Original paper
Stratigraphic revisions for a key Ordovician/Silurian boundary section, Anticosti Island, Canada
Copper, Paul; Long, Darrel G. F.
published: 8/30/1989
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ArtNo.: ESP026002101007
Abstract
A new formation, the Merrimack Formation, is proposed for the 25 m thick shaly upper part of the Becscie Formation, which caps the Ordovician-Silurian boundary reference section in the shallow carbonate platform sequence of Anticosti Island. This is substantially thicker than previously suspected. Its relatively poor exposure and inaccessibility until recently has left this a poorly known part of one of die best reference sections across the system boundary in die world. The formation appears to span the Coronograptus cyphus Zone of the late Rhuddanian (Early Llandovery, Silurian). Shelly faunas discovered in die Merrimack Formation suggest that it marks a deepening phase from the Stricklandia through Clorinda equivalent brachiopod communities, in water depths from 50 to 120 m. This coincides with increasing water depths known elsewhere from North America and other parts of the world, corroborating a global sea level rise and probably continued climatic warming in the Early Silurian.