SUMMARY
Fossil zones and
stratigraphic correlation of the Middle Triassic sediments
of East Bắc Bộ
Đặng Trần Huyên, Nguyễn
Đình Hữu, Komatsu T.
Middle Triassic sediments of the East Bắc Bộ region
contain assemblage zones of Bivalves, Ammonoids and Foraminiferas. In these
zones, Bivalves include Costatoria praenapengensis - Langsonella elongata,
Trigonodus tonkinensis - Costatoria goldfussi ones; Ammonoids: Balatonites,
Kellnerites samneuaensis, Leiophyllites - Norites, Kellnerites –
Acrochordiceras ones; Foraminiferas: Meandrospira insolita, Pilamnina
densa ones. These divided zones form the basis for identifying the age of
sediments, as well as dividing and correlating the Middle Triassic stratigraphy
in this region and adjacent areas.
During Middle Triassic in the An Châu structural
zone, Anisian rifting activities had formed the volcanic members of Khôn Làng
Formation and in the Late Anisian – Ladinian time, the Điềm He and Nà Khuất
Formations were formed in carbonate and terrigenous shelf environment. While in
that stage (Anisian) the Yên Bình and Lân Páng Formations consisting of
terrigenous and carbonate beds were formed in the Sông Lô and Sông Hiến zones.
Biogeographically, the Lower-Middle Triassic mollusc
fauna in the East Bắc Bộ in particular, and Việt
Ngày nhận bài: 10/5/2008
Người nhận xét: Vũ Khúc.