• Economic and Environmental Geology
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• v.4 no.1
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• pp.19-32
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• 1971

Summarizing the past and recent data on pre-Cambrian System in Eastern Asia, it can be concluded that the pre-Cambrian System are composed of the sediments of having four cycles of sedimentation. It is also known that most of pre-Cambrian Systems known so far belong to either one of transgression facies or regression facies in the four sedimentation cycles. The pre-Cambrian Systems can be divided into four stages, that is, Sinian, Hutoan, Liahoan, and Taishanian stage. It is supposed that all pre-Cambrian Systems in Korea will belong to one of these four cycle sedimentations. Therefore, the reasonable way of study of Korean pre-Cambrian Systems is to investigate which stage they belong to.

• 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.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.

• Journal of the Korean earth science society
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• v.28 no.2
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• pp.248-254
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• 2007

Recently lots of the Early Cambrian fauna were described from the Yunnan Province of China. The fauna occurs from the Maotiangshan shale that dated between 525 and 520 ma, which is about 10-20 million years earlier than the Burgess Shale fauna of Canadian Rocky Mountain and Sirius Passet fauna in North Greenland. The Chengjiang fauna comprises an extremely diverse faunal assembly, and soft body parts of the fauna are well preserved. Such condition probably resulted from repeated rapid burial environment that prevented the bodies from destruction by currents, bioturbation, and biolchemical activities.

• 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.

• 한국석유지질학회:학술대회논문집
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• 2005.09a
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• pp.41-44
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• 2005

• Economic and Environmental Geology
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• v.6 no.2
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• pp.81-114
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• 1973

The purpose of the present study is to clarify the stratigraphy and geologic structure of the Great Limestone Series by means of study on fossil conodonts and detail investigation of geologic structure. In recent years very few geologists in Korea argue without confident evidences against the age and stratigraphy of the Great Limestone Series which have been rather well established previously in most parts of the regions although it is ambiguous and has not been studied in other areas. Five type localities in the Kangweon basin where the Great Limestone Series is well cropped out were chosen for the study. Total 26 genus and 66 species of conodont were identified from 290 samples collected and treated. From the study on conodonts the age of each formations of the Great Limestone Series has been determined as follows: The Great Limestone Series of Duwibong type Duwibong limestone: Caradocian (mid-Ord.) Jikunsan shale: Landeilian (mid-Ord.) Maggol limestone: Llanvirn-Llandeilian (mid-Ord.) Dumugol: Arenigian (Ord.) Hwajeol: Upper Cambrian The Great Limestone Series of Yeongweol type Mungok (Samtaesan) : Ordovician Machari: upper Cambrian The Great Limestone Series of Jeongseon type Erstwhile Jeongseon limestone: mid-Ord. The erstwhile Jongseon Limestone formation in Jeongseon district is separated into Hwajeol, Dongjeom, Dumudong, and Maggol formations which were cropped out repeatedly by folding and faulting, but Maggol is predominant in areal distribution. Yemi Limestone Breccia bed is not a single bed but distributed in several horizons so that it bears no stratigraphic significance. The limestone bed above Yemi Limestone Breccia, which was believed by some geologists to be much younger than Ordovician, is identified to be Maggol and its age is determined to be mid-Ordovician. Sambangsan formation in Yeongweol district was believed to be Cambrian age and lower horizon than Machari formation by Kobayashi, but C. M. Son believed that it might belong to later than Ordovician and lies above the Great Limestone Series of Yeongweol type. It was identified to be upper Cambrian and lies beneath the Machari formation and above the Daeki formation, the lower most horizon of the Great Limestone Series. The age of Yeongweol type Choseon system is contemporaneous with that of Duwibong type Choseon system. The difference in lithofacies is not due to lateral facies change, but due to the difference in its depositional environment. The Yeongweol type Choseon system is believed to be deposited in the small Yeongweol basin which was separated from the main Kangweon sedimentary basin. Judging from these facts it is definitely concluded that there exists no Gotlandian formation in the regions studied. Structurally the Kangweon basin comprises five basins and two uplifted areas. These structures were originated by at least two crustal movements, that is, Songrim disturbance of Triassic and Daebo orogeny of Jurasic age.

• The Journal of Engineering Geology
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• v.13 no.4
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• pp.429-444
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• 2003

Domestic marbles are mostly distributed in Gyeonggi and Yeongnam Massifs, southwest and northeast Ogcheon Belts, which belong to Precambrian, age-unknown, Cambrian-Ordovician ages, respectively. The former marbles occur as interbedded rocks in metasediments and xenoliths in granitic gneisses. Age-unknown ones occur as interbedded in the formations of Hyangsanri, Gyeomyeongsan, Hwajeonri and Munjuri, and some in metasedimentary rocks. The latter ones occur as interbedded in Pungchon Limestone, and in Jeongseon Limestone, Hwacheonri Formation and Great Limestone Group, respectively. Among physical properties, porosity shows irregular patterns to density and compressive strength, respectively. Absorption ratio has a linear pattern of positive trend to porosity, and compressive strength mostly shows a positive trend to tensile strength. Compressive strengths of the marbles are as follows : Precambrian $1,106{\;}kg/\textrm{cm}^2$, age-unknown $935{\;}kg/\textrm{cm}^2$. Cambrian $1,162{\;}kg/\textrm{cm}^2$ and Ordovician $1,560{\;}kg/\textrm{cm}^2$, respectively. Tensile strengths have decreasing trends as the above order of geologic age. In diagrams of major elements, $Al_2O_3,{\;}Fe_2O_{3(t)}{\;}and{\;}Na_2O+K_2O$ generally show positive trends with increasing $v_2$. MgO/CaO of Precambrian and age-unknown marbles have much higher values than Cambrian and Ordovician marbles as follows, Precambrian 0.31, age-unknown 0.30, Cambrian 0.03 and Ordovician 0.08. And MgO shows a negative trend with increasing CaO, which nay be caused by dolomitization. By MgO contents they can be classified into calcitic dolomite, dolomitic limestone, limestone and dolomitic limestone, respectively.

• 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.

• Economic and Environmental Geology
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• v.30 no.2
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• pp.153-161
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• 1997

Diagrams of $^{87}Sr/^{86}Sr$ versus Ba/Nb and MgO/FeO are scattered, and $^{87}Sr/^{86}Sr$ variation with the increase of $SiO_2$ are scattered in Gwangju granitoid. Diagrams of $(^{87}Sr/^{86}Sr)$i versus $(^{143}Nd/^{144}Nd)$i and ${\varepsilon}Nd$ versus 1/Nd variation are also scattered in Gwangju granitoid. It shows that the source magma of Gwangju granitoid are derived from partial melting materials of heterogeneous upper crust. Very low ${\varepsilon}Nd$ values (-15.19~-19.49) and very high ${\varepsilon}Sr$ values (92.72~308.85) mean that the source magma of Gwangju granitoid is derived from sedimentary substance melting. According to $(^{87}Sr/^{86}Sr)$ 180Ma, and the plot of ${\varepsilon}Sr$ versus ${\varepsilon}Nd$, the Gwangju granitoid shows that the source magma is derived from upper crust materials. Nd model ages of Gwangju granitoid (1.82~2.42G.A.) are older than meta-sediments of Okcheon formation (1.15~1.60G.A.) and similar or close to Pre-Cambrian gneiss complex of Ryoungnam massif (2.17~2.47G.A.or 2.11~2.38G.A.).Therefore, the source magma of the Gwangju granitoid could be derived from the partial melting of Pre-Cambrian gneiss complex of Ryoungnam massif.