SUMMARY

On the Nậm Mặn Formation and the datation of the Upper Triassic coal-bearing formation

Vũ Khúc

Recently, an article occurred in the Series A of this Journal of Geology, presenting a new document on the Carnian age of hexacorals collected from a section of the “Nậm Mặn Fm” in the Mường Tè area. Based on this, authors of this article have been proposing the Carnian factor in the Late Triassic age of the coal-bearing Suối Bàng Formation in the West Bắc Bộ region. The present article demonstrates the invalid character of the “Nậm Mặn Fm” and that the studied section belongs to the coal-bearing Suối Bàng Fm; it demonstrates also the inexact character of the correlation of limestone beds in the section attributed to the “Nậm Mặn Fm” to the Pác Ma Fm of Carnian age by many reason, especially it is impossible to base on hexacorals for rejecting the dating by ammonites and bivalves; therefore, the Upper Triassic coal-bearing formation in West Bắc Bộ has only the Norian-Rhaetian age.

Người biên tập: ThS. Nguyễn Bá Minh.