Grypania spiralis Walter et al., 1976 - fossil eucaryote ribbons from the Negaunee Iron-Formation (Paleoproterozoic, 2.11 Ga or 1.874 Ga) at the Empire Mine southeast of Ishpeming in Marquette County, Upper Peninsula of Michigan, USA. (public display, Seaman Mineral Museum, Houghton, Michigan, USA)
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The oldest known fossils on Earth are 3.7 billion year old stromatolites from Greenland. The oldest currently known macroscopic body fossils are Grypania spiralis - distinctive spirally coiled “algae” - from the Negaunee Iron-Formation of Michigan’s Upper Peninsula (UP). They come from the “fossiliferous zone” of the lower “magnetite-carbonate-silicate-chert iron formation” interval of the lower Negaunee Iron-Formation (= unit 2 of Han in Gair, 1975, USGS Professional Paper 769: 77), upper Menominee Group, Marquette Range Supergroup. The Negaunee Fe-Fm. dates to the mid-Paleoproterozoic, at 2.11 billion years, although a 1.874 billion year date for this unit was published in the 2000s.
Fossil material from this area has been documented in Han & Runnegar (1992) (Science 257: 232-235). The sample shown here is from the same locality cited in the Han & Runnegar (1992) paper. It comes from the Empire Mine, an open-pit iron mine exploiting the Negaunee Fe-Fm.
Locality: Empire Mine, just northwest of the town of Palmer & southeast of the town of Ishpeming, Marquette County, western Upper Peninsula of Michigan USA (46° 27’ 18” North, 87° 36’ 32” West).
What does Grypania represent? The safest identification is that they are eucaryotes (Domain Eucaryota). In a generalized way, they are often simply referred to as fossil algae.
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