- GeoRef, Copyright 2005, American Geological Institute. Reference includes data from Bibliography and Index of North American Geology, U. S. Geological Survey, Reston, VA, United States. Reference includes data supplied by Society of Exploration Geophysicists, Tulsa, OK, United States
The Dawn No. 156 pool in southwestern Ontario was discovered by the Union Gas Company of Canada Limited, in January, 1952, by drilling on a gravity maximum. The drilling supported the original interpretation that this maximum was produced by a Silurian reef. Initial production of 6.5 million cubic feet per day was obtained from the upper fourteen feet of the Guelph in highly porous reef dolomite at a depth from 1,720 to 1,734 feet below the surface.The geology of the area is discussed as a background for the gravity interpretation. Bouguer and residual gravity maps of the original survey are presented.