A CASE FOR NEOTECTONIC JOINTS ALONG THE NIAGARA ESCARPMENT

In a search for proof that some joints on the Appalachian Plateau are neotectonic, orientation data were collected on more than 1800 fractures in exposures of the Lockport Dolomite in western New York and southern Ontario. Of greatest interest was a late-forming ENE joint set present in the central and western portions of the field area. These joints increase in abundance with proximity to the Niagara Escarpment. The shape of the east-west trending Niagara Escarpment is defined by a series of asymmetric reentrants with a strong ENE linear trend, reflecting the bedrock joint pattern. The joints appear to have formed near the Earth's surface in response to low tensile stresses developed in bedrock adjacent to the retreating escarpment. Since the current shape and position of the escarpment were controlled by glacial activity during the last 3 m.y., it is possible that the ENE joints and reentrants are neotectonic features.