The Attawapiskat Formation is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...

. It preserves

fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in ...

dating back to the

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...

period.

Location

The Attawapiskat Formation encompasses a large portion of the Hudson Bay Basin. The formation remains visible from northern

. A small portion of the formation does extend onto

Nunavut Nunavut ( , ; iu, ᓄᓇᕗᑦ , ; ) is the largest and northernmost Provinces and territories of Canada#Territories, territory of Canada. It was separated officially from the Northwest Territories on April 1, 1999, via the ''Nunavut Act'' ...

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 Hudson Bay Lowlands is a vast wetland located between the Canadian Shield and southern shores of Hudson Bay and James Bay. Most of the area lies within the province of Ontario, with smaller portions reaching into Manitoba and Quebec. Many wide ...

, the formation consists of

dolomite Dolomite may refer to: *Dolomite (mineral), a carbonate mineral *Dolomite (rock), also known as dolostone, a sedimentary carbonate rock *Dolomite, Alabama, United States, an unincorporated community *Dolomite, California, United States, an unincor ...

and

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

rich in both coral and sponge. The formation is a haven for

lithotope A lithotope is either an environment in which a sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the fo ...

s, 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

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. Silurian Ontario Silurian southern paleotropical deposits {{Ontario-geo-stub

Location

Composition

Fossil content

See also

References