Nantun Fm
Type Locality and Naming
Hailar Basin. Upper formation of the Xinganling Gr. The Nantun Formation was named by the No 109 Team of the Second Geological Exploration Bureau of Northeast China in 1987. The type locality is down the boreholes of 81-33, 81-34 and 86-5 in Nantun of Hailar.
Synonym: Yilikede Fm for the upper part. Potentially also Ganhe Fm and Jiufengshan Fm, depending upon publication? See Additional Information in Xinganling Gr entry about confusing comparisons between Erlian and Hailar basins and need for reclassifications..
Lithology and Thickness
The Nantun Formation is a group of grayish white, grey sandy conglomerate, sandstone, siltstone, grayish black mudstone, and yellowish tuffaceous sandstone with coal bed intercalations. It is about 1000 m thick. "The Nantun Formation is mainly composed of lacustrine mudstones, interbedded with fan delta, braided delta, and alluvial fan sandy conglomerates and is subdivided into the Lower Nantun Member and the Upper Nantun Member. … Moreover, the Tongbomiao Fm and Nantun Fm contain abundant volcanic rocks that were produced during the climax of volcanism and rifting." (Ji et al., 2020)
Relationships and Distribution
Lower contact
It is unconformably overlying the Tongbomiao Fm.
Upper contact
Disconformably overlain by Damoguaihe Fm conglomerates.
Regional extent
It distributed in the area of eastern Inner Mongolia and western Heilongjiang. The Tongbomiao Fm and Nantun Fm are widely distributed in the Hailar Basin and constitute the main part of the basin fill.
GeoJSON
Fossils
The Nantun Formation yields fossils of ostracods, bivalves, gastropods, conchostracans, spores and pollen.
Age
Depositional setting
Additional Information
Lithology and Thickness:
The Nantun Formation is a group of grayish white, grey sandy conglomerate, sandstone, siltstone, grayish black mudstone, and yellowish tuffaceous sandstone with coal bed intercalations. It is about 1000 m thick. "The Nantun Formation is mainly composed of lacustrine mudstones, interbedded with fan delta, braided delta, and alluvial fan sandy conglomerates and is subdivided into the Lower Nantun Member and the Upper Nantun Member. … Moreover, the Tongbomiao Fm and Nantun Fm contain abundant volcanic rocks that were produced during the climax of volcanism and rifting." (Ji et al., 2020)
Lithology-pattern: Coarse-grained sandstone
Relationships and Distribution:
Lower contact:
It is unconformably overlying the Tongbomiao Fm.
Upper contact:
Disconformably overlain by Damoguaihe Fm conglomerates.
Regional extent:
It distributed in the area of eastern Inner Mongolia and western Heilongjiang. The Tongbomiao Fm and Nantun Fm are widely distributed in the Hailar Basin and constitute the main part of the basin fill.
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Fossils:
The Nantun Formation yields fossils of ostracods, bivalves, gastropods, conchostracans, spores and pollen.
Age:
[Zheng Ji et al. (2020, " Chronostratigraphic framework of late Mesozoic terrestrial strata in the Hailar–Tamtsag Basin, Northeast China, and its geodynamic implication", Geol. Jour.) conclude that the Upper Member spans ca. 119 to 111 Ma => Aptian; and Lower Member spans ca. 134 to 120 Ma => upper Valanginian through Barremian.]
Age Span:
Beginning stage: Valanginian
Fraction up in beginning stage: 0.7
Beginning date (Ma):
Ending stage: Albian
Fraction up in ending stage: 0.2
Ending date (Ma):
Depositional setting:
Depositional-pattern:
Additional Information