Event stratigraphy of Yeonil Group, Pohang Basin : Based on correlation of 21 deep cores and outcrop sections

황인걸(In Gul Hwang),손정희(Junghee Son),조순미(Soonmi Cho) 대한지질학회 2021 지질학회지 Vol.57 No.5

Well-to-well correlation of 21 deep cores were carried out using key beds such as basinwide megaturbidites, ash layers and a group of sandstone layers as well as abrupt changes in sedimentary facies. Key beds in these wells were correlated with outcrops, revealing event stratigraphy of the Yeonil Group in Pohang Basin. During the early stage of the basin formation (Stage P1; late Early Miocene), coarse-grained sediments were supplied from the western margin of the basin, forming shallow marine fan deltas. In the basin center, however, the basement is directly overlain by hemipelagic mudstone. The basin experienced rapid tectonic subsidence (Stage P2; latest Early Miocene), forming large-scale truncation surface between the topset and foreset successions of the Doumsan and Duksung fan deltas in the western part of the basin. The unstable sediments on the fault scarp were resedimented, depositing a group of sandstone layers in the basin center. During the third stage (Stage P3; Middle Miocene), progradation of fine-grained fan deltas on the steeply-inclined slope in the western part of the basin resulted in the deposition of thick hemipelagic mudstone in the basin center with intercalating turbidite sand stone/mudstone, showing a coarsening-upward trend (Stage P3.1). Chaotic resedimentation of the steepy-inclined slope deposits, probably related to the seismic event, formed two layers of basinwide megaturbidite (Stage P3.m1.1 and P3.m1.2). Further progradation of the fan deltas on the unstable slope resulted in the deposition of hybrid flow deposits (Stage P3.2). An eruptive volcanism formed thick dacitic ash layers (Stage P3.ash). Sediment supply from the western basin margin gradually decreased, depositing fining-upward trends of turbidite sandstone/mudstone and hemipelagic mudstone (Stage P3.3). A giant tsunami scoured most of the fine-grained foreset deposits, forming a second megaturbidite (Stage P3.m2). The basin was, then, covered by thick diatomaceous mudstone (Stage P4; late Middle Miocene), probably related to the closure of the basin and related decrease in clastic sediment supply.

Variation in depositional environments controlled by tectonics and volcanic activities in the lower part of the Seongdongri Formation, Janggi Basin

구희찬(Hui-Chan Gu ),김정환(Jeong-Hwan Gim),황인걸(In Gul Hwang) 대한지질학회 2018 지질학회지 Vol.54 No.1

The Seongdongri Formation in the Janggi Basin is composed of dacitic volcaniclastic and clastic sediments, deposited in fluvial and lacustrine environments. In the cores, individual beds of volcaniclastic sediments and the patterns of depositional systems were used for correlation. Prograding and retrograding patterns of depositional systems were also used for correlation. Based on these features, the lower part of the Seongdongri Formation can be divided into six depositional units. The Unit S-1 is composed of dacitic tuff, conglomerate beds showing a fining-upward trend, and massive and laminated mudstones with thin, graded sandstones, in ascending order. The vertical succession suggests a volcanic eruption and high rates of volcaniclastic sediment supply, resulting in the deposition of fluvial sediments. The basin was, then, subsided rapidly, depositing thick mudstones in lacustrine environments. In the western part of the basin (JG-1, -4 wells), the Unit S-2 is composed of thick (∼80 m) conglomerates and gravelly sandstones, interpreted as gravelly braided stream deposits. In the eastern part (JG-3, -5, -6 wells), however, relatively thin (< 30 m) mudstones were deposited in lake or lake margin environments Rapid subsidence along the western boundary fault resulted in the westward tilting of the basin. However, deposition of braided stream and swamp sediments suggests high rate of sediment supply. In Unit S-3, JG-1, -4, -6 wells are represented by 50 m thick resedimented volcaniclastic rocks showing fining-upward trends, deposited in braided stream environments. The JG-3, -5 wells, however, comprise thick (< 75 m) mudstone, muddy sandstone and fine sandstone with a coarsening-upward trend, representing a prograding depositional system to the lake environment. The abrupt changes can be interpreted as activation of a normal fault between JG-3 and -6 wells. The Unit S-4 is composed of thick dacitic tuffs and clastic sediments. Massive feature, abundant ash matrix, and carbonized wood fragments in the dacitic tuffs are indicative of deposition by pyroclastic density currents. The Unit S-5 is composed of 70 m thick dacitic volcaniclastic rocks. Fractured crystals in lapilli tuffs, ash-depleted matrix in the lower part of the tuff, carbonized wood fragments and accretionary lapilli suggest deposition by pyroclastic density currents entering into subaqueous environments that were generated from subaerial eruption. The Unit S-6 is dominated by thick laminated mudstones, suggesting sediment depleted lacustrine environments after the volcanic eruptions. Variations in sedimentary facies and thickness in each depositional unit suggest that sedimentary architecture and depositional environments were controlled by tectonic subsidence and related volcanic activities, resulting in rapid variation of sediment supply rate.

Depositional history of the Janggi Conglomerate controlled by tectonic subsidence, during the early stage of Janggi Basin evolution

구희찬(Hui-Chan Gu),황인걸(In Gul Hwang) 대한지질학회 2017 지질학회지 Vol.53 No.2

Using six drilling cores, depositional history in Janggi Conglomerate in the Early Miocene Janggi Basin was reconstructed. Lithofacies of the Janggi Conglomerate can be divided into 4 facies associations (FA-1 to FA-4). FA-1 consists of conglomerates with erosional lower boundary, interpreted as gravelly braided stream deposits. FA-2 contains coaly shale, suggesting deposition in floodplain environment. FA-3 consists of massive muddy sandstones in the lower part and coarse sandstones to conglomerates in upper part, inferred to have been deposited in mouth-bar or prograding delta. FA-4 is dominated by massive mudstones with laminated mudstone and normally graded sandstones, interpreted as lacustrine deposits. Based on vertical and lateral variations in facies associations, the Janggi Conglomerate can be divided into 4 depositional units (Unit J-1 to J-4) related with tempo-spatial variations in accommodation space. In the western part (JG-4, -6 wells) of the basin, the Unit J-1 is dominated by FA-1, whereas the eastern part (JG-3 well) is composed mostly of FA-2 and FA-4. The spatial distributions of the lithofacies in Unit J-1 is inferred to result from tectonic subsidence in the eastern part of the Janggi Basin. In JG-1 and -5 wells, Unit J-1 is absent, indicating physiographic highland during the early stage of basin evolution. The Unit J-2 is composed of up to 35 m thick FA-1, suggesting a decrease in accommodation space either by a decrease in subsidence rates or an increase in rates of sediment supply. The lower part of Unit J-3 is represented by FA-2, -3 and -4, whereas the upper part is dominated by FA-1, showing a coarsening-upward trend. The vertical distribution of facies associations in Unit J-3 suggest continuous filling of the basin after rapid subsidence with gradual decrease in rate of subsidence or increase in sediment supply. The lower part of Unit J-4 is represented by FA-1 and -2. In the upper part of Unit J-4, volcanic ash layers are common. Here, the western part (JG-1, -4 wells) is composed of thickly stacked units of conglomerate (FA-1), whereas the eastern part (JG-3, -5, -6 wells) is dominated by thick lacustrine mudstone (FA-4). Abrupt changes in the depositional environments between JG-4 and -6 wells are interpreted to result from syndepositional tectonic subsidence, probably related to the volcanic activity as reflected by ash layers.

Tectonics and related depositional pattern in the SW margin of Ulleung Basin

윤봉식(Bong-Sic Yoon),황인걸(In-Gul Hwang) 대한지질학회 2009 지질학회지 Vol.45 No.4

The Miocene-Recent succession in the SW continental shelf of the Ulleung Basin can be divided into seven sedimentary units separated by six regional unconformities. Seismic facies and sequence stratigraphic analysis, integrated with interpretation of exploratory well data revealed that the sedimentary units formed in response to tectonic movement and related variation in sediment supply rate as well as eustatic sea-level fluctuation. During the initial rift (Late Oligocene-Early Miocene) sedimentary unit Ⅰ formed in basement depressions, controlled by NE-SW trending normal faults. The sequence was deposited in subaerial to shallow marine environments. Sedimentary unit Ⅱ formed during the rapid subsidence of the basin (Early Miocene). Fine-grained sediments were deposited mainly in continental slope to basin floor environments. Inferred directions of paleocurrent indicate that sediments were derived from the peripheral highlands. Sedimentary unit Ⅲ was deposited during the transitional period (Middle Miocene) between the opening (sedimentary unit Ⅱ) and closing stage (sedimentary unit Ⅳ) of the basin. During this time, high rate of sediment influx resulted in rapid progradation of shelfbreak deltas. Sedimentary unit Ⅳ was deposited during the early phase of regional compression (Middle Miocene), forming thrust belts in the southwestern part of the basin. The sediments were deposited mainly in subaerial and shallow marine environments. Sedimentary unit Ⅴ (Late Miocene) formed during the main phase of regional compression, in which rapid erosion of unconsolidated sediments in the uplifted highlands resulted in rapid progradation as evidenced by basinward shift of seismic facies boundary. Large?scale channels were formed near the shelfbreak. During the final stage of the compression, sedimentary unit Ⅵ (Late Miocene) was deposited on an angular unconformity. High rate of sediment supply from the uplifted highlands resulted in the basinward retreat of shoreline and most sediments were deposited in subaerial environment. During the Pliocene, sedimentary unit Ⅶ was deposited mainly in shallow marine environment probably due to thermal subsidence and eustatic sealevel rise. Strike?slip movement formed local contraction in the southern part of the basin, forming local anticline and depression in the shelf area.

18개 심부 시추공에서 확인되는 포항분지의 기반암

황인걸(In Gul Hwang),손정희(Junghee Son),조순미(Soonmi Cho) 대한지질학회 2021 대한지질학회 학술대회 Vol.2021 No.10

포항분지 18개의 심부 시추공에서는 페름기에서 초기 마이오세에 이르는 다양한 기반암이 나타난다. A-, B- C-공의 심부에서는 (화강)섬록암이 확인되며, 저어콘 SHRIMP 연대측정결과 페름기(259.0±3 Ma, C-1,242 m; 276.2±6 Ma, C-1,453 m)에 형성되었음을 지시한다. (화강)섬록암은 각섬석 화강암에 의해 관입되었으며, 연대측정 결과는 쥬라기(199.0±2 Ma, C-2,347 m)를 지시한다. 이 연대측정결과는 Lee et al .(2008)이 측정한 Rb/Sr 연대측정 결과(60±12 Ma ~ 94±43 Ma)와 다르다. 대부분의 시추공에서 확인되는 백악기 화산암류는 저어콘 SHRIMP 연대측정 결과 초기 백악기 말(110 Ma, D-1,174 m; 105 Ma, E-1,184 m; 107 Ma, G-902 m)에서 후기 백악기 말(66.96 Ma, C-1,221 m; 66.52±0.55 Ma, PH-CLH-1-575 m)까지 분출하였음을 지시한다. 일부 화산암류는 재동되어 화산재 기질이 없는 역암 및 사암 또는 적색의 이암으로 나타나기도 한다. 백악기 화산암 내부에는 적색을 띠며, 행인상 구조를 보이는 안산암질 용암류도 분포한다. 백악기 화산암 사이에는 하성 및 호성 환경에서 퇴적된 백악기 퇴적암류도 분포한다. BH-1공의 876 m ~ 1100 m 구간의 하성 및 호성 사암 및 이암은 재동된 화산암이 거의 나타나지 않는 점으로 보아 신동층군 혹은 하양층군과 유사하다. 그러나, 470 m ~ 530 m 구간의 역암, 사암 및 이암도 하성 및 호성환경에서 퇴적되었으나 다량의 재동된 화산퇴적물을 포함하는 점으로 보아 유천층군과 대비된다. A, C, D, E 공 등에서도 다량의 화산 퇴적물을 포함하는 하성 및 호성 퇴적물이 분포하며, 특히 A-공과 C-공의 퇴적암은 열변성을 심하게 받았고 교란이 심하여 화구 인근에서 퇴적된 것으로 추정된다. B-공의 672.5 m ~ 950 m 구간과 E-공의 668 m ~ 890 m 구간의 고화가 심하지 않은 적색 및 녹색 이암, 사암 및 역암은 기존 연구에서 연일층군으로 기재되어 있으나 역의 원마도가 양호하고 부분적으로 고화된 점으로 보아 백악기 퇴적층으로 추정된다. PYDC-공에서는 불국사 화강암과 대비되는 화강암도 분포한다(65.9±1.4 Ma; PYDC–923 m). 백악기 화산암 및 퇴적암 상부는 팔레오세 ~ 에오세에 분출한 곡강동 유문암과 대비되는 화산암으로 구성되어 있다(49.4±3.7 Ma, PH-CLH-2-570 m). F-공 및 PYDC-공에서는 장기분지의 성동리층과 유사한 데 사이트질 화산재와 이암, 탄질셰일, 사암 및 역암도 분포하며, 영일만 내부의 탄성파 탐사 결과 주로 이암으로 구성되어 진폭이 약한 연일층군 하부에 분포하는 강한 진폭을 보이는 반사면은 화산 퇴적물이 교호하는 장기층군으로 추정된다. PH-CLH-3공에서는 시대 미상의 현무암질 안산암이 분포하며, 이는 장기분지의 뇌성산 현무암질암과 대비되는 것으로 추정된다.

시추공과 야외노두에서 확인되는 영해분지 제3기 퇴적층 층서

황인걸(In Gul Hwang),손정희(Junghee Son),손정희(Soonmi Cho) 대한지질학회 2023 대한지질학회 학술대회 Vol.2023 No.11

학천-초곡 거대저탁류 퇴적층 : 이중으로 증폭된 거대 쓰나미에 의한 대규모 사면 붕괴

황인걸(In Gul Hwang),손정희(Junghee Son) 대한지질학회 2022 대한지질학회 학술대회 Vol.2022 No.10

시추공과 육상노두에서의 열쇠층 대비를 통한 포항분지 연일층군의 퇴적환경 진화사

황인걸(In Gul Hwang),손정희(Junghee Son),조순미(Soonmi Cho) 대한지질학회 2021 대한지질학회 학술대회 Vol.2021 No.10

포항분지의 연일층군은 육상 노두와 시추공에서 확인되는 급격한 퇴적상 변화, 대규모 절단면 등의 열쇠층을 기준으로 4개의 퇴적단위로 구분되며, 각 퇴적단위는 시추공 대부분에서 확인되는 거대저탁류 퇴적층, 화산재 퇴적층 등의 열쇠층에 의해 세분된다. 분지형성 초기단계(Stage P1)인 초기 마이오세에는 분지 서쪽에서 조립질 퇴적물이 공급되어 천해형 선상지 삼각주가 발달하였으며, 분지가 침강함에 따라 길버트형 선상지 삼각주로 진화하였다. 이에 반해 분지 내부의 기반암 저지대에는 각력암, 이질 사암 및 사질이암, 탄질셰일과 재동된 화산재 퇴적층이 형성되었고(Stage P1.1) 기반암 고지대는 침식되었다. 분지가 침강함에 따라 분지 전체에는 반원양성 이암이 침전되었다(Stage P1.2). 초기 마이오세 말(Stage P2)에 들어와 분지 내부에서 침강이 일어나며 도음산 및 덕성 선상지 삼각주에서는 대규모의 절단면이 형성되었고 그 상부에는 조립질 선상지 삼각주가 퇴적되었다. 단층면의 불안정한 퇴적물은 재동되어 분지 내부에서는 두꺼운 이암 사이에 분포하는 사암군집이 퇴적되었고, 그 상부에는 두꺼운 이암만 퇴적되었다. 중기 마이오세(Stage P3)에 들어와 분지 서쪽에서 퇴적물 공급량은 급격히 감소하여 조립질 선상지 삼각주 상부에 세립질 선상지 삼각주가 형성되었다. 분지 내부에는 반원양성 이암과 저탁류에 의해 퇴적된 사암/이암이 교호한다. 시추공에서 이 구간의 최하부(Stage 3.1)는 상향 조립화 경향을 보이는 이암 및 사암이 특징이며, 이는 세립질 선상지 삼각주가 점차 분지 쪽으로 전진 구축하며 형성된 것으로 보인다. 두께 1.5 m ~ 18 m에 이르는 사암/이암으로 구성된 거대저탁류 퇴적층(Stage P3.m1.1)이 대부분의 시추공에서 확인되며, 이는 분지 주변의 대규모 지진에 의해 사면 퇴적물이 대부분 재동된 결과로 해석된다. 불안정한 침식면은 다시 재동되어 그 상부에 수 m 내외의 거대저탁류 사암/이암(Stage P3.m1.2) 퇴적되었다. 거대저탁류 퇴적층 상부는 반원양성 이암, 저탁류 사암/이암 및 혼합류(hybrid flow)에 의해 퇴적된 이질 역암이 퇴적되었으며(Stage P3.m2), 그 상부에는 분지 외곽의 화산 분출에 의한 데사이트질 화산재 퇴적층이 피복되었다(Stage P3.ash). 이후 분지 서측의 퇴적물 공급량이 점차 감소하면서 상향 세립화 경향을 보이는 반원양성 이암 및 저탁류 사암/이암이 퇴적었으며, 이 시기 후반부에 들어와 쓰나미에 의한 것으로 추정되는 2차 거대저탁류 사암/이암(Stage P3.m2)이 육상 노두에서 확인된다. 분지 형성 후기 인 중기 마이오세 후반부(Stage P4)에는 분지 서측에서 쇄설성 퇴적물 공급이 중단되어 두꺼운 규조질 이암이 퇴적되었다.

폐경기 여성에서 ApoE 유전자 다형성에 따른 호르몬 대치요법 후 혈중 지질 변화

황정규(Chung Kyu Hwang),정필호(Phil Ho Jung),황창선(Chang Sun Hwang),문인걸(In Gul Moon),조동희(Dong Hee Cho),정호연(Ho Yeon Chung),한기옥(Ki Ok Han),장학철(Hak Chul Jang),신현호(Hyun Ho Shin) 한국지질동맥경화학회(구 한국지질학회) 2000 韓國脂質學會誌 Vol.10 No.2

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Distribution of dissolved methane on the seafloor at the gas hydrate drilling sites, Ulleung Basin, Korea

강년건(Nyeonkeon Kang),황인걸(In-Gul Hwang),권영인(Youngin Kwon) 대한지질학회 2008 지질학회지 Vol.44 No.5

In 2007, gas hydrate drilling expedition was conducted at 5 gas hydrate potential sites in Ulleung Basin, East Sea, Korea. During the LWD(Logging While Drilling) phase, seafloor topography and distribution of methane concentration were investigated using depth and methane sensors, attached on the ROV(Remotely Operated Vehicle). Seafloor topography is represented by pockmarks and small mounds, along which high concentration of methane was detected. In the inner part of the pockmark, methane concentration is higher than that of the marginal part. Seepage of methane from deep and over-pressured sediments may be responsible for development of dome shape mounds and pockmark. During the drilling, methane concentration on the seafloor changed with drilling depth. These changes are thought to be related to the leakage of methane which is dissolved in the sediment pore and free gas zone below the BSR(Bottom Simulating Reflector), stimulated by the drilling.