地史时期森林的变迁主要是由于生态环境的变动；
The former is due to the variations of the ecological factors.
当然，我们现在谈论的是地史时期，是以数万年测量的。
Of course, we're talking geological time here, which is measured in tens of thousands of years.
最后，对潮汐韵律层在推测地史时期地-月系的演化历史中的意义作了评述。
Finally, the implications of tidal rhythmites for the Earth's rotation and the history of the Earth-Moon system in geological past are concluded.
三个衰退期受到地史时期中的二大冰期，五次海平面变化和大气降雨量的影响。
Three failing periods of conodont are influenced by two ice ages, five sea-level changes and rainfalls in the geological history time.
基准面的变化是构造、气候的函数，对于地史时期的滨海盆地，基准面就是相对海平面。
Base level was the function of tectonic movements and climate circles, and base level for coastal basin in geological history was relative sea level.
前者必须根据剥蚀厚度恢复地层在地史时期的最大埋深，否则将会对油气的勘探带来不良影响。
The greatest buried depth of strata of the former during geological history should be restored according to the eroded thickness, otherwise it will bring adverse effect on the petroleum exploration.
前者必须根据剥蚀厚度恢复地层在地史时期的最大埋深，否则将会对油气的勘探带来不良影响。
The greatest buried depth of strata of the former during geological history should be restored according to the eroded thickness, otherwise it will bring adverse effect on the petroleum exploration.
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