【摘要】 本文根据古植物研究,并结合现代植物地理、板块构造及古地磁学等理论综合分析,提出古植物地理分区应根据:(1)古植被本身性质、(2)古地域分异性、(3)古“三向”地带性等三项原则。据此原则,并综合前人部分分区意见,作者提出我国晚三叠世植物应划分为三个植物区:北方植物区(Danaeopsis-Symopteris植物区)、南方植物区(Dictyophyllum-Clathropteris植物区)及雅鲁藏布江植物区;并推测后者晚三叠世植被可能属于冈瓦纳地区Dicroidium-Lepidopteris植物群性质。更多还原

【Abstract】 Three principles are proposed here for determining palaeophytogeographic divisions and accordingly, a new scheme of Late Triassic phytogeographic divisions of China is put forward. The three principles for drawing up the palaeophytogeographic divisions are as follows:1) The demarcation of geofloras should be based on floristic characteristics of the varied floras themselves. These characteristics include types of the dominant floras, the compositional pattern of the varied communities and the existence of dominant genera or those genera and species characteristic of the regional.2) The palaeogeographic position of the flora during its growth should be considered.3) The division should refer to characteristices of floral zonation formed in three directions--atitudinal, longitudinal and vertical zonations in the geological time.In China, according to a number of palaeobotanists, the palaeophytogeographic division was only based on the factor of latitude neglecting floristic characteristics and the influence from the floral zonation in the longitudinal direction, such a division has been called as "the Latitudinal tectonic Zone". However, discovery of the Tianqiaoling flora (located at 43.5°N in NE China) which contains numerous genera and species of the Dipteridaceae and Cycadophyta indicates tropic or subtropic conditions, while, according to researches on magnetism and plate-tectonics, etc., the palaeophytogeographic division of southern Xizang (Tibet) is a rather complicated subject. As the climatic conditions controlling the growth of vegetation is changeable in three directions, in researches on the palaeophytogeography, we should consider not only the influence of latitudinal change which usually causes temperature variation from south to north, but also the influence of longitudinal change which usually brings about variations in humidity from sea to inland and, even the influence of vertical or altitudinal change which also leads to variations in temperature, humidity, etc. At the same time, it is necessary that we should take into a consideration about the past geographic positions of the studied floristic regions.It is suggested therefore that the Late Triassic geoflorase in China should be divided into three floristic regions (Fig. 4):1. North floristic region with the Danaeopsis-Symopteris Flora. It includes the famous Yanchang (Yenchang) flora (Sze, H. H., 1956; Zhou, H. Q. et al., 1980), Xiaohekou flora (Mi, J. R. et al., 1977), Mole flora from Qinghai (He, Y. L., 1980), etc.2. South floristic region with the Dictyophyllum-Clathropteris Flora. It comprises many "Southern type" floras previously described from South China, including the Tianqiaoling and Laoheishan floras from NE China recently reported by the author.3. Yarlung Zangbo River floristic region. It is deduced from the data on plate-tectonics, palaeomagnetism and the clue to plant remains questionable in a thin coal-seam intercalated, in the carbonaceous shale of the Langjixue Group (Norian) in Xiukang, south of the Yarlung Zangbo River and about 28 km east of Lhazi, Xizang (Tibet). Palaeogeographically, this floristic region might have lain by the southern shore of the Tethys within the northern Indian Plate in Late Triassic. Based on palaeomagnetic data, the Tingri County near Xiukang was located 24.3° S in the Triassic. The flora concerned may be identical with the Dicroidium-Lepidopteris flora of North India during late Triassic.更多还原