Tongfosi Fm

Yanji Basin.

Synonym: Local volcanic unit in lower portion is called the Quangshuicun Fm in the same Yanji Basin. That Quanshuicun Fm was designated by the Jilin Regional Geological Survey Team in 1974. The section for the designation is at the Quanshui Village of the Helong County (128°59′E ; 42°29′40″N).

The Tongfosi Fm is mainly composed of grey to black, off-white, greyish-brown, and greyish-yellow (mostly in the western part of the basin) conglomerates, sandstones, fine-grained sandstones, siltstones, oil-bearing sandstones, mudstones, and rare coal seams, and locally at the base of the Tongfosi Fm there are greyish-green and greyish-purple andesites, andesitic volcanic breccias, lavas and tuffs (Futong Fm and Quanshuicun Fm) (Sha, 2007a). The Quanshuicun Fm is represented by gray purple andesite, andesitic agglomerate, andesitic tuff lava and andesitic breccia lava. The Quanshuicun Fm is 295.2 m thick.

It yields a large number of plant mega- and microfossils, charophytes, dinocysts, chlorophyte algae, acritarchs, conchostracans, ostracods, gastropods and bivalves, and rare skeletal fragments. The palynoflora consists of two brackish to brackish-marine dinocysts assemblages. The Vesperopsis cf. zhaodongensis - V. tongfosiensis assemblage occurs in the middle part of the formation. Apart from the two index species, this assemblage mainly consists of V. granulata, V. cf. sanjiangensis, V. yanjiensis, Balmula cf. granorugosa, Pseudoceratium sp. and Nyktericysta sp. V. zhaodongensis is the index species for the top of the Denglouku Fm; V. granulata has also been recorded from the Damoguaihe Fm, Shahezi Fm and at the base of the Yimin Fm; V. sanjiangensis also occurs in the Chengzihe Fm; B. granorugosa and Pseudoceratium sp. both occur in the Yingcheng Fm, and the latter also in the Chengzihe Fm and Damoguaihe Fm; and Vesperopsis, Nyktericysta and Pseudoceratium have been recorded from the Fuxin Fm. Furthermore, V. sanjiangensis and B. granorugosa have been found in the Damoguaihe Fm. Although V. granulata may range as low as the (mainly) Barremian-Aptian Shahezi Fm and extends upwards into the base of the Albian Yimin Fm, the assemblage is mainly encountered at the level of the Denglouku Fm, Fuxin Fm, Chengzihe Fm, Damoguaihe Fm, and probably parts of upper Yingcheng Fm and lower Sunjiawan Fm (Sha, 2007a). The acritarch and dinocyst Filisphaeridium - Sentusidinium assemblage occurs in the upper part of the formation and mainly consists of the acritarchs Filisphaeridium sp. and Granodiscus sp., and the first stratigraphic occurences of the dinocysts Cometodinium sp., Sentusidinium bifidum, Dinogymniopsis granulata and D. spinulosa. Except for Cometodinium sp., the other three dinocyst species have all been recorded from the mainly Cenomanian Qingshankou Fm, implying that this palynoflora assemblage is younger than Aptian, but the overlying Albian Dalazi Fm constrains its age to no younger than Albian. The formation also yields an assemblage of ostracods dominated by Vlakomia jilinensis, co-occurred with Scabriculocypris tonfosiensis, S. yanbianensis, Mongolianella kyranbeki, Lycopterocypris infantilis, Candona spp., Vlakomia ustinovskii. The assemblage is dated as Albian to possibly Upper Cretaceous. Hence, based on the palynofloral and ostracods assemblages, the Tongfosi Fm is Aptian-Albian. Bivalves include Nippononaia yanjiensis and Sphaerium (Sphaerium) chientaoense (=S. (S.) yanbianense). The stratigraphic range of N. yanjiensis is Barremian-Albian (Sha, 2007b) and it has been recorded from the upper Jiufotang Fm, Fuxin Fm and Sunjiawan Fm, and S. (S.) chientaoense has been recorded from the Albian Khuren Dukh Fm in southeast Mongolia (Sha et al., 2006) and the Albian Houshigou Fm /Xiachengzi Formation, which does not contradict the correlation based of the palynoflora assemblages.

The Quanshuicun Fm equivalent at Duhuangzi of Wangqing yields floras Onychiopsis sp. and O. elongata.

It belongs to volcanic facies.