FRAMEWORK OF PALEOTETHYAN ARCHIPELAGO OCEAN OF WESTERN YUNNAN AND ITS ELONGATION TOWARDS NORTH AND SOUTH
LIU Ben pei 1, FENG Qing lai 1, C. CHONGLAKMANI 2, D. HELMCKE 3 (1.Faculty of Earth Science, China University of Geosciences,Wuhan 430074, China; 2.Institute of Resources Technology, School of Geotechnology, Suranaree University of Technology
Based on the deepening research of the Paleotethyan tectono paleogeographic framework in western Yunnan, we have suggested a scale of time and space standard concerning the differentiation between archiopelagic sea and archiopelagic ocean. According to the comparison study of the Paleotethyan sedimentary geology among northwestern Tibet, northern Thailand and western Yunnan, we demonstrate that the Changning Menglian belt of western Yunnan elongates towards north to the Gangmacuo suture zone of northwestern Tibet and towards south to the cryptic suture zone in northern Thailand respectively. The Nan Uttaradit suture zone of northeastern Thailand is probably elongated to north and hidden under the Mesozoic Cenozoic red beds of Simao basin. Of course, there is no evidence concerning a stable Simao block during the Paleotethyan stage. Tectono sedimentary mélanges consist of oceanic bedded cherts, seamount carbonates and passive margin clastics that are found in the Mae Sariang zone of northwestern Thailand; moreover, Early Carboniferous and Late Triassic (Carnian) radiolarian faunas are also discovered in previously so called "Devonian" strata of this area. It indicates that the tectono paleogeographic framework of eastern Paleotetethys probably exists as the Gemini type archipelagic ocean with double main branches. Mae Sariang zone probably connects northward the Luxi ophiolitic mélange zone between Baoshan and Tengchong blocks in western Yunnan. The discovery of Jurassic radiolarian fauna in previously so called "Late Triassic" Hagong Formation in northwestern Yunnan also inspires the variety and complexity of geological history in southeastern Asia during the transitional stage between Paleaotethys and Neotethys.