Spilitic Rocks in South-east Devonshire

Abstract

AbstractVolcanism began in South-east Devonshire with the extrusion of keratophyric tuffs in the Lower Devonian. The majority of extra ves in the Middle and Upper Devonian are basic spilites but there are intermediate varieties. Volcanism in the Middle Devonian was local and in the Ashprington area appears to have been continuous throughout the epoch. At the beginning of the Upper Devonian keratophyric crystal and vitric tuffs were extruded in the Dartington area. Later in the Upper Devonian the Chipley pillow lavas were extruded: it is shown that these lavas were widespread and may probably be correlated with similar lavas at Pentire Head in North Cornwall. The final phase of volcanism is represented by the intrusion of swarms of sill-like bodies of spilitic dolerites in Upper Carboniferous times. Intrusive and extrusive rocks are distinguished, mapped, and classified petrographically