt basic beds biotite breccias Bwana M'Kubwa Series chlorite colour composition contain cordierite Cornbrash crystals Dartmoor deposits described diorite district dykes east epidote evidence exposed exposure facies fault fauna feet felsite felspar fine-grained flakes fossils fragments gabbro garnet Geol Geological Survey glacial glaciers Gneisses grains granite granophyre gravel grey grits groundmass Hill hornblende hybrid iddingsite igneous rocks intrusion Lake lavas leucite limestone Loch Doon Lower Cornbrash magma magnetite margin mass metamorphism mica microcline mile minerals mudstones N'Changa Newry granite norite occur oligoclase olivine Ordovician orthoclase outcrop Pentamerus phenocrysts plagioclase plates plutonic porphyritic porphyritic granophyre present probably Prof pyroxene quarry quartz quartzite Rhiw ring-dyke sand sandstones scapolite schists sediments shales shows sills species specimens sphene thickness tonalite tuffs Upper Cornbrash Valentian valley volcanic xenocrysts xenoliths zone