‘Singwang strike-slip duplex’ around the Pohang Basin, SE Korea: its structural evolution and role in opening and fill of the Miocene basin

Choi, Pom-yong

doi:10.1007/bf02910359

Cited by 16 publications

(14 citation statements)

References 15 publications

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“…경주시 양북면에서 감포읍에 이르는 지역에 걸쳐 형성된 분지는 어일분지로 통칭되었으나 (Yoon, 1986;Lee et al. 1992 Geology: 1=Cretaceous sediments (1a=Hayang Group; 1b=Balsandong Formation); 2=Yucheon Group volcanics; 3=Granitic rocks; 4=Gokgandong Rhyolitic Tuff; 5=Eocene volcanics in Guryongpo area; 6=Gampo Conglomerate; 7=Andongri Formation; 8=Janggi/Jeongcheolli Conglomerate; 9a=Churyeong Breccia; 9b=Galpyeongdong Breccia; 10=Hyodongri Volcanics; 11=Waeupri Tuff; 12=Yongdongri Tuff; 13a=Beomgokri Volcanics; 13b=Volcanics in Churyeong area; 13c=Volcanics in Jinjeonri area; 14=Ocheon Formation (14a=trachytic andesites and andesites, i.e., Nultaeri Volcanics; 14b=lignite-bearing sediments; 14c=dacitic tuffs; 14d=Geumori dacitic tuff); 15=Manghaesan Formation; 16=basaltic rocks in Janggi Basin (Yeonil basalts & andesites); 17a=Eoil Formation; 17b=Eoil Basalt; 18=basalt in Daljeonri area; 19=andesitic-basaltic dykes around Daljeonji Reservoir; 20=Yeonil Group sediments (modified from Tateiwa, 1924;Chwae et al, 1988;Yun et al, 1994;Hwang et al, 1996;Son et al, 2000aSon et al, ,b, 2002Son et al, , 2005Son et al, , 2009Choi, 2006;Paik et al, 2010) (Ma,±1σ); un-underlined=single measurement; underlined= average value from multiple data; Asterisked* italics=thermally-affected age.…”

Section: ) 전기 에오세 화산암mentioning

confidence: 99%

Revised Fission-track Ages and Chronostratigraphies of the Miocene Basin-fill Volcanics and Basements, SE Korea

Shin¹

2013

The Journal of the Petrological Society of Korea

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Erroneous fission-track (FT) ages caused by an inappropriate calibration in the initial stage of FT dating were redefined by re-experiments and zeta calibration using duplicate samples. Revised FT zircon ages newly define the formation ages of Yucheon Group rhyolitic-dacitic tuffs as Late Cretaceous to Early Paleocene (78±4 Ma to 65±2 Ma) and Gokgangdong rhyolitic tuff as Early Eocene (52.1±2.3 Ma). In case of the Early Miocene volcanics, FT zircon ages from a dacitic tuff of the upper Hyodongri Volcanics (21.6±1.4 Ma) and a dacitic lava of the uppermost Beomgokri Volcanics (21.3±2.0 Ma) define chronostratigraphies of the upper Beomgokri Group, respectively in the southern Eoil Basin and in the Waeup Basin. A FT zircon age (19.8±1.6 Ma) from the Geumori dacitic tuff defines the time of later dacitic eruption in the Janggi Basin. Based on FT zircon ages for dacitic rocks and previous age data (mostly K-Ar whole-rock, partly Ar-Ar) for basaltic-andesitic rocks, reference ages are recommended as guides for stratigraphic correlations of the Miocene volcanics and basements in SE Korea. The times of

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Section: ) 전기 에오세 화산암mentioning

confidence: 99%

Revised Fission-track Ages and Chronostratigraphies of the Miocene Basin-fill Volcanics and Basements, SE Korea

Shin¹

2013

The Journal of the Petrological Society of Korea

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“…The deformation might have resulted from movement on the strike-slip Yangsan Fault before 17 Ma (e.g., Sohn & Son, 2004; because both sedimentary (Cretaceous to Paleogene) and volcanic (early Eocene) basement rocks at the northwestern margin of the Pohang Basin are intersected by the Yangsan Fault, and indicate dextral displacement of ca. 35 km (Chang et al, 1990;Choi, 2006, Figure 1).…”

Section: Deformation Structures In the Basement Rocksmentioning

confidence: 98%

Tectono‐sedimentary development of early synrift half‐graben subbasins in the Miocene Pohang Basin, southeastern Korea

2022

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Early synrift half‐grabens, herein named the Chilpo and Sinheung subbasins, have been newly recognised in the north‐central area of the Miocene Pohang Basin, Korea. The subbasins are closely aligned along an array of NNW‐trending strike‐slip faults and are bounded by ENE‐striking normal faults. The sediment infill of the subbasins consists of a deepening‐ and fining‐upward sequence of alluvial cobble to boulder conglomerate (FA1), alluvial to nearshore granule to pebble conglomerate and sandstone (FA2) and hemipelagic mudstone (FA3). The younger strata sequentially onlap the older strata in the hangingwall basement or transfer zones, whereas the footwall basement is directly onlapped by the younger hemipelagic mudstone. These patterns may have resulted from a series of domino‐style block rotations, in which subsidence along normal faults caused the differential creation of accommodation space, whilst simultaneous uplift in the upslope of rotated hangingwall blocks controlled denudation, the shedding of sediments to downslope areas and asymmetric stacking of sediments in both subbasins. In contrast to the western margin of the Pohang Basin, where large footwall‐derived fan‐delta systems developed along the bounding faults, in the Chilpo and Sinheung subbasins, small hangingwall‐derived alluvial‐fan deltas formed during rifting. The development of these domino‐style half‐grabens would have resulted from the detachment and simultaneous transrotation of the crustal block away from the northwest during accelerated extension in the Pohang Basin. Recent geophysical studies have detected very thin basin‐fill sediments in the north‐central Pohang Basin and faults that are similar in orientation to those identified in this study, thereby supporting our observations. These findings confirm the early opening of the Pohang Basin, supporting the hypothesis that all of the Miocene basins in southeastern Korea formed in a setting of NW–SE extension, and further suggest the development of the wedge‐shaped transtensional basin, in response to the opening of the East Sea (Sea of Japan) after 17 Ma.

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“…The Yangsan Fault has slipped tens of kilometres (~35 km according to [33]; 50 km according to [43]), displacing the contacts between zones of Cretaceous mineralization (e.g., [40]). A relatively complex fault pattern is thus evident in the Pohang area at this rightward step in right-lateral faulting (e.g., [33,41,42]). Right-lateral slip on the Yangsan Fault continues to the present day, evidenced by palaeoseismic studies (e.g., [44]), historical earthquakes (e.g., [45]), and instrumentally recorded events.…”

Section: Conditions At the Pohang Egs Sitementioning

confidence: 99%

“…the Pohang area as the NNE-SSW-oriented right-lateral Yangsan Fault (e.g., [33,41,42]; Figure 1). The Yangsan Fault has slipped tens of kilometres (~35 km according to [33]; 50 km according to [43]), displacing the contacts between zones of Cretaceous mineralization (e.g., [40]).…”

Section: Conditions At the Pohang Egs Sitementioning

confidence: 99%

Fault “Corrosion” by Fluid Injection: A Potential Cause of the November 2017 MW 5.5 Korean Earthquake

Westaway

Burnside

2019

Geofluids

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The November 2017 MW 5.5 Pohang earthquake is one of the largest and most damaging seismic events to have occurred in the Korean peninsula over the last century. Its close proximity to an Enhanced Geothermal System (EGS) site, where hydraulic injection into granite had taken place over the previous two years, has raised the possibility that it was anthropogenic; if so, it was by far the largest earthquake caused by any EGS project worldwide. However, a potential argument that this earthquake was independent of anthropogenic activity considers the delay of two or three months before its occurrence, following the most recent injection into each of the wells. A better understanding of the physical and chemical processes that occur following fluid injection into granite is thus warranted. We show that hydrochemical changes occurring while surface water, injected into granite, reequilibrates chemically with its subsurface environment, can account for time delays for earthquake occurrence of such duration, provided the seismogenic fault was already critically stressed, or very close to the condition for slip. This candidate causal mechanism counters the potential argument that the time delay militates against an anthropogenic cause of the Pohang earthquake and can account for its relatively large magnitude as a consequence of a relatively small-volume injection. The resulting analysis places bounds on combinations of physical and chemical properties of rocks, injected volume, and potential postinjection time delays for significant anthropogenic seismicity during future EGS projects in granite.

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‘Singwang strike-slip duplex’ around the Pohang Basin, SE Korea: its structural evolution and role in opening and fill of the Miocene basin

Cited by 16 publications

References 15 publications

Revised Fission-track Ages and Chronostratigraphies of the Miocene Basin-fill Volcanics and Basements, SE Korea

Revised Fission-track Ages and Chronostratigraphies of the Miocene Basin-fill Volcanics and Basements, SE Korea

Tectono‐sedimentary development of early synrift half‐graben subbasins in the Miocene Pohang Basin, southeastern Korea

Fault “Corrosion” by Fluid Injection: A Potential Cause of the November 2017 MW 5.5 Korean Earthquake

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