Paleomagnetic and rock magnetic studies of Cretaceous rocks in the Eumsung basin, Korea

Seong-Jae Doh, Dong Woo Suk, Bang Yeon Kim

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Paleomagnetic results are obtained from 41 sites from the Chopyeong Formation within the Eumsung basin, located along the northern boundary of the Ogcheon Belt, Korea. The Chopyeong Formation, deposited in early Cretaceous, yields the mean direction of D/I = 347.8°/57.3°(k = 92.8, α95 = 2.5°) before tilt correction, and D/I = 0.7°/61.7°(k = 19.6, α95 = 5.5°) after tilt correction. The parameter estimating fold test and the stepwise unfolding test of the red bed and greenish mudstone of the Chopyeong Formation yield the maximum value of k at 21.9% and at 20% untilting, respectively, indicating that the remanence whose mean direction of D/I = 350.8°/57.9°(k = 177.9, α95 = 1.8°) at 20% untilting was acquired during or after tilting of the strata. The comparison of the paleomagnetic pole from the Chopyeong Formation with those from the Youngdong basin and the Euiseong area in the Gyeongsang basin indicates that the remanence was acquired during late Cretaceous to early Tertiary. Electron microscope observations and rock magnetic experiments show that secondary hematite and magnetite grains of single domain to pseudo-single domain size were authigenically formed under the influence of fluids presumably triggered by the igneous activities, thus confirm the chemical remagnetization. It is revealed that the age of the granite in the east is Jurassic because the mean direction of the east granite (D/I = 347.0°/47.7°, k = 40.2, α95 = 3.6°) is similar to the Jurassic direction of Korea Peninsula. The age of the granite in the west, however, is left undetermined whether it is Cretaceous or Jurassic because of the weak intensity and instability of the remanence of the granite during demagnetization treatments.

Original languageEnglish
Pages (from-to)337-349
Number of pages13
JournalEarth, Planets and Space
Volume51
Issue number5
Publication statusPublished - 1999 Dec 1

Fingerprint

Korea
granite
remanence
rocks
Cretaceous
Jurassic
tilt
basin
rock
remagnetization
red bed
demagnetization
peninsulas
strata
hematite
magnetite
mudstone
beds
estimating
poles

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)

Cite this

Paleomagnetic and rock magnetic studies of Cretaceous rocks in the Eumsung basin, Korea. / Doh, Seong-Jae; Suk, Dong Woo; Kim, Bang Yeon.

In: Earth, Planets and Space, Vol. 51, No. 5, 01.12.1999, p. 337-349.

Research output: Contribution to journalArticle

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