• Economic and Environmental Geology
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• v.45 no.5
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• pp.565-578
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• 2012

Sedimentary facies of the Middle to Upper Cambrian Sesong Formation, Taebacksan Basin, are analyzed using detailed field mapping and stratigraphic section measuring. As a result, five sedimentary facies are recognized in the formation, which include lime nodule bearing shale facies, anastomosing wackestone-packstone facies, well-laminated siltstone facies, fine to medium sandstone facies and lime pebble conglomerate facies. Together with sedimentary facies analysis, study on vertical facies variation indicates that the Sesong Formation was deposited in an outer to inner shelf during relative sea-level fall. Especially, shallow marine aspects of the upper part of the Sesong Formation including 10-m-thick, fine to medium-grained sandstones appear to be very similar with the shallow marine strata accumulated during the Steptoean Stage (Dunderbergia) in Laurentia. These lithofacies comparisons of coeval strata between two continents suggest that sedimentation in the Sesong Formation reflects the influence of global sea-level fall occurred during the late Middle Cambrian to early Late Cambrian. As well, a stratigraphic discontinuity surface that may have sequence stratigraphic significance is recognized within the shallow marine sandstone beds of the uppermost Sesong Formation. This stratigraphic discontinuity surface may correspond to the Sauk II-III sequence boundary in Laurentia. Therefore, results delineated in this study will use a new stratigraphic paradigm for regional correlation of the Middle to Late Cambrian strata (e.g., the Sesong Formation) in the Taebacksan Basin, and will provide very useful information on intercontinental stratigraphic correlation in the future.

• Journal of the Korean earth science society
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• v.32 no.5
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• pp.437-452
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• 2011

The Steptoean Positive Carbon Isotope Excursion (SPICE) is found in the Machari Formation which was interpreted to have been deposited on the middle to outer carbonate ramp environment. The Machari Formation is the Middle to Late Cambrian in age and distributed in the Yeongweol area, Gangweon Province, Korea. The SPICE event in the Machari Formation begins with the first appearance datum of trilobite Glyptagnostus reticulatus and ends with the first appearance of datum of trilobite Irvingella. The SPICE is found in approximately 120 m thick sequence and ${\delta}^{13}C$ values in the SPICE interval range from 0.6 to 4.4‰. The SPICE in the Machari Formation is interpreted to be caused by burial of organic matter in the sea floor and subsequent increase of $^{13}C$ isotope of the Late Cambrian ocean. The SPICE interval in the Machari Formation corresponds to the highstand to transgressive systems tracts.

• Economic and Environmental Geology
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• v.52 no.5
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• pp.381-393
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• 2019

Carbonate breccias occur sporadically in the Middle Cambrian Daegi Formation on the southern limb of the Baegunsan Syncline, Taebaeksan Basin. These carbonate breccias have been largely interpreted either as sedimentary breccias or as tectonic, fault-related breccias. Recent study, however, indicates that the majority of these breccias are a solution-collapse breccia which is causally linked to the paleokarstification. Extensive karstification is attributed to prolonged subaerial exposure of the carbonate platform. The exposed surface is a record of interruption in sedimentation on the carbonate platform. In the stratigraphic record, such karst-related post-depositional features are recognized as meteoric diagenetic features, paleosols, and solution-collapse breccias. Solution-collapse breccias are particularly well preserved and most profound in the carbonate rocks below the major unconformities, which also are evidence of prolonged subaerial exposure. The Middle Cambrian Daegi Formation provides an example of solution-collapse breccias. The formation and preservation of the solution-collapse breccias imply that a stratigraphic discontinuity surface (unconformity) can be designated within the Daegi Formation.

• Journal of the Korean earth science society
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• v.23 no.1
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• pp.72-86
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• 2002

The Middle to Late Cambrian Machari Formation in the Machari area, Yeongweol, Korea consists of 7 lithofacies and 3 facies associations, which are thought to be deposits of carbonate ramp (mid to outer ramp) to basin environment. These lithofacies are bedded lime mudstone, laminated lime mudstone, bioclastic/peloidal packstone to grainstone, poloidal/bioclastic wackestone, conglomerate, mottled lime mudstone, and shale. Bedded lime mudstone facies, a few cm thick lime mudstone alternating with shale layer, is believed to have been deposited by intermittent dilute turbidity currents. Laminated lime mudstone facies, alternating lime mudstone with laminated shale, is interpreted to have been formed by fine-grained turbidity currents. Bioclastic/peloidal packstone to grainstone facies was deposited by turbidity current and peloidal/bioclastic wackestone faceis was deposited by debris flow. Conglomerate facies is thought to be deposits of storm activities. Mottled lime mudstone facies is interpreted to have been formed by bioturbation. Shale facies is interpreted to have been formed by suspension settling. Seven lithofacies of the Machari Formation are divided into three facies associations. Facies association I consisted of bedded lime mudstone facies, mottled lime mudstone facies, conglomerate facies, and bioclastic/peloidal packstone to grainstone facies, is interpreted to have been deposited on the mid ramp. Facies assocaition II consisted of bedded lime mudstone facies, laminated lime mudstone facies, bioclastic/peloidal packstone to grainstone facies, and peloidal/bioclastic wackestone facies is thought to be deposits of the outer ramp. Facies association III consisted of laminated lime mudstone facies and shale facies is interpreted to have been formed on the basin environment.

• Economic and Environmental Geology
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• v.45 no.3
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• pp.317-333
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• 2012

The Yeongweol Group is a Lower Paleozoic mixed carbonate-siliciclastic sequence in the Taebaeksan Basin of Korea, and consists of five lithologic formations: Sambangsan, Machari, Wagok, Mungok, and Yeongheung in ascending order. Sequence stratigraphic interpretation of the group indicates that initial flooding in the Yeongweol area of the Taebaeksan Basin resulted in basal siliciclastic-dominated sequences of the Sambangsan Formation during the Middle Cambrian. The accelerated sea-level rise in the late Middle to early Late Cambrian generated a mixed carbonate-siliciclastic slope or deep ramp sequence of shale, grainstone and breccia intercalations, representing the lower part of the Machari Formation. The continued rise of sea level in the Late Cambrian made substantial accommodation space and activated subtidal carbonate factory, forming carbonate-dominated subtidal platform sequence in the middle and upper parts of the Machari Formation. The overlying Wagok Formation might originally be a ramp carbonate sequence of subtidal ribbon carbonates and marls with conglomerates, deposited during the normal rise of relative sea level in the late Late Cambrian. The formation was affected by unstable dolomitization shortly after the deposition during the relative sea-level fall in the latest Cambrian or earliest Ordovician. Subsequently, it was extensively dolomitized under the deep burial diagenetic condition. During the Early Ordovician (Tremadocian), global transgression (viz. Sauk) was continued, and subtidal ramp deposition was sustained in the Yeongweol platform, forming the Mungok Formation. The formation is overlain by the peritidal carbonates of the Yeongheung Formation, and is stacked by cyclic sedimentation during the Early to Middle Ordovician (Arenigian to Caradocian). The lithologic change from subtidal ramp to peritidal facies is preserved at the uppermost part of the Mungok Formation. The transition between Sauk and Tippecanoe sequences is recognized within the middle part of the Yeongheung Formation as a minimum accommodation zone. The global eustatic fall in the earliest Middle Ordovician and the ensuing rise of relative sea level during the Darrwillian to Caradocian produced broadly-prograding peritidal carbonates of shallowing-upward cyclic successions within the Yeongheung Formation. The reconstructed relative sea-level curve of the Yeongweol platform is very similar to that of the Taebaek platform. This reveals that the Yeongweol platform experienced same tectonic movements with the Taebaek platform, and consequently that both platform sequences might be located in a body or somewhere separately in the margin of the North China platform. The significant differences in lithologic and stratigraphic successions imply that the Yeongweol platform was much far from the Taebaek platform and not associated with the Taebaek platform as a single depositional system. The Yeongweol platform was probably located in relatively open shallow marine environments, whereas the Taebaek platform was a part of the restricted embayments. During the late Paleozoic to early Mesozoic amalgamations of the Korean massifs, the Yeongweol platform was probably pushed against the Taebaek platform by the complex movement, forming fragmented platform sequences of the Taebaeksan Basin.

• Economic and Environmental Geology
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• v.1 no.1
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• pp.35-46
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• 1968

Some of geologists in Korea recently postlated that Okchon system previously known to be precambrian age was the metamorphosed sediments of post-Chosen (Ordovician and pre-Kyeongsang (late Jurassic to Cretaceous) periods, or even definitely of Triassic period simply on the basis of the fact that Okcheon system overlies the Great Limestone series of Chosen system of Camber-ordovician age, and of other few assumptions of minor importance. As a result of such correlation, thick series of metasediments and Okcheon system of unknown age were established in this particular region and vaguely correlated to Paleozoic and Mesozoic sediments. Recent study done by the author reveled that: 1) only the upper Okcheon bed of S. Nakamura was true Okcheon system, and the middle and lower Okcheon beds were excluded, because they were correlated to Cambrian and Permian sediments resfectively, 2) Sangnaeri, Seochangri, and rengam formations of unknown age, and Baekhwasan, Jobong, and Ihwaryeong formations of Okcheon system of also unknown age were the metamorphosed Yangdeok system of Cambrian age, all of these formations were differentiated by the previous workers and were equivalent to the middle Okcheon system of S. Nakamure, and. 3) These metamorphosed Yangdeok system overlaid apparently the Great Limestone series in forms of overthrust and klippe which were produced by the orogeny took place during post-Daedong and pre-Kyeongsang period (probably middle to the Jurassic). The Sobaeksan Range, folded mountain Chains was also formed by this orogeny. Thus, Okcheon system newly defined by the author is precambrain age and consists in ascending order of Kemyenogsan, Hyangsan dolomite, and Daehangsan quartzite formation which were previously classified into metasediments of unknown age, and Munjuri, and Hwangkanri, formations which were differentiated into Okcheon system unknown age by the previous workers, but are of reversed sequence. Myeongori and Bukrori formations of Okcheon System are regard by the author as part of Hwangkanri formation. Few other assumption of minor important taken by the previous workers as their positive evidences are carefully explained that they were misinterpreted.

• Journal of the Korean earth science society
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• v.36 no.7
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• pp.617-631
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• 2015

The Sesong Formation, mixed carbonate-siliciclastic deposits of late Middle Cambrian (Series 3) to Furongian in age, in the Taebaeksan Basin shows the Steptoean Positive Carbon Isotope Excursion (SPICE) with the ${\delta}^{13}C$ values ranging from 1.14 to 2.81‰ in the approximately 15-m-thick stratigraphic interval. The SPICE in the Sesong Formation occurs in the lower part of the Paibian Stage which contains trilobite biozones of the Fenghuangella laevis Zone, Prochuangia mansuyi Zone and the lower part of the Chuangia Zone. The Sesong Formation is composed of six lithofacies including laminated mudstone, nodular shale, laminated sandstone, massive sandstone, limestone conglomerate, and limestone-shale couplet facies. The Sesong Formation is known to have been deposited in the outer shelf below storm wave base. The SPICE occurs in the stratigraphic interval associated with highstand systems tract, correlative conformity and transgressive systems tract of the Sesong Formation. The peak carbon isotope value in the SPICE may coincide with the correlative conformity formed by relative sea-level fall. The occurrence of the SPICE in the Sesong Formation suggests that the SPICE can be used as a tool of global correlation for the successions of mixed carbonate-siliciclastics which lack fossils.

• Economic and Environmental Geology
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• v.52 no.5
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• pp.427-448
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• 2019

This study reconstructed the paleoenvironments and paleogeography of the Taebaeksan Basin, through a review of the previous researches on sedimentology, paleontology and stratigraphy. This study also carried out a sequence stratigraphic analysis on regional tectonism and sea-level fluctuations on the basin during the Early Paleozoic. The basin broadly occur in the Taebaek, Yeongweol-Jecheon, Jeongseon-Pyeongchang, and Mungyeong areas, Gangwon province, South Korea. The basin-fills are composed mainly of mixed carbonates and siliciclastics, divided into the Taebaek, Yeongweol, Yongtan, Pyeongchang and Mungyeong groups according to lithologies and stratigraphic characteristics. Recently, there are a lot of studies on the provenance and depositional ages of the siliciclastic sequences of the basin. The detrital sediments of the basin would be derived from two separated provenances of the core-Gondwana and Sino-Korean cratons. In the Early Cambrian, the Taebaek and Jeongseon-Pyeongchang platforms have most likely received detrital sediments from the provenance of the Sino-Korean craton. On the other hand, the detrital sediments of the Yeongweol-Jecheon platform was probably sourced by those of the core-Gondwana craton. This separation of provenance can be interpreted as the result of the paleogeographic and paleotopographic separation of the Yeongweol-Jecheon platform from the Taebaek and Jeongseon-Pyeongchang platforms. The analyses on detrital zircons additionally reveal that the separation of provenance was ceased by the eustatic rise of sea-level during the Middle Cambrian, and the detrital sediments of the Taebaeksan Basin were entirely supplied from those of the core-Gondwana craton. During that period, sediment supply from the Sino-Korean craton would be restricted due to inundation of the provenance area of the craton. On the other hand, the Jeongseon-Pyeongchang platform sequences show the unconformable relationship between the Early Cambrian siliciclastic and the Early Ordovician carbonate strata. It is indicative of presence of regional uplift movements around the platform which would be to the extent offset of the effects of the Middle to Late Cambrian eustatic sealevel rise. These movements expanded and were reinforced across the basin in the latest Cambrian and earliest Ordovician. After the earliest Ordovician, the basin was tectonically stabilized, and the shallow marine carbonate environments were developed on the whole-platform by the Early Ordovician global eustatic sea-level rise, forming very thick carbonate strata in the basin. In the Late Ordovician, the Early Paleozoic sedimentation on the basin was terminated by the large-scale tectonic uplift across the Sino-Korean platform including the Taebaeksan Basin.

• Economic and Environmental Geology
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• v.56 no.6
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• pp.831-846
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• 2023

The Jucheon-Pyeongchang area in the northwestern Taebaeksan Zone of the Okcheon fold-thrust belt preserved several thrust faults placing the Precambrian basement granite gneisses of the Gyeonggi Massif on top of the Early Paleozoic Joseon Supergroup and the age-unknown Bangrim Group. Especially, the thrust faults in the study area show the closed-loop patterns on the map view, showing older allochthonous strata surrounded by younger autochthonous or para-autochthonous strata. These basement-involved thrusts including Klippes will provide important information on the hinterland portion of the fold-thrust belt. For defining Klippe geometry in the thrust fault terrains of the Jucheon-Pyeongchang area by older on younger relationship, the stratigraphic position of the age-unknown Bangrim Group should be determined. The Middle Cambrian maximum depositional age by the detrital zircon SHRIMP U-Pb method from this study, together with field relations and previous research results suggest that the Bangrim Group overlies the Precambrian basement rocks by nonconformity and underlies the Cambrian Yangdeok Group (Jangsan and Myobong formations). The structural geometric interpretation of the Pyeongchang area based on newly defined stratigraphy indicates that the Wungyori and Barngrim thrusts are the same folded thrust, and can be interpreted as a Klippe, having Precambrian hanging wall granite gneisses surrounded by younger Cambrian strata of the Joseon Supergroup and the Bangrim Group. Further detailed structural studies on the Jucheon-Pyeongchang area can give crucial insights into the basement-involved deformation during the structural evolution of the Okcheon Belt.

• The Korean Journal of Quaternary Research
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• v.14 no.2
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• pp.125-135
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• 2000

The late Quaternary stratigraphy and basal unconformity (nonconformity) of the intertidal deposits (upper tidal flat) in the Banweol tidal basin in the Kyunggi Bay, west coast of Korea has been investigated and established. The Unit I (middle to late Holocene upper intertidal deposit) and Unit II (pre-Holocene fluvial to alluvial deposit) in descending order are classified and interpreted. The basement rocks of the Banweol tidal basin is dominantly preCambrian metamorphic rocks on which Unit II is overlying unconformably. In short, the late Quaternary stratigraphy and unconformity of the Banweol tidal flat deposits are established and interpreted in terms of sedimentology and sea-level fluctuation history during late Quaternary.