stratigraphy and oil shale potential - Geology Ontario

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The Algonquin Arch trends in a southwest direction
beneath southern Ontario, forming a broad positive lineament
from which the overlying Paleozoic strata dip westward into
the Michigan Basin or southward into that part of the
Appalachian Basin which is commonly termed the Allegheny
Trough (e.g. Winder and Sanford 1972). Within the central
Michigan Basin the Paleozoic strata reach a maximum thickness
of about 4,300 m. Within the Allegheny Trough, in
Pennsylvania and West Virginia, the Paleozoic sequence is up
to 6,700 m in thickness. In contrast, the maximum thickness
of Paleozoic strata in southwestern Ontario (at the southern
end of Lake Huron) is about 1,525 m (Winder and Sanford 1972).
The Findlay Arch (Fig. 2) trends obliquely to the
Algonquin Arch, extending through western Ohio, southeastern
Indiana, and beneath the extreme western part of southern
Ontario. The two arches are separated by the Chatham Sag
(Fig. 2), which is a locally developed broad depression within
which the Paleozoic strata are generally horizontal. Away fr
om the Chatham Sag and the crests of the two arches, Paleozoic
strata have a consistent regional dip of 5.5 to 8.5 m per km
into the Michigan Basin or Allegheny Trough (Winder and
Sanford 1972).
Upper Cambrian and Lower Ordovician strata of the initial
Paleozoic marine transgression in the southern Ontario region
are truncated against the southeastern flank of the Algonquin
Arch. This, together with the onlap and overlap of subsequent