南设得兰群岛是晚中生代以来古太平洋板块向南极板块俯冲消减过程中形成的,目前对整个群岛的地层特征及沉积演化无统一认识.通过归纳总结国内外研究成果,认为该群岛出露的地层具明显的时空规律.群岛主体的西南部出露上侏罗统-下白垩统,发育海底扇、深海、斜坡裙、扇三角洲等沉积相,相伴随的火山作用主要为钙碱性玄武岩和玄武安山岩的喷发,记录了弧前盆地-火山岛弧的演化过程；群岛主体的东北部主要出露上白垩统-下渐新统,其中上白垩统-始新统发育一套玄武质熔岩、火山碎屑-沉积岩建造,为温暖气候下的陆相沉积,火山活动具有岛弧拉斑玄武岩与钙碱性火山岩的过渡性质.渐新统-下中新统则记录了从间冰期正常海相到冰期冰海相沉积的转变过程.%The South Shetland Islands were formed from the subduction of the palaeo-Pacific plate beneath the Antarctic Plate in the late Mesozoic.However,there are no comprehensive records of the stratigraphic characteristics and sedimentary evolution of the entire islands.We examined the distribution of strata by reviewing the literature on the islands published nationally and internationally.The exposed strata in the southwestern South Shetland Islands were mainly from the upper Jurassic-lower Cretaceous.The sedimentary facies included submarine fan,deep sea,marine slope apron,and fan delta.The volcanism was manifested by the eruption of alkaline basalt and basaltic andesite.The evolution from fore-arc basin to volcanic islands has been recorded.The strata in the northeastern South Shetland Islands is mainly upper Cretaceous to Neogene.The sedimentary environment of the upper CretaceousEocene is continental basin in warm climate.The lithology is mainly consisted of basaltic lava,pyroclastic debris and sedimentary rock.Geochemically,the volcanics were transitional from alkaline basalt to tholeiite.The Oligocene-Miocene yielded the transformation from normal marine facies in the interglacial stage to glacio-marine facies in the glacial stage.
展开▼
