SUMMARY
On
the Nậm Mặn Formation and the datation of the Upper Triassic
coal-bearing formation
Vũ Kh�c
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 T� area. Based on this, authors of this article have been proposing the Carnian factor in the Late Triassic age of the coal-bearing Suối B�ng 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 B�ng Fm; it demonstrates also the inexact character of the correlation of limestone beds in the section attributed to the �Nậm Mặn Fm� to the P�c 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 bi�n tập: ThS. Nguyễn
B� Minh.