Dak Rium Fm

Lam Dong Province. The type section is located along the source of the Dak Rium Stream, in the section extending near Highway No. 20 (N = 11°35’; E = 108°07’). Abramov N. et al. 1984. The continental red beds covering the andcsite of the Deo Bao Loc Fm were described as Dak Rium Fm during geological mapping at 1:200,000 of the Ben Khe - Dong Nai Sheet series.

Synonym: - Hệ tầng Đăk Rium: Abramov N. el al. 1984; Nguyễạ Ngọc Hoa et al. 1996; Nguyễn Đức Thắng et al. 1999; Vũ Khuc et al. 2000. - Non Hệ tầng Đăk Rium: Trần Tinh et al. 1998 (=Hệ lẳng Bình Sơn).

Continental red beds. The Dak Rium Stream section consists of: (1). Thick-beddcd (1-2 m) conglomerate interbedded with coarse-grained sandstone, chocolate- colored, cross-bedded siltstone, 70 m thick: conglomerate pebbles are well rounded, consisting mainly of quartz together with sandstone, homfels; the cement of chocolate- colored gritstone and coarse-grained sandstone. (2). Chocolate-colored, sometimes greenish-grey siltstone and silty sandstone with some interbeds of conglomerate in the upper part, 50 m thick. The total thickness of the formation in this section is 120 m.

Along a dry stream extending east of Tung Nghia Townlet the formation occurs with 2 members. (1). Violet-brown, thick-bedded (1-2 to 5-7 m) conglomerate, boulderstone, gritstone and coarse-grained sandstone, 60 m thick; pebbles and boulders consist of sandstone, maculate homfels, quartz, biotite granite with size varying from 1-2 to 10-15 cm, sometimes up to 60 cm; they are poorly rounded and sorted; their cement is silty sandstone. (2). Chocolate-colored, medium-bedded siltstone, brownish, sometimes calcareous sandstone containing white grains of feldspar, 40 m thick; siltstone yields the phyllopod Nemestheria sp. of Early Cretaceous age and the palynomorphs Polypodiaceae, Schizeaceae, Pinaceae, Euphorbiaceae, Rubiaceae, Poaceae, Rhizophoraceae, Chenopodiaceae, Fagaceae, Picea sp., Lagerstroemia sp. and Albizia sp. of Cretaceous-Paleogene age. The total thickness of the formation in this section reaches 100 m.

An interbed of greenish-grey siltstone of the lower part of the higher member yields leaf impressions of Lycopodites cf. tenerium, Elatocladus sp., and Pagiophyllum cf. crassifolium of Middle-Late Jurassic - Cretaceous age. Also Picea sp., Lagerstroemia sp. and Albizia sp.