SUMMARY

Proposing the hypostratotype for the Si Phai Formation in Đồng Văn - Mèo Vạc area, Hà Giang Province

Tạ Hòa Phương, Nguyễn Đức Phong, Nguyễn Văn Vượng

The Si Phai Formation at the lectostratotype is not completely exposed by some tectonic faults that occurs between its upper part and the overlying Tốc Tát Formation. The highest part of the Si Phai Formation is discovered at the Mã Pì Lèn section and is composed of limestone interbedded with siliceous limestone bearing tentaculite and conodont fossils (Nowakia sp., Polygnathus sp., Palmatolepis hassi, Pa. triangularis, Ancyrodella nodosa). The uppermost layers of the Si Phai Formation transit gradually to the stripped limestone of the Tốc Tát Formation. According to the new paleontological and structural data, the age of the Si Phai Formation varies in the Emsian-Famennian interval (D₁em-D₃ fm). The Mã Pì Lèn section in the Đồng Văn - Mèo Vạc area, Hà Giang Province, has been proposed as hypostratotype for the Si Phai Formation.

Ngày nhận bài: 10/8/2007

Người biên tập: Nguyễn Hữu Hùng