湖相地层剖面中有机碳总量旋回及其层序地层意义

Total organic carbon cycles in lacustrine facies stratigraphic section and their significance of sequence layer

烃源岩中的有机碳总量在地层剖面上呈现周期性的循环模式,这种周期性的变化与地层层序的充填演化密切相关。地层层序在垂向上周期性的充填演化决定了沉积地层剖面中有机碳的周期性循环模式:在层序边界处,水体较浅,甚至处于暴露状态,沉积物堆积速度快且氧化作用活跃,剖面上往往出现有机碳总量最小值;在最大湖泛面附近,沉积物供应速度慢,为欠补偿沉积段,有利于有机质的富集,常出现有机碳总量最大值。利用声波曲线与视电阻率曲线交会的方法,可获得全剖面有机碳总量的演化模式,将其用于层序地层学研究,能够为层序地层单元的识别与划分提供有力依据,同时也有助于恢复古地理环境。

The total of organic carbon in source rocks presents periodic circle patterns in the stratigraphic section, and this periodic change is closely related to the filling evolution of the stratigraphic sequence. The periodic cycle model of the organic carbon in the sedimentary stratigraphic section is determined by the vertical periodic filling evolution of stratigraphic sequence： on the sequence boundary, due to the shallow water, fast sediment accumulation and active oxidation, the minimum of the total of organic carbon often appear on the section; near the maximum flooding surface, the sediment supply was slow, the under-compensation sediment segments are conducive to the enrichment of organic matter, the maximum of the total of organic carbon often appear on the section., the evolution model of the total of the organic carbon on the whole section can be got by the crossplotting acoustic log curves with apparent resistivity curves, and the result can not only provide a strong basis for the identification and classification of sequence stratigraphic units, but also conducive to restore the ancient geography.