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龙门山国家地质公园飞来峰成因的新证据 总被引：1，自引：0，他引：1
近来发现四川彭州（原称彭县）、什邡一带的飞来峰是第四纪冰川作用形成的。笔者等在塘坝子、葛仙山等飞来峰的底界及周边，多次发现飞来峰是压在早更新世的冰水堆积层之上。葛仙山北寨门、丁家湾，什邡大垭口等剖面的地质现象，充分说明塘坝子、葛仙山等飞来峰是第四纪中更新世时“飞”来，压盖上去的。同时可见飞来峰与第四系之间是“冷接触”，找不到确切的断层证据。笔者等还用现有的区域地质调查资料及新的地质成果，编制了1：10万更新世时的彭县至汶川的地质剖面图，并设想了冰雪层掩盖情况。那时岷江尚未剥蚀下切，按现在标高计的5000m处，即在光光山、太子城之上约1000m的“天”上。当时应在该处出露的石炭系-二叠系石灰岩，就是塘坝子、葛仙山飞来峰的根部。塘坝子、葛仙山就是从那里被冰川作用剪切、从母体分离的石灰岩，滑动、随冰川固体流，滑移到彭县来的。笔者还从理论上阐述了塘坝子、尖峰顶、天台山等如此巨大的山体，能被冰川作用拔起、挖掉、推走的原因和根据。从而解释了飞来峰“飞”行的过程。顺理成章，合乎自然，揭开了飞来峰之迷。 相似文献
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塘坝子葛仙山碳酸盐岩外来体中各种岩溶形态十分丰富。通过对岩溶形态特征的总结和岩溶与地层、构造关系的分析,讨论了外来体的成因,认为外来体是构造作用形成的飞来峰。 相似文献
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韩建辉 《沉积与特提斯地质》2006,26(1):55-59
龙门山飞来峰群带状分布在映秀-北川断裂以东的狭长区域,在分布、构造线方向、内部变形以及组成等方面具有清晰规律性。在研究了飞来峰群的特征,并在实地调查和地震解释基础上,提出一种新的演化模式,认为飞来峰群主要是推覆作用的产物,并辅以滑覆作用;映秀-北川断裂在飞来峰的形成过程中发挥了重要作用。 相似文献
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The arcuate nappe structure on the north edge of the Wuliang Mountains in westernYunnan Province is a complex nappe structural system with multiple superimposed structures.The autochthonous system is a WNW-trending arcuate fold belt consisting of the Jurassic andCretaceous and the allochthonous system is mainly composed of Upper Triassic rocks. Generally,the nappe structure moved from south to north, with the hanging wall thrusting in a WNW direc-tion for a distance of over 10km. The deep nappe structural system was formed at depths ofabout 5-10km in an environment not exceeding the greenschist facies. It occurred in theOligocene (about 40-20 Ma). 相似文献
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《International Geology Review》2012,54(7):779-798
High-pressure (HP) rocks are critical for palinspastic restorations because they mark inferred subducted/extruded oceanic crust; knowledge of their geometric, geodynamic, and age relationships provide essential constraints on palaeogeographic reconstructions. The westernmost HP belt (Ixcamilpa) in the Acatlán Complex of southern Mexico has been inferred to be a mid-Late Ordovician backarc basin on the southern Iapetan margin that was subducted beneath eastern Laurentia and extruded up the subduction zone during the Early Silurian. Re-examination of Ixcamilpa HP rocks has revealed that they comprise lower Palaeozoic rift-passive margin protoliths and occur in a W-vergent klippe (not a suture) formed during polyphase deformation. Peak metamorphic mineral assemblages of blueschist-amphibole eclogite facies underwent retrogression through epidote amphibolite to greenschist facies. 40Ar/39Ar dating of various rocks yielded plateau ages of 344–339 Ma for calcic amphibole, 318 ± 4 Ma for glaucophane, and 329–325 ± 2 Ma for muscovite (excess argon), which clearly indicate a Carboniferous tectonothermal event. We interpret the 20 million years range in amphibole ages as reflecting progressive unroofing. The terminal stage of progressive thrusting placed the HP rocks above the middle Mississippian Zumpango Unit, during which a single penetrative sub-greenschist fabric was produced. Subsequent Permian or Laramide deformation refolded all the rocks about NE-trending upright folds. We postulate that the root zone of the HP nappe lies to the east in the median HP belt, which has a structure consistent with an extrusion zone. Inasmuch as similar units of the Acatlán Complex bound this HP root zone on either side, it is inferred to have been extruded into the upper plate above the subduction zone, and thus is not an oceanic suture. Our new data provide constraints for a Carboniferous palaeogeographic reconstruction, whereby subduction erosion of passive margin rocks took place along the western margin of Pangea and were subsequently extruded into the upper (Acatlán) plate. 相似文献