The age of the Gunflint Formation, Ontario, Canada: single zircon U–Pb age determinations from reworked volcanic ash

Canadian Journal of Earth Sciences - Tập 39 Số 7 - Trang 1085-1091 - 2002
Philip Fralick1, D. W. Davis2, S. A. Kissin1
1Department of Geology, Lakehead University, Thunder Bay, ON P7B 5E1, Canada
2Earth Sciences Department, Royal Ontario Museum, 100 Queen’s Park, Toronto, ON M5S 2C6, Canada.

Tóm tắt

The Gunflint Formation, a Paleoproterozoic chemical–clastic sedimentary assemblage outcropping to the immediate northwest of Lake Superior, became famous in 1954 as containing the oldest fossil assemblage known at that time. Older microfossils have since been discovered, but the Gunflint procaryotes remain one of the most diverse Precambrian fossil communities. The finding of possible multicellular organisms in correlative lithic units in Michigan has recently added to the need for an exact age of the Formation. Zircons were extracted from rainout and storm reworked volcanoclastic beds in the upper portion of the Gunflint Formation. A euhedral zircon population has yielded a 1878.3 ± 1.3 million years BP U–Pb age, believed to be nearly synchronous with the depositional age. This not only provides a precise age for the community of organisms, but also strongly supports a back-arc extensional setting for the Animikie Basin, rather than a foreland trough.

Từ khóa


Tài liệu tham khảo

Barovich K.M., 1989, Geological Society of America Bulletin, 101, 333, 10.1130/0016-7606(1989)101<0333:NIATOO>2.3.CO;2

Bell R., 1870, Report for, 1866, 313

Davis D.W., 1982, Canadian Journal of Earth Sciences, 19, 2141, 10.1139/e82-188

Edhorn A-S, 1973, Proceedings of the Geological Association of Canada, 25, 37

Faure G., 1969, Geological Society of America Bulletin, 80, 1725, 10.1130/0016-7606(1969)80[1725:TAOTGI]2.0.CO;2

Fralick P.W., 1995, Special Publication, 137

Franklin J.M., 1978, Report 2, Geological Survey of Canada, Paper, 77, 35

Gerlach D.C., 1988, EOS, 69, 1515

Grout F.F., 1919, American Journal of Science, 48, 199, 10.2475/ajs.s4-48.285.199

Hassler S.W., 1989, Canadian Journal of Earth Sciences, 26, 1574, 10.1139/e89-134

Hemming S.R., 1990, EOS, 71, 654

Hemming S.R., 1995, The Journal of Geology, 103, 147, 10.1086/629733

Hoffman P.F., 1987, Geodynamics Series, 17, 85, 10.1029/GD017p0085

Hurley P.M., 1962, Journal of Geology, 70, 489, 10.1086/626839

Jaffey A.H., 1971, Physical Review, 4, 1889

Kissin S.A., 1994, Proceedings of the Institute on Lake Superior Geology, 40, 18

Krogh T.E., 1973, Geochimica et Cosmochimica Acta, 37, 485, 10.1016/0016-7037(73)90213-5

Krogh T.E., 1982, Geochimica et Cosmochimica Acta, 46, 637, 10.1016/0016-7037(82)90165-X

Moorhouse W.W., 1962, Royal Society of Canada Transactions, 56, 97

Morey G.B., 1995, Economic Geology, 90, 1983, 10.2113/gsecongeo.90.7.1983

Peterman Z.E., 1966, Geological Society of America Bulletin, 77, 1031, 10.1130/0016-7606(1966)77[1031:RDOMPM]2.0.CO;2

Pufahl P.K., 1995, In Proceedings of the Institute of Lake Superior Geology, 41, 59

Sims P.K., 1985, Geological Society of America Bulletin, 96, 1101, 10.1130/0016-7606(1985)96<1101:TDGDIF>2.0.CO;2

Sims P.K., 1989, Canadian Journal of Earth Sciences, 26, 2145, 10.1139/e89-180

Stille P., 1986, Geochemica et Cosmochimica Acta, 50, 1141, 10.1016/0016-7037(86)90395-9

Ueng W.C., 1988, Canadian Journal of Earth Sciences, 25, 528, 10.1139/e88-052

Thông tin
Thông tin xuất bản

Canadian Journal of Earth Sciences

Tập 39 Số 7

1085-1091

Thông tin tác giả