Rao Chan Fm

Lower formation of Hon Son Gr. The section along Rao Chan Stream near height 323, Chuc A Commune, Huong Khe District, Ha Tinh Province (N = 18° 03'; E = 105° 40'), the formation is named after the stream of the same name.

Synonym: - Hệ tầng Rào Chan: Trần Tính et al. 1979, Nguyền Quang Trung et al. 1983, Nguyễn Đức Khoa (Tống Duy Thanh 1986), Vũ Khúc, Bùi Phú Mỹ eí aỉ. 1990, Nguyễn Hữu Hùng, Nguyễn Đửc Khoa (Phạm Kim Ngân 1994); Tống Duy Thanh, Nguyễn Đức Khoa (in VQ Khúc et al. 2000), Phạm Huy Thông el at. 2001 (D₁). - Trầm lích Eifeh Mareichev A.M., Trần Đức Lương (Dovjikov A.E. et al. 1965). - Các trầm (ích Devon hạ: Dương Xuân Hảo (Trần Văn Trị et al 1977). - Hệ tầng Lý Hoà (part.): Phạm Huy Thông, Tạ Hoà Phương, Nguyễn Hữu Hùng, Đoàn Nhật Trường 1999.

Claystone and Sandstone: (1). Black clayey shale interbedded with thin-beddcd limestone beds or lenses, 124 m thick. (2). Calcarcous shale, scricite schist containing limestone lenses and clayey limestone, 123 m thick. (3). Thin bedded clayey shale, carbonaceous clayey shale, 230 m thick. (4). Clayey shale, carbonaceous shale interbedded with small limestone lenses, 130 m thick. (5). Black calcareous shale, sericite schist and siltstone, 90 m thick. (6). Black calcareous - clayey shale, and clayey shale, 60 m thick. (7). Black, thin schistose clayey shale bearing many mica flakes, 175 m thick. (8). Calcarcous - clayey shale, interbeds of micaceous sandstone, 140 m thick. (9). Black calcareous - clayey shale with small lenses of crystallized limestone, 125 m thick. (10). Black, regular thin-bedded clayey shale, 80 m thick. (11). Sandstone, siltstone, clayey shale with small lenses of chert containing poorly preserved crinoids and brachiopods, 125 m thick. (12). Black calcarcous shale, variegated sandstone, siltstone, 155 m thick. (13). Blue grey sandstone, siltstone containing remains of crinoids and brachiopods, 128 m thick. (14). Thin-beddcd sandstone, siltstone, 230 m thick. (15). Black sandstone, siltstone intcrbedded with shale and some intcrbcds of micaceous sandstone 100 m thick. (16). Clayey shale-bearing loaf-form limestone and calcarcous chcrt, and interbeds of fine-grained sandstone, 155 m thick. The total thickncss of the section reaches 2170 m.

Desquamatia vijaica, Levenea aff. transversa, the corals Pachyfavosites cf. delicatus, Alveolites sp., Coenites cf. simakovi, Heliolites cf. insolens, Chaetetes ninae, Desmidopora sp., and the crinoid Lissocrinus curtus.