关键词: 石笋微层, 气候周期, 滑动谱图象分析

Abstract: The stalagm ite lam ina is one ofthe high-resolution records in the paleoclim ate research. In order to study the cycles ofclim ate oscillation in Beijing area and their shifts in the last1 ka, a m oving spectralanalysis is used to revealthecharacteristicsofcyclesin the lam inathicknesssequence ofa stalagm ite from Shihua Cave. Itisfound thatthedom i- nantcycles in the tim e series are of2yr, 3.3yr, 5～6yr, 10～12yr, 16～18yr, 133yr and 194yr. Som e ofthese cyclesare close to thecycle of3.5yr, the cycleof5～6yrand the cy- cle of11yrthatare found in m any m odern clim aticrecord. Itm eansthatthe dynam icforc- ing and the clim ate oscillationsin thelast1ka are sim ilarto thoseofm odern clim ate. The 3.3yrcycle isstrongerand continuous before D4 and the 5.8yrcycle is m ore distinctthan the 3.3yrcycle after D4. There are differentdom inant clim ate cycles in different periods. Usually, the dom i- nantcyclesare strongerand clearerwhen thelam inaearethicker. Thedom inantcyclesare weak when the lam inae are thinner. Itm ay reflectthatthe stronger clim ate cycles in the wetperiod could leave m uch clearer prints in the stalagm ite lam inae. Therefore the lam i- nae thicknesscan beused asaproxy ofclim ateoscillation in northern Chinaifthesam ples are carefully selected. Itis noticed thatthe cycles m ay m erge, branch, replace, abruptly appear, disappear or shift in frequency w ith the clim ate evolution. These phenom ena dem onstrate that the clim ate oscillation is nonlinear. Itis very im portantforunderstanding the clim aticoscilla- tion ofBeijing area in the last1 ka.

Key words: stalagm ite lam ina, clim ate cycle, m oving spectralanalysi