New materials on the Nặm Mặn Formation, Mường T area

Bi Ph Mỹ, Đon Nhật Trưởng, Nguyễn Đnh Hữu,
Nguyễn Văn Honh, Nguyễn Văn Lồng

The Nặm Mặn Formation (T3c-n nm) was established in 2001 by authors of the Geological and Mineral Map of the Mường T map sheet group at 1:50.000 scale [3]. According to these geologists, this Formation is composed of conglomerate, gritstone, sandstone, shale, marl and limestone, 150-200 m thick. It rests unconformably upon granite of the Pu Si Lung Comphex (γC1 pl) and under the Suối Bng Formation (T3n-r sb). Sediments of the Nặm Mặn Formation contains Carnian and Norian bivalves and Middle-Late Triassic foramiferas and hexacorals. On the other hand, the Formation was correlated to the Pc Ma Fm with the remark that the Nặm Mặn is younger.

In March-April of this year, the authors of this article carried out the field survey of the study of Formation stratotype. Two fossil collections were obtained. Corals have been yielding the Late Carnian age, while bivalves Norian. The formation is composed of terrigenous and carbonate sediments. It is the lowest part of the Suối Bng Formation.

Người bin tập: Vũ Khc