CAJ | 학술논문

宁夏香山群徐家圈组是由灰绿、黄绿色轻微变质中-细粒砂岩、钙质砂岩及粉砂岩和页岩(板岩)组成的深水沉积.在上部灰绿色页岩所夹的中层钙质粉砂岩中发现了复合流层理、准平行层理、不对称小型丘状交错层理;在下部灰绿色厚层-块状中-细粒长石石英砂岩的顶面发现了小型波痕,波痕的形态、波长与波高的分布规律均表现出复合流(combined-flow)的沉积特征.本文根据水槽实验和现代海洋沉积观测所总结出的复合流底床相图和前人在研究地层中较浅海浊流(超重流)与波浪所形成的复合流沉积时给出的复合流沉积示意图,分别对徐家圈组所发现的①小型2D波痕至小型3D波痕的演化和②复合流层理、平行层理、准平行层理和小型丘状交错层理的叠置关系及其纹层所反映的流动方向与沉积时浊流方向的关系,进行了解释.结果表明,所发现的复合流层理、准平行层理、不对称小型丘状交错层理及小型波痕应为复合流沉积,并依据徐家圈组存在内波、内潮汐沉积的事实,推测为深水短周期内波与浊流形成的复合流沉积.这可能是地层中深水复合流沉积构造的首次发现,同时也是内波与浊流形成的复合流沉积的首次发现.
저하향산군서가권조시유회록、황록색경미변질중-세립사암、개질사암급분사암화혈암(판암)조성적심수침적.재상부회록색혈암소협적중층개질분사암중발현료복합류층리、준평행층리、불대칭소형구상교착층리;재하부회록색후층-괴상중-세립장석석영사암적정면발현료소형파흔,파흔적형태、파장여파고적분포규률균표현출복합류(combined-flow)적침적특정.본문근거수조실험화현대해양침적관측소총결출적복합류저상상도화전인재연구지층중교천해탁류(초중류)여파랑소형성적복합류침적시급출적복합류침적시의도,분별대서가권조소발현적①소형2D파흔지소형3D파흔적연화화②복합류층리、평행층리、준평행층리화소형구상교착층리적첩치관계급기문층소반영적류동방향여침적시탁류방향적관계,진행료해석.결과표명,소발현적복합류층리、준평행층리、불대칭소형구상교착층리급소형파흔응위복합류침적,병의거서가권조존재내파、내조석침적적사실,추측위심수단주기내파여탁류형성적복합류침적.저가능시지층중심수복합류침적구조적수차발현,동시야시내파여탁류형성적복합류침적적수차발현.
Deep-water deposits in the Xujiajuan Formation of Xiangshan Group are composed of grayish green, yellowish green, fine- to medium-grained light metamorphic sandstone, calcareous sandstone, siltstone and shale (slate). Combined-flow-ripple lamination, quasi-planar lamination and asymmetric small-scale hummocky cross stratification are found in the medium-bedded calcareous siltstone interlayer of the upper grayish green shale, and small ripples are also found at top of the lower grayish green thick-bedded, massive and medium-grained feldspar-quartz sandstone. The configuration and wavelength of wave and distribution of wave height all suggest sedimentary characteristics of combined-flow. Based on the flume experiment and observation of modern ocean sedimentation, this study in combination with previous researches set up a facies diagram of combined flow bottom, and a schematic diagram of combined flow sedimentation caused by flows and waves in relatively shallow water, both of which can interpret (1) the evolution of small-scale 2-D ripple marks to 3-D ripple marks and (2) superimposed relation of combined-flow ripple lamination, quasi-planar lamination to small-scale hummocky interleaving stratification as well as the lamina reflecting the relationship between flow direction and turbidity current direction. The result shows that the combined-flows are responsible for the formation of the combined-flow ripple lamination, quasi-planar lamination and asymmetric small-scale hummocky cross stratification in the Xujiajuan Formation. Based on the fact of existence of internal wave deposition in the Xujiaquan Formation, it can be assumed that combined-flow deposition was the result of interaction of short- period internal wave and turbidity currents. This perhaps is the first discovery of deep-water sedimentary structures of combined-flow origin as well as the combined-flow deposition produced by the internal wave and turbidity currents.