Abstract

A total of 243 Bouguer gravity readings have been completed over a 9 km2 area covering the terminus of the Dundas buried valley, a prominent reentrant in the Niagara Escarpment. A 1.5 mGal (15 μm s−2) Bouguer anomaly clearly defines an abrupt closure of the bedrock topography west of Copetown, confirming and extending the results of earlier seismic reflection and refraction surveys. An apparent tributary in the contoured gravity, entering the terminus from the south, is unfortunately poorly resolved. It underlies property to which access was denied. The Bouguer gravity data are transformed to a model of the bedrock depth via a three-dimensional model. The mean error between data and model gravity, after correcting the former for a regional gradient, is less than 0.1 mGal (1 μm s−2). The estimated error in the observations themselves is ± 0.11 mGal (1.1 μm s−2). The observed Bouguer gravity is compared with that which would be produced by the present Niagara Gorge were it to underlie the survey area. The magnitude and dimensions of the computed anomalies are remarkably similar.

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