摘要
砂岩作为山脉隆升过程中在盆地内的直接记录,其碎屑组分在分析造山带及沉积物源区构造背景等方面具有较好的效果。本文应用砂岩碎屑组分特征对比、单井碎屑组分垂向演化特征、Dickinson图解及砂岩的成分成熟度Q/(F+L)与F/L的演变特征四种方法,对川西中段地区侏罗系进行了系统的研究。结果表明:(1)根据砂岩碎屑组分的空间分布特征分析,认为研究区中侏罗世沙溪庙组受到了来自西部龙门山造山带和北部米仓山—大巴山造山带的复合造山运动的共同影响;(2)通过对川西地区单井碎屑组分垂向对比及砂岩成分成熟度分析,发现在千佛崖组与沙溪庙组界线附近,沉积物源发生了明显的变化,暗示川西地区此时发生了一次重要的沉积转型事件,这与米仓山—大巴山的构造演化密切相关。(3)砂岩碎屑组分的变化反应盆地周缘造山带的活动:早侏罗世—中侏罗世早期,构造相对稳定,砂岩成分成熟度高;中侏罗世中晚期,在米仓山—大巴山逆冲推覆作用的影响下,砂岩成分成熟度低,且具有火山岩岩屑增多的特征;晚侏罗世早期,构造相对稳定,砂岩成分成熟度增高,至晚侏罗世晚期川西地区主要受龙门山造山带的影响,其砂岩特征与龙门山前缘砂岩特征趋于一致。
Sandstone is the direct record of mountain uplift in the basin, and its detrital components have a good effect in analyzing orogenic belts and tectonic setting of sedimentary provenances. Jurassic sediments were systematically investigated with four main methods, i.e., features comparison in detrital components, vertical evolution characteristics of detrital components in single well, Dickinson chart and evolution characteristics between Q/(F+L) and F/L of component maturity. Some conclusions have been reached: (1) On the basis of spatial distribution features of the detrital components of sandstones, the authors believe that the middle Jurassic Shaximiao Formation in the study area was effected by the western Longmenshan orogenic belt and the northern Micang-Daba orogenic belt simultaneously. (2) According to the vertical correlation of the detrital components and the analysis of compositional maturity of sandstones in a single well, the authors have found that near the boundary between Qianfoya Formation and Shaximiao Formation, the provenance had a significant change, suggesting that there existed an important sedimentary transformation event in western Sichuan area at that time, which was closely connected with the tectonic evolution of Micang-Daba Mountain. (3) The detrital components of sandstones reflect the activity of the orogenic belts around the basin. With relatively stable structures, sandstones had a high compositional maturity from the early Jurassic to the middle Jurassic. In middle and late Middle Jurassic, due to the influence of the thrusting of the Micang-Daba Mountian, sandstones showed a low compositional maturity, and volcanic detritus increased. In the early Late Jurassic, the structures got relatively stable, and the compositional maturity of sandstones increased. Towards the late Late Jurassic, due to the influence of the Longmenshan orogenic belt in western Sichuan, the feature of sandstones became similar to that of the front sandstones in Longmenshan area.
出处
《中国地质》
CAS
CSCD
北大核心
2013年第2期517-528,共12页
Geology in China
基金
国家自然科学基金重点资助项目(40739901)
国家科技重大专项项目(2011ZX05002-004-006HZ)资助
关键词
川西中段
侏罗纪
砂岩碎屑组分
构造演化
middle part of western Sichuan
Jurassic
detrital components
tectonic evolution