Geoelectrical Structure of the Kyongsang Basin from Magnetotelluric Sounding

초록

The Kyongsang Basin is the most representative Cretaceous basin in the Korean Peninsula where extensive crustal deformation and non-marine sedimentation took place in the early Cretaceous period. The lithology of the basement of the basin and adjacent areas is comprised of mainly Precambrian gneiss complex and Mesozoic granite intrusions. We have carried out magnetotelluric (MT) surveys to investigate the deep geoelectric structure around the Kyongsang Basin. The MT data were collected in the frequency range from 0.00042 to 320 Hz at 24 sites along a profile across the northern part of Kyongsang Basin. The results of MT inversion show that the thickness of sediments is estimated about 3 km to 9 km and the depth to base of granite intrusion is about 20 km. A remarkable discovery in this study is the highly conductive layer beneath the basin, having the resistivity of 1 ohm-m to 30 ohm-m and the thickness of about 3 km to 4 km or more. Although we are not able to reveal the nature of this layer, the result of this study could provide some basic information with respect to the formation process and deposit environment of the proto-Kyongsang Basin.

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