Geomagnetic Sounding of an Ancient Plate Margin in the Canadian Appalachians

Comparison of analogue model and field station results for the Newfoundland region.

“…Based mainly on geochemical argument, STRONG et al (1974) suggest that there was an eastward dipping subduction zone beneath the Gander margin. The presence of a geomagnetic anomaly in this region (WRIGHT and COCHRANE, 1980) is generally supportive of this suggestion. Finally, the easternmost Avalon Zone is associated with the ancient continental margin on the eastern side of the Iapetus.…”

“…The field results viewed in this way show that the Carboniferous sedimentary basins in western Newfoundland and offshore in the Gulf of St. Lawrence have a significant effect on the transfer functions at periods of 100s and 300s. The conductive feature proposed by WRIGHT and CocHRANE (1980) to be associated with the Gander zone in eastern New-foundland is clearly seen in the difference arrows for stations near the Gander zone at periods of 100s and 300s. There is a suggestion that many of the stations may be influenced at periods of 900s and 1800s by a conductive feature to the south of the island of Newfoundland.…”

“…At Exploits, New World Island, North West Gander, Bonavista and Little Heart's Ease, the field results are highly attenuated with respect to the model results. This is not expected, especially for the inland stations of NWG and EXP and is an expression of the conductivity anomaly associated with the Gander zone discussed by WRIGHT and CoCHRANE (1980). This anomaly shows clearly in the difference arrow presentation (Fig.…”

“…There is little indication of the Gander zone anomaly as is expected from a two-dimensional model study of the anomalous conductor (WRIGHT and CoCHRANE, 1980). For the stations to the west, the difference arrow points towards the Cabot Strait and Gulf of St. Lawrence.…”