Redefinition Of Tunlonggongba Formation And Its Tectonic Significance Of Yibug Caka Area In Nyima County，Northern Tibet

Recently, the Late Paleozoic strata of South Qiangtang Basin has always been to1:250,000geological survey or geological area as determined by TunlonggongbaFormation of the Early Permian and Runge Formation of Early Permian.However,Tunlonggongba Formation have a clear difference relatively Mesozoic strata, so somepeople doubt whether it should classify as sequential strata.Through the work of1:50000regional geological survey, they work on a relative systematic research Thestratum of Tunlonggongba Formation at Rong Ma township from lithologicalassociation, position, sequence, time biogenic assembly and so forth and think thestrata has a biggish distinction with Tunlonggongba Formation.Tunlonggongba Formation was named in1976, the representative sectionis is inwestern Tunlonggongba group of Duoma area, Ritu country, the original definition islithology a set of clastic rocks included the strata of multilayer limestone ormudstone.Current definition is a set of clastic rocks and limestone or marlstoneindifferent thickness.Infossil produced.Fusulininapedunclebesides, some-corals,foraminifers, bryozoans and so on.This survey, they have found basalt, andesite,Volcanic breccia and tuff and found radiolarian sillicates in Tunlonggongba Formation.From sedimentary facies speculation, it is slope abysmal facies.they found fossil inconglomerate, and found fusulinina in bioclastic conglomerate.Bypreliminaryidentification, the Fusulinina is larger.Diameter is between2-5mm.Transversalsurface is round.parachomata develops inside. it is in the Early-Mid permian.So thisfossil existed gravel with high psephicity and output in gravel.So they doubtwhether the gravel is later than he Early-Mid permian and query its formationage.According to the geological section, the most part of the latter part is siltyargillaceous or mudstone.Metamorphic grade is deep.And it had obvious gravitycharacter different from Tunlonggongba Formation.And different from moraine rockshaving the characteristics of Cameng formation pebbly slate and Zhanjin formationslate that containing volcanic, with turbidite deposition characteristics, it is considered that at least a little part is not Tunlonggongba formation.1:250000geologic map in research area, research area changed from north tosouth and by the new and old.After Tunlonggongba Formation disintegrated inresearch area,they will further probe the adaptability of pattern and TunlonggongbaFormation ectonic meanings will be discussed.