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首页> 外文期刊>Geoscience frontiers >Middle–Late Triassic sedimentation in the Helanshan tectonic belt: Constrain on the tectono-sedimentary evolution of the Ordos Basin, North China
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Middle–Late Triassic sedimentation in the Helanshan tectonic belt: Constrain on the tectono-sedimentary evolution of the Ordos Basin, North China

机译：贺兰山构造带中下三叠世沉积：对华北鄂尔多斯盆地构造-沉积演化的制约

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The Helanshan tectonic belt is located to the west of the Ordos Basin, and separates the Alxa (or Yinshan) Massif to the west from the Ordos block to the east. Triassic sedimentation in the Helanshan tectonic belt records important information about tectono-sedimentary process between the Alxa Massif and the Ordos block. Detailed geological mapping and investigation on the lithological package, sedimentary facies and paleocurrent orientation have been conducted on the Middle to Upper Triassic clastic rocks in the Helanshan tectonic belt. The succession is characterized by upward-fining sequence and comprises coarse grained alluvial-fluvial facies in the lower part as well as deltaic-lacustrine facies in the upper part. Based on detailed study and comparisons on the sedimentary sequence along various sections, the Middle to Upper Triassic strata have been revealed that show clear southeastward-deepening sedimentary differentiation and transgression from southwest to northeast, which are consistent with the southeastward flowing paleocurrent. These features indicate a southeastward-dipping paleogeography in the Helanshan tectonic belt, which was original western part of southeastward orientated fluvial-lacustrine system in the northwestern proto-Ordos Basin. Further to the east, the Triassic succession in the Ordos Basin displays gradually thickening and alluvial-fluvial system flowed from southeast to northwest, showing a huge thick sedimentary wedge in the western basin margin. Together with the Late Permian–Early Triassic closure of the Paleo-Asian Ocean to the north, the Late Triassic extensional structures and diabase dykes in the Helanshan tectonic belt, all the above sedimentary features could be mostly interpreted as records of an extensional basin correlated to post-collisional collapse of the Central Asian Orogenic Belt.
机译：贺兰山构造带位于鄂尔多斯盆地以西，将鄂尔多斯地块以西的阿拉善（或银山）地块分隔为西。贺兰山构造带的三叠纪沉积记录了有关阿拉善地块和鄂尔多斯地块之间构造沉积过程的重要信息。在贺兰山构造带中—上三叠统碎屑岩中进行了详细的地质测绘，并进行了岩性，沉积相和古流向的调查。演替的特征是向上精细排列，下部包括粗粒冲积-河流相，上部包括三角洲-湖相。通过对各断面沉积序列的详细研究和比较，揭示了中三叠世上-上三叠统地层，显示了西南向东北明显的东南向加深的沉积分异和海侵，这与东南向古流一致。这些特征表明，贺兰山构造带向东南倾斜的古地理，是原始鄂尔多斯盆地西南向东南的河流—湖相系统的原始西部。在东部以东，鄂尔多斯盆地的三叠纪演替逐渐增厚，冲积-河流系统从东南向西北流动，在盆地西部边缘显示出巨大的厚厚沉积楔。再加上北亚古海晚二叠世-早三叠世封闭，贺兰山构造带的晚三叠世伸展构造和辉绿岩堤，上述所有沉积特征都可以解释为与该盆地相关的伸展盆地记录。中亚造山带碰撞后的崩溃。

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