Depositional ages and characteristics of Middle-Upper Jurassic and Lower Cretaceous lacustrine deposits in southeastern Mongolia

Hitoshi Hasegawa, Hisao Ando, Noriko Hasebe, Niiden Ichinnorov, Tohru Ohta, Takashi Hasegawa, Masanobu Yamamoto, Gang Li, Bat Orshikh Erdenetsogt, Ulrich Heimhofer, Takayuki Murata, Hironori Shinya, G. Enerel, G. Oyunjargal, O. Munkhtsetseg, Noriyuki Suzuki, Tomohisa Irino, Koshi Yamamoto

    Research output: Contribution to journalArticle

    1 Citation (Scopus)

    Abstract

    Lower Cretaceous lacustrine oil shales are widely distributed in southeastern Mongolia. Due to the high organic carbon content of oil shale, many geochemical studies and petroleum exploration have been conducted. Although most of the oil shales are considered to be Early Cretaceous in age, a recent study reveals that some were deposited in the Middle Jurassic. The present study aims at establishing depositional ages and characteristics of the Jurassic and Cretaceous lacustrine deposits in Mongolia. The Lower Cretaceous Shinekhudag Formation is about 250m thick and composed of alternating beds of shale and dolomite. The Middle Jurassic Eedemt Formation is about 150m thick and composed of alternating beds of shale, dolomitic marl, and siltstone. The alternations of shale and dolomite in both formations were formed by lake level changes, reflecting precipitation changes. Shales were deposited in the center of a deep lake during highstand, while dolomites were formed by primary precipitation during lowstand. Based on the radiometric age dating, the Shinekhudag Formation was deposited between 123.8±2.0 Ma and 118.5±0.9 Ma of the early Aptian. The Eedemt Formation was deposited at around 165-158Ma of Callovian-Oxfordian. The calculated sedimentation rate of the Shinekhudag Formation is between 4.7±2.6 cm/ky and 10.0±7.6 cm/ky. Shales in the Shinekhudag Formation show micrometer-scale lamination, consisting of algal organic matter and detrital clay mineral couplets. Given the average thickness of micro-laminae and calculated sedimentation rate, the micro-lamination is most likely of varve origin. Both Middle-Upper Jurassic and Lower Cretaceous lacustrine oil shales were deposited in intracontinental basins in the paleo-Asian continent. Tectonic processes and basin evolution basically controlled the deposition of these oil shales. In addition, enhanced precipitation under humid climate during the early Aptian and the Callovian-Oxfordian was another key factor inducing the widespread oil shale deposition in Mongolia.

    Original languageEnglish
    JournalIsland Arc
    DOIs
    Publication statusAccepted/In press - 2018 Jan 1

    Fingerprint

    lacustrine deposit
    Jurassic
    Cretaceous
    dolomite
    shale
    Callovian
    oil
    Oxfordian
    oil shale
    lamination
    Aptian
    sedimentation rate
    varve
    lowstand
    marl
    highstand
    lake level
    basin evolution
    siltstone
    clay mineral

    Keywords

    • Cretaceous
    • Humid climate
    • Jurassic
    • Lake
    • Mongolia
    • Oil shale
    • U-Pb age
    • Varve

    ASJC Scopus subject areas

    • Geology

    Cite this

    Depositional ages and characteristics of Middle-Upper Jurassic and Lower Cretaceous lacustrine deposits in southeastern Mongolia. / Hasegawa, Hitoshi; Ando, Hisao; Hasebe, Noriko; Ichinnorov, Niiden; Ohta, Tohru; Hasegawa, Takashi; Yamamoto, Masanobu; Li, Gang; Erdenetsogt, Bat Orshikh; Heimhofer, Ulrich; Murata, Takayuki; Shinya, Hironori; Enerel, G.; Oyunjargal, G.; Munkhtsetseg, O.; Suzuki, Noriyuki; Irino, Tomohisa; Yamamoto, Koshi.

    In: Island Arc, 01.01.2018.

    Research output: Contribution to journalArticle

    Hasegawa, H, Ando, H, Hasebe, N, Ichinnorov, N, Ohta, T, Hasegawa, T, Yamamoto, M, Li, G, Erdenetsogt, BO, Heimhofer, U, Murata, T, Shinya, H, Enerel, G, Oyunjargal, G, Munkhtsetseg, O, Suzuki, N, Irino, T & Yamamoto, K 2018, 'Depositional ages and characteristics of Middle-Upper Jurassic and Lower Cretaceous lacustrine deposits in southeastern Mongolia', Island Arc. https://doi.org/10.1111/iar.12243
    Hasegawa, Hitoshi ; Ando, Hisao ; Hasebe, Noriko ; Ichinnorov, Niiden ; Ohta, Tohru ; Hasegawa, Takashi ; Yamamoto, Masanobu ; Li, Gang ; Erdenetsogt, Bat Orshikh ; Heimhofer, Ulrich ; Murata, Takayuki ; Shinya, Hironori ; Enerel, G. ; Oyunjargal, G. ; Munkhtsetseg, O. ; Suzuki, Noriyuki ; Irino, Tomohisa ; Yamamoto, Koshi. / Depositional ages and characteristics of Middle-Upper Jurassic and Lower Cretaceous lacustrine deposits in southeastern Mongolia. In: Island Arc. 2018.
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    abstract = "Lower Cretaceous lacustrine oil shales are widely distributed in southeastern Mongolia. Due to the high organic carbon content of oil shale, many geochemical studies and petroleum exploration have been conducted. Although most of the oil shales are considered to be Early Cretaceous in age, a recent study reveals that some were deposited in the Middle Jurassic. The present study aims at establishing depositional ages and characteristics of the Jurassic and Cretaceous lacustrine deposits in Mongolia. The Lower Cretaceous Shinekhudag Formation is about 250m thick and composed of alternating beds of shale and dolomite. The Middle Jurassic Eedemt Formation is about 150m thick and composed of alternating beds of shale, dolomitic marl, and siltstone. The alternations of shale and dolomite in both formations were formed by lake level changes, reflecting precipitation changes. Shales were deposited in the center of a deep lake during highstand, while dolomites were formed by primary precipitation during lowstand. Based on the radiometric age dating, the Shinekhudag Formation was deposited between 123.8±2.0 Ma and 118.5±0.9 Ma of the early Aptian. The Eedemt Formation was deposited at around 165-158Ma of Callovian-Oxfordian. The calculated sedimentation rate of the Shinekhudag Formation is between 4.7±2.6 cm/ky and 10.0±7.6 cm/ky. Shales in the Shinekhudag Formation show micrometer-scale lamination, consisting of algal organic matter and detrital clay mineral couplets. Given the average thickness of micro-laminae and calculated sedimentation rate, the micro-lamination is most likely of varve origin. Both Middle-Upper Jurassic and Lower Cretaceous lacustrine oil shales were deposited in intracontinental basins in the paleo-Asian continent. Tectonic processes and basin evolution basically controlled the deposition of these oil shales. In addition, enhanced precipitation under humid climate during the early Aptian and the Callovian-Oxfordian was another key factor inducing the widespread oil shale deposition in Mongolia.",
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    AU - Hasegawa, Hitoshi

    AU - Ando, Hisao

    AU - Hasebe, Noriko

    AU - Ichinnorov, Niiden

    AU - Ohta, Tohru

    AU - Hasegawa, Takashi

    AU - Yamamoto, Masanobu

    AU - Li, Gang

    AU - Erdenetsogt, Bat Orshikh

    AU - Heimhofer, Ulrich

    AU - Murata, Takayuki

    AU - Shinya, Hironori

    AU - Enerel, G.

    AU - Oyunjargal, G.

    AU - Munkhtsetseg, O.

    AU - Suzuki, Noriyuki

    AU - Irino, Tomohisa

    AU - Yamamoto, Koshi

    PY - 2018/1/1

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    N2 - Lower Cretaceous lacustrine oil shales are widely distributed in southeastern Mongolia. Due to the high organic carbon content of oil shale, many geochemical studies and petroleum exploration have been conducted. Although most of the oil shales are considered to be Early Cretaceous in age, a recent study reveals that some were deposited in the Middle Jurassic. The present study aims at establishing depositional ages and characteristics of the Jurassic and Cretaceous lacustrine deposits in Mongolia. The Lower Cretaceous Shinekhudag Formation is about 250m thick and composed of alternating beds of shale and dolomite. The Middle Jurassic Eedemt Formation is about 150m thick and composed of alternating beds of shale, dolomitic marl, and siltstone. The alternations of shale and dolomite in both formations were formed by lake level changes, reflecting precipitation changes. Shales were deposited in the center of a deep lake during highstand, while dolomites were formed by primary precipitation during lowstand. Based on the radiometric age dating, the Shinekhudag Formation was deposited between 123.8±2.0 Ma and 118.5±0.9 Ma of the early Aptian. The Eedemt Formation was deposited at around 165-158Ma of Callovian-Oxfordian. The calculated sedimentation rate of the Shinekhudag Formation is between 4.7±2.6 cm/ky and 10.0±7.6 cm/ky. Shales in the Shinekhudag Formation show micrometer-scale lamination, consisting of algal organic matter and detrital clay mineral couplets. Given the average thickness of micro-laminae and calculated sedimentation rate, the micro-lamination is most likely of varve origin. Both Middle-Upper Jurassic and Lower Cretaceous lacustrine oil shales were deposited in intracontinental basins in the paleo-Asian continent. Tectonic processes and basin evolution basically controlled the deposition of these oil shales. In addition, enhanced precipitation under humid climate during the early Aptian and the Callovian-Oxfordian was another key factor inducing the widespread oil shale deposition in Mongolia.

    AB - Lower Cretaceous lacustrine oil shales are widely distributed in southeastern Mongolia. Due to the high organic carbon content of oil shale, many geochemical studies and petroleum exploration have been conducted. Although most of the oil shales are considered to be Early Cretaceous in age, a recent study reveals that some were deposited in the Middle Jurassic. The present study aims at establishing depositional ages and characteristics of the Jurassic and Cretaceous lacustrine deposits in Mongolia. The Lower Cretaceous Shinekhudag Formation is about 250m thick and composed of alternating beds of shale and dolomite. The Middle Jurassic Eedemt Formation is about 150m thick and composed of alternating beds of shale, dolomitic marl, and siltstone. The alternations of shale and dolomite in both formations were formed by lake level changes, reflecting precipitation changes. Shales were deposited in the center of a deep lake during highstand, while dolomites were formed by primary precipitation during lowstand. Based on the radiometric age dating, the Shinekhudag Formation was deposited between 123.8±2.0 Ma and 118.5±0.9 Ma of the early Aptian. The Eedemt Formation was deposited at around 165-158Ma of Callovian-Oxfordian. The calculated sedimentation rate of the Shinekhudag Formation is between 4.7±2.6 cm/ky and 10.0±7.6 cm/ky. Shales in the Shinekhudag Formation show micrometer-scale lamination, consisting of algal organic matter and detrital clay mineral couplets. Given the average thickness of micro-laminae and calculated sedimentation rate, the micro-lamination is most likely of varve origin. Both Middle-Upper Jurassic and Lower Cretaceous lacustrine oil shales were deposited in intracontinental basins in the paleo-Asian continent. Tectonic processes and basin evolution basically controlled the deposition of these oil shales. In addition, enhanced precipitation under humid climate during the early Aptian and the Callovian-Oxfordian was another key factor inducing the widespread oil shale deposition in Mongolia.

    KW - Cretaceous

    KW - Humid climate

    KW - Jurassic

    KW - Lake

    KW - Mongolia

    KW - Oil shale

    KW - U-Pb age

    KW - Varve

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