• Title/Summary/Keyword: 남중국지괴

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Petrogenesis of Early Cretaceous Magmatism in Eastern China and the Gyeongsang Basin, Korean Peninsula (동중국과 한반도 경상분지의 백악기초기 화성활동의 성인 고찰)

  • Choi, Sung Hi
    • 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.

Paleomagnetic Study of the Proterozoic and Mesozoic Rocks in the Kyeonggi Massif (경기육괴에 분포하는 원생대 및 중생대 암석에 대한 고지자기 연구)

  • 석동우;도성재;김완수
    • Economic and Environmental Geology
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    • v.37 no.4
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    • pp.413-424
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    • 2004
  • A paleomagnetic investigation of the Mesozoic Daedong Supergroup and the Precambrian Seosan Group in the Kyeonggi massif is carried out to elucidate the tectonic evolution of Korea under the effect of the collision between Korea and the North/South China Blocks. For the Daedong Supergroup, the characteristic direction of D/I=74.5$^{\circ}$/36.7$^{\circ}$(k=60.7, $\alpha$=5.1$^{\circ}$) after tilt correction is better clustered than that before tilt correction (D/I=61.9$^{\circ}$/52.8$^{\circ}$, k=4.4,$$\alpha$_{95}$=21.5$^{\circ}$), indi-cating that it is a primary magnetization acquired during the formation of the rock. Paleomagnetic pole position of the formation locates at 208.0$^{\circ}$E, 24.5$^{\circ}$N (n=14, K=67.5, $A_{95}$=4.9$^{\circ}$), statistically similar to those of Middle Triassic period of the SCB, revealing that the two had occupied the same tectonic unit during this period. It is observed that only 6 out of 33 sites of the Seosan Group yield remagnetized paleomagnetic direction. The rest of the sampling sites reveals severe dispersion of magnetic directions presumably due to the consequences of the collision between Korea and the North/South China Blocks. The characteristic direction of the Seosan Group is D/I=45.7$^{\circ}$/60.1$^{\circ}$(k=41.2,$$\alpha$_{95}$=10.6$^{\circ}$) and the corresponding pole is at 195.0$^{\circ}$E, 51.6$^{\circ}$N (n=6, K=20.8, $A_{95}$=12.4$^{\circ}$). Although the pole position is close to those of Jurassic period of the Kyeonggi massif and Early Cretaceous of the Kyeongsang basin. it is interpreted that the Seosan Group was remagnetized by the influence of the emplacement of the Jurassic Daebo Granite after or at the closing stage of the orogenic episode rather than under the direct effect of deformation and/or metamorphism caused by the collision.

충남지역 경기육괴에 분포하는 서산층군에 대한 자기특성 연구

  • 김완수;석동우;도성재
    • Proceedings of the KSEEG Conference
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    • 2003.04a
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    • pp.254-257
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    • 2003
  • 한반도에 대한 고지자기 연구는 유라시아 대륙의 지구조운동이 진행되었던 중생대 및 고생대암석에 대해 여러 사람들에 의해 활발히 수행되어왔다. 특히 1980년대 후반부터는 북중국지괴와 남중국지괴 사이의 충돌대인 친링-다비-수루 (Qinling-Dabie-Sulu) 조산대가 서해를 지나 한반도로 연장될 가능성에 대한 관심이 높아지고 있다. 한반도의 중부를 가로지르는 옥천대는 경기육괴와 영남육괴의 경제부로서 변성시기가 초기 Triassic으로 보고되고 있으며, 경기육괴 북부 휴전선 인접지역의 동서방향의 주향을 갖는 습곡-단층대인 임진강대는 남북 경계에 대한 정확한 정의는 성립되어있지는 않지만 Triassic에 광역변성작용을 받았다는 보고가 있으나, 이들 임진강대와 옥천대의 성인에 대한 논란은 현재에 이르기까지 계속되고 있다. (중략)

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Sr-Nd-Pb Isotopic Compositions of Lavas from Cheju Island, Korea (제주도 화산암류의 Sr-Nd-Pb 동위원소 연구)

  • 박준범;박계헌;정창식
    • The Journal of the Petrological Society of Korea
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    • v.5 no.1
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    • pp.89-107
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    • 1996
  • Sr, Nd and Pb isotopic characteristics of alkaline lavas and tholeiites in Cheju Island show that the isotopic compositions of the former slightly overlap, but have relatively more depleted than the latter. However, in viewpoint of the two eruptional stratigraphies of tholeiites, the isotopic compositon of the older one is similar to those of alkaline rocks in Lava Plateau Stage after Lee (1982). These suggest that the parental magmas of alkaline lavas and tholeiites might have originated from the homogenous mantle sourve and that the characteristics of the mantle source to be partially melted might be different between the eruption stages. The isotopic signatures of the bolcanic rocks in Cheju Island overlap with those in Samoa Islands and South China Basin, indicating the DMM-EM IImixing trend. This is distingushed from the DMM-EM I trend of the Cenozoic volcanic rocks in Korea except for cheju Island and Northeastern China. The modelled binary mixing calculation between MM and EM IImaterials indicates that the mantle source of the volcanic rocks in Cheju Island has been mixed about less than 10% of enriched mantle material (EM II) with depleted mantle material (DMM). Concerned with the indentation model between North China Block (NCB) and South China Block (SCB) after Yin an Nie (1993), we suggest that the distinct isotopic features of DMM-EM I and DMM-EM IIof the Cenozoic volcanic rock in Korea as well as China can be explained by the difference of the nature of subcontinental lithospheric mantle as enriched mantle materials, i.e. EM I of NCB, while EM II of SCB.

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CHIME Ages of Monazites from Metamorphic Rocks from the Precambrian Gyeonggi Gneiss Complex in the Shiheung and Seosan Group of the Gyeonggi Massif, South Korea (경기 편마암복합체 변성암의 CHIME 절대연대측정)

  • Kim, Kyu-Han;Suzuki, Kazuhiro;Lee, Jong-Ik;Jang, Hyun-Kyung
    • Economic and Environmental Geology
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    • v.41 no.2
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    • pp.173-181
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    • 2008
  • CHIME ages were obtained from monazites in metamorphic rocks from the Seosan and Siheung Groups in the Gyeonggi gneiss complex, Korean peninsula. Monazite CHIME ages range from 234 to 257 Ma, corresponding to the late Permian to middle Triassic Songrim disturbance due to the collision event between the North and South China blocks within the Gyeonggi gneiss complex in the Korean peninsula. The CHIME ages are consistent with the metamorphic ages from the Hongseong area (231 Ma, Kim et al., 2006) and the Odesan area (245-248 Ma, Oh et al., 2006b) in the Gyeonggi gneiss complex and are older than those from the Dabie-Sulu collision belt (220${\sim}$242 Ma, Yang or of., 2003; Liu et al., 2003, 2004) suggesting that the collision between the North and South China blocks had occurred earlier in Korea than China.

Sr, Nd and Pb Isotopic Compositions of the Pyeongtaek-Asan Alkali Basalts: Implication to the Contrasting Compositional Boundary for the Mantle beneath Korean Peninsula (평택-아산 알칼리 현무암의 Sr, Nd 및 Pb 동위원소 조성: 한반도 아래 맨틀의 대조적인 조성 경계에 대한 의미)

  • Park, Kye-Hun;Cheong, Chang-Sik;Jeong, Youn-Joong
    • The Journal of the Petrological Society of Korea
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    • v.17 no.3
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    • pp.144-153
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    • 2008
  • Sr, Nd, Pb isotopic compositions of the Cenozoic basaltic rocks distributed in Pyeongtaek-Asan area display significantly enriched values compared with mid-ocean ridge basalts just like other Cenozoic basalts of Korea. The isotopic compositions of most of the Cenozoic basaltic rocks of Korea including those from Pyeongtaek-Asan area can be explained as mixing between enriched mantle component with relatively low $^{206}Pb/^{204}Pb$ ratios and depleted mantle component. In contrast, Jejudo basalts can be explained as mixing between enriched mantle component with realtively higher $^{206}Pb/^{204}Pb$ ratios and depleted mantle componsnt. Combined with that very similar division of enriched mantle components is applied to the Cenozoic basalts of northeast China and southeast China, it is suggested that subcontinental lithospheric mantle of central and southern parts of Korea represents eastern extension of North China Block and South China Block respectively. The indentation model for the late Paleozoic to early Mesozoic continental collision of China contradicts to such an interpretation, because it cannot explain occurrence of subcontinental lithospheric mantle component of South China Block-affinity under the Jejudo area. Instead, it is more probable that suture zone of the two continental blocks crosses between central and southern Korea and its location is further south from the Pyeongtaek-Asan area. Such distinct location compared with Imjingal belt, supposedly collisional boundary suggested before, suggests that mantle boundary may not be coincide with crustal boundary for the continental collision.

Palaeomagnetism of the Okchon Belt, Korea: Paleozoic Rocks in Yemi Area (옥천대에 대한 고자기 연구: 예미지역 고생대 지층의 잔류자기)

  • 김인수;김성욱;최은경
    • Economic and Environmental Geology
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    • v.34 no.4
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    • pp.355-373
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    • 2001
  • Palaeomagnesim of Paleozoic Tuwibong Type Sequence in Yemi area was studied with a total of 256 core-samples collected from 23 sites. The study area (geographical coordinates: 37.l8$^{\circ}$N, l28.610E) is located between Taebaek and Yongwol belonging to the northeastern part of the Okchon Belt. Thermal cleaning was a most effective method to extract stable characteristic remanent magnetization (ChRM) direction, even though AF cleaning also worked on some specimens. Mean ChRM direction of the Cambrian Hwajol Formation was different from the present-day field direction and showed maximum clustering (max. k value) at 100% bedding-tilt correction. However, it could not pass the fold test. Ordovician Makkol and Kosong Limestones as well as Permian Sadong and Kobangsan Formations have very weak NRM, and were remagnetized into the present-day field direction. ChRM directions from the Carboniferous Hongjom Formation passed both fold and reversal tests. IRM experiments and blocking temperature spectrum indicate that both magnetite and haematite are carrier of the primary magnetization. Palaeomagnetic pole position from the Carboniferous Hongjom Formation is very similar to that of contemporary North China Block (NCB) suggesting that the study area was a part of, or located very near to, the NCB during Carboniferous.

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LA-ICP-MS U-Pb Zircon Age of the Granite Gneiss from Jeungsan-Pyeongwon Area of North Korea (북한 증산-평원지역 화강편마암의 LA-ICP-MS U-Pb 저콘 연대)

  • Song, Yong-Sun;Park, Kye-Hun;Lee, Ho-Sun;Lin, Cao;Yuji, Orihashi
    • The Journal of the Petrological Society of Korea
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    • v.18 no.2
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    • pp.171-179
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    • 2009
  • LA-ICP-MS U-Pb zircon age was determined from the granite gneiss from Jeungsan-Pyeongwon area located to the west of Pyeongan Basin, North Korea, yielding concordant age of $1,873{\pm}19(2{\sigma})$Ma interpreted as Paleoproterozoic granitic magmatism. Considering relatively precise data reported recently using SHRIMP and LA-ICP-MS, ages around 1,870 Ma have been most frequently reported from Precambrian basement rocks of Korean peninsula, including Yeongnam, Gyeonggi, and Nangnim massifs altogether. Geologic events of this period are interpreted as not only granitic magmatism but also hightemperature regional metamorphism depending on their localities. The magmatic and regional metamorphic events of similar periods have also been reported from neighboring cratons of both North China and South China. Therefore, we need more data and efforts to decipher correlation between Precambrian basements between Korea and China.

이온현미분석기를 사용한 남서부 경기육괴 변성암류의 U-Pb 저어콘 연대: 남중국지괴와의 대비 가능성

  • 조문섭
    • Proceedings of the Mineralogical Society of Korea Conference
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    • 2001.06a
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    • pp.141-142
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    • 2001
  • 남서부 경기육괴의 편마암류로부터 분리된 저어콘(zircon) 입자를 대상으로, 이온현미분석기(ion microprobe)를 사용한 U-Pb 연대를 구하였다. 그 결과는 후기 원생대(약 820 Ma) 뿐만 아니라 오르도비스기에 상당한 화성활동이 한반도에 있었음을 지시한다. 우리 나라 후기 원생대의 화성-변성 활동에 대해 알려져 있는 바는 극히 제한적이어서 후속연구가 필수적이며, 이러한 연구는 한반도의 지체구조적 변천사를 로디니아 초대륙(Rodinia supercontinent)의 생성-분리와 관련해 재조명할 수 있는 기회를 제공할 것이다. 또한 오르도비스기의 화성작용은 그동안 논란이 되어 왔던 소위 “칼레도니아(Caledonian)” 변동 (cf. 조문섭, 2000)에 대한 또 다른 증거를 제공해준다. 저어콘의 연대측정은 서호주의 커튼공업대학교에 설치되어 있는 SHRIMP-II(Sensitive High-Resolution Ion Microprobe-II; 고감도-고분해능 이온현미분석기)를 사용하였으며, 시료 준비 및 분석방법은 기존에 보고된 바와 같다 (e.g., Kinny et al., 1999). 분석된 3개의 암석 시료(1006-5, 8, 9)는 경기육괴의 남서부에 위치한 홍성 지역의 정편마암들이다. 1006-8 시료는 Turek and Kim (1996)이 전통적인 방법을 사용해 687$\pm$5 Ma의 U-Pb 저어콘 연대를 보고한 바 있는 화강암질 편마암 (시료번호, KJ43)에 해당된다. 두 개의 다른 시료는 1006-8 주변에서 산출하는 전형적인 경기육괴의 편마암류로서 화강암질 정편마암이다. 이들 시료로부터 분리된 저어콘 입자들은 대부분 화성기원의 누대구조와 자형의 결정형태를 보여준다. 과성장띠(overgrouth rims)는 1006-5 시료에서 흔하게, 그리고 1006-9 시료에서 매우 드물게 관찰된다. 음극선발광(cathodoluminescence) 영상의 해석을 통해 저어콘 결정의 성장사를 유추하였으며, 이를 바탕으로 이온현미분석 점(spot)을 정하였다. U-Pb-Th 자료는 퍼스(Perth) 저어콘 스탠다드 (CZ3, 564 Ma, $^{206}$Pb/$^{238}$U=0.0914)를 사용하였다. 아래에 기술하는 연대는 모두 $^{206}$Pb/$^{238}$U 연대에 해당된다. 두 개의 화강암질 편마암 시료로부터 구한 U-Pb 저어콘 연대는 각각 812 $\pm$ 14 Ma(1006-8)와 822 $\pm$ 17 Ma(1006-9)로 분석오차 내에서 서로 일치한다. 이 결과는 춘천 및 전곡 지역의 석류석 각섬암에서 보고된 Sm-Nd 전암연대(852 $\pm$ 24 Ma 및 824 $\pm$ 143 Ma; Lee and Cho, 1995; Ree et al., 1996)와 잘 부합한다. 따라서 후기 원생대 기간 중 화성활동이 한반도에서 광범위하게 일어났음을 시사한다. 한편, 1006-9 시료에서는 예외적으로 한 개의 저어콘 입자 주변부(rim)에서 매우 얇은 과성장띠가 관찰되었으며, 두 개의 점 분석으로부터 구한 U-Pb 저어콘 연대는 약 235 Ma이다. 이 띠는 또한 변성기원의 저어콘에서 흔히 관찰되는 작은 W (<0.05) 비를 보인다. 1006-5 시료는 위 두 시료로부터 수 km 떨어진 지점에서 채집하였으나, 저어콘 연대는 상이한 기록을 보여준다. 즉 매우 작은 Th/U (<0.01) 값을 갖는 저어콘의 주변부에서 223 $\pm$ 5 Ma의 연대가 잘 정의되며, 이는 1006-9 시료에서 관찰된 결과와 함께 트라이아스기의 고온변성작용이 백립암상에 가까운, 매우 높은 온도에 달하였음을 지시한다. 한편 저어콘의 중심부는 335-473 Ma의 비교적 넓은 연대 분포를 보인다. 이는 저어콘이 실제 성장한 연대를 지시하기보다는 트라이아스기의 변성작용에 따른 납손실(Pb loss) 그리고 누대 규모보다 더 큰 빔 크기(beam size, 약 30 $\mu\textrm{m}$)의 영향일 것으로 해석된다. 또한 저어콘이 다양한 외래물질로부터 기원했다는 증거가 관찰되지 않으므로, 이 정편마암의 모암은 오르도비스기(약 430-470 Ma)에 관입하였을 것으로 생각된다. 따라서 그동안 논란이 되어 왔던 소위 “칼레도니아” 변동이 한반도 내에 실존하였을 가능성을 시사한다. 이상의 결과를 종합하여 볼 때, 경기육괴의 변성암류는 후기 원생대 이후 다양한 저어콘의 성장사를 기록하고 있음을 알 수 있다: 즉 (1) 후기원생대(약 820 Ma)의 화성작용; (2) 오르도비스기(약 450 Ma)의 화성작용: 그리고 (3) 트라이아스기 (약 223 Ma)의 부분용융을 수반한 고온 변성작용으로 대표된다. 이러한 지질연대는, 옥천변성대에서 얻어진 756 Ma의 저어콘 연대(Lee et al., 1998)와 더불어, 친링-다비-수루(Qinling-Dabie-Sulu) 대륙 충돌대와 양쯔 지괴에서 보고된 지질연대 결과와 잘 부합한다. 따라서 지구연대학적으로 경기육괴가 북중국보다는 대륙충돌대를 포함하는 남중국지괴에 속할 것으로 결론지을 수 있다.

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Stratigraphic response to tectonic evolution of sedimentary basins in the Yellow Sea and adjacent areas (황해 및 인접 지역 퇴적분지들의 구조적 진화에 따른 층서)

  • Ryo In Chang;Kim Boo Yang;Kwak won Jun;Kim Gi Hyoun;Park Se Jin
    • The Korean Journal of Petroleum Geology
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    • v.8 no.1_2 s.9
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    • pp.1-43
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    • 2000
  • A comparison study for understanding a stratigraphic response to tectonic evolution of sedimentary basins in the Yellow Sea and adjacent areas was carried out by using an integrated stratigraphic technology. As an interim result, we propose a stratigraphic framework that allows temporal and spatial correlation of the sedimentary successions in the basins. This stratigraphic framework will use as a new stratigraphic paradigm for hydrocarbon exploration in the Yellow Sea and adjacent areas. Integrated stratigraphic analysis in conjunction with sequence-keyed biostratigraphy allows us to define nine stratigraphic units in the basins: Cambro-Ordovician, Carboniferous-Triassic, early to middle Jurassic, late Jurassic-early Cretaceous, late Cretaceous, Paleocene-Eocene, Oligocene, early Miocene, and middle Miocene-Pliocene. They are tectono-stratigraphic units that provide time-sliced information on basin-forming tectonics, sedimentation, and basin-modifying tectonics of sedimentary basins in the Yellow Sea and adjacent area. In the Paleozoic, the South Yellow Sea basin was initiated as a marginal sag basin in the northern margin of the South China Block. Siliciclastic and carbonate sediments were deposited in the basin, showing cyclic fashions due to relative sea-level fluctuations. During the Devonian, however, the basin was once uplifted and deformed due to the Caledonian Orogeny, which resulted in an unconformity between the Cambro-Ordovician and the Carboniferous-Triassic units. The second orogenic event, Indosinian Orogeny, occurred in the late Permian-late Triassic, when the North China block began to collide with the South China block. Collision of the North and South China blocks produced the Qinling-Dabie-Sulu-Imjin foldbelts and led to the uplift and deformation of the Paleozoic strata. Subsequent rapid subsidence of the foreland parallel to the foldbelts formed the Bohai and the West Korean Bay basins where infilled with the early to middle Jurassic molasse sediments. Also Piggyback basins locally developed along the thrust. The later intensive Yanshanian (first) Orogeny modified these foreland and Piggyback basins in the late Jurassic. The South Yellow Sea basin, however, was likely to be a continental interior sag basin during the early to middle Jurassic. The early to middle Jurassic unit in the South Yellow Sea basin is characterized by fluvial to lacustrine sandstone and shale with a thick basal quartz conglomerate that contains well-sorted and well-rounded gravels. Meanwhile, the Tan-Lu fault system underwent a sinistrai strike-slip wrench movement in the late Triassic and continued into the Jurassic and Cretaceous until the early Tertiary. In the late Jurassic, development of second- or third-order wrench faults along the Tan-Lu fault system probably initiated a series of small-scale strike-slip extensional basins. Continued sinistral movement of the Tan-Lu fault until the late Eocene caused a megashear in the South Yellow Sea basin, forming a large-scale pull-apart basin. However, the Bohai basin was uplifted and severely modified during this period. h pronounced Yanshanian Orogeny (second and third) was marked by the unconformity between the early Cretaceous and late Eocene in the Bohai basin. In the late Eocene, the Indian Plate began to collide with the Eurasian Plate, forming a megasuture zone. This orogenic event, namely the Himalayan Orogeny, was probably responsible for the change of motion of the Tan-Lu fault system from left-lateral to right-lateral. The right-lateral strike-slip movement of the Tan-Lu fault caused the tectonic inversion of the South Yellow Sea basin and the pull-apart opening of the Bohai basin. Thus, the Oligocene was the main period of sedimentation in the Bohai basin as well as severe tectonic modification of the South Yellow Sea basin. After the Oligocene, the Yellow Sea and Bohai basins have maintained thermal subsidence up to the present with short periods of marine transgressions extending into the land part of the present basins.

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