盆地火山地层时空属性和岩石地层单位

火山地层具有如下显著特征:建造短暂和剥蚀长久的时间属性,受喷发方式和古地形控制的空间属性,地层产状变化规律与喷出口相关。尝试以地层界面反映时间属性、岩石组合和几何外形反映空间属性,结合产状变化规律对火山地层单位进行了厘定,从常用的地层单位中选用术语,从小到大依次是层、堆积单元、火山机构、段、组和群。本文详细介绍前三类单位的分类和识别标志:层是根据颜色、化学成分和岩石组构的差异划分;堆积单元依据喷发方式和就位环境划分为熔岩流/火山碎屑流/再搬运火山碎屑流3类,单元内地层产状变化连续,单元之间常以喷发不整合/整合界面分隔;火山机构是堆积单元有序叠置的产物,火山地层沿喷发口向四周倾斜、向边缘过渡时地层倾角逐渐变缓,火山机构间常以喷发间断不整合界面分隔。指出盆地火山地层格架的建立需要突出地层的空间属性、火山地层埋藏史应该基于火山机构的中心和远源两个区域来分析,基于重新厘定的火山地层单位建立的地层格架更有利于对储层分布规律的认识。

Spatio-Temporal Attributes of Volcano Stratigraphy and Its Lithostratigraphic Units in a Basin

Volcano stratigraphy has three distinguishing features:temporal attributes of ephemeral construction and long erosion, spatial attributes controlled by eruption style and paleo-topography, and occurrence changed with volcanic vents.In this paper,the classification and identification marks of bed, deposit unit and volcanic edifices are introduced in detail.Volcano stratigraphic units were determined by using stratigraphic boundary to reflect temporal attributes, and by using lithology succession and geometrical shape to reflect spatial attributes and occurrence characteristics.The stratigraphic units include bed, deposit unit, volcanic edifice, member, formation, and group.The bed was determined by the differences between rock colors, chemical components,and fabrics.According to an eruptive style and emplacement environment, the deposit units were divided into 3 types,namely lava, volcanic clastics,and reworked volcanic clastics.The occurrence changes continuously within a deposit unit, and the units are separated by an eruptive unconformity/eruptive conformity.A volcanic edifice is a product of ordered stacked deposit units.Volcanic strata lean along volcano vents,and their dip angles decrease gradually from central belt to distal belt.Volcanic edifices were divided by eruptive interval unconformity boundary.More attentions should be paid to the spatial attributes so as to establish a volcano stratigraphic framework.The buried history of volcano stratigraphy should base on the analysis of central belt and distal belt of volcanic edifices.On the basis of the new framework of volcano stratigraphic units,the reservoir distribution are more reasonable