The Latest Cretaceous Flora of Heilongjiang Province and the Floristic Relationship Between East Asia and North America (Cont.)

Abstract

Abstract:

The present paper deals with a collection of plant fossils from the Wu-

yun Group of Heilongjiang Province. These fossils belong to 28 families, 39 genera

and 53 species. The flora is composed of 7 species of pteridophytes, 8 of conifers and 37

of angiosperms. All have been fully described, of which ten are new species.

Most elements of this flora are subtropic or warm-temperate, with only a few of

them are temperate ones. The flora consists of conifers and broad-leaved trees adapted

to humid warm-temperate or subtropic climate.

With the physiognomy of leaves, 40 per cent of them are of entire margin, and most

are medium-sized, with some megaphyllous. The nervation is mostly palmate. These

characters indicate that the climate was warm-temperate or subtropic.

Among 35 genera known from the Late Cretaceous of East Asia, 27 are also found

in North America, which indicates that the floristic relationship between East Asia and

North Americal was closer at that time than it is now. Therefore the number of

genera in common has been decreasing through the age, because these two regions have

been detached from each other since the late Eocene, as a result of continental drift.

Only some relic forms left on both sides, and only 4.1% of genera are common to both

continents. After the early Tertiary the floras of East Asia and North America have

been developing independently.

The Chinese flora of the Late Cretaceous may be divided into three Zones from the

north to the south: (1) warm temperate-subtropic zone, rich in Metasequoia, Ginkgo,

Trochodendroides, Platanus, Trochodendron, Protophyllum, Ampelopsis Pterospermites

and Menispermites; (2) subtropic or dry subtropic transitional zone; and (3) subtropic-

tropic zone, rich in Brachyphyllum, Cinnamomum, Nectandra and Palms.

The Wuyun flora is considered closely related to the Chajiayang Group and Sikhote-

Alin flora of USSR, with 15 genera in common and also related to the Kuji flora of

Japan (Cenonian), with 11 genera in common. It is interesting to note that 11 genera

are also found in North America (Canada and Alaska) of the Late Cretaceous. The pa-

lynological assemblage of the Wuyun flora is closely related to Minshui flora of the So-

uliao Basin, 15 genera being common to the both. Seventy per cent of megafossils of

the Wuyun flora have become extinct, which seems to show that the age of the flora is

older than Paleocene and is assigned to the Latest Late Crataceous (Maestrichtian-Dani-

an).

Key words: Wuyun Formation, Late Cretaceous, Physiognomy, Flora, Geoflora

Tao Jun-Rong, Xiong Xian-Zheng. The Latest Cretaceous Flora of Heilongjiang Province and the Floristic Relationship Between East Asia and North America (Cont.)[J]. .

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The Latest Cretaceous Flora of Heilongjiang Province and the Floristic Relationship Between East Asia and North America (Cont.)

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