青藏高原隆升对中国构造-地貌形成、气候环境变迁与古人类迁徙的影响
Tectonic uplift of the Xizang Plateau: Impacts on the formation of landforms, climate changes and ancient human migration in China
-
摘要: 对中国新生代以来构造-地貌形成的认识, 必须建立新生代重大环境事件的年代序列, 既需要不同地区构造变形、隆升年代学的依据, 又需要宏观背景的把握。现今中国大陆构造-地貌格架及相关问题, 诸如青藏高原的隆升、西部北西西向盆-山地貌和东部北北东向阶梯状盆-山地貌的形成时代、发育过程等, 一直是地学界关注但尚未得到统一认识的一些重要科学问题。20世纪70年代以来通过青藏高原隆升的研究、提供了大量隆升年代学和古高程信息的数据, 使得对其开展定量分析成为可能。青藏高原何时形成现今的高原面貌?这是国内外学者长期争议的科学问题。笔者从20世纪80年代对柴达木盆地及其邻区开展了20余年研究, 发现柴达木作为一个现今的高原盆地经历了青藏高原隆升的全过程, 高原隆升和环境变迁的所有事件, 在盆地的沉积、构造上都有比较完整的记录, 因此它可以作为青藏高原隆升大阶段划分的最佳参考时空坐标, 并依此提出古近纪期间(55~24 Ma)青藏高原整体并未隆升; 青藏—闽粤高原的初次隆升发生在中新世早—中期(23~17 Ma), 上新世晚期—早更新世基本被夷平; 形成现今高原面貌的末次快速隆升发生在上新世晚期—早更新世(3.6~0.8 Ma)和中更新世之间。新生代以来由于青藏高原的隆升和中国构造-地貌格架的形成, 直接影响了中国和全球气候环境的变迁以及古人类迁徙的路径, 因此需要地质学家、古气候和古人类学家共同探索, 对中国及亚洲新生代以来古地貌、古气候变迁的历史和中国古人类的发源与迁徙得出科学的结论。本文通过青藏高原分阶段隆升依据的论证, 阐明青藏高原隆升与中国构造地貌形成、气候环境变迁的关系, 并探讨中国古人类迁徙的可能路径。Abstract: It is imperative to build the geochronological sequence for key and important Cenozoic events based on studies of tectonic deformation, geochronological data of uplifting and general tectonic framework, so as to get an overall recognition of the Cenozoic tectonic-geomorphological framework of China's mainland. Several key issues on the continental tectonics and geomophological framework, although widely discussed, remain unresolved, e.g., the uplifting of the Xizang Plateau which is the highest mountain range on the earth, and the formation of the WNW-trending basin-range system in Northwest China as well as the development of the stepped NNE-trending basin-range system in East China. Through studies of the Xizang Plateau since the 1970's, lots of geochronological data on the uplifting and paleao-elevation have been obtained, which makes it possible to conduct quantitative analysis. The problem when the plateau was formed has been the subject of studies for decades. The authors have conducted continued studies of the Qaidam Basin and neighboring regions for more than 20 years since 1980's and, as a result, found that the Qaidam Basin, as a basin-in-plateau, has experienced the entire uplifting history of the plateau. There exists complete sedimentary and structural evidence recording the Cenozoic geological events and variation of the environment during the uplifting of the plateau. The evidence can be utilized as a temporal-spatial reference for the subdivision of various stages of plateau uplifting. It is therefore suggested that the plateau was not uplifted in Paleogene(55-24 Ma), and the initial uplifting of a Xizang-FujianGuangdong plateau occurred in early-middle Miocene(23-17 Ma). The present plateau was configured by a final uplift in late Pliocene or early to middle Pleistocene(3.6-0.8 Ma). The uplift of the Xizang Plateau and the formation of the tectonic-geomorphologic framework of China led to the variation of the environment of China and of the World, and also affected the paths of migration of ancient people. Joint studies by geologists, paleoclimatologists and paleoanthropologists will contribute to the deep understanding of the paleaogeomorphologic evolution and variation of paleaoclimate as well as the birth of ancient people and their migration. The present paper focuses on the relationship between the uplifting of the plateau, the formation of the geomorphological framework of China and the variation of paleaoclimate. The possible migration paths of ancient Chinese are discussed.
下载: