Foraminifera from the Permian-Triassic transition in western Slovenia

摘要

Foraminifers from the Upper Permian Bellerophon Formation, Permian-Triassic "transitional beds" and lowermost Tri-assic "streaky limestone member" of the Lukac Formation in the Lukac section, western Slovenia are described and illustrated. Four new species of foraminifers are described: Multidiscus zhiriensis, M. dinaridicus and Globivalvulina lukachiensis from the Upper Permian, and Lingulonodosaria slovenica from the lowermost Triassic. The assemblage of Late Permian foraminifers consists of species characteristic of the Changhsingian of many regions in the Tethys: northwestern Caucasus, Transcaucasia, Iran, Turkey, northern Italy, northwestern Serbia, northeastern Hungary, and South China. Unfortunately, the uppermost part of the Bellerophon Formation in the Lukac section is represented by dolomite and does not contain foraminifers. The Permian-Triassic boundary interval is represented by carbonate "transitional beds" deposited in a shallow restricted marine environment that contains foraminifers and conodonts. The species "Cornuspira" mahajeri, "Earlandia" gracilis, and "E." tintinniformis, marking the lower boundary of the Triassic worldwide based on foraminifers, are found both below and above the first appearance of the conodont species Hindeodus parvus in the LukaC section. These species appear to be ecological species and their appearance coincides with a stressful shallow water environment. The first interval with nodosariid foraminifers appears 2m above the P/T boundary and a second one is approximately 5m above the boundary. Both of these intervals with nodosariids are within the range of the conodont species H. parvus and within the /. staeschei -1. isarcica conodont Range Zone.