金浦지역 大同累層群에 대한 古磁氣 연구

Palaeomagnetism of the Taedong supergroup in the Kimpo area

A total of 111 independently oriented core samples were drilled at 12 sites in the Kimpo area (37.70°N, 126.55°E) of the Taedong Supergroup. The Taedong strata are composed of sandstone, conglomeratic sandstone, shale and thin coal seams. The age of the strata is known to be Late Triassic-Early Jurassic according to fresh-water Estherites and plant fossil (Dictyophyllum-Clathropteris flora) contents. Through AF and thermal demagnetization, an area-mean ChRM direction of D=48.3° I=40.3° α95=7.9° k=59.5, n=7 was obtained. It passed fold and reversal test in the formation-mean level. Fold test was not significant in the area-mean level. The palaeomagnetic north pole calculated from the area-mean lies at 46.3°N, 222.0°E with dp =5.7, dm =9.5°. This pole position is very similar to those of the South China Block (SCB) in Triassic times. Palaeolatitude of the Kimpo area in the Taedong times was 23.0°N, again very similar to the palaeolatitude of the South China Block in the Late Triassic. This low latitude of the study area at the time of deposition explains the tropical-subtropical nature of fossil contents of the Taedong Supergroup.