活动古地理重建的实践与思考——以青藏特提斯为例

On Paleogeographic Reonstruction:An Example for Application in Tibetan Tethys

由于石油工业的推动,特提斯构造域一直作为活动古地理重建的重点研究地区,并取得大量研究成果,直接推动了全球古地理研究工作的深入。近年来对位于该构造域东部的青藏高原地区进行了活动古地理重建的研究工作实践,其主要思路是:在古地理重建数据库和古地理重建模拟系统开发的基础上,依据古地磁学运动轨迹研究古大陆位置,结合古构造和古生物对青藏高原喜马拉雅(印度北缘)、拉萨、东和西羌塘地体的古大陆位置进行复位;利用深部地球物理、地表地质断裂证据,借助生物古地理资料,对古大陆和盆地的边界、规模予以限制;利用变形缩短率、构造平衡剖面恢复技术等对原型盆地进行复原;在沉积和生物环境识别划分基础上,编绘基于古大陆重建的岩相和生物古地理图;进一步通过沉积学、沉积地球化学、古生物有关方法和技术,对古海洋海水参数特征、海洋气候参数进行分析研究,探讨古地理和古构造格局控制下的古海洋、古气候条件与盆地、储集岩和烃源岩的形成环境。通过活动古地理重建的研究趋势分析和青藏特提斯的实践认为,古地理重建是现代地质科学的集成,是一项复杂的系统工程。它的研究不仅具有从过去走向未来,从固定走向活动,从古大陆再造到古地理重建,从示意性的小比例尺到大比例尺,以及模拟技术、信息技术、全球定位技术(GPS)等特点;而且具有从单一沉积学要素到古环境、古气候、古海洋等多种要素,可以表现地质历史中各种地质作用及其结果(如古构造和地貌、岩浆和变质作用与各种岩体的剥露)的优势。我们相信,活动古地理重建研究将会成为未来我国沉积地质学重点研究领域之一。

The Tethyan tectonic zone has been always the focus of paleogeographic reconstruction financially granted by lots of oil companies,which has been promoting the global paleogeographic reconstruction.Recently,the reconstruction of the eastern Tethys,i.e.,Qinghai-Tibetan Plateau Tethys,has been practicing.The main itinerary is summarized as：firstly,recovering the original locations of terranes or plates in Qinghai-Tibetan Plateau by paleomagnetism with combination of the paleotectonic and paleontology;secondly,confining the border and scale of terranes and basins on deep geophysics,surface geology and biogeography;thirdly,restoring original basins by recovering techniques of deformed-shorten strata and balanced cross-section;fourthly,composing maps of biogeography and lithofacies paleogeography on the basis of the identification and classification of sedimentary and biological facies;and finalhy,exploring the prosperous hydrocarbons on paleoceanography,paleoclimate and paleogeography in Tibetan Tethys.In summary,the paleogeographic reconstruction is an integration of modern geological science.That is characterized by ways of past to future,inactive to movable,paleocontinental to paleogeographic,small to large in scale with help of 3S（simulation,information,global position） technology.It is also featured by multidisciplines of paleoenvironment,paleoclimate,paleoceanography and other geoscientific subjects,for which all kinds of geological elements,for instance,lithology,tectonics,topography,magmatism,metamorphism,can be shown in a modern palaeogeographic map.Therefore,it is suggested that the paleogeographic reconstruction would follow the new contents and techniques for the future of sedimentary geology in China.