Grypania spiralis ribbons on gray, finely-laminated, iron-rich mudshale (slab is 9.0 cm across; each fossil ribbon is ~0.5 to 0.6 mm wide) from the Negaunee Iron-Formation at the Empire Mine near Ishpeming, UP of Michigan, USA.

The oldest known fossils on Earth are 3.5 billion year old stromatolites and bacterial body fossils from western Australia and southern Africa. 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).