• 대한자원환경지질학회:학술대회논문집
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• 대한자원환경지질학회 2003년도 춘계 학술발표회 논문집
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• pp.330-330
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• 2003

Several volcanics are found within the Tertiary sedimentary basins, southeastern part of Korea. The sedimentary basins have been interpreted to have formed in the framework of separation of the East Sea. The volcanics are Eocene or Early and Middle Miocene in ages, showing a distincetve chronological gap, and show mafic and silicic (bimodal) in composotion. The Miocene volcanics were regionally and stratigraphically grouped into two varieties along the Hyeongsan fault; younger volcanics (13.6-15.2 Ma, K) from the north of the fault, erupted after the opening of the East Sea, and older volcanics (16.2-21.1 Ma) from the south of the fault. (omitted)

• 자원환경지질
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• 제14권2호
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• pp.77-91
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• 1981

An airborne magnetometer survey was carried out over an offshore area of about $200,000km^2$ from the southeastern, southern and western part of Korea. Detailed magnetic studies on the geological structure of the southern part of above area ($100,000km^2$) was accomplished. Residual aeromagnetic map was made in order to delineate magnetic provinces, magnetic lineaments and sedimentary basins by application of least square method using computer system. To determine the depth of the sedimentary basins pseudo-gravimetric method was applied. 1. The area studied is divided into four magnetic provinces for the purpose of interpretation on the basis of the magnetic maps. 2. Near shore area and its attached islands of southern part (fiirst and second magnetic province) can be regarded as being the extension from the land geology due to presentation of strong magnetic anomalies and shallow magnetic basements. 3. Magnetic lineament 1-1 is strong magnetic anomalous region which is presumably relevant to volcanic activities in Cretaceous. The depth of magnetic basement of the lineament was determined to 1,500 m. Negative magnetic anomalous zones B1-1 and B1-2 which represent Tertiary basins showed depth of magnetic basement 3 km and 4 km each. The latter can be interpreted as extension of the Taiwan basin which is consisted of Tertiary sediments. 4. Magnetic lineament 2-1 coincide with Rainan-Fukien massif running NE-SW direction. A lineament located in central part of magnetic lineament 2-1 is well connected with extension of Sobacksan anticlinal axis on land. Volcanic rocks in Gyongsang system concentrated along this lineament. 5. The characteristics of magnetic pattern in the southern Yellow sea basin of western part of Jeju island show weaker magnetic anomalies and deeper magnetic basements than first and second magnetic provinces indicating geological structure of this basin seems to be quite different from that of Jeju strait. 6. In southern part of Jeju island, smoother magnetic pattern develope southward. Maximum depth of magnetic basement in sedimentary basins BIV-1 and BIV-2 were determined down to 6,000 m increasing its thickness toward Taiwan up to 11,000 m in the shelf area off Taichung, Taiwan. Judging from the fact that hydrocarbon was founded in the Tertiary sediments of western coastal area of Taiwan, it can be expected that hydrocarbon will be existed in these sedimentary basins of southern part of Jeju island.

• 자원환경지질
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• 제29권4호
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• pp.509-522
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• 1996

A total of 460 palaeomagnetic samples was collected from the Tertiary Chongja-Ulsan basins and surrounding area in the southeastern part of Korean peninsula. All samples were stepwise demagnetized by either alternating field or thermal method. It was found that most sample-sites have ChRM declination which has been rotated clockwise from the north-south reference direction of Tertiary East Asia, although other two extrusive sample-sites within the Chongja sedimentary basin show counterclockwise rotation of ChRM declination. Fold tests for the site-mean ChRMs of the latter two sites reveal insignificant result and negative result with 95% confidence level, respectively. The amount of the clockwise deflection of declination varies from about $20^{\circ}$ upto about $80^{\circ}$ according to the block to which each sample-site belongs. The amount of the counterclockwise deflection is about $20^{\circ}$. It is concluded that the clockwise ChRM rotation has been caused by dextral simple shearing accompanied by NNW-SSE spreading of the East Sea which has been active until about 16Ma, and that the counterclockwise rotation is a result of sinistral simple shearing associated with WNW-ESE contraction in the Korean Strait-SW Japan region at about 15 Ma.

• 자원환경지질
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• 제25권3호
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• pp.337-349
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• 1992

The Tertiary basins in Korea have widely been studied by numerous researchers producing individual results in sedimentology, paleontology, stratigraphy, volcanic petrology and structural geology, but interdisciplinary studies, inter-basin analysis and basin-forming process have not been carried out yet. Major work of this study is to elucidate evidences obtained from different parts of a basin as well as different Tertiary basins (Pohang, Changgi, Eoil, Haseo and Ulsan basins) in order to build up the correlation between the basins, and an overall picture of the basin architecture and evolution in Korea. According to the paleontologic evidences the geologic age of the Pohang marine basin is dated to be late Lower Miocence to Middle Miocene, whereas other non-marine basins are older as being either Early Miocene or Oligocene(Lee, 1975, 1978: Bong, 1984: Chun, 1982: Choi et al., 1984: Yun et al., 1990: Yoon, 1982). However, detailed ages of the Tertiary sediments, and their correlations in a basin and between basins are still controversial, since the basins are separated from each other, sedimentary sequence is disturbed and intruded by voncanic rocks, and non-marine sediments are not fossiliferous to be correlated. Therefore, in this work radiometric, magnetostratigraphic, and biostratigraphic data was integrated for the refinement of chronostratigraphy and synopsis of stratigraphy of Tertiary basins of Korea. A total of 21 samples including 10 basaltic, 2 porphyritic, and 9 andesitic rocks from 4 basins were collected for the K-Ar dating of whole rock method. The obtained age can be grouped as follows: $14.8{\pm}0.4{\sim}15.2{\pm}0.4Ma$, $19.9{\pm}0.5{\sim}22.1{\pm}0.7Ma$, $18.0{\pm}1.1{\sim}20.4+0.5Ma$, and $14.6{\pm}0.7{\sim}21.1{\pm}0.5Ma$. Stratigraphically they mostly fall into the range of Lower Miocene to Mid Miocene. The oldest volcanic rock recorded is a basalt (911213-6) with the age of $22.05{\pm}0.67Ma$ near Sangjeong-ri in the Changgi (or Janggi) basin and presumed to be formed in the Early Miocene, when Changgi Conglomerate began to deposit. The youngest one (911214-9) is a basalt of $14.64{\pm}0.66Ma$ in the Haseo basin. This means the intrusive and extrusive rocks are not a product of sudden voncanic activity of short duration as previously accepted but of successive processes lasting relatively long period of 8 or 9 Ma. The radiometric age of the volcanic rocks is not randomly distributed but varies systematically with basins and localities. It becomes generlly younger to the south, namely from the Changgi basin to the Haseo basin. The rocks in the Changgi basin are dated to be from $19.92{\pm}0.47$ to $22.05{\pm}0.67Ma$. With exception of only one locality in the Geumgwangdong they all formed before 20 Ma B.P. The Eoil basalt by Tateiwa in the Eoil basin are dated to be from $20.44{\pm}0.47$ to $18.35{\pm}0.62Ma$ and they are younger than those in the Changgi basin by 2~4 Ma. Specifically, basaltic rocks in the sedimentary and voncanic sequences of the Eoil basin can be well compared to the sequence of associated sedimentary rocks. Generally they become younger to the stratigraphically upper part. Among the basin, the Haseo basin is characterized by the youngest volcanic rocks. The basalt (911214-7) which crops out in Jeongja-ri, Gangdong-myon, Ulsan-gun is $16.22{\pm}0.75Ma$ and the other one (911214-9) in coastal area, Jujon-dong, Ulsan is $14.64{\pm}0.66Ma$ old. The radiometric data are positively collaborated with the results of paleomagnetic study, pull-apart basin model and East Sea spreading theory. Especially, the successively changing age of Eoil basalts are in accordance with successively changing degree of rotation. In detail, following results are discussed. Firstly, the porphyritic rocks previously known as Cretaceous basement (911213-2, 911214-1) show the age of $43.73{\pm}1.05$ 및 $49.58{\pm}1.13Ma$(Eocene) confirms the results of Jin et al. (1988). This means sequential volcanic activity from Cretaceous up to Lower Tertiary. Secondly, intrusive andesitic rocks in the Pohang basin, which are dated to be $21.8{\pm}2.8Ma$ (Jin et al., 1988) are found out to be 15 Ma old in coincindence with the age of host strata of 16.5 Ma. Thirdly, The Quaternary basalt (911213-5 and 911213-6) of Tateiwa(1924) is not homogeneous regarding formation age and petrological characteristics. The basalt in the Changgi basin show the age of $19.92{\pm}0.47$ and $22.05{\pm}0.67$ (Miocene). The basalt (911213-8) in Sangjond-ri, which intruded Nultaeri Trachytic Tuff is dated to be $20.55{\pm}0.50Ma$, which means Changgi Group is older than this age. The Yeonil Basalt, which Tateiwa described as Quaternary one shows different age ranging from Lower Miocene to Upper Miocene(cf. Jin et al., 1988: sample no. 93-33: $10.20{\pm}0.30Ma$). Therefore, the Yeonil Quarterary basalt should be revised and divided into different geologic epochs. Fourthly, Yeonil basalt of Tateiwa (1926) in the Eoil basin is correlated to the Yeonil basalt in the Changgi basin. Yoon (1989) intergrated both basalts as Eoil basaltic andesitic volcanic rocks or Eoil basalt (Yoon et al., 1991), and placed uppermost unit of the Changgi Group. As mentioned above the so-called Quarternary basalt in the Eoil basin are not extruded or intruaed simultaneously, but differentiatedly (14 Ma~25 Ma) so that they can not be classified as one unit. Fifthly, the Yongdong-ri formation of the Pomgogri Group is intruded by the Eoil basalt (911214-3) of 18.35~0.62 Ma age. Therefore, the deposition of the Pomgogri Group is completed before this age. Referring petrological characteristics, occurences, paleomagnetic data, and relationship to other Eoil basalts, it is most provable that this basalt is younger than two others. That means the Pomgogri Group is underlain by the Changgi Group. Sixthly, mineral composition of the basalts and andesitic rocks from the 4 basins show different ground mass and phenocryst. In volcanic rocks in the Pohang basin, phenocrysts are pyroxene and a small amount of biotite. Those of the Changgi basin is predominant by Labradorite, in the Eoil by bytownite-anorthite and a small amount pyroxene.

• 자원환경지질
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• 제29권6호
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• pp.753-765
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• 1996

It is a well known fact that the remanent magnetization direction of the Tertiary rocks is deflected significantly clockwise (about $50^{\circ}$) in the Tertiary basins of the southeastern part of Korean peninsula. This fact has been interpreted as an evidence of north-south spreading of the East Sea (Sea of Japan) and dextral strike-slip motion of the Yangsan fault. As deflection (rotation) of remanent magnetizations is frequently reported from various regions of the world in the vicinities of strike-slip fault, such phenomena are to be expected in the Yangsan fault region also. It was the purpose of this study to clarify whether such premise is right or not. A total of 445 independently oriented core samples were collected from Cretaceous rocks of various lithology (sedimentary rocks, andesites and I-type granites) in the Yangsan fault area. In spite of through AF and thermal demagnetization experiments, no sign of remanent magnetization deflection was found. Instead, palaeomagnetic poles calculated from formation-mean ChRM directions are very similar to those of contemporary (Barremian, and late Cretaceous-Tertiary) sedimentary and plutonic rocks in the other parts of $Ky{\check{o}}ngsang$ basin as well as those of China. Therefore, possibility of tilting of granite plutons and horizontal block rotation of study area is excluded. It is also concluded that the Yangsan fault did not take any significant role in the Cenozoic tectonic evolution of southeast Korea and the East Sea region. The boundary between rotated and unrotated region of remanent magnetization is not the Yangsan fault line, but must lie further east of it.

• 한국석유지질학회:학술대회논문집
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• 한국석유지질학회 2000년도 제7차 학술발표회 발표논문집
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• pp.57-72
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• 2000

The Murzuk Basin covers an area in excess of $350,000{\cal}km^2$, and is one of several intra-cratonic sag basins located on the Saharan Platform of North Africa. Compared with some of these basins, the Murzuk Basin has a relatively simple structure and stratigraphy, probably as a result of it's location on a the East Saharan Craton. The basin contains a sedimentary fill which reaches a thickness of about $4,000{\cal}m$ in the basin centre. This fill can be divided into a predominantly marine Paleozoic section, and a continental Mesozoic section. The principal hydrocarbon play consists of a glacial-marine sandstone reservoir of Cambro-Ordovician age, sourced and sealed by overlying Silurian shales. The present day borders of the basin are defined by tectonic uplifts, each of multi-phase generation, and the present day basin geometry bears little relation to the more extensive Early Palaeozoic sedimentary basin within which the reservoir and source rocks were deposited. The key to the understanding of the Cambro-Ordovician play is the relative timing of oil generation compared to the Cretaceous and Tertiary inversion tectonics which influenced source burial depth, reactivated faults and reorganised migration pathways. At the present day only a limited area of the basin centre remains within the oil generating window. Modelling of the timing and distribution of source rock maturity uses input data from AFTA and fluid inclusion studies to define palaeo temperatures, shale velocity work to estimate maximum burial depth and source rock geochemistry to define kinetics and pseudo-Ro. Migration pathways are investigated through structural analysis. The majority of the discovered fields and identified exploration prospects in the Murzuk Basin involve traps associated with high angle reverse faults. Extensional faulting occurred in the Cambro-Ordovician and this was followed by repeated compressional movements during Late Silurian, Late Carboniferous, Mid Cretaceous and Tertiary, each associated with regional uplift and erosion.

• 자원환경지질
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• 제27권1호
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• pp.65-80
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• 1994

The Tertiary $Ch{\check{o}}ngja$ basin is located in the southeastern coastal area of the Korean Peninsula. It is a lozenge shaped fault-bounded basin with circa $5{\times}5km$ areal extent, isolated from other Tertiary basins by the Cretaceous Ulsan Formation in-between. The northwestern boundary of the basin is a domino/listric type normal fault trending $N30^{\circ}E$, whereas its southwestern boundary is a dextral strike-slip fault (trending $N20^{\circ}W$) with a lateral offset of more than 1 km. The basin is bounded by the East Sea on the eastern margin. Basin-fills consist of extrusive volcanic rock (Tangsa Andesites) of Early Miocene (16~22 Ma in radiometric age), unconsolidated fluviatile conglomerate (Kangdong Formation) and shallow brackish-water sandstone ($Sinhy{\check{o}}n$ Formation). The latter yields abundant Vicarya-Anadara molluscan fossils of early Middle Miocene age. The Tertiary strata become younger toward the northwestern boundary-fault of the basin, showing a zonal distribution pattern parallel to the fault: the younger sedimentary formations occupy a narrow zone of 2 km width along the northwestern boundary-fault, whereas the older Tangsa Andesites underlie them unconformably in the eastern and southeastern portions of the basin. The strata in the basin, including the Tangsa Andesites, are tilted (about $20^{\circ}$) toward the northwestern boundary-fault Sedimentary strata thicken toward the boundary-fault, forming a wedge shaped half-graben structure. A number of small-scale syndepositional normal growth faults and graben structures are observed in the sedimentary strata. These extensional structures have the same trend as the normal northwestern boundary-fault which we interpret as a pull-apart detachment fault. These characteristics imply persistent extension during the basin evolution, caused by a NW-SE directed tensional force. The $Ch{\check{o}}ngja$ basin is, thus, a kind of syndepositional tectonic basin evolved in a strike-slip (pull-apart) regime. The latter was caused by a dextral simple shear associated with the NNW-SSE opening of the East Sea. In view of the fact that the normal growth faults do not cut through the uppermost portion of the youngest $Sinhy{\check{o}}n$ Formation, it is inferred that the tensional force came to be inactive in the early Middle Miocene. This is coincident in timing with the termination of the East Sea opening (15 Ma).

• 자원환경지질
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• 제25권2호
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• pp.167-177
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• 1992

The gravity measurement has been conducted at 53 and 34 stations with an interval of 1~1.5 km along the national roads of about 47 km and 34 km running from Duksungri to Yangpori and from Angangri to Byungpori, Kyungsangbookdo, respectively. The subsurface geology and geologic structure of Tertiary Pohang and Janggi basins along two survey lines are interpreted quantitatively by applying Fourier series and Talwani methods for Bouguer gravity anomaly. The depths of Conrad discontinuity vary from 11.8 to 12.5 km and 11.5 to 13.2 km along the survey lines between Duksungri and Yangpori, and Angangri and Byungpori, respectively. The depths of pre-Cambrian Gneiss complex underneath Kyungsang Supergroup vary from 3.8 to 4.2 km and 3.8 to 4.6 km along the survey lines between Duksungri and Yangpori, and Angangri and Byungpori, respectively. Massive granite bodies which are not exposed along the survey line between Duksungri and Yangpori are distributed on a large scale at the subsurface between Duksungri and Ochun, and Daegokri and Yangpori. Along the survey line between Angangri and Byungpori, it is exposed at Angangri, and extends underneath Chungrimdong, Pohang city. Andesite is distributed on a small scale underneath Pohang city and Ochun. The thicknesses of Tertiary Yonil and Janggi Groups are 0.2~0.9 km and 0.1~0.5 km, respectively. The Tuffaceous rocks which are the lowest formation of Tertiary sedimentary rocks are distributed with the thickness of 0.2 km at the surface and between Kyungsang Supergroup and Yonil or Janggi Groups. The Yonil and Janggi Groups are in fault contact by a fault running through Ochun and Chungrimdong, Pohang city. Two other faults are newly found near Heunghae-eup and Hyungsan river.

• 한국광물학회지
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• 제24권3호
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• pp.165-178
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• 2011

우리나라 육상의 제3기 포항분지와 백악기 경상분지, 그리고 동해와 서해의 대륙붕 퇴적분지에 대하여 일라이트-스멕타이트 점토광물 변화에 의하여 퇴적층 온도를 인지하고, 이를 근거로 하여 석유생성과의 관련성을 연구하였다. 포항분지는 불규칙배열의 일라이트-스멕타이트만 산출되며, 이것은 석유가 생성되기 어려운 $100^{\circ}C$ 이하의 매우 낮은 온도를 지시한다. 이에 반해, 경상분지는 일라이트만 산출되면, 일라이트 결정도 값에 의하면 이 지역은 $200^{\circ}C$ 이상의 높은 온도를 지시한다. 따라서 경상분지는 석유생성 단계를 이미 지난 상태인 것으로 생각된다. 동해의 대륙붕 지역은 상위 지층에서 불규칙배열의 일라이트-스멕타이트가 산출되지만, 약 2,500 m 이상의 매몰심도에서는 석유생성을 기대할 수 있는 온도를 지시하는 R=1 규칙배열의 일라이트-스멕타이트가 신출된다. 서해 대륙붕 지역은 상위 구간에서는 불규칙 배열의 일라이트-스멕타아트(R=0 I-S)가 나타나며, 중간의 구간에서는 R=1 규칙배열의 일라이트-스멕타이트(R=1 I-S)가 나타나고, 하위의 심부 구간에서는 R=3 규칙배열의 일라이트-스멕타이트(R=3 I-S)가 나타난다. 이 지역은 석유생성단계에서 가스생성 단계에 이르는 양호한 탄화수소 생성의 온도 조건을 보여주고 있다. 일라이트-스멕타이트 점토광물로 측정된 온도는 우리나라 육상분지에서는 석유가 존재하기 어렵다는 것을 보여준다. 그러나 대륙붕 지역은 석유와 가스를 생성하기 좋은 온도조건이므로 석유가스의 발견이 기대된다.

• 자원환경지질
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• 제8권4호
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• pp.223-230
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• 1975

남한(南韓)은 지구조적(地構造的)으로 4개의 지질구(地質區)로 나누어 진다. 경기육괴(京畿陸塊)와 영남육괴(嶺南陸塊)는 선(先)캠브리아기(紀)의 편마암(片麻岩)과 편암(片岩)으로 구성되어 있다. 결천지향사대(決川地向斜帶)는 소위 지나방향(支那方向)인 서남남동(西南南東)으로 한반도(韓半島)를 비스듬히 가로지르고 있다. 옥천지향사대(沃川地向斜帶)의 북동부(北東部)는 주(主)로 고생대(古生代)와 중생대(中生代) 초기의 퇴적암층(堆積岩層)으로 되어있고 서남부(西南部)는 후기 선(先)캠프리아기(紀)의 변성암층군(變成岩層群)으로 되어있다. 경상분지는 백악기(白堊紀)의 두꺼운 육성퇴적층(陸成堆積層)과 안산암류(安山岩類)로 되어있다. 제3기(第三紀)의 몇 개의 소분지(小盆地)가 한반도 동남부와 제주도에 분포(分布)하고 주로 해성층(海成層)과 현무암류로 되어있다. 쥬라기(紀)의 대보화강암(大寶花崗岩)이 경기육괴(京畿陸塊), 영남육괴(嶺南陸塊), 결천지향사대내(決川地向斜帶內)에 지나방향(支那方向)으로 관입분포(貫入分布)한다. 한편 백악기(白堊紀)의 불국사(佛國寺) 화강암(花崗岩)은 경상분지에 분산분포(分散分布)한다.