Dalangshan Fm
Type Locality and Naming
The Dalangshan Formation was erected by Zhang Xianqiu in 1974. The section for the designation is down the borehole No.2 of Dalangshan, Sanshui City, Guangdong. The Dalangshan Formation represents the set of gray purple and dark Purple red clastic rocks overlying the Sanshui Fm and underlying the Xinzhuang Fm in the Sanshui City. The formation is Late Cretaceous in age.
Lithology and Thickness
The Dalangshan Formation comprises a set of rhythms of purple red and gray purple clastic sediments, which is divided into two members. Lower member is built up by gray purple and dark purple conglomerate and sandstone interbedded with siltstone. Upper part is purple red and dark purple red siltstone and sandstone interbedded with gray green mudstone. Basal part is gray purple and dark purple conglomerate and sandstone with siltstone. It exceeds 359.5 m thick. Regionally, it is intercalated with several basalt beds and is 200-500 m thick.
Relationships and Distribution
Lower contact
It is differentiated from the purple red mudstone of the Sanshui Fm. The formation lies unconformably over the underlying strata.
Upper contact
It top is conformably bounded by the appearance of the purple red thick-bedded conglomerate of the Paleogene Xinzhuang Fm.
Regional extent
It occurs in the Sanshui basin, the Gaoyao-Baitu basin and the Xinhui basin of central Guangdong. In the Gaoyao-Baitu basin, the lower part of the formation is dominated by brown gray conglomerate and sandy conglomerate with siltstone and fine sandstone, with a thickness of 530 m, while the upper part gray brown clayey siltstone and fine sandstone with sandy conglomerate, with a thickness of 1135 m. In the Xinhe basin, the lower part of the formation is mainly built up by brown red conglomerate, sandy conglomerate and sandstone, with siltstone and mudstone; while the middle and upper parts brown red silty mudstone, sandy conglomerate and conglomerate. Its total thickness is 2000 m.
GeoJSON
Fossils
It yields ostracods Limnocuythere orientalis, Candona declivis, Porpocypris globra, Talicypridea quadrata, Cypridea cavernosa, C. diplonoda, C.xindianensis, Eucypris imparilis; Charophytes Harnichara dalongshanensis, Mesochara rubeda, Obtusochara lanpingensis.
Age
Depositional setting
It is of fluvial-lacustrine facies.
Additional Information