晚奥陶世五峰期上扬子海南缘的 同生变形构造形成机制
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本文为国家自然科学基金资助项目(编号 41162003)、国家科技重大专项(编号 2011ZX05007 003 01)的成果。


The Forming Mechanism about Contemporaneous Deformed Structures in Upper Ordovician Wufeng Formation from the Southern Edge of Upper Yangtze Sea
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    摘要:

    晚奥陶世上扬子海南缘以黑色碳质页岩为特征的五峰组笔石页岩段中见有由小型褶皱和层间阶梯状断层等构成的同生变形构造,其上下地层均为正常沉积的黑色页岩。同生变形构造开始于凯迪阶末期Dicellograptus complexus,结束于Paraorthograptus pacificus。在空间分布上表现为靠近滇黔桂古陆一侧的上扬子海盆内(古蔺—桐梓—松桃)的变形构造层以小型褶皱为特征;向海一侧(綦江—秀山)则逐渐过渡为以小型阶梯状断层为主,同时伴有小型褶皱,但川南长宁一带的五峰组中未发现有同生变形构造。同生变形构造在滇黔桂古陆向海一侧较近陆一侧发育,其变形强度逐渐增强,且由西向东同生变形构造的发育强度增强,表明扬子海在沿滇黔桂古陆的西侧可能为较平坦的古海底地貌,而东侧具有较陡的斜坡存在。在渝东南秀山,仅同生变形构造层内发育有地震事件成因的火焰状岩脉。另外,在桐梓地区,同生变形构造层的上、下与正常沉积的黑色页岩之间均见有斑脱岩层,因而推测火山喷发可能是导致变形构造形成的主要诱因。在火山事件引起地壳多期震荡的背景下,处于陡坡上的塑性泥(页)岩发生滑动形成同生变形构造。同时,奥陶纪末期是加里东运动的剧烈活动期,导致滇黔桂古陆西侧较为平坦,而东侧较陡的古海底地貌可能与奥陶纪晚期扬子陆块与华夏陆块发生的碰撞相关。

    Abstract:

    The contemporaneous deformed structures have been founded in the Graptolite shale Member of the Wufeng Formation which is characterized by black carbonaceous shale in the Late Ordovician from the southern edge of upper Yangtze Sea, which is composed of small sized folds and graded faults and is overlaid and underlain normal sedimentary black shale. From the temporal distribution, the contemporaneous deformed structures began in Dicellograptus complexus of later Katian Stage, and ended in Paraorthograptus pacificus, the ending of the Katian Stage. From spatial distribution of deformed structures which close to Yunnan—Guizhou—Guangxi ancient continent on the side of the upper Yangtze sea basin (Gulin—Tongzi—Songtao) characterized by small sized folds; seaward side (Qijiang—Xiushan) gradually transited to the graded fault, and accompanied with several small sized folds, but the contemporaneous deformed structures were not found in Changning area, southern Sichuan. The contemporaneous deformed structures located seaward side of Yunnan—Guizhou—Guangxi ancient continent is more strengthen than landward, and the deformed intensity gradually increased from landward to seaward, and the deformed intensity is gradually increased from west to east. It is shows that west side of Yangtze Sea may be relatively flat topography of ancient seabed along the Yunnan—Guizhou—Guangxi ancient continent, and the east has a steep slope. Flame dikes formed earthquake events which layered distribution within the contemporaneous deformed structures only at Xiushan area, Southeast Chongqing. In addition, a bentonite layer is separately on and under the deformed structures and between deformed structures and black shales at Tongzi area, Thus, volcanic eruptions may be the main factors. Sliding plastic mudstone in a steep slope formed contemporaneous deformed structures at the background of multi cruatal shake caused by volcano events. Caledonian movement was intense activity during the Late Ordovician, and leading to a steep submarine topography in the east than west, it may be related to Yangtze block and Cathaysia block collision during the late Ordovician.

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赵明胜,田景春,王约.2014.晚奥陶世五峰期上扬子海南缘的 同生变形构造形成机制[J].地质论评,60(2):299-309,[DOI].
.2014. The Forming Mechanism about Contemporaneous Deformed Structures in Upper Ordovician Wufeng Formation from the Southern Edge of Upper Yangtze Sea[J]. Geological Review,60(2):299-309.

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  • 收稿日期:2013-02-26
  • 最后修改日期:2013-05-21
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  • 在线发布日期: 2014-03-18
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