• Journal of the Korean earth science society
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• v.23 no.7
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• pp.575-586
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• 2002

Authigenic minerals found in sandstones and mudrocks of the Lower Hayang Group (Cretaceous) in the central part of the Kyungsang Basin are carbonate minerals (calcite, dolomite), clay minerals (illite, chlorite, C/S, I/S and kaolinite), albite, quartz and hematite. Characteristic diagenetic mineral assemblages are as follows: albite-chlorite (including C/S)-hematite in the Chilgog Formation, albite-illite-calcite in the Silla Conglomerate, illite-chlorite-hematite in the Haman Formation and albite-chlorite-dolomite in the Panyawol Formation, respectively. Among clay minerals reflecting the physical and chemical change of the diagenetic process, illite, the dominant clay mineral, occurs in every formation in the study area. Chlorite occurs mainly in green or gray sandstones and mudrocks, or in sandstones and mudrocks of the Chilogok Formation which contains a high content of volcanic materials. Based on the mineral assemblage, diagenetic minerals are strongly related with source rocks. Judging from the illite crystallinity, diagenesis of sandstones and mudrocks in the study area reached the late diagenetic stage or low grade metamorphisim. The diagenetic process was much influenced by intrusion of the Bulguksa granite, content of organic materials, grain size, and depositional environment rather than burial depth.

• The Journal of the Petrological Society of Korea
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• v.18 no.3
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• pp.181-194
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• 2009

The Cheongryangsan Formation was reported to stratigraphically overlie the Gasongdong Formation and underlie the Dogyedong Formation in the northern part of the Yeongyang subbasin, and be divided into the lower Cheongryangsan Member and the Osipbong Member. But the members have more widely called as the Cheongryangsan Conglomerate and the Osipbong Basalt, because the latter have initially meant that thin basalt flows several times intercalate sedimentary rocks in the northern part but later must consider that they have a very dominant volume in the eastern one. Both formations are based on classifying the stratigraphy and play a role of an excellent key bed for stratigraphic correlation between local spaces in the subbasin dominant absolutely for reddish beds. Both formations play a role of excellent key bed in the northern and northwestern areas of the subbasin; the Osipbong Basalt, the midwestern, eastern and southern ones; the Cheongryangsan Conglomerate, the southeastern one.

• The Journal of the Petrological Society of Korea
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• v.25 no.1
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• pp.51-67
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• 2016

Geochemical characteristics of the Early Cretaceous igneous rocks from eastern China and the Gyeongsang Basin, Korean Peninsula has been summarized. They have wide range of lithological variation with extrusive picrite-basalt-andesite-trachyte-rhyolite and lamprophyre, and intrusive gabbro-diorite-monzonite-syenite-granite and diabase in eastern China, mostly belonging to the high-K calc-alkaline or shoshonitic series. The volcanic rocks intercalated with the Hayang Group sedimentary assemblages in the Gyeongsang basin are high-K to shoshonitic basaltic trachyandesites. The Early Cretaceous basaltic rocks studied mostly fall within the field of within-plate basalts on the Zr/Y-Zr and Nb-Zr-Y tectonic discrimination diagrams. On a Sr-Nd isotope correlation diagram, basaltic rocks from the North China block (NCB) and the continent-continent collision zone (CZ) between the North and South China blocks plot into the enriched lower right quadrant along the extension of the mantle array. The initial $^{87}Sr/^{86}Sr$ ratios of basaltic rocks from the South China block (SCB) are indistinguishable from those of the NCB and CZ basaltic rocks, but their ${\varepsilon}_{Nd}$ (t) values are relatively more elevated, plotting in right side of the mantle array. Basaltic rocks from the NCB and CZ are characterized by low $^{206}Pb/^{204}Pb(t)$ ratios, lying to the left of the Geochron on the $^{207}Pb/^{204}Pb(t)$ vs. $^{206}Pb/^{204}Pb(t)$ correlation. Meanwhile, the SCB basaltic rocks have relatively radiogenic Pb isotopic compositions compared with those of the NCB and CZ basaltic rocks. Basaltic rocks from the Hayang Group plot within the field of the NCB basaltic rocks in Sr-Nd and Pb-Pb isotope spaces. Metasomatically enriched subcontinental lithospheric mantle (SCLM) is likely to have been the dominant source for the early Cretaceous magmatism. Asthenospheric upwelling under an early Cretaceous extensional tectonic setting in eastern China and the Korean Peninsula might be a heat source for melting of the enriched SCLM. Metasomatic agents proposed include partial melts of lower continental crust delaminated and foundered into the mantle or subducted Yangtze continental crust, or fluid/melt derived from the subducted paleo-Pacific plate.

• Journal of the Korean Geophysical Society
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• v.3 no.1
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• pp.1-12
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• 2000

A palaeomagnetic study was carried out on Early through Late Cretaceous sandstones and volcanic sequences (the Songnaedong Formation, Chaeyaksan Volcanics, Konchonri Formation, and Jusasan Andesite it ascending order) from Konchonri area in the northern Milyang subbasin of the Kyongsang Basin, Korea. A high-temperature stable remanence with direction of $d=22.9^{\circ},\;i=59.1^{\circ}\;({\alpha}_{95}=3.0^{\circ})$ has been isolated and a corresponding pole was $71.6^{\circ}N,\;199.6^{\circ}E\;(A_{95}=4.2^{\circ})$. The characteristic high-temperature component resides in both hematite and magnetite. The primary nature of this remanence is confirmed from positive fold and reversals tests, The palaeopole is consistent with those of the Hayang Group in other parts of the Kyongsang Basin. A comparison of the palaeomagnetic pole position from the studied area with the contemporary pole from China west of the Tan-Lu fault presents that Konchonri area has experienced little latitudinal displacement nor vertical-axis block rotation relative to the Chinese blocks since the Cretaceous. Based on the formations indicating dual polarity, radiometric and paleontologic data, the magnetostratigraphic age of the studied sequence from the Songnedong Formation to the Jusasan Andesite ranges from upper Albian to lower Campanian reverse polarity chronozone. On the other hand, volcanic samples of the Chaeyaksan Volcanics and the Jusasan Andesite showed the scattered directions considered in group, even though individual sample showed a stable remanent magnetization in response to thermal demagnetization. It indicates that they have been reworked after acquisition of the stable remanent magnetization.

• The Journal of Engineering Geology
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• v.23 no.1
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• pp.47-55
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• 2013

To analyze lateral displacement of excavation walls exposed during the construction of Subway Line 1 in the Daegu region, inclinometer measurement data for sites D4, D5, and Y6 are investigated from the perspective of engineering geology. The study area, in the Banyawol Formation, Hayang Group, Gyeongsang Supergroup, is in the lower part of bedrock of andesitic volcanics, calcareous shale, sandstone, hornfels, and felsite dykes that are unconformably overlain by soil. The rock mass around the D4 site is classified as RMR-V grade and the maximum lateral displacement of 101.39 mm, toward N34W, was measured at a bedding-parallel fault, at a depth of 12 m. The rock mass around the D5 site is classified as RMR-IV grade and the maximum lateral displacement of 55.17 mm, toward the south, was measured at a lithologic contact between shale and felsite, at a depth of 14 m. The rock mass around the Y6 site is classified as RMR-III grade and the maximum lateral displacement of 12.65 mm, toward S52W, was measured at an unconformity between the soil and underlying bedrocks, at a depth of 7 m. The directions of lateral displacement in the excavation walls are vector sums of the directions perpendicular to the excavation wall and horizontally parallel to the excavation wall. Lateral displacement graphs according to depth in the soil profile show curvilinear trajectories, whereas those in bedrock show straight and rapid-displacement trajectories.