Status of Ordovician and Silurian Radiolarian Studies in North America

Abstract

Polycystine radiolaria that produce siliceous tests are known to range from Cambrian to Holocene. They have proven to be enormously useful in providing age control for siliceous marine sequences of Middle Devonian and younger ages, particularly for cherts and shales that are commonly devoid of other biostratigraphically useful fossils. The utility of radiolarian biostratigraphy became widely recognized in the 1970s and 1980s when it was applied in dating deformed marine siliceous sequences in orogenic belts around the world, most notably in Cordilleran North America and other areas along the Pacific rim (e.g., Jones and Murchey, 1986; Aitchison and Murchey, 1992; Ichikawa et al., 1990).