Precambrian paleobiology, now one of the most exciting and challenging paleontological fields, came into being as a result of the casual curiosity of an economic geologist whose real interest lay with iron ore

Jasper stromatolites from Gunflint Formation near Mackies, northern Ontario. (GSC specimen. Photo by BDEC (c))

In 1953 Stanley Tyler of the University of Wisconsin was investigating the origin of the iron deposits in the 2 billion year old Gunflint Formation of Minnesota and Ontario. He traced these rocks from the enormous open-pit iron mines in the Mesabi Range across the US-Canada boundary at Gunflint Lake to exposures at Kakabeka Falls near Thunder Bay and, finally, to small isolated outcrops near Schreiber on Lake Superior.

The Gunflint is a succession of peculiarly banded silica- and iron-rich rocks -- iron oxide (hematite) alternating with layers of red, yellow and grey chert. The red chert, or jasper, is particularly diagnostic of the Gunflint. At some localities, the lower part of the formation contains stromatolites up a metre across and, where these stromatolites are preserved in jasper, the chert can be polished to a stunningly beautiful red rock.

In addition to his red, iron-rich specimens, Tyler collected some jet black chert samples from the Gunflint exposed at Kakabeka Falls and on the north shore of Lake Superior near the small town of Schreiber. When he examined thin-sections of this chert under a petrographic microscope, he was astonished to find that it was infused with thousands of minute spheres, flasks and long segmented filaments; all less than 10 microns across. He could see that they occurred within the chert and, therefore, they could not be modern contaminants. He began to suspect that they were fossils -- minute, three-dimensionally preserved fossils of algae and fungi vastly older than all other fossils known. But Tyler needed confirmation from a paleobotanist if he were to be believed by other geologists.

When Elso Barghoorn, recently appointed paleobotanist at Harvard University, saw photographs of the "fossils", he concurred that they were indeed structurally preserved unicellular organisms. He was immediately enlisted as co-author of a paper with Tyler which was published in Science in 1954. As the first documentation of well-preserved fossils deep in the Precambrian -- in effect, quadrupling the duration of the fossil record on Earth -- this paper should have predicated a tidal wave of interest. But this was the early 1950s when scientific issues were not given priority, and the paper was filed away and quietly forgotten by most earth scientists.

Gunflint microfossil Eosphaera 20 microns across. (Photo by H. Hofmann, McGill Univ.)

Ten years later, in 1965, Barghoorn and Tyler published a more comprehensive paper on the Gunflint biota in which they underscored these fossils as organisms that have names -- Gunflintia, Kakabekia, Eoastrion and five others. Unlike their previous paper, this one caused a sensation in both the scientific and popular press and it triggered a flurry of research on fossils in Precambrian cherts in the late '60s.

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