亚洲东部的志留系

亚洲东部包括西伯利亚,科累马,塔里木—中朝和华南等古板块,以及围绕或穿插其间的活动带.不同古板块基本上被归于不同大区,同一大区中的稳定和活动地带属不同的一级地层区,同一区中的不同岩相和生物相带为不同的二圾地层区.志留纪时期除冈瓦纳古陆之外,其他各板块都分布在赤道两侧的低、中纬度地带,而且以南半球为主.在各古板块内的志留纪古地理面貌上,本文着重剖析华南古板块.志留纪的生物地理区系划分,虽然基于不同门类有不同的认识,但亚洲东部范围内均属北方大区.本文用生态地层学、沉积学,古地理学等方法研究了华南早志留世海平面升降的规律变化.

THE SILURIAN SYSTEM IN EAST ASIA

Silurian rocks in East Asia are encountered in the Siberia, Kolyma, Tarim-Sino-Korea, South China and other plates, as well as in those mobile belts composed of two or more ancient continental margins among these plates. A basic hierarchy for subdividing stratigraphic realms is here pro-posed. The largest unit of stratigraphic realm may be designated as a domain. Different plates generally belong to different domains)stable and mobile areas within the same plate may be attributed to different provinces; various litho-and bio-facies belts may be assigned to the subordinate unit, subprovinces. In the light of this schedule, the subdivisions of the Silurian stratigraphic realm in East Asia are summarized as follows: 1.Kolyma province (I1) Kolyma domain (I)(2. Chukochi-New Siberia province ( I2) Chukochi subprovince ( I23) New Siberia Archipelago subprovince ( I 2b) 3. Siberia province (II1) 4.Taimir province (II2) Siberia domain (II) 5.Altai-Sayan province (II3) ,6.Hinggan province (II4) West Mongolia subprovince (II3a) Tuva subprovince ( II3b) Soviet Altai subprovince (II3e) Salair subprovince (II 3d) W. Sayan subprovince (II3e) Altai subprovince (II3f) a) Tarim-Sino - 7. Inner Mongolia-jilin Inner Mongolia subprovince(Ⅲta) Korean Domain province (Ⅲ 1 ) Jilin subprovince (Ⅲ tb) (III ) 8. Tarim province (Ⅲ2) Kazakhstan Domain (Ⅳ)- 9. Yining-Tianshan Yining subprovince (Ⅳta) province (Ⅳ1) W. Junggar subprovince (Ⅳ lb) Qin-Qi 11. Qinling province V2 Qinling subprovince (V2a) Domain (V) E. Qinling subprovince (V2b) Longmenshan subprovince (Ⅵta)Dabashan subprovince (Ⅵ lb)Upper Yangtze subprovince (Ⅵle)South China Domain(Ⅵ) 12. Yangtze province. Guizhou subpro 13. Xuefeng provincce (Ⅵ 2 ). l4.Yunkai province (Ⅵ 3 ) S.Yarlung Zangbo subprovince l5. Tibet-W. Yunnan N. 16. Southeast Asia West circum-Pacific Domain (Ⅷ)-17. Japan province During the Silurian period most plates were distributed in tropical and/or subtropical latitudes;only the Gondwana was situated in a polar region and its adjacent high latitudes. There occurred a Mongolia-Okhotsk Sea among the Siberia, Razakhstan and Tarim-Sino-Korea plates and a Cathaysi-an Sea between the South China and Sino-Korea Plates. The Kala Sea was located south of the Kazakhstan plate during late early Palaeozoic time. Palaeogeographic features and their evolution in south China during Silurian time are treated herein as an example. The main features are as follows:(l) The Cathaysian and Dian-Qian-Gui Lands were united during the late Llandovery;(2) South China platform was mostly elevated above sea level in the latest Llandorery to earliest Wenlock, with a few exceptions: in western Sichuan, eastern Yunnan and the Yunkai area, where sedimentation occurred in small platforms, basins, or troughs during late Silurian time. Two realms, the North Silurian Realm and the Malvino-Kaffric Realm, have been recognized in Silurian biogeography, although there are different interpretations in studies of various kinds of fossils. The North Silurian Realm represents broad, high diversity faunas in a relatively warm-water environment, which is known to occur in many parts of East Asia. The Malvino-Kaffric Realm contains cold-water, restricted and low diversity faunas, which have not been encountered in East Asia. Based on abundant material of various kinds of fossils in East Asia, the study of Silurian ecostratigraphy offers good examples of community succession and replacement in South China, Tuva and other areas. They in turn indicate a notable influence of environmental change on marine com-munities through time. Eustatic sea-level fluctuations of Llandovery age in East Asia have been studied with an ecostratigraphic approach associated with paleogeography, sedimentology and tectonics. Due to the effect of the initial mass melting of the Gondwana glaciation at the start of the Llan-dovery, four cycles of sea-level fluctuation were recorded by recurreut shelly faunas in some parts of