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    准噶尔盆地南缘三工河组和西山窑组辫状河三角洲水动力条件与砂体分布规模定量分析

    Quantitative analysis of hydrodynamic conditions and sand body distribution dimensions of the braided river delta in Sangonghe Formation and Xishanyao Formation on the south margin of Junggar Basin

    • 摘要: 提要:不同主控水动力条件的三角洲具有不同的平面形态、砂体分布频率和规模尺寸。为了定量表征陆相三角洲的主控水动力条件,将其按水动力相对强度分为浪控、河流影响型浪控、波浪影响型河控、河控4类。实测层段的露头岩心柱状图定量分析结果表明三工河组为河流影响型浪控辫状河三角洲前缘沉积,而西山窑组为波浪影响型河控辫状河三角洲前缘沉积。两类辫状河三角洲前缘均主要发育3种类型的砂体,分别为水下分流河道、河口坝、席状砂。但河流影响型浪控辫状河三角洲前缘以席状砂为主,分布频率高达57%;波浪影响型河控辫状河三角洲前缘以水下分流河道和河口坝砂体为主,分布频率分别为42%和33%。河流影响型浪控辫状河三角洲前缘水下分流河道和席状砂的宽厚比均明显大于波浪影响型河控辫状河三角洲前缘相应砂体的宽厚比;河口坝砂体属于残余成因单元,宽厚比定量关系不明确。

       

      Abstract: Abstract:Deltas, controlled by different dynamical conditions, are characterized by different plane shapes, distribution frequencies and dimensions of sand bodies. In order to quantitatively characterize the major dynamical conditions of lacustrine deltas, the authors divided the lacustrine deltas into four types on the basis of relative strength of hydrodynamic force, i.e., wave dominated, fluvialin fluenced-wave dominated, wave influenced-fluvial dominated and fluvial-dominated delta respectively. According to the quantitative analysis of measured outcrop columnar section, Sangonghe Formation was assigned to fluvial influenced-wave dominated braided river delta front, while Xishanyao Formation was considered to be of wave influenced-fluvial dominated braided river delta front. Three types of sand bodies were mainly developed in these two kinds of delta front, which are underwater distributary channel, river mouth bar and sheet sand. However, fluvial influenced-wave dominated braided river delta front was dominated by sheet sand, where the distribution frequency was up to 57%; wave influenced-fluvial dominated braided river delta front was dominated by underwater distributary channel and river mouth bar, where the distribution frequency was 42% and 33% respectively. The width/thickness ratio of the underwater distributary channel and river mouth bar in fluvial influenced-wave dominated braided river delta front was obviously larger than that in wave influenced-fluvial dominated braided river delta front. Because river mouth bar sand body is a residual genetic unit, the quantitative relation of its width/thickness ratio remains unclear.

       

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