Dabaidi Fm
Type Locality and Naming
The formation was named by the Zhejiang Party of Regional Geological Survey in 1966. The type section is at Dabaidi Village, about 55 km northwest of the Xiaofeng seat, Anji County in northwestern Zhejiang Province. It was first published by the Zhejiang Bureau of Geology and Mineral Resources in 1989.
Synonym: （大白地组）, The Tantou Fm, which shares similar lithology and identical fossils so far with those of the Dabaidi Fm, is probably a synonym of the latter as the opinion of Rong Jiayu (1998, in Lin et al., 1998). [See Additional Information]
Lithology and Thickness
The formation, 1280 m thick, consists of dark grey, yellow green siltstone, argillaceous siltstone and fine-grained sandstone. The upper part of this formation is purple fine-grained sandstone intercalated with mudstone; cross bedding developed.
Relationships and Distribution
Lower contact
It conformably contacts with the underlying Anji Fm
Upper contact
It conformably contacts with the overlying Kangshan Fm.
Regional extent
It is exposed in northwestern and western Zhejiang Province. The sandstone increases gradually in the upper part and the grains of the sandstone become coarser and coarser in the middle and lower parts southwestwards, with the tendency of both the clastic debris and the thickness increasing as well.
GeoJSON
Fossils
It bears mainly brachiopod, bivalve Modiolopsis、gastropod、trilobite Encrinuroides and graptolite Glyptograptus, Climacograptus.
Age
Depositional setting
Additional Information
Lithology and Thickness:
The formation, 1280 m thick, consists of dark grey, yellow green siltstone, argillaceous siltstone and fine-grained sandstone. The upper part of this formation is purple fine-grained sandstone intercalated with mudstone; cross bedding developed.
Lithology-pattern: Siltstone
Relationships and Distribution:
Lower contact:
It conformably contacts with the underlying Anji Fm
Upper contact:
It conformably contacts with the overlying Kangshan Fm.
Regional extent:
It is exposed in northwestern and western Zhejiang Province. The sandstone increases gradually in the upper part and the grains of the sandstone become coarser and coarser in the middle and lower parts southwestwards, with the tendency of both the clastic debris and the thickness increasing as well.
GeoJSON:
Fossils:
It bears mainly brachiopod, bivalve Modiolopsis、gastropod、trilobite Encrinuroides and graptolite Glyptograptus, Climacograptus.
Age:
Age span:
Beginning stage: Rhuddanian
Fraction up in beginning stage: 0.4
Beginning date (Ma):
Ending stage: Aeronian
Fraction up in ending stage: 0.45
Ending date (Ma):
Depositional setting:
Depositional-pattern:
Additional Information
The Tantou Fm was proposed by the Zhejiang Party of Regional Geological Survey in 1966. The type section is located at Tantou-Wangjia, Chun’an County in western Zhejiang Province. It consists of dark grey sandstone and mudstone. It is the purplish red fine-grained sandstone interbedded with siltstone or mudstone at the top; a suit of rhythmic deposits of dark grey fine-grained sandstone, siltstone and mudstone in the upper part; mainly yellow green fine-grained sandstone intercalated with silty mudstone and argillaceous siltstone at the middle part; interbeds of grey green fine-grained arkosic quartzose sandstone with silty mudstone at the lower part. The thickness varies from 320 m to 1400 m (The Compiling Group of Zhejiang Regional Stratigraphical Scale, 1979). The Tantou Fm, which shares similar lithology and identical fossils so far with those of the Dabaidi Fm, is probably a synonym of the latter as the opinion of Rong Jiayu (1998, in Lin et al., 1998).