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We analyze the structure and assess the deformation history of the Tierra Caliente Metamorphic Complex (TCMC) of southern Mexico, where Laramide accretion of exotic terranes is in debate. The TCMC consists of a south-plunging antiform fault that is bounded on both its eastern and western flanks. Tierra Caliente Metamorphic Complex rocks show at least two phases of compressional deformation. The first and most prominent records a mean tectonic transport direction of 068 degrees. This phase is responsible for east-verging asymmetrical folding and thrusting of both metamorphic and superjacent sedimentary rocks. The second phase has an average transport direction of 232 degrees and is restricted to the western portion of the TCMC. A third phase is responsible for normal faulting. Lack of discernible deformation before Late Cretaceous time indicates that the main deformation phase is coincident with Laramide orogenesis elsewhere in the North American Cordillera. The stratigraphy, structure, and deformational history of the TCMC do not require accretion of exotic terranes. We explain the Mesozoic tectonostratigraphic evolution of the TCMC in terms of deposition and deformation of Mesozoic volcanic and sedimentary strata over the attenuated continental crust of the North American plate. 相似文献
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黑龙江省嘉荫县晚白垩世渔亮子组及所产鸭嘴龙类化石特征 总被引：5，自引：0，他引：5
黑龙江省嘉荫县晚白垩世渔亮子组产丰富的鸭嘴龙类化石,此外,还有霸王龙等化石。１９９５年,黑龙江地质博物馆组装了一具恐龙骨架,本文对装架标本进行了描述,认为其仍为黑龙江满洲龙（Ｍａｎｄｓｃｈｕｒｉｓａｕｒｕｓ ａｍｕｒｅｎｓｉｓ）。嘉荫县龙骨山恐龙化石从被发现至今已一个世纪,目前为止,已组装了九具鸭嘴龙化石骨架。 相似文献
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苗雨雁 《吉林大学学报(地球科学版)》2003,33(3):263-269
薄果穗属(Leptostrobus)以往在中国的确切报道仅见于川东北、青海和辽西等地，且缺少详细研究。报道了该属的模式种——疏叶薄果穗(Leptostrobus laxiflora)在新疆准噶尔盆地西北缘的额敏白杨河中侏罗世地层的首次发现。对新发现的、保存较完整的果穗及蒴果等做了较详细的描述。同时，报道了与其伴生的其它12属近20种植物化石的组成，分析其古地理环境为有利于成煤的湖泊—沼泽相，认为其地质时代为中侏罗世。 相似文献
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水体中微生物对环境的改变有着敏感的响应。16S rRNA基因克隆文库可以同时反映标本中的细菌种类和各种细菌的相对比例。本研究构建环境样品16S rRNA基因的克隆文库,解析长白山小天池入水口和长白瀑布下水潭两个典型水体样本中的细菌种属多样性特征,并探讨其与水体性质的关系。小天池文库共获得89条16S rRNA基因序列,分别属于10个类群,其中Betaproteobacteria是主要类群(占总数的23.6%)。长白瀑布文库共获得88条序列,分别属于8个类群,以Betaproteobacteria为主要类群(占总数的35.2%)。Bacteroidetes、Betaproteobacteria、Alphaproteobacteria和Gammaproteobacteria是两个样本共有的优势类群,而Deltaproteobacteria、Acidobacteria和Armatimonadetes只在小天池入水口处检出。长白瀑布水潭中的细菌群落多样性明显偏低,种群均匀度指数也较低,但两样本的地理距离极短,认为人类活动可能是导致这种差异的原因。 相似文献