CLIMATES AND CLIMATE ZONALITY OF THE VENDIAN: GEOLOGICAL EVIDENCE

Abstract

In view of the difficulties of stratigraphic correlation, the absence of being able to position continents reliably, the scarcity of climate indicators, and the fact that Vendian sequence crops out over a wide area and can be far apart, it has only so far been possible to identify the most general climatic features for three Vendian units. Late Vendian (Nemakit-Daldyn), and possibly Early Tommotian (Early Cambrian), time was characterized by a glacial climate with pronounced climatic zonation. It appears that there were northern and southern cold zones and a low-latitude, possibly mid-latitude warmer zones. Throughout the time the Middle Vendian sequence was being deposited (Redkino-Kotlin), a warm, possibly and zone was characteristic of low and mid-palaeolatitudes. In southern high latitudes, there is evidence of a warm humid climate at some periods during this time. The Early Vendian (Laplandian or Varangian) time was characterized by a glacial climate. Some palaeocontinental reconstructions based on magnetism suggest that these glaciations affected high, middle and most of the low latitudes, extending to the palaeoequator. The timing of glacial events in the late Neoproterozoic and their extent across the globe and severity is a topic of great debate at the moment - some researchers suggesting glaciations that lasted for millions of years that locked the entire Earth in solid ice ('Snowball Earth'). Others suggest that some ice-free oceans were present even during the most severe of glacial events and certainly some geological evidence seem to fit this latter hypothesis well.