| 构造旋回与大地构造年表 |
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| 引用本文：任纪舜,徐芹芹,邓平,肖黎微.2016.构造旋回与大地构造年表[J].地球学报,37(5):528-534. |
| DOI：10.3975/cagsb.2016.05.03 |
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| 基金项目:中国地质调查局地质调查项目(编号:121201102000150009-01;121201102000150009-02;12120115070301) |
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| 中文摘要:构造旋回的划分是大地构造研究的基础之一。但板块学说兴起以来, 一些学者基于均变论的哲学思想, 却试图抛弃构造旋回的概念。然而, 随着时间的推移, 地球系统科学的提出, 大规模、多学科地学观测, 人们已认识到突变与灾变的重要性, 认识到渐变与突变相结合的螺旋式向前发展的旋回演化论, 才是更全面、更深刻地认识地质规律的有力武器。
在大地构造研究中, 一些学者常用地层年表, 而不用构造旋回。然而, 以生物地层学为主要依据的显生宙地层年表与构造旋回和构造岩浆事件并不完全耦合。这是因为, 地层年表是在研究地球表生作用, 即岩石圈、水圈、大气圈、生物圈之间相互作用的基础上建立的; 而构造旋回则是地球内生作用, 即壳、幔、核以及壳、幔、核不同层次间多层圈相互作用的历史记录。一些学者在研究大地构造时, 只用同位素年龄表示的构造事件, 不使用构造旋回。然而, “事件”只是单个现象的呈现, 只是构造发展的片段, 旋回则阐明过程, 反映事物发展中各“事件”(片段)之间的内在联系, 反映事物演化的本质。事实上, 威尔逊旋回的建立, 已为构造旋回和构造事件之间的联系赋予了全新的科学内涵, 这也是地质科学发展过程中, 正确处理继承与创新关系的一个光辉范例。一些学者由于对全球造山运动是否是同时性的质疑, 认为建立全球统一构造年表是不可能的, 也是不必要的。可是, 地球作为一个整体, 其动态活动应该基本上同时的, 在受同一地球动力系统控制的一个大区域内, 构造运动在各地虽然不是完全同时, 但却大致是同时的。北美、欧洲、亚洲加里东、华力西旋回的各次构造运动基本上可以互相对比, 就是证明。既然如此, 我们就可以按照优先原则, 将早古生代的构造旋回称为加里东旋回, 将晚古生代的构造旋回称为华力西(海西)旋回。
超大陆和超大陆旋回的提出, 深化了构造旋回的研究, 同时也为建立构造年表开辟了道路。目前已初步提出古元古代哥伦比亚、中元古代罗丁尼亚、新元古代冈瓦纳和显生宙潘吉亚等几个超大陆旋回, 这样, 我们便可以用超大陆旋回作为构造年表中最大一级的时间单位, 每个超大陆旋回又可进一步分为几个旋回, 如潘吉亚旋回可分为加里东、华力西两个旋回。我们相信, 随着地质学、地球化学、地球物理学研究的深入, 随着对固体地球系统和全球地质构造更加深入、全面、系统的观测研究, 不久的将来我们将会像建立显生宙地层年表一样, 建立起大区域以至全球的构造年表。 |
| 中文关键词:构造旋回 构造年表 超大陆旋回 角度不整合 造山运动 |
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| Tectonic Cycles and Tectonic Timescale |
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| Abstract:The subdivision of the tectonic or geological cycle affords a basis for research on geotectonic evolution. However, since the emergence of plate tectonics, some scholars who adopt the philosophy of uniformitarianism have tried to abandon the concept of tectonic cycle. Nevertheless, with the elapse of time, the appearance of earth system science, and the observations based on large-scale and multidisciplinary geoscience, people have got to know the importance of sudden and catastrophic changes in the course of crustal evolution, and recognized that the idea of cyclic evolution arguing that the structure of the earth crust develops cyclically and in a spiral-like manner with gradual and sudden changes in combination with each other is a powerful weapon for more comprehensive and profound understanding of the geological laws.
In the study of geotectonics, a number of geologists are inclined to substitute the stratigraphic timescale for the tectonic cycle. However, the Phanerozoic chronostratigraphic chart framed according to biological stratigraphy does not fully agree with tectonic cycle and tectonic-magmatic event. This is because the chronostratigraphic chart is established on the basis of the study of the earth’s exogenesis characterized by the interaction between the lithosphere, hydrosphere, atmosphere and biosphere, whereas the tectonic cycle is the historical record of earth’s endogenesis characterized by the multisphere interaction of the crust, mantle and core, as well as different layers within them. Some scholars have used tectonic (tectonic-magmatic) events represented by isotopic ages instead of tectonic cycles in studying the geotectonics. However, the “event” is just a display of a single phenomenon, and the “cycle” is the illumination of process, which reflects the internal links between “events” and the essence of the evolution. In fact, the establishing of the Wilson cycle has bestowed new scientific connotations on the connections between tectonic cycles and tectonic events, which can serve as a shining example of handling the relationship between inheritance and innovation properly. Doubting about the synchroneity of the global orogeny, some scholars consider that it is impossible and unnecessary to establish a unified global tectonic timescale. Nevertheless, the dynamic activities of the earth as a whole should be substantially simul-taneous. Within a mega-region under the control of a unified geodynamic system, the tectonic movements did not take place exactly at the same time in different places, but they were roughly simultaneous. The tectonic movements of the Caledonian and Variscan cycles in North America, Europe and Asia are basically comparable with each other, which can serve as a convincing proof. It is therefore held that, in accordance with the principle of priority, the early and late Paleozoic cycles can be called the Caledonian and Variscan (Hercynian) cycles, respectively.
The emergence of the theory of the supercontinent and supercontinent cycle has not only deepened the study of tectonic cycles, but also paved the way for establishing tectonic timescale. Some proposed supercontinent cycles, such as the Paleoproterozoic Columbia, Mesoproterozoic Rodinia, Neoproterozoic Gondwana and the Phanerozoic Pangea, could be used as the first-order time unit for the tectonic timescale. Each supercontinent cycle can be further divided into several cycles, such as the Pangea with the subdivision of the Caledonian and Variscan cycles.
It is believed that, like the Phanerozoic chronostratigraphic chart, the mega-regional or even global tectonic timescale will be established in the near future with the deepening of geological, geochemical and geophysical research and the more comprehensive and systematic observation of the solid earth system. |
| keywords:tectonic cycle tectonic timescale supercontinent cycle angular unconformity orogeny |
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