The long sediment core BDP98 obtained from Lake Baikal was analyzed in order to discuss the periodicity of glacial cycles in the terrestrial climatic record of the past 2.6 Ma.Spectral analysis shows that the Baikal grain size record has been dominated by orbit-related cycles with periods of about100 ka,41 ka,and 23 ka,similar to those in the marine isotope record.However,there are some notable differences between the Baikal and oceanic records.In the marine isotope record,the 41 ka cycle was dominant before 1 Ma and the 100 ka cycle became significant only afterward.Conversely,in the Baikal record,the 100 ka period has appeared continuously throughout the past 2.6 Ma,and no appreciable shift in period is detected.These results suggest that the terrestrial climatic response to orbital forcing,as imprinted in the Baikal sediment,is different from the oceanic response.The 100 ka cycle detected in the Baikal record from before 1 Ma may be attributable to relatively long interglacials with skipping of two or three 41 ka obliquity cycles.This result may support the hypothesis that the 100 ka cycle is paced by the obliquity cycle.
展开▼
