in Jurassic and Cretaceous Stratigraphy

Earth Science Frontiers, Vol. 17, Special Issue, Aug. 2010 ISSN 1005-2321
be of Lower Jurassic (J1).
However, there are still too little data to confirm
the age of Early Jurassic. Moreover, this is the matter of
boundary between Triassic and Jurassic in Vietnam,
which is in general difficult.
Therefore, additional detailed investigation should
be carried out for verification.
- Another new problem is to find out the relation-
ship between the Jurassic spores and pollens and the
"Hon Gai flora" in terms of geological time and space.
- The attribution of coal-bearing sediments to
Rhaetian in Suoi Bang Formation may be appropriate,
but this still depends on the results of studying the Nong
Son and Yen Tu sections together with the study of the
Hon Gai flora.
- In 1995, Cat Nguyen Hung et al. divided the Suoi
Bang Formation, and upgraded the Nong Son
Formation aged Norian–Rhaetian to Nong Son series
and divided it into two formations:
The upper part containing coal, plant fossils, is
called Suon Giua Formation, aged Rhaetian.
The lower part with neither fossils nor coal found
is called An Diem Formation, aged Norian.
To be persuasive, it is necessary to find fossils in
the lower part of the Nong Son section — i.e. An Diem
Formation and in the lower part of Yen Tu section as
well (currently placed in Norian–Rhaetian by the
authors).
More detailed studies of the Nong Son coal-
bearing sediments would not only serve scientific
purposes, but also serve the prospecting of mineral
resources, including coal and associated uranium ore,
which are also very important.
The Nong Son coal deposit has been mined for a
long time, but uranium-radioactive anomalies were
newly discovered only after the reunification of the
country (by the Geological Subdivision No. 501 of
Geological Division No. 5, Hoang Dinh Kham, 1978
and Subdivision No. 500, Geological Mapping Division,
Huynh Trung, 1979). Both mineral and environmental
researches are necessary here.
Acknowledgements: On the occasion of the pub-
liccation of this paper, the authors sincerely thank the
Association of Paleontology and Stratigraphy, the
Institute of Geosciences and Mineral Resources,
paleontologist Nguyen Duc Tung, who has determined
134
the fossils and prepared the paleontological photos, and
Dr. Ta Hoa Phuong, who has kindly assisted us to
conduct this interesting geological field trip, reviewed
the manuscript and highly evaluated the new
discoveries of the authors, in the mean time contributed
valuable recommendations to improve the contents of
the paper.
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