准中4区块侏罗系头屯河组滩坝及风暴沉积特征

Sedimentary characteristics of beach bar and storm deposits in Toutunhe formation of Jurassic in block 4 of the middle of Junggar Basin

在准噶尔盆地中部(简称准中)4区块侏罗系岩心观察的基础上,考虑粒度分析、薄片镜下观察及古气候恢复成果,认为该区头屯河组沉积时期发育滨浅湖滩坝沉积;以典型风暴沉积构造的识别为基础,提出一种与滩坝相伴生出现的新的风暴岩类型——滨浅湖风暴岩,并建立理想垂向序列模型,自下至上依次为:递变、块状层段(Sa),平行层段、冲洗交错层段(Sb),波状层段(Sc);断续纹层段(Sd)和滨浅湖泥岩段(Se).该类风暴岩发育在正常浪基面之上的滨浅湖地区,与半深湖风暴岩相比,更易遭受后期波浪改造而难以完整保存;因其发育的平面位置不同,滨浅湖风暴岩序列顶底的沉积物可以是氧化色调的滨浅湖泥坪沉积物或是正常的滨浅湖滩坝沉积物.滨浅湖风暴岩的提出完善了滨浅湖滩坝沉积体系,为研究区古地理、古气候特征的恢复提供线索,为滩坝的成因和沉积环境研究提供思路,对准噶尔盆地隐蔽油气藏的勘探具有一定指导意义.

Based on core observation,with the help of grading analysis,slice microscopic observation and recovered achievements of paleoclimate in this area by predecessors,this thesis believes that Toutunhe formation in the 4th block of the middle of Junggar Basin developed into shore-shallow lacustrine beach bar deposit in sedimentary period.From the recognition of typical storm deposit structures,this thesis puts forward a brand new tempestite type that accompanying appeared with beach bar and built ideal shore-shallow lacustrine tempestite vertical sequence model: Sa graded,block bedding segments parallel,swash cross bedding segments wave bedding segment,Sd intermittent bedding segment,Se shore-shallow lacustrine mud rock bedding segment.This kind of tempestite developed on shore-shallow lacustrine area that above the everyday wave base,and are more easily to be reformed by waves in later stage compared with semi deep lake tempestite;and because of the different developing planimetric position of deposit sediments on top and bottom of shore-shallow lacustrine tempestite,it could be oxidation tonal of shore-shallow lacustrine shale level ground deposit sediment or normal shore-shallow lacustrine dam deposit sediment.