轨道周期转型时间及模式分析

Study on Time and Mode of Middle Pleistocene Transition

诸多研究表明在第四纪阶段,气候变化的主导周期曾发生了从41 ka向100 ka转变。但对于周期转型发生的时间,周期转型的模式是渐变还是突变,以及周期转型发生的原因仍处于纷争之中。笔者运用带通滤波、奇异谱分析和小波分析等数学方法,对柴达木盆地达参1井自然伽玛(GR)曲线、宝鸡黄土粒度曲线,以及ODP677孔、ODP659孔、ODP758孔的δ18O记录进行了对比研究,结果表明,周期转型开始时间大致始于1.4 Ma～1.2 Ma,此后经历了一个地轴倾斜周期逐渐减弱,偏心率周期逐渐增强的过程,至0.8 Ma之后偏心率周期的主导地位才最终确立,因此周期转型的模式是逐渐过渡的。

Middle Pleistocene transition is one of the unsolved problems of astronomical plaeoclimate theory. The debates focus on when and how the transition has taken place. The authors use several math methods such as band - pass filter, singular spectrum anal-ysis(SSA) ,and wavelet analysis, to correlate six climate curves from different areas of the world,which include Qaidam basin Gamma logging curve, grain size of the Baoji loess- soil sequence, δ18O curve of ODP677,ODP659,ODP758 sites and ice simulated curve. It is showed that the time of transition began at 1.4 Ma-1.2 MaBP, then the obliquity cycle was gradually becoming weaker, and the eccentricity cycle becoming stronger, only after 0.8Ma BP, the eccentricity cycle held in the highest flight.