Scientia Sinica

THE CORRELATION AND THE AGE OF THE YENCHANG FLORA, NORTHERN SHENSI*

H. C. Sze (7 fF fe)

(Insitute of Paleontology, Academia Stntcd)

From what has been said about the botanical character of the Yenchang flora in a paper published in Scientia Sinica Vol. IV, No. 4 (1955)"), it is evident that the composition of this flora is quite different from the commonly known Rhaeto-Liassic and the Middle Jurassic floras in Eastern Asia and the whole world as well. The Yenchang flora is characterized by a dominant assemblage of Bernoullia zeilleri and Danaeopsis fecunda which occur throughout the whole complex of the formation and in the majority of its fossil localities. This flora is apparently older than the Tonking flora of IndoChina"! and the Pinghsiang flora'* *) of Southern China, which is characterized by a dominant assemblage of Dictyophyllum, Clathropteris, etc. The writer is quite prepared to agree with Dr. C. H. P’an!! that the Yenchang flora of Northern Shensi cannot be younger than the Rhaetic or older than the Keuper and that it is, most probably, mainly of Keuper—perhaps Middle and Upper Keuper—and the uppermost part of it is possibly Rhaetic. Dr. P’an concluded that the Yenchang formation in Northern Shensi might be tentatively designated as Keuper-Rhaetic in age, and with this view the present writer is in. complete accord.

As far as the present knowledge goes, the Yenchang flora is more or less equivalent to the floras of the Lunzer Keuper of Austria"! and the Basler Keuper™” *) of Neuewelt, Switzerland. Both are characterized by a dominant assemblage of Bernoullia, Danaeopsis, Glossophyllum, etc. and both belong to the Middle Keuper. The other new species of the Yenchang flora which show a close relationship with the characteristic forms of the Lunz and Basel floras may be mentioned: Cladophlebis shensiensis P’an. It is closely related to Cl. riitimeyeri Heer'*! of Basel in regard to the shape of the pinnules and the pattern of the venation. The only difference between these two forms is that the shape of the pinnules of the former is much more varied than that of the pinnules of the latter. There are considerable variations of the form and size

*First published in Chinese in Acta Paleontologica Sinica, Vol. 1V, No. 1, pp. 25—44, 1956.

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