Sinh Vinh Fm
Type Locality and Naming
Right bank of the Song Da River, from the Sinh Vinh Stream Mouth to Nam Ton Stream Mouth, Moc Chau District, Son La Province (N= 23°21', N= 114°40'), and the formation is named from the location of the holostratotype
Synonym: Hệ tầng Sinh Vinh (part): Dovjikov A.E. el at. 1965,1971 (0 5 - St). Etage de calcaires de Ban Horn (part): Deprat J. 1914; Dussault L. 1929, Puding de Hang Mieng (part): Dussault L. 1929 (D1 hoặc T). Điệp Sinh Vinh (part): Trần Văn Trị et al. 1968, 1970, 1977 (O3 - S); Nguyễn Xuân Bao et al. 1969, 1970 (O3 - S); Nguyễn Văn Hoành et al. 1974 (O3 - S); Phan Cự Tiến et al. 1977, 1988 (O - S); Bùi Hừu Lạc et al. 1983 (O3 - S); Trần Đăng Tuyết et al. 1989 (Oj - S); Nguyễn Đình Hợp et al. 1989 (O3 - S); va Khúc, Bùi Phú Mỹ et al. 1990 (O3 - S); Nguyễn Công Lượng et al. 1992 (O3 - S). Hệ tầng Sinh Vinh: Trần Xuyên et al. 1984 (O 3 - S); Phạm Kim Ngân et al 1986, 1995 (O3 - S); Nguyễn Văn Hoành et al. 2001 (O3 - S)
Lithology and Thickness
Conglomerate, Calcareous Sandstone, Dolomitic Limestone. The Sinh Vinh Fm is clearly distinguished by three following parts. (1) Conglomerate, pebbles of which consist of quartzite similar to those of the underlying Ben Khe Fm, 40 m thick. (2) Calcareous sandstone and mudstone, dolomite, sandy limestone and marl, bearing corals Reuschia sp., Plasmoporella kiaeri, Favositella alveolata, thickness about 400 m. (3) Light grey, thickly bedded dolomitic limestone and calcareous shale interbeds bearing corals Favosites sp., F. aff. forsbesi, F. ex gr. gothlandica, F. cf. hisinger, F. cf. coreaniformis, Mesofavosites sp., Squameofavosites sp., Pa- rastriatopora sp. Thickness about 350 m.
Relationships and Distribution
Lower contact
The Sinh Vinh Fm unconformably overlies different formations. At Sinh Vinh Mouth and Suoi Nhap, Nam Ton Streams, Ban Ban Village its basal conglomerate rests unconformably upon the banded mudstone of the Ben Khe Fm (mid-Cambrian). In So San, Ban Non Villages it unconformably overlies the dolomite of the Da Dinh Fm (Ediacaran). At the source of the Suoi Nanh Stream it lies upon the biotite gneiss of the Sinh Quyen Fm.
Upper contact
The Sinh Vinh Fm conformably underlies the Bo Hieng Fm.
Regional extent
The formation is mainly exposed in the Song Da River downstream in two discontinuous narrow bands from the Khoang, Nhap, and Sinh Vinh streams (Son La Province) through Seo Ngu and Tu Ly villages (Hoa Binh Province) to the Luoi Hai Mountain area of Thanh Son District (Phu Tho Province).
GeoJSON
Fossils
Bearing corals Favosites sp., F. aff. forsbesi, F. ex gr. gothlandica, F. cf. hisinger, F. cf. coreaniformis, Mesofavosites sp., Squameofavosites sp., Pa- rastriatopora sp. Apart from the above mentioned fauna, the following fossils were collected in different areas, Crinoids Bistrowicrinus quinquelobatus (at Nhap Trong Village); Corals Reuschia sp. (at Co San Village), Favositella alveolata (at Ban Ban Village), Favosites sp., F. aff. forbesi var. similis, F. ex gr. gothlandicus, F. cf. hisingeri, F. cf. coreaniformis, Squameofavosites sp., Mesofavosites sp., Parastriatopora sp. (from Nam Ton Stream Mouth), and Multisolenia ex gr. tortuosa (4 km southeast of Lang Ngu Village.
Age
Depositional setting
Late Ordovician corals were collected from small limestone lenses of the lower beds near the Sinh Vinh Mouth, and Late Silurian (Ludlow) corals - from the upper part of the formation. These faunal data create strong support for referring the Sinh Vinh Fm to the Late Ordovician - Silurian.
Additional Information