江汉盆地潜江凹陷古近系潜江组含盐岩系沉积特征与沉积环境

SEDIMENTARY CHARACTERISTICS AND ENVIRONMENTS OF THE SALT-BEARING SERIES OF QIANJIANG FORMATION OF THE PALEOGENE IN QIANJIANG SAG OF JIANGHAN BASIN

潜江组盐层间的层段(盐间段 )由砂岩和非砂岩两部分组成。其中非砂岩分布广泛 ,主要由单层厚度为毫米—厘米级、累积厚度达几十厘米至几米的含盐韵律组成 ,并多为复成分的蒸发盐矿物、碳酸盐矿物及陆源的粘土和细碎屑矿物组成的混积岩。过去 ,人们对盐间段非砂岩的研究主要基于对岩性的认识 ,对于其沉积特征和沉积环境方面的研究较薄弱。文中通过对潜江凹陷西北部王场构造 3口井共约 1 51m岩芯的精细研究 ,对盐间段沉积特征和沉积环境进行了系统分析。认为潜江组盐间段湖盆环境为常年性较深水分层盐湖 ,大体可分为微咸水湖、半咸水湖、咸水湖和盐湖 ,水体深度自下而上逐渐变浅。

The intervals between salt beds in the Qiangjiang Formation of Upper Eocene-Lower Oligocene of Paleogene consist of sandstones and non-sandstones. The non-sandstones are widely distributed and mainly composed of miltimeter-scale to centimeter-scale of single bed, a total of several decimeters to several meter thick salt-bearing rhythms,most of which are polymictic mixed rocks composed of evaporite minerals, carbonate minerals and terrigenous clays and fine clastic minerals. For a long time, the study of the non-sandstones between salt beds has been limited to the lithological characters and less attention has been paid to sedimentary characteristics and sedimentary environments. Through the detailed study of a total of 151 m thick in Wangchang Structure of northwestern Qianjiang Sag on the cores of three wells, this paper gives a systematic analysis of the sedimentary characteristics and environments of the intervals between salt beds, and suggests that the lake basin was a perennial relatively deepwater meromictic salt lake which can be roughly divided into brackish-water lake, semisalt-water lake, salt-water lake, and brine lake when the intervals between salt beds were deposited. During the peroid of Qianjiang Formation,the water depth of lake basin was gradually from deeper to shallower.