Aeromagnetic Interpretation of Southwestern Continental Shelf of Korea

Czango Baag and Chang-Eob Baag

Analysis of the "project magnet" aeromagnetic data acquired by the US Navy in 1969 permits us to predict a new sedimentary basin, Heugsan Basin, south of the known Gunsan Basin in Block II. The basin appears to consist of three sub-basins trending NNW-SSE. The results of our analysis provide not only an independent assessment of the Gunsan Basin, but also new important information on the tectonic origin and mechanism for the two basins as well as for the entire region. The basin forming tectonic style is interpreted as rhom- bochasm associated with double overstepped left-lateral wrench faults. From magnetic evidence, a few NE-SW trending major onshore faults are extended to the study area. We also interpreted the nature of the faults to be left-lateral wrenches. This new gross structural style is consistent with the results of re- cent Yeongdong Basin analysis by Lee. The senses of fault movement are also supported by the paleomagnetic evidence that the Philippine Sea had experienced an 80-degree clockwise rotation since the Eocene. Based on a 2 1/2-D model study the probable maximum thickness of the sediments in the Gunsan Basin is approximately 7500 meters. We believe that the new Heugsan Basin was left unidentified because a high velocity layer may be overlying the basin. Because the overall structural configuration of the Heugsan Basin appears to be favorable for hydrocarbon accumulation, a detailed airborne magnetic survey is recommended in the area in order to verify the magnetic expressions of both this thick basin and the tectonic style.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California