ABSTRACT: Bedrock Influence on the Quaternary Geology of Essex County, Southern Ontario

T. F. Morris

A Quaternary Geology Mapping program of Essex County was initiated during the summer of 1988 by the Ontario Geological Survey. Several glacial and postglacial landforms and features were subsequently discovered. Bedrock topographic information was required to help explain these features and their distributions.

A bedrock surface topography map of Essex County was constructed from borehole and water well records. This map when combined with the knowledge of the distribution of Quaternary materials illustrates: (1) bedrock surface topography rises north to south; (2) high points on the bedrock surface across southern Essex County likely acted as pinning points for glacial ice, stabilizing the ice sheet margin long enough for deposition of proglacial subaquatic fans; (3) minor overburden surface ridges are not a reflection of bedrock ridges; and (4) southeast-trending rivers in southwestern Essex County may not be controlled by faults but by minor recessional moraine.

Fields of individual circular to ellipsoid spots were identified on black and white air photographs and verified by field mapping. These features may be hydrocarbon seeps as: (1) they are associated with known oil and gas pools; (2) agricultural crops grow poorly at these sites; and (3) some are aligned with aeromagnetic anomalies and proposed fault patterns. More detailed studies should be made of these potential hydrocarbon seeps as: (1) they may be useful as a hydrocarbon exploration tool, and (2) they could be an environmental hazard.

AAPG Search and Discovery Article #90998 AAPG Eastern Section Meeting, London, Ontario, Canada, September 10-12, 1990