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首页> 外文期刊>Canadian journal of earth sciences >Cannibalism of contourites by gravity flows: explanation of the facies distribution of the Ordovician Pingliang Formation along the southern margin of the Ordos Basin, China
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Cannibalism of contourites by gravity flows: explanation of the facies distribution of the Ordovician Pingliang Formation along the southern margin of the Ordos Basin, China

机译：重力流量的同纲岩：鄂尔多斯盆地南部边缘的奥陶涅师平凉面部的相同学解释

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The Late Ordovician Pingliang Formation accumulated along the southern margin of the Ordos Basin in China. The convergence of the Yangtze Plate and Sino-Korean Plate led to a trench-arc-basin system during the Middle Ordovician, with a platform- and slope-dominated setting in the east where a graben complicated the overall simple paleogeographical picture, relatively parallel zones of a platform and a slope setting in the middle, and a change from platform to slope to deep marine to a trench setting in the west. This configuration resulted in various types of gravity flow deposits and contourites with different compositions and pathways. The present study focuses on the typical characteristics of contourites in the geological record and the relationships between contour currents and gravity flows. The Pingliang Formation contains eleven lithofacies grouped into five facies associations. These facies associations represent deep sea autochthonous deposits, several types of debrites, turbidites, and contourites, as well as turbidites within which the fine-grained top portion was reworked by a contour current. The various lithofacies are concentrated in different parts of the study area: micritic contourites and debrites are concentrated in the eastern part; debrites, and sandstone and siltstone turbidites are concentrated in the middle part; and calcarenitic turbidites, contourites, and reworked turbidites occur in the western part. The main contour current ran parallel to the contour lines from east to west. Although most of the contour current continually moved westward in the eastern part of the study area, a minor part split off and followed a semicircular pathway through the Fuping Graben; its velocity became reduced here so that micritic contourites were deposited. The velocity of the contour current was increased locally when it entered a confined trough in the western part of the study area. The relatively high energy of the contour current here resulted in calcarenitic contourites. The velocity of the contour current was low where it ran through an open environment, resulting in fine-grained, thin contourites in the middle part of the study area. Large turbidity currents and debris flows occurred here, and their high energy destroyed almost all earlier deposited contourites. This explains why traces of contour currents in the middle part of the study are very scarce, although the east-west-running contour current must have passed through this area.
机译：曾在中国鄂尔多斯盆地的南部边缘积累的末奥陶涅师平。长江板和中韩板的融合导致了中间奥陶诺维安的沟渠 - 弧盆地系统，在东部的平台和斜坡主导的环境中，抓住整体简单的古地理图片，相对平行的区域在中间的平台和斜坡设置，以及从平台到斜坡到深海的变化到西方的沟渠环境。这种配置导致各种类型的重力流沉积物和具有不同组成和途径的轮廓。本研究重点研究了地质记录中的轮廓石的典型特征，以及轮廓电流与重力流动之间的关系。平凉形成含有11个岩石遗传学分为五个相协会。这些相关联代表深海自加沉积物，几种类型的碎屑，浊度和轮廓，以及浊度内部通过轮廓电流重新加工细粒顶部。各种锂缺失集中在研究区域的不同部分：微菌素和卵布集中在东部;碎屑，砂岩和硅铁晶越越浓缩;和钙化浊磁带，连续石和倒置浊度发生在西部。主要轮廓电流与东部到西方的轮廓线平行。虽然大多数轮廓电流在研究区域的东部不断地移动，但是一部分缩小部分分开并遵循半圆形的途径;它的速度在这里减少，以便沉积微亚连续岩。当它在研究区域的西部进入狭窄的槽时，在本地增加轮廓电流的速度。这里的轮廓电流的相对高的能量导致钙化轮廓。轮廓电流的速度低于开放环境，导致研究区域的中间部分的细粒度，薄的轮廓。此处发生了大的浊度电流和碎片流动，并且它们的高能量几乎损坏了几乎所有早期的沉积的轮廓。这解释了为什么研究中间部分的轮廓电流的痕迹非常稀缺，尽管东西方运行的轮廓电流必须通过该地区。

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