CAJ | 학술논문

贺兰山以南中奥陶统香山群为一套遭受轻微区域变质的陆源碎屑岩,并夹有少量碳酸盐岩和硅质岩,属于深海浊流沉积.其下部徐家圈组由灰绿、黄绿色轻变质细粒砂岩、钙质砂岩及粉砂岩和页岩组成,沉积环境为深水斜坡环境,并在该组发现了内波、内潮汐沉积,主要表现为双向交错层理.本文通过对徐家圈组指向沉积构造所显示的古水流资料进行研究,综合分析了香山群徐家圈组沉积时浊流方向和古斜坡方向,并利用古水流资料探讨了内波流和内潮汐流的方向.结果表明,槽模古水流方向从北向南略呈扇形发散状,代表了沉积时的浊流方向;交错层理古水流方向主要分散在NWW-NE之间,可以代表内波流和内潮汐流方向.对古水流平面分布特征进行综合分析,可以判断出沉积时区域斜坡方向与浊流方向基本一致,大致为SSW向,沉积时内波和内潮汐的传播方向则大致为NW向.
하란산이남중오도통향산군위일투조수경미구역변질적륙원쇄설암,병협유소량탄산염암화규질암,속우심해탁류침적.기하부서가권조유회록、황록색경변질세립사암、개질사암급분사암화혈암조성,침적배경위심수사파배경,병재해조발현료내파、내조석침적,주요표현위쌍향교착층리.본문통과대서가권조지향침적구조소현시적고수류자료진행연구,종합분석료향산군서가권조침적시탁류방향화고사파방향,병이용고수류자료탐토료내파류화내조석류적방향.결과표명,조모고수류방향종북향남략정선형발산상,대표료침적시적탁류방향;교착층리고수류방향주요분산재NWW-NE지간,가이대표내파류화내조석류방향.대고수류평면분포특정진행종합분석,가이판단출침적시구역사파방향여탁류방향기본일치,대치위SSW향,침적시내파화내조석적전파방향칙대치위NW향.
The Xiangshan Group, Middle Ordovician, in the south of Helan Mountains, belongs to deep-sea turbidity current deposits which are mainly a set of light metamorphic terrigenous clastic rocks with some carbonate rocks and siliceous rock interbed. The Xujiajuan Formation of the Lower Xiangshan Group is made up of grayish green, yellowish green, light metamorphic fine sandstone, calcareous sandstone, siltstone and mudstone(slate), whose sedimentary environment was a slope environment. The deposits of internal wave and internal tide which characterized by bidirectional cross beddings are found in this Formation. In this paper, the palaeocurrent data recorded in directional sedimentary structure were collected for determining the direction of turbidity currents, the dip of regional slopes in the study area, and the direction of internal wave and internal tide current. The result shows that the palaeocurrent direction of flutes presents a slightly fan-shaped from the north to the south and suggests the direction of turbidity currents when depositing. Distribution from the north area and a SSW dipping slope, while the palaeocurrent direction of cross beddings are mainly restricted within an elongated zone extending in a NWW-NE direction suggest the direction of internal-wave and internal-tide current. Analyzing comprehensively the plane distribution of Paleocurrent, the result is that the dip of regional slope and the direction of turbidity current are the same--SSW direction, and the propagating direction of internal-wave and internal-tide when depositing are NW direction.