Windermere group

For the UK supergroup, see Windermere Supergroup.
Windermere Group
Stratigraphic range: Neoproterozoic
TypeGeological group or supergroup
Sub-unitsMany
UnderliesVarious units
OverliesPurcell Supergroup (Belt Supergroup)
Thicknessmore than 8,000 metres (26,250 ft)[1]
Lithology
PrimaryConglomerate, sandstone
OtherShale, carbonate rocks
Location
RegionMontana, Idaho, Washington; Alberta, British Columbia, Northwest Territories, Yukon
Country United States  Canada
Type section
Named forWindermere map-area, British Columbia
Named byJ.F. Walker[2]

Called the Windermere Group in the United States and the Windermere Supergroup, Windermere Series, and Windermere System in Canada,[3] the Windermere sequence of North America is an extensive assemblage of sedimentary and volcanic rocks of latest Precambrian (Neoproterozoic) age. It is present in the northern part of the North American Cordillera, stretching from Montana, Idaho, and Washington in the northwestern United States, through Alberta, British Columbia, the Northwest Territories, and the Yukon in western Canada.[1][3][4][5] It was named for the Windermere map-area in the East Kootenay region of southeastern British Columbia by J.F. Walker in 1926.[2]

The Windermere rocks include Ediacaran fossils and stromatolites,[4] and host deposits of base and precious metals.[2]

Lithology

The Windermere consists primarily of coarse-grained feldspathic conglomerates and pebbly sandstones, with lesser amounts of pelitic shales, dolomites, and limestones.[5][4] Mafic igneous rocks are present in some areas.[1][3] In most areas the Windermere rocks are highly sheared, faulted, and metamorphosed.[3]

Environment of deposition

Most of the Windermere rocks were deposited as deep-water turbidite flows along a continental margin or in an active volcanic rift basin.[4] Glacial events such as the Sturtian and Marinoan glaciations that occurred during Neoproterozoic time strongly influenced sedimentation,[4] and some of the Windermere conglomerates are believed to be till or diamictite of glacial origin.[3]

Paleontology

Trace fossils, Ediacaran fossils, and Ediacaran-like fossils have been described from the Windermere Suprgroup in the Mackenzie and Werneke Mountains of the eastern Northwest Territories, the Cariboo Mountains of British Columbia, and the Canadian Rockies near Jasper, Alberta.[4] Stromatolites are present in some of the carbonate beds.[5]

Thickness and distribution

The Windermere is both thick and extensive. It reaches thicknesses of more than 8,000 metres (26,250 ft),[1] and is present parts of Montana, Idaho, and Washington in the United States, and parts of Alberta, British Columbia, the Northwest Territories, and the Yukon in Canada.

References

  1. ^ a b c d Miller, F.K. and Burmester, R.F. 2003. "U.S. Geological Survey, Miscellaneous Field Investigations, MF-2426". Retrieved 12 April 2018.{{cite web}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
  2. ^ a b c Walker, J.F. 1926. Geology and mineral deposits of the Windermere map-area, British Columbia. Geological Survey of Canada, Memoir 148, 69 p.
  3. ^ a b c d e Miller, F.K., McKee, E.H. and Yates, R.G. 1973. Age and correlation of the Windermere Group in northeastern Washington. Geological Society of America Bulletin, vol. 84, no. 11, p. 3723-3730.
  4. ^ a b c d e f Hein, F.J. and McMechan, M.E. 1994. "Atlas of the Western Canada Sedimentary Basin (Mossop, G.D. and Shetsen, I., compilers), Chapter 6: Proterozoic and Lower Cambrian strata of the Western Canada Sedimentary Basin". Retrieved 11 April 2018.{{cite web}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
  5. ^ a b c Glass, D.J. (editor) 1997. Lexicon of Canadian Stratigraphy, vol. 4, Western Canada including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba. Canadian Society of Petroleum Geologists, Calgary, 1423 p. on CD-ROM. ISBN 0-920230-23-7.