The Principles of Stratigraphical Geology

abundant accordingly accumulations amongst Arenig Ashgill series beds Britain British calcareous Cambrian Cambrian rocks Carboniferous Chalk changes CHAPTER characteristic classification Clay climatic Coal composed consist containing contemporaneous continental Cretaceous crystalline schists denudation deposits Devon Devonian district divisions earth Eocene evidence existence extent fauna flora formation formed fossils genera Geol geologist glacial graptolites igneous rocks indicated invertebrates Journ Jurassic Jurassic rocks land limestone lithological lithological characters Llandeilo Llandovery marine period marked mechanical sediments Mesozoic Miocene nature North occur ocean Olenellus Oolites Ordovician organisms origin orogenic palæontological Permian Permo-Carboniferous physical planes Pliocene Precambrian Precambrian rocks present Prof Quart regions represented sand sandstones schists sedimentary separate shales shallow-water phase shells Silurian similar South strata stratigraphical geology structure student subdivisions surface term terrestrial Tertiary thickness tracts Triassic trilobites unconformity uplift Upper volcanic Wales Wenlock whilst zones