摘要
以蒙古桌子山地区中奥陶统乌拉力克组砾屑灰岩为主要研究对象，在野外工作的基础上，从沉积背景、岩性、结构和构造等方面分析了砾屑灰岩的特征，探讨了其成因。通过对乌拉力克组岩性特征，古生物特征及地球化学特征的研究，认为乌拉力克组沉积环境为深水斜坡一盆地环境。乌拉力克组大套页岩中所夹的砾屑灰岩呈块状，内部不具层理，砾屑大小混杂，无分选，无粒序，反映了碎屑流沉积特征。中奥陶世期间，贺兰坳拉谷发生强烈裂陷，在贺兰坳拉谷边缘发育碳酸盐重力流沉积，主要受同生断裂控制。贺兰地堑具有南强北弱的特征，桌子山地区同生断裂的构造强度相对不大，因此所形成的斜坡坡度不大，碎屑流沉积总体上不是十分发育。上斜坡坡度较大，为沉积物过路带。砾屑灰岩主要沉积于下斜坡，少数被搬运至盆地边缘，甚至盆地中，但是被搬运至不同位置的砾屑灰岩在发育规模、对下伏地层的侵蚀程度、颗粒大小和磨圆等方面存在着明显差异：下斜坡处沉积的砾屑灰岩规模大，底部具有明显的截切面，颗粒大且磨圆差；到盆地处时，由于远离物源区，砾屑灰岩规模小，底部平坦，颗粒小且磨圆相对更好。
Based on fieldwork, the causes of the calcirudite of the Wulalike formation of Middle Ordovician, in Zhuozi mountain area of Inner Mongolia was explored in the aspects of sedimentary background, lithology, structure and construction characteristics. Through the lithological, paleontology and geochemistry features of the Wulalike Formation, the sedimentary environment of Wulalike Formation is recognised as deep-water slope - basin environment. Wulalique calcirudite folder group sets of shale in bulk, intemal unstratified, gravels mixed sizes, no separation, no grading, reflecting sedimentary characteristics of debris flow. Duringthe Middle Ordovician, Helan aulacogen was strong rifting, in Helan aulacogen edge, carbonate gravity flow deposits were mainlycontrolled by synsedimentary fault. The Helan graben has the characteristics of strong the tectonic strength of the north Helanaulacogen was weak, while the tectonic strength of the north Helan aulacogen was strong. The tectonic strength of contemporaneous faults in the zhuozi mountain area was relatively weak, so the debris flow deposit in general was not very developed. Due to the steep slope, calcirudite mainly deposited on the foot of slope, and minority was transported to the basin edge, even in the basin. However the calcirudite transported to different positions had different Characteristics in many aspects, such sa scale, particle size, grinding, erosion degree to the underlying strata. The calcirudite at the foot of slope owned large scale, large particles, rounded appearance, with section clear bottom; The calcirudite in the basin, as far away from the source area, were in small scale, small particles, with relatively better grinding and a flat bottom.
出处
《地球科学期刊（中英文版）》
2013年第4期119-127,共9页
Scientific Journal of Earth Science
基金
本文受高等学校博士学科点专项学科基金（20104220110002）与国家自然科学基金“鄂尔多斯盆地西缘中奥陶统深水牵引流沉积研究”（41072086）联合资助
致谢参加野外工作的还有宁夏地矿局的郑昭昌教授级高级工程师和昆明理工大学的李向东老师,对他们的野外指导和辛勤劳动表示感谢.另外,长江大学硕士生霍宇琦、孙芳和汤睿协助收集了相关文献资料,在此表示感谢.
关键词
桌子山地区
乌拉力克组
砾屑灰岩
碎屑流沉积
沉积模式
Zhuozi Mountain Area
Wulalike Formation
Calcirudite
Debris Flow Deposits
Sedimentary Model
