A Synthesis of Cretaceous Paleomagnetic Data From South Korea and its Tectonic Significance in East Asia
Abstract
South Korea is tectonically divided into the Gyeonggi massif, Ogcheon belt, Ryeongnam massif and Gyeongsang basin from northwest to southeast. The Cretaceous strata are mainly exposed in the Gyeongsang basin, a southeastern part of Korea, and in several small basins along the boundaries of the Ogcheon belt and on the Gyeonggi massif. A total of 43 Cretaceous paleomagnetic poles from 33 published studies in South Korea were collected and reviewed to elucidate the geodynamic evolutions of the Korean Peninsula in the tectonic framework of East Asia during Cretaceous. As a result, 24 paleopoles from 17 studies have satisfied more than four reliability criteria of Van der Voo (1990). Paleomagnetic pole positions from the Gyeongsang basin and from small basins in the Gyeonggi massif and the Ogcheon belt show a good agreement, indicating that the Korean Peninsula was a single terrane since Cretaceous. Within the Gyeongsang basin, the paleomagnetic pole of the geographically northern area (Yeongyang block) is displaced westward from those of southern area (Milyang and Uiseong blocks). Also, the late Early Cretaceous paleolatitude of the Yeongyang block is similar to or slightly lower than those of the Milyang and Uiseong blocks. These paleomagnetic results and some geological features in the Gyeongsang basin suggest that the Yeongyang block underwent counter-clockwise rotations accompanied by northwestward protrusion with respect to the Milyang and Uiseong blocks during the Late Cretaceous. These relative tectonic movements within the Gyeongsang basin were probably due to the northwestward subduction of the proto-Pacific plate during the Late Cretaceous. The average paleopole positions of the Korean Peninsula for the middle Early, late Early and Late Cretaceous are Lat./Long.=59.6° N/194.7° E (A95=4.6° ), 68.1° N/207.7° E (A95=3.2° ) and 70.9° N/215.4° E (A95=5.3° ), respectively, showing the gradual eastward displacement with respect to the Cretaceous mean pole of Eurasia as the age of rock units is getting older. This result indicates that the Korean Peninsula underwent clockwise rotations with respect to Eurasia during the Cretaceous Period. The clockwise rotation of Southwest Japan with respect to Eurasia is ascribed to the Miocene opening of the East Sea, and has no connection with the Cretaceous clockwise rotations of the Korean Peninsula. Thus, it is interpreted that the Korean Peninsula and Southwest Japan might not behave as a tectonically single terrane during Cretaceous.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2003
- Bibcode:
- 2003AGUFMGP41C0051P
- Keywords:
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- 1500 GEOMAGNETISM AND PALEOMAGNETISM;
- 1525 Paleomagnetism applied to tectonics (regional;
- global)