【作者】 余光明； 兰伯龙； 王成善；

【Author】 Yu Guangming Lan Bolong Wang Chengshan (Chengdu college of Geology)

【机构】 成都地质学院；

【摘要】 <正>西藏江孜地区白垩系的研究工作早在50年代初期即已开始。近年来,由于板块学说的兴起,混杂堆积作为板块俯冲带的主要证据已受到重视。因此,不少人从研究地层或构造的角度出发论述过江孜地区白垩系内混杂堆积的成因(陈国铭,1980;吴浩若、王东安, 1981;王连成,1982)。一部分意见认为是构造混杂岩,并与 A．Gasser(1974)所描述过更多还原

【Abstract】 The Cretaceous strata in Gyangze (江孜) of Xizang (Tibet) were studied as early as in the late 1950’s.On its south it is next to Tethys Mesozoic pa- ssive continental margin,and it adjoins Yarlungzangbo ophiolite belt on its north. Having studied this region,especially the sedimentary feature,the wri- ters consider that some special facies such as:greyish、red-greyish、white micritic limestone containing micro-organisms;purplish red calcareous mud- stone containing micro-organisms;black shale rich in pyrite and radiolarian silicalite are the deposits of the starved basin,which are associated with tur- bidite and slumping accumulation-olistostrome.Being similar to the Alps, they belong to the deposits of pre-flysh of pre-orogenic period.Espeially worth noting is the black shale facies mainly of Middle Cretaceous which is comparable with the famous Schiller Schist. Because the olistostrome exists in definite horizons;being no intensely shearing phenomena in matrix;no ophiolite rock mass;closely associated with turbidite sedimentation;a lot of clastic substances of the same rock material as in the slumping accumulation beds contained in turbidite;no rock blocks of younger age than matrix being found etc.,All thess show that the Cretaceous olistostrome of Gyangz(?) should be formed by sedimenta- tion. The sediment characteristics mentioned above are very similar to those of Alps in the same era;which show that the East-Tethys has the similar developing history as West-Tethys in Cretaceous.更多还原