冰碛物建造型相及天秦运动的讨论

Tectonic Facies of Tillite and Tianqin Movement

以往对冰碛物的研究 ,只重视其沉积特征及古地理的恢复 ,未讨论其建造型相。笔者通过对其沉积特征、产出构造环境的讨论 ,认为山麓冰碛物是造山期后的产物 ,属于磨拉石建造 ,大陆冰碛物代表寒冷地区风化壳产物 ,可作底砾岩看待 ;冰蚀面可当作沉积间断面或寒冷地区的风化壳。并认为我国新元古代末期罗圈组及其相当层位的冰碛岩属磨拉石建造。由此推断在新元古代末期 -早古生代初期存在一期未被认识的、在地史上具划时代意义的构造运动 ,命名为天秦运动。天秦运动是晋宁运动后的另一期构造运动 ,是新元古代与古生代的分界运动 ,时限在80 0Ma以后 ,70 0～ 5 4 0Ma是主构造期 ,前期以造山为主 ,后期以裂解为主 ,是Rodinia超大陆的裂解、古亚洲洋和古特提斯海形成期 。

Glacier tillite was studied mainly on the characters of its sedimentary petrology and paleogeography. The teotonic facies were negleticed. In this paper, the piedmont tiuite is sugested as a kind of molass formation,the continental tillite as decomposed rock, a type of basd conglomerat, and the ice worn surface as depositional break or the crust of weathering in the cold region. In China, Neoproterozoic tillite in Luoquan Formation and its analog are molass formation. So it can be deduced that there is a great tectonic movement, named Tianqin Mevement, in China Block in Neo proterozoic earlycambrian, ～700 to 540 after Jinning Movement. The movement had formed a high mountain in Sinian like today's Himalaya , lt's the division of Sinian and Cambrian. with this movement, some blocks in Rodinia cracked from Austrailia, such as Yangzi and Tarim, and peleo Asian ocean and peleo Tethyan sea formed.