Microfossil-like tourmaline microlites in early Proterozoic nodular chert at Kiihtelysvaara, eastern Finland

Abstract

Many Proterozoic silicified sedimentary carbonates have been reported to contain remains of early micro-organisms. One of these localities in the Fennoscandian Shield is the village of Hyypiä at Kiihtelysvaara in eastern Finland, where a nodular chert contains microfossil-like objects, named Hyypiana jatulica n. gen., species R. Tynni. The original thin sections and grain mounts from Kiihtelysvaara were reinvestigated petrographically, and similar objects in a new grain mount from the original drill core specimen were analysed using microprobe. Petrographical and geochemical results prove that the microfossil-like objects in these samples from the nodular chert at Kiihtelysvaara are mineralogic pseudomicrofossils consisting of tourmaline microlites. Their chemical composition is similar to dravitic tourmalines from a cherty dolomite formation located in Kuusamo, eastern Finland.

Keywords

• microfossils
• pseudomicrofossils
• Hyypiana jatulica
• tourmaline
• dravite
• chert
• dolostone
• Proterozoic
• Hyypiä
• Kiihtelysvaara
• Finland