那丹哈达岭地层与地体的关系

<正> 位于中国东北隅的那丹哈达岭(实为完达山北段,近年来地质文献中多称为那丹哈达岭),是我国北方唯一出露海相中生代地层的地区。该区森林覆盖面广,全面认识地层有困难;相对出露较多的硅质岩又缺乏大化石;此外对该区构造演化历史的认识也影响了对地层归属的研究。王秀璋(1959)根据放射虫和藻类的研究将地层划分为上三叠统镇江岩

Relationship between strata and terrane of the Nadanhada Range

The Nadanhada Range in northeastern China is a typical Mesozoic tcrrane in the northwestern region of the circum-Pacific.It is bounded on the west and on the south by Yuejinshan (Hamatong-he) and Dunhua-Mishan fault felts respectively, and differs strongly from the Jiamusi block in the west and the Khanka block in the south.The northern extension of this terrane is concealed by the Quaternary sedimentary cover.Its eastern boundary should be within central Sikhote-Alin fault belt.On the basis of the micropaleontologic and paleomagn etic data, the Nadanhada terrane has a drifting history from low-paleolatitute area with Tethyan fauna to the area about the same latitude 'as at present and with boreal fauna during Middle Triassic to Late Jurassic time.According to stratigraphical features of different periods in relation to tectonic development, three tectono-stratigraphical evolutionary stages can be recognized as follows: 1.Middle Triassic-early Laic Jurassic stage that was allochthonous terrane formed and moved northwards, basically continous; 2.Late Jurassic approximately equivalent to Kimmeridgiam, was a stage during which the terrane collided with the Jiamusi and the Khanka blocks, formed chaotic melange terrane and welded into a single tectonic unit with the surrounded blocks; 3.Latest Jurassic to earliest Cretaceous was a depositioral stage of continental margin after the terrane collison, r,n universal epicontinential sea deposits covering a large area, including the Jiamusi and the Khanka blocks.It was suggested that allochthonous stratigraphical system and endemic stratigraphical system could be differentiated when we study a complicated terrane like Nadanhada one.It is unnecessary to give allochthonous melange a stratigraphical formation name, and beuer to express allochthonous system with a column marked by arrow-head as Mizutani s.(1987) and Kojima s.(1989) had done in their papers.