Paleobiogeographal study of the Late Ordovician brachiopods of Iran based on quantitative analysis

Brachiopods, as one of the most important benthic fauna in the Late Ordovician, show great abundance and diversity in many continents. In this study, a quantitative approach of multivariate analysis were conducted in order to study the paleobiogeography of the brachiopods of Iran and their relationship with the brachiopods from other parts of the world such as Baltica, Avalonia, Laurentia, South China, Kazakhstan, France, and Prtugal during the Late Ordovician (early Katian). Based on the results of the cluster analysis (CA), six main clusters and two sub-clusters were distinguished. The results obtained from the principal component analysis (PCA) method indicate the differentiation of seven main groups and show a high similarity with the main clusters obtained from the cluster analysis method. Based on the results of the cluster analysis (CA), the brachiopods of Bojnourd, Iran, are placed in a separate cluster together with the Avalonian brachiopods such as Shropshire, Powys (Wales), Anglesey (Wales), and Meath (Ireland). Based on the PCA scatter plot, the brachiopods of Bojnourd are placed in the same group with the Avalonian brachiopods and are distinguished from the brachiopods of the Zagros and Anarak regions in central Iran, which form a separate group with the brachiopods of France, Portugal, and Morocco. The results of the PCA method indicate that the brachiopods from intracratonic Laurentian basin such as New York, Manitoulin Island, Kentucky, and Indiana form a distinct group and are differentiated from brachiopods from continental margin such as the Appalachian Basin, Tyrone (Northern Ireland), and Girvan (Scotland).