中国科学院南京地质古生物研究所机构知识库

Compilation of the marine, benthic megafossils from approximately the mid-Ashgill of the Mediterranean region, including much of Central and Southern Europe plus North Africa, and elsewhere indicates a warm interval featuring bioclastic limestone and a warm climate marine fauna. These mid-Ashgill faunas immediately precede the latest Ashgillian, Hirnantian, cool interval that featured widespread glaciation, and are underlain by typical, cold water, Mediterranean Realm, older Ordovician rocks and faunas. The cause or causes responsible for the brief warm interval are uncertain, but may have involved a warm water gateway that is geographically still not located. There is a possibility that South Africa was similarly affected by this roughly mid-Ashgillian marine situation. Early Paleozoic bauxite minerals and kaolins in northwestern Sudan and kaolins elsewhere in North Africa may represent the same time interval, which would suggest that there was a non-marine amelioration of the local climate as well as the marine effects.