Towards an orbital time scale for chinese loess deposits

摘要: Abstract In this study, we analyzed the grain size of Baoji loess-soil sequence at 10 cm intervals. Results show that variations are very sensitive to alternations, with loess units being much coarser than soils. Such a change in grains is interpreted as result glacial-interglacial cyclic intensity winter monsoon winds out Siberia. The record thus employed proxy indicator circulation and tuned orbital records calculated recently by Berger Loutre (1991) under control major magnetic reversals. tuning independent any correlation δ18O signals deep-sea sediments. resulting time scale tightly constrained, suggested following facts: (1) filtered obliquity precession components from data on closely match theoretical records; (2) ages reversals estimated good agreement K Ar -dated ages; (3) there close coherence between series frequency bands over entire 0–2.5 Ma period; (4) shows similarity orbitally-tuned DSDP Site 607 ODP 677 records. Examination time-dependent characteristics suggests two shifts dominant periodicities long-term monsoonal cycles, one occurring about 0.8 BP other around 1.7 BP.