helderbergian

Century Dictionary and Cyclopedia

1. n. In geology, a group of strata, regarded by New York geologists as of earliest Devonian age, lying on the water-limes of the late Silurian and overlain by the Oriskany sandstone. It takes its name from its typical development in the Helderberg Mountains of New York, where its members, from the base upward, are Coeymans limestone, New Scotland beds, and Becraft limestone. In the earlier nomenclature of the New York rocks it was termed first the Helderberg group and subsequently the Lower Helderberg. See group.