• Title/Summary/Keyword: Middle Carboniferous Period

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Conodont Biostratigraphy of the Middle Carboniferous System in the Taebaek Area, Kangwondo, Korea (강원도 태백 지역의 중부 석탄계 코노돈트 생층서)

  • Park, Soo-In;Sun, Seung-Dae
    • Journal of the Korean earth science society
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    • v.22 no.6
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    • pp.558-570
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    • 2001
  • The Middle Carboniferous Manhang and Geumcheon Formations exposed in the Taebaek area, Kangwondo, Korea consist of sandstones and shales with some intercalation of limestone beds. The limestones of the formations contain abundant conodonts and other fossils. The purpose of this study is (1) to investigate the conodont fauna, (2) to assign conodont biozones of the Manhang and Geumcheon Formations, and (3) to refine their geologic age more exactly. The conodonts of the Manhang and Geumcheon Formations are 6 genera distributed into 11 species. Conodonts found from limestones of the Manhang Formation are Idiognathodus delicatus, Hindeodus minutus, Streptognathodus sp., Diplognathodus coloradoensis, N. bothorops, and N. medexultimus. This conodont fauna can be assigned to the Neognathodus bothrops Zone. This conodont biozone indicates that the geologic age of the Manghang Formation is the Atokan stage of the Middle Carboniferous Period. Conodonts came from limestones of the Geumcheon Formation are Idiognathodus delicatus, N. medexultimus, N. roundyi, N. dilatus, Diplognathodus edentulus, Hindeodus minutus, Streptognathodus elegantulus, and Gondolella bella. These conodonts permit them to be assigned to the Neognathodus roundyi Zone. This Conodont biozone indicates that the geologic age of the Geumcheon Formation is the Desmoinesian stage of the Middle Carboniferous Period.

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The Vegetational and Environmental History of the Pre-Holocene Period in the Korean Peninsula (한반도 식생 및 환경변천사(홀로세 이전 시대를 중심으로))

  • Kong, Woo-Seok
    • The Korean Journal of Quaternary Research
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    • v.6 no.1
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    • pp.1-11
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    • 1992
  • The reconstruction of the vegetational and environmental history of the Korean peninsula by the use of various fossil floral data from the Carboniferous period to the Pre-Holocene is reviewed. Though the oldest plant fossil in Korea (Neuropteris) dates back to the Carboniferous period, the first appearance of many of the present-day floristic genera indeed dates back to the Oligocene (c. 40 to 20 million years B.P.), and includes many thermophilous genera. The presence of thermophilous genera in the Oligocene at up to four degrees north of their present distributional limits implies that the climate of the Oligocene was warmer than that of today. The occurrence of similar thermophilous floristic element at up to six degrees north of their present range during the Middle Miocene suggests a maximum northward expansion of warmth-loving evergreen broadleaved vegetation for, recent Korean vegetation history. The continued occurrence of numerous present-day genera since the Oligocene period indicates a long-term stability of Korean vegetation, along with minor fluctuations within it. The admixture of evergreen coniferous plants and deciduous breadleaved plants, however, indicates a probable temperate climate for much of the Middle Pleistocene. There are couple of evidences which are indicative of an early-stage anthropogenic disturbance of natural vegetation during the Middle Pleistocene of Korea. The presence of cold-episodes during the Upper Pleistocene caused a general expansion of deciduous plants and cryophilous evergreen coniferous, plants. It is likely that the maximum southward expansion of cryophilous arctic-alpine and alpine floras in Korea occured during the penultimate glacial period. The disappearance of some cryophilous genera from 10,000 years B.P. marks the continued climatic amelioration since then, along with minor climatic fluctuations during the Holocene period.

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Conodont Fauna and Its Paleoecology of the Middle Carboniferous System in Taebaek Area, Gangwon, Korea (강원도 태백 지역의 중기 석탄계의 코노돈트와 고생태)

  • Park, Soo-In;Oh, Jae-Kyung
    • Journal of the Korean earth science society
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    • v.21 no.3
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    • pp.337-348
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    • 2000
  • The Middle Carboniferous Manhang and Geumcheon formations in Taebaek area consist of sandstones, shales, and limestones. The limestones of the formations contain abundant conodonts, fusulinids, crinoids, brachiopods, bryozoans, corals, etc. This study was carried out to investigate the microfacies of limestones and conodont faunas of the formations and to determine their paleoecology in detail. The limestones of the Manhang and Geumcheon formations of the study area consist of wackestone and packstone which are composed of crinoid fragments and other various fossil fragments. Some limestone beds of the Geumcheon Formation consist of only Chaetetes corals which indicate that the limestones deposited in a warm shallow sea. Conodonts found from limestones of the Manhang Formation are Neognathodus bothrops, N. medexultimus, Hindeodus minutus, Diplognathodus coloradoensis, D. edentulus, Idiognathodus delicatus, Streptognathodus elegantulus, and S. sp. And conodonts found from the limestones of the Geumcheon Formation are Neognathodus medexultimus, N. roundyi, N. dilatus, Gondolella bella, Diplognathodus coloradoensis, D. edentulus, Hindeodus minutus, Idiognathodus delicatus, and Streptognathodus elegantulus. Among these conodonts, Diplognathodus coloradoensis, D. edentulus, and Hindeodus minutu, are found generally from limestones which deposited in the shallow seas. According to the limestone facies and conodont faunas of the Manhang and Geumcheon formations of the study area, it can be concluded that the limestones of the formations deposited in the shallow sea.

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Stratigraphic response to tectonic evolution of sedimentary basins in the Yellow Sea and adjacent areas (황해 및 인접 지역 퇴적분지들의 구조적 진화에 따른 층서)

  • Ryo In Chang;Kim Boo Yang;Kwak won Jun;Kim Gi Hyoun;Park Se Jin
    • The Korean Journal of Petroleum Geology
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    • v.8 no.1_2 s.9
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    • pp.1-43
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    • 2000
  • A comparison study for understanding a stratigraphic response to tectonic evolution of sedimentary basins in the Yellow Sea and adjacent areas was carried out by using an integrated stratigraphic technology. As an interim result, we propose a stratigraphic framework that allows temporal and spatial correlation of the sedimentary successions in the basins. This stratigraphic framework will use as a new stratigraphic paradigm for hydrocarbon exploration in the Yellow Sea and adjacent areas. Integrated stratigraphic analysis in conjunction with sequence-keyed biostratigraphy allows us to define nine stratigraphic units in the basins: Cambro-Ordovician, Carboniferous-Triassic, early to middle Jurassic, late Jurassic-early Cretaceous, late Cretaceous, Paleocene-Eocene, Oligocene, early Miocene, and middle Miocene-Pliocene. They are tectono-stratigraphic units that provide time-sliced information on basin-forming tectonics, sedimentation, and basin-modifying tectonics of sedimentary basins in the Yellow Sea and adjacent area. In the Paleozoic, the South Yellow Sea basin was initiated as a marginal sag basin in the northern margin of the South China Block. Siliciclastic and carbonate sediments were deposited in the basin, showing cyclic fashions due to relative sea-level fluctuations. During the Devonian, however, the basin was once uplifted and deformed due to the Caledonian Orogeny, which resulted in an unconformity between the Cambro-Ordovician and the Carboniferous-Triassic units. The second orogenic event, Indosinian Orogeny, occurred in the late Permian-late Triassic, when the North China block began to collide with the South China block. Collision of the North and South China blocks produced the Qinling-Dabie-Sulu-Imjin foldbelts and led to the uplift and deformation of the Paleozoic strata. Subsequent rapid subsidence of the foreland parallel to the foldbelts formed the Bohai and the West Korean Bay basins where infilled with the early to middle Jurassic molasse sediments. Also Piggyback basins locally developed along the thrust. The later intensive Yanshanian (first) Orogeny modified these foreland and Piggyback basins in the late Jurassic. The South Yellow Sea basin, however, was likely to be a continental interior sag basin during the early to middle Jurassic. The early to middle Jurassic unit in the South Yellow Sea basin is characterized by fluvial to lacustrine sandstone and shale with a thick basal quartz conglomerate that contains well-sorted and well-rounded gravels. Meanwhile, the Tan-Lu fault system underwent a sinistrai strike-slip wrench movement in the late Triassic and continued into the Jurassic and Cretaceous until the early Tertiary. In the late Jurassic, development of second- or third-order wrench faults along the Tan-Lu fault system probably initiated a series of small-scale strike-slip extensional basins. Continued sinistral movement of the Tan-Lu fault until the late Eocene caused a megashear in the South Yellow Sea basin, forming a large-scale pull-apart basin. However, the Bohai basin was uplifted and severely modified during this period. h pronounced Yanshanian Orogeny (second and third) was marked by the unconformity between the early Cretaceous and late Eocene in the Bohai basin. In the late Eocene, the Indian Plate began to collide with the Eurasian Plate, forming a megasuture zone. This orogenic event, namely the Himalayan Orogeny, was probably responsible for the change of motion of the Tan-Lu fault system from left-lateral to right-lateral. The right-lateral strike-slip movement of the Tan-Lu fault caused the tectonic inversion of the South Yellow Sea basin and the pull-apart opening of the Bohai basin. Thus, the Oligocene was the main period of sedimentation in the Bohai basin as well as severe tectonic modification of the South Yellow Sea basin. After the Oligocene, the Yellow Sea and Bohai basins have maintained thermal subsidence up to the present with short periods of marine transgressions extending into the land part of the present basins.

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