ABSTRACT: The Salina Group: Salt Solution and the Algonquin Arch: Relation To Reservoir Porosity and Salt Caverns, Southwestern Ontario

SMITH, LEIGH, Queen's University, Kingston, Ontario, Canada

The Salina Group of Late Silurian age is a subsurface succession of dolostone, shaly dolostone, anhydrite, and halite units. The "A" unit is intimately related in depositional and erosional history to the Guelph Formation reef bioherm reservoirs, which it encloses. The overlying Salina units, from upper "A-2 Carbonate" to "G," are interregional in extent and lithically consistent.

The "A" unit between pinnacle reef bioherms overlies a breccia paleosol atop the Lockport Formation. The Guelph is not present. This paleokarst is overlain by laminated dolostones ("A-O," "Eramosa," or "Brown Niagaran"), followed by nodular sulfates ("A-1 Evaporite"). This depositional cycle also ended with subaerial erosion, as did those forming the "A-1 Carbonate" and the "A-2 Evaporite." Such cyclic units are common higher in the Salina.

The Salina suffered differential erosion of subsurface halite causing collapse breccias, vertical fracture systems, lateral "facies" changes, and variable thicknesses in overlying units. These show intermittent groundwater flow from early Salina (A-1) time to the present.

Regional thinning in the Salina is due primarily to this loss of halite from within the section, mainly during pre-Bass Island exposure. These losses resulted from postdepositional "arching," during a major subsidence episode in the Michigan basin.

Anhydrite and halite related to "A" evaporites fills some porosity in Guelph bioherms; but only halite cements tectonic fractures. This maintained the reservoir seal while occluding some porosity.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)