Geography of olenid trilobite distribution and its influence on Cambro-Ordovician correlation

Abstract

A polar projection map showing Paleozoic tectonic belts of the western and northern half of the eastern hemisphere is used as a base on which to plot world-wide occurrences of late Cambrian and Tremadocian olenid trilobites and to compare their position with that of typical North American and oriental faunas of similar age. . . . The map and accompanying faunal data charts show that olenid trilobites the world over are apparently a dark-shale-and-limestone extracratonic fauna found in and near the borders of troughs which now almost in all cases coincide with Paleozoic mountain belts. Different faunas inhabited the major cratonic areas, e.g., the Siberian Koldinia, the Changshanian- Fengshanian, and the North American Elvinia, Conaspis, Ptychaspis, and saukid faunas. These are vertically more diversified, and the genera have shorter ranges than those in the geosynclinal belts where conditions were more uniform and evolution was slower. At various times expansion of trilobite stocks from the geosynclines across the craton resulted in genera preserved in both provinces; these afford some degree of correlation.