The Attawapiskat Formation is a geologic formation in Ontario, Manitoba and Nunavut. It preserves fossils dating back to the Silurian period.
Location The Attawapiskat Formation encompasses a large portion of the Hudson Bay Basin. The formation remains visible from northern Ontario. A small portion of the formation does extend onto Nunavut territory.
Composition It is widely believed that the formation originally deposited on a shallow rimmed shelf, followed by the development of barrier reefs into an nonlinear and uncoordinated "belt" around the Hudson Basin. Within the Hudson Bay Lowlands, the formation consists of dolomite and limestone rich in both coral and sponge. The formation is a haven for lithotopes, or media for sediments to deposit, with various types including: Mottled to Nodular Skeletal Wackestone Stromatoporoid-Coral Framestone Pelodial Intraclastic Bindstone Graded Oolitic Grainstone The formation's depth reaches 62 meters at its deepest.
Fossil content
Brachiopods Genus Species Presence Material Notes ImagesEocoeliaE. akimiskiiInter-reef beds of the formation, on Akimiski Island.Over 300 specimens.ErilevigatellaE. euthylomata GypidulaG. akimiskiformisMeristinaM. expansaEkwan River.Now deemed a junior synonym of Pentameroides septentrionalis.PentameroidesP. septentrionalisEkwan River and Attawapiskat River.ProtanastrophiaP. repandaReticulariaR. septentrionalisEkwan River.Now deemed a junior synonym of Pentameroides septentrionalis.SapelnikoviaS. (=Reveroides) norfordiAttawapiskat River.Now deemed a junior synonym of Pentameroides septentrionalis.
Trilobites Genus Species Presence Material Notes ImagesAcidaspisA. sp.Ekwan River at portage at Strong Rapids.ChiozoonC. cf. cowieiEkwan River at portage at Strong Rapids.DicranopeltisD. sp.Ekwan River at portage at Strong Rapids. EkwanoscutellumE. ekwanensis Limestone Island, Severn River."Nested stacks of mostly inverted (concave-up) large sclerites, the majority of which are pygidia". A scutelluine.MeroperixM. aquilonariusEkwan River at portage at Strong Rapids.A scutelluine.OpoaO. sp.Ekwan River at portage at Strong Rapids.PerryusP. severnensisLimestone Island, Severn River.Several cranidia, pygidia and disarticulated exoskeletons.An encrinurid.StenopareiaS. sp.Ekwan River at portage at Strong Rapids.An illaenid.
See also
List of fossiliferous stratigraphic units in Ontario
References
Ramdoyal, A., Nicolas, M.P.B. and Chow, N. 2013: Lithofacies analysis of the Silurian Attawapiskat Formation in the Hudson Bay Lowland, northeastern Manitoba; in Report of Activities 2013, Manitoba Mineral Resources, Manitoba Geological Survey, p. 144–155. Gass, Kenneth & Mikulic, Donald. (2011). Observations on the Attawapiskat Formation (Silurian) trilobites of Ontario, with description of a new encrinurine. Canadian Journal of Earth Sciences. 19. 589–596. 10.1139/e82-047.