Silurian Reefs of Southwestern Ontario
REEFS of Silurian age are recognized in southwestern Ontario, both in outcrop and from subsurface information. This paper deals with the so-called 'pinnacle' reefs witch are known only in the subsurface. For the purpose of this paper, the pinnacle reefs are arbitrarily defined as those structures having a height of over 250 feet and a length of less than two miles. This definition eliminates numerous mounds and other broader, more subdued, structures of less certain origin, found in subsurface beds.