Petrology of a series of igneous dikes in central western Virginia
Introduction Although the Great Valley region, extending from Pennsylvania to Alabama, inclusive, and lying immediately northwest of the eastern crystalline province, has been the subject of serious study by many geologists, the essential though not entire absence of igneous rocks in general is noteworthy. There are very few recorded occurrences of igneous rocks found within the limits of this vast areal extent and thickness of Paleozoic sediments. Naturally, therefore, the discovery of new occurrences of igneous rocks within this region, although of common types, is of importance; but when igneous rocks, belonging to types hitherto unknown to the region and by no means common elsewhere, are found, their geologic occurrence and petrologic character become of still greater scientific interest and importance. The occurrence of igneous rocks as dikes in the Paleozoic sediments of middle western Virginia, west of the Blue Eidge, has been known for many years. Fontaine, 2 John L. . . .