试论西藏二叠纪(竹蜓)类及非(竹蜓)有孔虫的生物地理区系与古地理及古构造的关系

ON PERMIAN BIOGEOGRAPHY OF FUSULINIDS AND NON-FU-SULINIDS IN TIBET AND ITS RELATION WITH PALEOTECTONICS

本文通过对西藏二叠系(竹蜓)类及非(竹蜓)有孔虫的研究认为,早二叠世早期(竹蜓)类以冷温型的Monodiexodina动物群为主,属冈瓦纳—特提斯生物区,冈瓦纳大陆与欧亚太陆及扬子地块的分界分别为昆仑山南坡断裂和金沙江断裂。早二叠世晚期(竹蜓)类Neoschwagerina-Polydiexodina动物群仍限于冈瓦纳北缘区,其生物区系以及扬子地块的分界与早二叠世早期相同,而冈瓦纳大陆北缘西部首先与欧亚大陆塔里木等地块接近,该动物群才越过了昆仑山北坡。晚二叠世晚期(竹蜓)类以Palaeofusulina动物群为主,与扬子地块相似属华夏—特提斯生物区,冈瓦纳与欧亚大陆的界线转为班公湖—怒江断裂,而冈底斯带与喜马拉雅带至今未见Palaeofusulina,该二带仍属冈瓦纳—特提斯生物区。

Based on the study of the Permian fusulinids and foraminifera of Tibet, a general outline of the biogeographic provinciality and its relation with the paleo-geography and the paleotectonic settings of Tibet have been discussed.In the early Early Permian, the Himalayan, Gangdese and the Qiangtang-Tanggula ( including Changdu district) tectonic zones in Tibet all set in the South Hemisphere and were within the north marginal region of the Oangdwana Continent, where the fusulinids were dominated by the Monodiexodina fauna of cold-temperate type. Compared with that on the Yangtze Platetorm, this fauna has lower aboundance and diversity, and biogeographically belongs to the Gangdwana-Tethyan realm, while the Yangtze Plateform belongs to the Cathaysia-Tethyan realm. The boundaries between the Gangdwana Continent and the Eurasia Continent as well as the Yangtze Plateform are respectively along the South Kunlun fault and the Jinshajiang fault. In the late Early Permian (Maokouan Period) , as the climate getting warm world-widely and the Gangdwana Continent moving northwards, the fusu-linids Neoschwagerina-Polydiexodina fauna was developed and on the north mar-ginal region of the Gangdwana, its boundary from the Yangtze Plateform was stil] along the Jingshajiang fault. However, as the western part of the north marginal region of the Gangdwana Continent moving close to the Tarim Block of the Eura-sia Continent, this fusulined fauna spread to the South Kunlun. In Late Permian ( Changxingian Period ) , with a General trend of the Gangdwana Continent drif-ting northwards, the Qiangtang-Tanggula Block split away from the Gangdwana Continent and merged with the Eurasia Continent and the Yangtze Block. The fusulinids there were dominated by the Palaeofusulina fauna and similar to those on the Yangtze Block, both of them belong to the Cathaysia-Tethyan realm. At that time the boundary between the Gangdwana and the Eurasia Continents was shifted to along the Bangong Lake-Nujiang River fault, while the Gangdese and Himalayan Zone was still within the Gangdwana-Tethyan realm.