TY - JOUR
T1 - Lower Triassic mixed carbonate and siliciclastic setting with Smithian-Spathian anoxic to dysoxic facies, An Chau basin, northeastern Vietnam
AU - Komatsu, Toshifumi
AU - Naruse, Hajime
AU - Shigeta, Yasunari
AU - Takashima, Reishi
AU - Maekawa, Takumi
AU - Dang, Huyen T.
AU - Dinh, Tien C.
AU - Nguyen, Phong D.
AU - Nguyen, Hung H.
AU - Tanaka, Gengo
AU - Sone, Masatoshi
N1 - Funding Information:
We thank T. Kumagae (Japan Petroleum Exploration Co., Ltd.) and H. Matsuda (Kumamoto University) for their useful discussion on the Lower Triassic stratigraphy and carbonate sedimentology. We are also indebted to two referees, Michael Hautmann (Universität Zürich) and Akihiro Misaki (Kitakyushu Museum of Natural History and Human History), for critical revisions. This study was partly supported by grants-in-aid from the Japanese Ministry of Education, Culture, Sports, Science, and Technology ( 20740300 to T. Komatsu), Japan Society for Promotion of Science ( 25400500 to T. Komatsu), the JSPS-VAST Joint Research Program , and a HIR grant UM.C/625/1/HIR/140 from the University of Malaya (to M. Sone).
PY - 2014/3/1
Y1 - 2014/3/1
N2 - In the An Chau basin in northeastern Vietnam, the Olenekian (Lower Triassic) stage comprises mixed carbonate and siliciclastic shallow marine to marginal basin deposits that extend into the southern Nanpanjiang basin in South China. The upper Lang Son Formation, which is dominated by siliciclastic facies, is composed of storm- and wave-influenced shallow marine and slope deposits. The overlying and interfingering Bac Thuy Formation consists of tidal flat, wave-influenced carbonate platform, slope, and marginal basin plain deposits. The tidal flat deposits are composed mainly of lenticular, wavy-bedded, or thin flat-bedded carbonates containing desiccation cracks and ripples that are indicative of bidirectional paleocurrents. The platform carbonates are characterized by wave ripples, ooids, and abundant marine mollusks and microfossils; the molluscan fossil assemblage primarily contains Smithian ammonoids such as Owenites koeneni. The slope deposits are characterized by limestone breccia and slump beds. The marginal basin plain deposits consist of classical turbidite beds, minor limestone breccia, and hemipelagic mudstone and marl containing the Spathian ammonoids Tirolites and Columbites. The turbidite sets may represent frontal splay environments in the marginal basin plain. These Olenekian carbonate and siliciclastic facies are typical of a transgressive succession.The Smithian-Spathian boundary and the anoxic to dysoxic facies of the latest Smithian are characterized by organic-rich dark gray limestone and mudstone deposits intercalated in the succession of slope to marginal basin plain facies, which are composed mainly of gravity flow and hemipelagic deposits. The organic-rich deposits show no evidence of bioturbation and are characterized by low-diversity fauna. Clastics in the marginal basin plain deposits were apparently supplied from the west; hence, the paleocurrent direction of the siliciclastic gravity flows was approximately eastward.
AB - In the An Chau basin in northeastern Vietnam, the Olenekian (Lower Triassic) stage comprises mixed carbonate and siliciclastic shallow marine to marginal basin deposits that extend into the southern Nanpanjiang basin in South China. The upper Lang Son Formation, which is dominated by siliciclastic facies, is composed of storm- and wave-influenced shallow marine and slope deposits. The overlying and interfingering Bac Thuy Formation consists of tidal flat, wave-influenced carbonate platform, slope, and marginal basin plain deposits. The tidal flat deposits are composed mainly of lenticular, wavy-bedded, or thin flat-bedded carbonates containing desiccation cracks and ripples that are indicative of bidirectional paleocurrents. The platform carbonates are characterized by wave ripples, ooids, and abundant marine mollusks and microfossils; the molluscan fossil assemblage primarily contains Smithian ammonoids such as Owenites koeneni. The slope deposits are characterized by limestone breccia and slump beds. The marginal basin plain deposits consist of classical turbidite beds, minor limestone breccia, and hemipelagic mudstone and marl containing the Spathian ammonoids Tirolites and Columbites. The turbidite sets may represent frontal splay environments in the marginal basin plain. These Olenekian carbonate and siliciclastic facies are typical of a transgressive succession.The Smithian-Spathian boundary and the anoxic to dysoxic facies of the latest Smithian are characterized by organic-rich dark gray limestone and mudstone deposits intercalated in the succession of slope to marginal basin plain facies, which are composed mainly of gravity flow and hemipelagic deposits. The organic-rich deposits show no evidence of bioturbation and are characterized by low-diversity fauna. Clastics in the marginal basin plain deposits were apparently supplied from the west; hence, the paleocurrent direction of the siliciclastic gravity flows was approximately eastward.
KW - Anoxic to dysoxic facies
KW - Depositional environment
KW - Lower Triassic
KW - Nanpanjiang basin
KW - Smithian-Spathian boundary
KW - Tethys
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U2 - 10.1016/j.sedgeo.2013.10.009
DO - 10.1016/j.sedgeo.2013.10.009
M3 - Article
AN - SCOPUS:84890853817
SN - 0037-0738
VL - 300
SP - 28
EP - 48
JO - Sedimentary Geology
JF - Sedimentary Geology
ER -
