포항 북부 유계-중산리에서 확인되는 양산단층의 제4기 단층운동 특성

이성준,한종원,하상민,임혜원,성영배,최정헌,이초희,김석진,강희철,김민철,임현지,손문 대한지질학회 2022 지질학회지 Vol.58 No.4

In this study, we conducted a geomorphologic analysis, fieldwork, geophysical survey, and trench survey to trace the Quaternary faulting along the northern Yangsan fault. We also complement the study with the Electron Spin Resonance and luminescence datings of the fault rocks and Quaternary sediments, respectively, to constrain the timing of the Quaternary faulting. As a result of geomorphological analysis, two lineaments with lengths 6.8 km and 0.35 km are recognized by the linear distribution pattern of fault saddles and deflected streams. The amount of deflection of deflected streams is 2.05-2.82 km, 1.72 and 0.74 km, and 0.43 km in Seojeongcheon, Cheonghacheon, and Gwangcheon stream, respectively, which decreases gradually toward the north. Faults cutting the unconsolidated sediments were found at an outcrop and trench site, and both the sites have the following similar features: slickenlines on the fault surface in contact with the Quaternary sediments, indicating a dextral strike-slip including a reverse component, and a mixed zone of Quaternary sediment and fault gouge between the fault core and the Quaternary sediment. Their cross-cutting relationship indicates at least two faulting events during the Quaternary. Luminescence ages obtained from the sediment layers indicate that the latest faulting event occurred between 154±13 ka and 0.9±0.1 ka. The slip rate, calculated by dividing the net displacement by the age gap, is 0.007 to 0.008 mm/yr. Also, the conversion of the vertical displacement of the Yugye site reported in the previous study into the net displacement gives rise to an estimated slip rate of about 0.08 mm/yr. Combining the results, the slip rate of the northern Yangsan fault in the study area is estimated to be in the range of 0.007 to 0.08 mm/yr. The moment magnitude (Mw) obtained using the net displacement in the empirical equation is about 6.7, and the magnitude of about 6.0 is derived using the lineament length as the surface rupture length. 기존에 제4기 단층으로 보고된 유계지점에서부터 송라면 중산리까지 1954년 항공사진과 고해상도 LiDAR 영상을 활용한 상세 지형분석, 지질조사, 지구물리탐사, 굴착조사 및 연대측정를 수행하였다. 이를 통해 북부양산단층의 제4기 단층운동 시기와 특성을 분석하고자 하였다. 선형구조 분석결과, 북북동 방향으로 연장되어보경사지점을 지나가는 길이 6.8 km의 선형구조 1매와 유계지점을 지나가는 길이 0.35 km의 선형구조 1매가확인하였으며, 두 선형구조는 굴절하천과 단층와지의 선형적인 분포 패턴과 뚜렷한 선형곡에 의해 인지되었다. 굴절하천의 굴절량은 서정천, 청하천, 광천에서 각각 2.05 또는 2.82 km, 1.72와 0.74 km 그리고 0.43 km로 북쪽으로 갈수록 점차 감소하는 양상이다. 이중 제4기 퇴적층이 발달하고 인위적인 개발이 거의 없는 광천을 대상으로 집중적으로 상세 지질조사와 전기비저항탐사를 수행하였고, 이를 통해 각 1개의 노두지점과 굴착지점에서 제4기 미고결 퇴적층을 절단하는 단층을 확인하였다. 제4기 퇴적층과 접하는 단층면에는 역이동 성분을포함하는 우수향 주향이동 운동을 지시하는 단층조선이 발달하고 제4기 퇴적층과 인접한 단층핵에는 제4기 퇴적층의 역들이 단층비지와 혼합된 특징을 보인다. 제4기 퇴적층과 단층의 절단 관계 그리고 절단된 퇴적층과단층을 피복하는 퇴적층에서 얻은 퇴적층의 루미네센스 연대를 종합하면, 이곳 단층의 최후기 운동은 154±13 ka와 0.9±0.1 ka 사이에 발생하였으며, 제4기 동안 최소 2회 이상의 단층 운동이 발생한 것으로 해석된다. 노두에서 확인되는 실변위량 그리고 절단된 퇴적층과 피복하는 퇴적층의 연대 시간차를 이용해 계산된 변위율은0.007~0.008 mm/yr로 계산되었다. 기존에 보고된 유계지점의 수직변위율을 단층자세와 단층조선을 통해 실변위율로 환산하면 0.08 mm/yr이다. 두 결과를 종합하여 얻은 연구지역 양산단층의 변위율은 0.007~0.08 mm/yr 범위를 가질 것으로 추정된다. 노두에서 확인되는 실변위량을 한 번의 지표파열의 변위로 가정하고 최대변위- 모멘트 지진규모 경험식에 적용하면 지진규모는 약 6.7로 계산되고, 선형구조의 길이를 지표파열 길이로 가정하여 파열길이-모멘트 지진규모 경험식에 적용하면 약 6.0의 규모가 도출된다.

The enigma of rare Quaternary oolites in the Indian and Pacific Oceans: A result of global oceanographic physicochemical conditions or a sampling bias?

Gallagher, S.J.,Reuning, L.,Himmler, T.,Henderiks, J.,De Vleeschouwer, D.,Groeneveld, J.,Rastegar Lari, A.,Fulthorpe, C.S.,Bogus, K.,Renema, W.,McGregor, H.V.,Kominz, M.A.,Auer, G.,Baranwal, S.,Casta& Elsevier 2018 Quaternary science reviews Vol.200 No.-

<P><B>Abstract</B></P> <P>Marine ooids are iconic indicators of shallow seawater carbonate saturation state, and their formation has traditionally been ascribed to physicochemical processes. The Indo-Pacific stands out as a region devoid of oolites, particularly during the Quaternary: the “ooid enigma”. Here we present results from recent coring by the International Ocean Discovery Program (IODP Expedition 356) off west Australia that shows that ooid horizons are common in Pleistocene strata up to 730,000 years old. Extensive “ooid factories” were created due to the presence of long-lived tidally influenced flat–topped tropical platforms suitable for intermittent ooid accretion over hundreds to thousands of years during highstands and times of lower sea level. This work suggests marine ooids may actually be more common in Indo-Pacific than previously reported. Past global ocean alkalinity was elevated during Pleistocene glacial periods and continental climate was generally more arid in the Indo-Pacific region compared to interglacials and the Holocene. Therefore, increased aridity associated with higher alkalinity conditions during the glacials facilitated ooid precipitation on adjacent tropical carbonate platforms particularly offshore from arid Australia. This confluence of factors suggests that more “ooid factories” may be encountered by further coring Indo-Pacific regions with Pleistocene flat long-lived carbonate shelves. However, Indo-Pacific Quaternary ooid occurrences outside Australia are rare, suggesting that the Northwest Shelf may be a unique archive of this non-skeletal precipitate. Further investigations into the petrography and geochemistry of pre-Holocene ooid occurrences will provide insights into their origin and the relative role of biotic, physicochemical and other factors in their formation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Oolites are rare in the Indo-Pacific, particularly during the Quaternary: the “ooid enigma”. </LI> <LI> IODP Expedition 356 off west Australia cored common ooid horizons in strata up to 730,000 years old. </LI> <LI> Extensive “ooid factories” were deposited on tidally influenced flat–topped tropical platforms. </LI> <LI> Oolites were deposited during low and high sea levels in generally arid conditions. </LI> <LI> More “ooid factories” may be found by coring regions with flat long-lived carbonate shelves. </LI> </UL> </P>

Stratigraphy of late Quaternary deposits using high resolution seismic profile in the southeastern Yellow Sea

Lee, G.S.,Kim, D.C.,Yoo, D.G.,Yi, H.I. Pergamon Press 2014 QUATERNARY INTERNATIONAL Vol.344 No.-

High-resolution (Chirp and Sparker system) seismic profiles were analyzed to investigate the sequence stratigraphy of late Quaternary deposits in the southeastern Yellow Sea. Approximately 1560 line-km data of chirp and sparker profiles were acquired, together with 11 piston cores. Two previous long drill cores (YSDP-102 and 103) were used for comparison with seismic data. High-resolution seismic profiles image the Holocene mud deposits and the complex sedimentary structure in this area. Sequence analysis of high-resolution seismic profiles reveals that the shelf deposits form a succession of high-frequency (five-order) sequences consisting of one depositional sequence developed during the late Quaternary. The depositional sequence includes five sedimentary units, each with different seismic facies and geometry: (1) incised channel fill and lowstand deltaic wedge (unit SY1), (2) sand ridges (unit SY2), (3) estuarine/deltaic mud (unit SY3), (4) redeposited mud (unit SY4), and (5) recent distal mud (unit SY5). Based on the interpretation of high-resolution seismic records and correlation with the YSDP-102, 103 long cores and piston cores, late Quaternary deposits in the southeastern Yellow Sea consists of a set of the lowstand (unit SY1), early transgressive (unit SY2), middle transgressive (unit SY3), late transgressive (unit SY4), and highstand systems tract (unit SY5) formed since the last-glacial period. The rather unusual stratigraphic architecture including three systems tracts is largely controlled by the postglacial sea-level changes and regionally circulation pattern associated with sediment erosion and redeposition. The results of this study present firstly clear seismic evidence that the southeastern Yellow Sea mud belt (SEYSM) can be divided into three stratigraphic units (units SY3, SY4, and SY5) bounded by distinct bounding surfaces.

The offshore Yangsan fault activity in the Quaternary, SE Korea: Analysis of high-resolution seismic profiles

Kim, H.J.,Moon, S.,Jou, H.T.,Lee, G.H.,Yoo, D.G.,Lee, S.H.,Kim, K.H. Elsevier Scientific Publishing Co 2016 Tectonophysics Vol.693 No.1

<P>The NNE-trending dextral Yangsan fault is a > 190-km-long structure in the Korean Peninsula traced to the southeastern coast. The scarcity of Quaternary deposits onland precludes any detailed investigation of the Quaternary activity and structure of the Yangsan fault using seismic reflection profiling. We acquired offshore high-resolution seismic profiles to investigate the extension of the Yangsan fault and constrain its Quaternary activity using stratigraphic markers. The seismic profiles reveal a NNE-trending fault system consisting of a main fault and an array of subsidiary faults that displaced Quaternary sequences. Stratigraphic analysis of seismic profiles indicates that the offshore faults were activated repeatedly in the Quaternary. The up-to-the-east sense of throw on the main fault and plan-view pattern of the fault system are explained by dextral strike-slip faulting. The main fault, when projected toward the Korean Peninsula along its strike, aligns well with the Yangsan fault. We suggest that the offshore fault system is a continuation of the Yangsan fault and has spatial correlation with weak but ongoing seismicity. (C) 2016 Elsevier B.V. All rights reserved.</P>

Stratigraphy and geochronology of Quaternary marine terraces of Tasmania, Southeastern Australia: implications on neotectonism

신재열 한국지질과학협의회 2013 Geosciences Journal Vol.17 No.4

This study documents emergent marine terraces of Tasmania in Southeast Australia that are commonly observed along the coasts with both the distribution and elevation of terraces varying around the island. The primary objective is to document existence, characteristics and geochronology of little known terrace sequences on each coastline and to establish correlations between them. In order to address variability in uplift in Tasmania this study attempts to correlate uplift records from a number of widely separated locations. Quartz OSL dating technique was applied to constrain the age of the late Quaternary terrace sequences. The results imply that the time-integrated uplift rates around the Tasmanian coasts ranged from 40 m/Ma to 112 m/Ma since the last interglacial period, suggesting a non-uniform uplift during the late Quaternary. In addition, likely Miocene paleo-shorelines ranging 160 to 270 m around Tasmania show a similar pattern with the non-uniform uplift during the Late Neogene. The vertical motion of Tasmania within a horizontal length scale of order 100 kms and amplitude of order 100 m accords well with the dynamic topography records documented elsewhere in Southern Australia over the Neogene.

Late Quaternary Sequence Stratigraphy in Kyeonggi Bay, Mid-eastern Yellow Sea

권이균 한국지구과학회 2012 韓國地球科學會誌 Vol.33 No.3

The Yellow Sea has sensitively responded to high-amplitude sea-level fluctuations during the late Quaternary. The repeated inundation and exposure have produced distinct transgression-regression successions with extensive exposure surfaces in Kyeonggi Bay. The late Quaternary strata consist of four seismic stratigraphic units, considered as depositional sequences (DS-1, DS-2, DS-3, and DS-4). DS-1 was interpreted as ridge-forming sediments of tidal-flat and estuarine channel-fill facies, formed during the Holocene highstand. DS-2 consists of shallow-marine facies in offshore area, which was formed during the regression of Marine Isotope Stage (MIS)-3 period. DS-3 comprises the lower transgressive facies and the upper highstand tidal-flat facies in proximal ridges and forced regression facies in distal ridges and offshore area. The lowermost DS-4 rests on acoustic basement rocks, considered as the shallow-marine and shelf deposits formed before the MIS-6 lowstand. This study suggests six depositional stages. During the first stage-A, MIS-6 lowstand, the Yellow Sea shelf was subaerially exposed with intensive fluvial incision and weathering. The subsequent rapid and high amplitude rise of sea level in stage-B until the MIS-5e highstand produced transgressive deposits in the lowermost part of the MIS-5 sequence, and the successive regression during the MIS-5d to -5a and the MIS-4 lowstand formed the upperpart of the MIS-5 sequence in stage-C. During the stage-D, from the MIS-4 lowstand to MIS-3c highstand period, the transgressive MIS-3 sequence formed in a subtidal environment characterized by repetitive fluvial incision and channel-fill deposition in exposed area. The subsequent sea-level fall culminating the last glacial maximum (Stage-E) made shallow-marine regressive deposits of MIS-3 sequence in offshore distal area, whereas it formed fluvial channel-fills and floodplain deposits in the proximal area. After the last glacial maximum, the overall Yellow Sea shelf was inundated by the Holocene transgression and highstand (Stage-F), forming the Holocene transgressive shelf sands and tidal ridges.

Correlation of TL layers for the synchronous paleoceanographic events in the East Sea (Sea of Japan) during the Late Quaternary

김부근,Ryuji Tada,박유현,박장준,Yoshiki Kido,Takuya Itaki,Ken Ikehara 한국지질과학협의회 2009 Geosciences Journal Vol.13 No.2

TL layers (i.e., dark mud layers), either thin or thick, as determined by the L* values with lithologic observation, are distinct paleoceanographic signatures in the East Sea (Sea of Japan), which were formed in response to the global eustatic sea-level fluctuations between interglacials and glacials during the Late Quaternary. These lithologic markers were consistently correlated among the three sediment cores (MD01-2407, 05GCRP21, and KR05-09PC1) collected from the Oki Ridge of the southern Yamato Basin, the South Korea Plateau of the northern Ulleung Basin, and the Matsumae Plateau of the northeastern Japan Basin, respectively. Reconstruction of age models for cores 05GCRP and KR05-09PC1 was aided in a good way by the AMS 14C ages of planktonic foraminifera and identification of the tephra layers, and mainly by lithostratigraphic correlation with TL layers of well-dated core MD01-2407, based on the L* values. The correlation of TL layers among the three sediment cores was remarkable, indicating that the East Sea (Sea of Japan) experienced the synchronous and basin-wide scale paleoceanographic events during the Late Quaternary. Our study exemplifies the significant usefulness of these lithologic markers for further Late Quaternary paleoceanographic investigation.

한반도 남동부 제4기 단층의 대자율이방성(AMS)

조형성(Hyeongseong Cho),김민철(Min-Cheol Kim),김현정(Hyeonjeong Kim),손문(Moon Son) 한국암석학회 2014 암석학회지 Vol.23 No.2

한반도 남동부 일원에는 주요 지질구조선(양산단층대, 울산단층, 연일구조선, 오천단층계 등)을 따라 제4기 단층들이 도처에 분포하고 있으며, 이들의 기하와 운동학적 특징은 한반도의 제4기 지각변형사와 현생응력상태 등을 이해하는 데 중요한 정보들을 제공한다. 이번 연구에서는 진티단층, 모화단층, 수성지2단층 그리고 왕산단층을 대상으로 대자율이방성 방법을 적용하여 단층가우지의 미세구조를 분석하고 단층의 운동감각을 해석하였으며, 그 결과를 바탕으로 단층암의 미세구조 발달과정과 제4기 응력장에 대해 논의하였다. 대자율이방성 측정을 통해 구해진 자기미세구조로부터 단층의 운동감각을 분석한 결과, 왕산단층을 제외한 나머지 세 단층은 모두 역이동성이 우세한 단층운동에 의한 미세구조가 발달되어 있다. 단층면에 거의 평행한 편평형의 미세구조가 발달하는 점과 이방성정도가 클수록 편평형의 정도가 증가하는 특징에 근거할 때, 단층 가우지의 미세구조는 점진적인 변형에 의한 최종응력변형이 기록된 것으로 해석된다. 또한, 최후기에 재활된 역단층운동으로 기존의 단층가우지 내에 존재하는 미세구조들은 모두 지워지고 최후기의 운동에 의한 미세구조만이 기록된 것으로 판단된다. 단층가우지의 자기미세구조 분석을 통해 유추된 운동감각으로부터 구해진 고응력장은 동북동-서남서 방향의 압축력이며, 이 응력장은 지진원 메커니즘, 수압파쇄시험 그리고 단층 지구조 분석결과를 통해 구해진 한반도 남동부의 고응력장과 부합된다. 결론적으로 한반도 일원은 제4기 동안 동-서내지 동북동-서남서 방향의 압축성 응력장이 지배적이었던 것으로 해석된다. The Quaternary faults are extensively observed along major inherited fault zones (i.e. Yangsan Fault System, Ulsan Fault, Yeonil Tectonic Line, Ocheon Fault System) in SE Korea. Their geometry and kinematics provide a very useful piece of information about the Quaternary crustal deformation and stress field in and around Korean Peninsula. Using magnetic fabrics (AMS), we attempted to determine the slip senses of Jinti, Mohwa, Suseongji2, and Wangsan faults and then interpreted the fabric development process of fault gouge and the characteristics of stress field during the Quaternary. All the magnetic fabrics of the faults, except the Wangsan Fault, consistently indicate a dominant reverse-slip sense with weak strike-slip component. Most of the oblate fabrics are nearly parallel to the fault surface and the anisotropy degrees generally increase in proportion to the oblatenesses. These results suggest that the fabrics of the fault gouges resulted from a progressive deformation due to continuous simple shear during the last reactivation stage as reverse faulting. It is also interpreted that the pre-existing fabrics were overwhelmed and obliterated by the re-activated faulting. Paleostress field calculated from the fault slip data indicates an ENE-WNW compressive stress, which is in accord with those determined from previous fault tectonic analysis, focal mechanism solution, and hydraulic fracturing test in and around Korean Peninsula.

장대 단층 중부 구간 모곡리 단층의 제4기 활동성 및 누적 변위

홍영민(Yeong-Min Hong),신재열(Jae-Ryul Shin) 대한지리학회 2021 대한지리학회지 Vol.56 No.4

본 연구는 장대 단층 중부 구간에 위치한 함안군 모곡리 단층을 중심으로 연구 지역 일대의 단층 운동 특성 및 운동 시기, 제4기 후기 동안의 누적 변위량을 논의하고 있다. 지금까지 장대 단층은 경사 이동이 포함된 좌수향 운동특성을 보이는 것으로 알려져 왔는데, 본 고에서는 모곡리 단층 및 지역 일대의 지형 분석을 통해 운동 감각과 제4기 활동성에 관한 직접적인 증거를 최초로 제시하고 있다. 모곡리 단층은 단층의 상반인 남서측 지괴가 북동측으로 ~0.8m 상향 이동한 역이동성 운동 감각을 보인다. 모곡리 단층 주변으로 나타나는 단층 구조 및 단층 지형의 발달 특성은 모곡리 단층의 역이동성 운동이 장대 단층 구간 중 가지 단층의 발달 분기점에서 장대 단층의 좌수향 이동 감각에 수반된 전달압축력에 의해 형성되었음을 시사하고 있다. 지형 변위 분석에서 모곡리 단층은 선상지 3면으로 분류된 미고결 퇴적층을 절단하며, 제4기 후기 동안 1~2.5m의 누적 수직 변위량을 보여준다. This study discusses the kinematic characteristics of the Mogok Fault (Mogok-ri Haman-gun Gyeongnam) located in the central part of the Jangdae Fault including its geometry, extension and timing with the amount of cumulative surface offset since the late Quaternary. The Jangdae Fault is known as NNW sinistral strike-slip faults with reverse dip-slip sense of shear, in this paper we address the results of fault tectonic analysis of the Mogok Fault and of analyzing fault-related landforms. As results, the Mogok Fault is a reverse fault with a top-up-to the northeast movement and the slip calculated from the offset of the unconformity between bedrock and Quaternary sedimentary units is approximately 0.8 m. The result of fault tectonic analysis with its positive half-flower structure and fault-related deformed geomorphic features indicate that the fault was activated by sinistral transpressional strike-slip displacement at a branch of the Jangdae Fault. Furthermore the Mogok Fault was deforming the 3<SUP>rd</SUP> alluvial fans in the area, and the cumulative vertical offset estimated by geomorphic surface displacement is likely to be 1.0~2.5 m during the late Quaternary.

Seismic reflection imaging of Quaternary faulting offshore the southeastern Korean Peninsula

Han-Joon Kim,YoungSook Baek,Hyeong-Tae Jou,Sang Hoon Lee,Seonghoon Moon,Jin Soo Kim,Su-hwan Lee,Gwang Hoon Lee,Seung-Goo Kang,Woo-Hyun Son,Ryeongsim Seok 한국지질과학협의회 2016 Geosciences Journal Vol.20 No.3

The Yangsan Fault System (YFS) is a dominating tectonic structure in the southeastern part of the Korean Peninsula. The YFS consists of NNE-striking dextral strike-slip faults that are traced to the southeastern coast of the Korean Peninsula. We acquired high-resolution seismic profiles offshore the southeastern Korean Peninsula to investigate how the YFS extends offshore and constrain the age of fault activity using stratigraphic interpretation. The seismic profiles image near-vertical faults trending NE to NNE that constitute a fault zone similar to a duplex structure at a releasing bend of a right-lateral strike-slip fault. The faults are interpreted as an offshore extension of the Ilgwang fault that is a member of the YFS. Stratigraphic interpretation of seismic profiles indicates that the offshore faults were activated repeatedly in the Pliocene and Quaternary. The right-lateral activity of the Ilgwang fault is consistent with the current stress regime in and around the southeastern Korean Peninsula that dictates the P-axis direction in the E-W or ENE-WSW since the Pliocene.