Grypania  spiralis


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 samples shown below are from the same locality cited in the Han & Runnegar (1992) paper.  They come from the Empire Mine, an open-pit iron mine exploiting the Negaunee Fe-Fm.  The Empire Mine is just northwest of the town of Palmer & southeast of the town of Ishpeming, in Marquette County (western UP of Michigan).  Pit location: 46° 27’ 18” North, 87° 36’ 32” West.


The first two specimens shown below were collected in the late 1990s by an Empire Iron Mine employee.  The next four samples were collected in the late 1980s by the Potomac Museum Group (Minneapolis, Minnesota, USA).


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.


Grypania spiralis (or Grypania cf. Grypania spiralis) - several specimens in gray, finely-laminated, iron-rich mudshale from the Negaunee Iron-Formation of Ishpeming, UP of Michigan, USA.  The largest specimen (at lower right) is about 2.4 cm at its widest.



Grypania spiralis ribbons on reddish-brown, finely-laminated taconite.  The large fossil ribbon fragment at left is about 1 mm wide.



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.



Grypania spiralis ribbon on taconitic mudshale, 2.5 cm across at its widest.  Ribbon is ~0.6 mm wide.



Grypania spiralis ribbons on taconite (field of view ~5.4 cm across).



Grypania spiralis ribbons on finely-laminated taconitic mudshale (field of view ~2.9 cm across).



Grypania spiralis from the 2.11 b.y. (or 1.874 b.y.) Negaunee Iron-Formation at the Empire Mine, Negaunee, Upper Peninsula of Michiga, USA (FMNH PP 45972, Field Museum of Natural History, Chicago, Illinois, USA).



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