青藏高原第四纪冰期旋回与构造隆升耦合机制及过程研究

In the recent 20 yeras，topics on tectonic uplift incuced climatic changes in the Tibetan Plateau are one of the research front and hot field in earthscience, most researchers believe the uplift force climate change of the world, or Asia. While the reason for the onset of Quaternary glaciation in the Tibetan Plateau, they simply give astronomic or climate variation explain, less connect it with the plateau uplift。Based on the facts and evidences that have been revealed, (1) the Quaternary strong uplift started from "Kunlun-Huanghe Movement", onset of "Kunlun Glaciation" followed, compare with the world glaciation records, therefore onset of glaciation on the Tibetan Plateau was the last of the world, and was the creative of tectonic movement. (2) in the eastern margin of the plateau, more than ten mountains with only Last Glacial evidences, they should be the creatures after "Gonghe Movement". (3) "Zhonglianggan Glaciation" was the biggest in the Tibetan Plateau, glacial landforms distributed in the central part; the "Penultimate Glaciation" maximum moved to futher eastern areas; the Last Glacial landforms distributed only in the eastern margins. The above facts agree with the plateau tectonic uplift model, the plateau moves eastward, that show interaction between lithosphere and cryosphere. (4) strong erosion during interlacial leads to crust isostatic compension, therefore the coupling of glaciation and tectonics were based on premiry facts. This project mainly focus on more glacial, tectonic, chronogy evidences, create new theory about the coupling of glaciation and tectonic uplift.

近20年来，关于青藏高原构造隆升引起气候变化的研究是学科研究的前沿和热点，认为高原隆升改变了全球气候或亚洲气候，观点众多，内容宽泛。涉及与第四纪冰川演化时多倾向与天文因素或气候波动等相联系，较少关注高原隆升因素。已知的事实和迹象是：1）青藏高原第四纪强烈抬升自"昆-黄运动",发生"昆仑冰期"，故青藏高原冰期的启动是全球最新的，是构造隆升的产物。2）高原东缘有十几个山地只有末次冰期遗迹，应是"共和运动"后的产物。3）"倒三冰期"(中梁贛)冰期规模最大，分布于高原核心部位；"倒二冰期"时最大规模分布移向外缘；而高原东部外缘山地只有末次冰期遗迹。以上事实与高原地壳动力学揭示的向东扩展模式吻合，显示岩石圈和冰冻圈相互作用之事实。4）间冰期冰融水强烈侵蚀，导致地壳均衡抬升，故冰期旋回与构造隆升有相互耦合的端倪。本项目旨在更多冰川、新构造、年代证据数据，提出具有中国特色的冰期-构造隆升耦合理论。

截止上世纪80年代，我国青藏高原第四纪冰川研究已认识到高原南北高山及中部山地冰期次数多（有三到四次）、年代老，而向高原东部外缘发现有十处山地只发育有末次冰期。这就需要查明是否因印度洋板块使高原向东扩展，在近期带动东缘山地抬升达到了雪线高度（4000m），而发育了末次冰期。本项目查明在已知“昆黄运动”（1.2-0.7Ma）和 “共和运动”（0.15-0.10Ma）之间存在一次岷山运动（0.4-0.2Ma），使得岷山在末次冰期时发育冰川，以实例在研究史上第一次验证了中低纬山地发育冰川与山体隆升有直接关系。这说明本课题完成了预设的研究成果及关键点，即（1）取得“昆黄运动”（1.2-0.7Ma）和 “共和运动”（0.15-0.10Ma）之间的构造运动及地貌证据和年代；（2）取得基于绝对年代约束的第四纪冰期系列，以螺髻山和白马雪山为例，前者测得最老冰碛距今58万年，这是近20年来所获得的我国古冰川研究中最可靠也是最老的年代，找到了中梁赣甚至是昆仑冰期的证据；（3）深入而具体地阐明青藏高原第四纪冰川发育与构造隆升之间的耦合机制和过程，提出的观点是高原地块向东扩展，使高原东缘山地吸收并积聚应力而抬升，东缘山地在末次冰期达到雪线高度而形成冰川。在此期间，还发现了古岷江砾石层的性质、高度、分布，以及砾石的岩性构成，揭示古岷江的存在。源头方向指向若尔盖和黄河上游大拐弯处，值得另设课题进行认真研究，可以期待此地貌上的重大发现。山地各种地质灾害地貌过程包括崩塌、滑坡、泥石流、堰塞湖、溃坝堆积等都是山地构造抬升的标志，其规模大、频率高则更是强烈构造活动的标志。本课题针对岷江上游叠溪镇大规模崩塌堰塞湖之崩塌体、湖湘层和溃坝堆积进行了测年和系统的沉积相研究。