Preliminary interpretation of the upper crustal structure beneath Prince Edward Island

A reconnaissance magnetotelluric survey of Prince Edward Island was undertaken to aid in the assessment of the geothermal energy potential of the province. At ten locations, measurements were made in the period range 0.0026-1820 s. Beneath the whole of the Island, to a depth of around 200-600m, is a moderately resistive zone of some 150 OMEGA m. Underlying this is a highly conducting zone of 10 OMEGA m down to 1250m at the most N-westerly point, and to about 3000m beneath the centre of the E part of the island. This layer can be associated with shale sequences found by drilling. Beneath these shale sequences, there is a dramatic difference in rock type for the W, compared to the E, part of the island. Underlying the E half, at depths of some km, is a moderately resistive sedimentary sequence of around 150 OMEGA m. For the W part of the Island there is a resistive zone which can be identified from the borehole logs as pre-Carboniferous bedrock. The topography of the upper surface of this resistive zone is shown to be consistent with the known gravity anomaly in the region. -Authors