New Areas of Alkaline Igneous Rocks in Central Arkansas

Two volcanic necks and a number of sills, recently discovered in central Arkansas, are of considerable interest because of the great thickness of sedimentaries which they intrude, and because of the variety of alkaline rock types found in them. The intrusions cut Pennsylvanian strata, and probably are the result of the same mid-Cretaceous vulcanism which is responsible for the other Arkansan igneous bodies. Diamonds, found in the only other described igneous neck in Arkansas, probably are not present in these newly described intrusions. The presence of these structures may be regarded as only slightly adverse to the possibilities of gas in the general area in which they occur.