THE VARISCAN MOVEMENT IN THE SOUTHWESTERN PART OF THE SANJIANG FOLD SYSTEM

From the data obtained in regional geological surveys in recent years this paper demonstrates that the area west of the line of Jingdong-Simao-Mengla, east of the Lanchengjiang deep fracture and south of Jingdong in southwest Yunnan is a Variscan fold belt. The late Paleozoic sediments in the area consist mainly of a considerable thickness（＞9500m） of volcanic-clastic rock formations, and there also occurs a spilite-keratophyre-radiolarian chert formation up to 1000 in in thickness, which undoubtedly implies a eugeosynclinal environment. In the entire Variscan cycle there existed two strong foldings; one took place between the Middle and Late Carboniferous, and the other at the end of the Late Permian. They both generated regional deformations and distinct angular unconformities, and were accompanied by relatively strong magmatism and metamorphism. The late Variscan movement is the principal folding episode that caused the Variscan geosyncline in the area to close and transform from the geosyncline stage to the platform stage. the overlying Triassic strata and those above them all possess the features of cover rocks. Therefore ihe principal cycle in the area should be the Variscan cycle, and this area should represent a Variscan fold belt.