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

• Main Authors: J. Karhu, H. O'Brien
• Format: Article
• Language: English
• Published: Geological Society of Finland 1992-06-01
• Series: Bulletin of the Geological Society of Finland
• Subjects: microfossils; pseudomicrofossils; Hyypiana jatulica; tourmaline; dravite; chert; dolostone; Proterozoic; Hyypiä; Kiihtelysvaara; Finland
• Online Access: http://www.geologinenseura.fi/bulletin/Volume64/sgs_bt_064_1_pages_113_118.pdf

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.