The Evae transgression: a major event?

Abstract

The most extensive sea-level event of the Early Ordovician is known as the Evae transgression. During the highstand of this event, the conodont index species Oepikodus evae reached its acme and often coincided with the peak in conodont generic diversity. The main objective of this study is to statistically evaluate the degree of similarity in conodont species composition between the Argentine Precordillera, Laurentia, Baltica, Kazakhstania, South China, and Australia at that time. Cluster analysis shows two main faunal groups moderately to poorly differentiated, indicating that some paleogeographic barriers may not have decreased during the Evae transgression. On the other hand, a paleolatitudinal control over the distribution of species is suspected, considering the occurrence of a higher number of species dwelling in mid-low latitudes than in mid-latitudes. This suggests that this event could have been of a lesser magnitude or duration than previously claimed.

Keywords

• ordovician
• conodonts
• marine transgression
• paleolatitudinal constraints