吉林省南部早奥陶世头足类生物地层—兼论有关地体的飘移

EARLY ORDOVICIAN BIOSTRATIGRAPHY WITH OEPHALOPODA IN SOUTHERN JILIN——A Discussin on Drift of the Related Terranes

吉林省南部早奥陶世头足类生物地层单元可建立9个化石带,代表了华北地体型早奥陶世鹦鹉螺生物群。通过与其它含早奥陶世鹦鹉螺生物群地体的对比,结合有关古地磁资料,提出识辨这些地体的移置、增生及聚合的历史。

The fossils of early Ordovieian Cephalopoda in southern Jilin are referred to the North China terrane-type fauna. Nine fossil zones are established. They are as follows (from bottom to top): 1. Levisonoceras-Laishuiceras zone; 2. Coreanoceras-Protrocameroceras zone; 3. Kaipingoceras-Manchuroceras zone; 4. Cyrtendoceras-Kirkoceras zone; 5. Deformoceras-Kiondefomoceras zone; 6. Polydesmia-Wutinoceras zone; 7. Ordosoceras-Kogenoceras zone; 8. Stereoplasmaceras-Sactoceras zone; 9. Tofangoceras-Dideroceras zone. Although the early Ordovician Cephalopoda in the Yangzi terrane is comparable with that of the North China terrane, there is a distinction 'Orthocerida in the south and Actinoceridain the north', and so, it is called as the Yangzi terrane-type Nautilida fauna, which can be comparable respectively with the Tibet-western Indosinian-Atusralia terrane, the Siberia terrane, North America-Greenland terrane and the Scandinavia terrane. According to the results of comprehensive palaeo-magnetic dating made by Whittington and Hughes (1972), it is proposed that a pole of the earth was situated in the western part of Africa and the other, in the Pacific during the Ordovician period. Combining with the palaeomagnetic data collected by Li Jilu (1989) and the geographical regions related to ecological balance of the fauna, it is held that from the south latitude 30° to the north latitude 60°, all the North China terrane-type terranes with a Actinoceras fauna are located in the early Ordovician lowerlatitude zones which are generally parallel with palaeo-latitude zones; in the later, geolgical histories underwent a complicated process including separation, transfer, accrehion and convergence.