桌子山中奥陶统克里摩里组下段薄层状石灰岩垂向序列分析

发布时间：2018-06-26 22:05

  本文选题：薄层石灰岩 + 米兰柯维奇旋回　； 参考：《地球科学进展》2017年03期

【摘要】：高旋回性薄层石灰岩一般沉积于斜坡和深水盆地环境中,良好地保存了有关天文旋回的信息,具有重要的研究意义。鄂尔多斯盆地西缘内蒙桌子山地区中奥陶统达瑞威尔阶克里摩里组下段发育韵律性极好的薄层石灰岩与页岩,是较为理想的研究层位。在详细的野外观察和测量的基础上,结合石灰岩稀土元素及其他相关微量元素测试结果,对克里摩里组下段薄层状石灰岩的垂向沉积序列进行详细分析,结果如下:(1)薄层石灰岩由4种垂向序列(旋回束)组成,分别为向上变薄序列、向上变厚序列、双向序列和波动序列;(2)在剖面上可划分出145个薄层石灰岩与极薄层页岩对、33个旋回束和7个超旋回束;(3)(La/Nd)_N值和Mn/Fe值总的变化趋势一致,从下到上呈减小趋势,但波动较大;(4)稀土元素总量和铕异常值曲线具有良好的镜像关系,与(La/Nd)_N值具有耦合关系;(5)石灰岩晶粒大小曲线、V/Cr和V/(V+Ni)值曲线形态相似,变化一致,总体上从下到上由小变大再变小,与(La/Nd)_N值曲线总体上具有相似性,但局部常出现镜像关系。依据沉积序列的类型、在剖面上的分布及各参数在垂向上的关系,在已有研究成果基础上可以得出以下结论:(1)双向序列可能受控于等深流强度(米兰柯维奇旋回),向上变薄序列与波动序列可能受控于海平面的变化,向上变厚序列可能受控于构造作用;(2)受米兰柯维奇旋回控制的等深流作用贯穿整个沉积,反映的沉积时限不少于2.9 Ma;(3)垂向上沉积演化受控于次级沉积控制因素构造作用和海平面上升,两者在垂向上交替作用,共反映出2个构造活跃阶段。
[Abstract]:High cycle thin layer limestone is generally deposited in the environment of slopes and deep water basins, which keeps the information of astronomical cycles well, which is of great significance in research. The lower member of the Middle Ordovician Darivier Tikimori formation in the Taijiaoshan area of Inner Mongolia on the western margin of Ordos Basin is an ideal study horizon because of its excellent rhythmic development of thin layer limestone and shale. On the basis of detailed field observation and measurement, combined with the test results of rare earth elements and other related trace elements in limestone, the vertical sedimentary sequence of thin layer limestone in the lower member of the Klimoli formation is analyzed in detail. The results are as follows: (1) Thin-layer limestone consists of four vertical sequences (cyclic bundles), which are the upward thinning sequence and the upward thickening sequence, respectively. Two-way series and wave sequence; (2) 145 thin layer limestone and polar thin shale pairs, 33 cyclic beams and 7 supercyclic beams can be divided into two sections; (3) the total variation trend of (La / ND) N value and mn / Fe value is the same, and the trend is decreasing from bottom to top. (4) the curve of the total amount of rare earth elements and the abnormal value of europium has a good mirror relation, which is coupled with the value of (La / ND) N, (5) the curve of V _ (r) Cr and V / (V _ (Ni) of limestone grain size curve is similar in shape and the variation is consistent. On the whole, from small to up, it changes from small to large and then becomes smaller, which is similar to (La / ND) N value curve as a whole, but there is a mirrored relation in some places. According to the type of sedimentary sequence, the distribution on the section and the relation of parameters in vertical direction, Based on the existing research results, the following conclusions can be drawn: (1) the bidirectional sequence may be controlled by the intensity of the isothermal current (Milankovich cycle), the upward thinning sequence and the wave sequence may be controlled by the sea level change. The upward thickening sequence may be controlled by tectonic processes; (2) the isothermal current controlled by the Milankovich cycle runs through the whole deposition, (3) the vertical sedimentary evolution is controlled by the tectonic processes of secondary sedimentary control factors and sea level rise, which alternates vertically, reflecting two tectonic active stages.
【作者单位】： 昆明理工大学国土资源工程学院;
【基金】：国家自然科学基金面上项目“阿拉善地块东南缘与鄂尔多斯盆地西缘中、上奥陶统浊流演化及其与内波相互作用研究”(编号41272119)资助~~
【分类号】：P534.42
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本文编号：2071562