陕西富平地区上奥陶统赵老峪组等深流沉积特征及影响因素*

陕西富平地区上奥陶统赵老峪组发育等深流沉积。以实测剖面、岩石光面、薄片资料以及地球化学资料为基础,结合前人研究成果,对赵老峪组等深积岩类型、层序以及等深流沉积发育的影响因素进行了分析。研究认为: (1)赵老峪组发育灰泥等深积岩和粉屑等深积岩2种类型,识别出由单一的灰泥等深积岩以及灰泥等深积岩与粉屑等深积岩组成的2种等深积岩层序;(2)等深流水团温度越低,盐度越高,则等深流强度越大;(3)等深流水团水温由高变低、再变高,盐度由低变高、再变低,可能造成了等深积岩层序由细变粗、再变细;(4)古水深变大、古气候变干热、古盐度变低有利于等深流和等深流沉积的发育。

Characteristics and influencing factors of contour current deposits in the Upper Ordovician Zhaolaoyu Formation in Fuping area of Shaanxi Province

The Upper Ordovician Zhaolaoyu Formation in Fuping area of Shaanxi Province developed contour current deposits. On the basis of the section measured in field survey,the smooth surface rock,rock thin sections and geochemical data,integrated with previous researches,the authors carried out detailed studies of the types of contourites,the contourite sequences and the influencing factors of contour current deposits. The results show that: (1)The contourites can be classified into two types,i.e. the calcilutitic contourite and the calcisiltitic contourite, and two types of contourite sequences were identified,a single contourite sequence and a calcisiltitic-calcilutitic contourite sequence;(2)As the temperature of contour current water mass gets lower and the salinity gets higher,the contour current strength becomes greater;(3)When the temperature of contour current water mass changes from high to low,then to high, and the salinity of the contour current water mass changes from low to high,then to low, the contourite sequences changes from fine to coarse and then to fine;(4)Larger palaeowater depth,drier and hotter paleoclimate,and lower paleosalinity were favorable for the development of contour current and contour current deposits.