Spectral analysis of a 1000-year stalagmite lamina-thickness record from Shihua Cavern, Beijing, China, and its climatic significance

Stalagmite laminae provide a high-resolution geological record of climate change. In this paper. moving spectral analysis is used to analyse a stalagmite lamina thickness record to study climatic variability. It was found that the dominant cycles of the lamina thickness sequence are 2, 3.3, 5-6, 10-12, 14-18, 133 and 194 years. Some of the cycles are the same as the cycles of modern climatic indices, such as the QBO (Quasi Biennial Oscillation) of 2 years. the QTO (Quasi Triple-year Oscillation) cycle of about 3.5 years, the QFO (Quasi Five-year Oscillation) cycle of 5-6 years and the QEO (Quasi Eleven-year Oscillation) cycle of 11 years. It was also found that there are different dominant cycles in different time periods. Usually, the dominant cycles are stronger in wet periods when the microlaminae are thicker. In dry periods, the microlaminae are thinner and the power of the dominant cycles is also weaker. Another feature is that the power of the dominant cycles and their long-term periods and frequencies appear to change. These phenomena are important for understanding the climatic changes in Beijing area over the last 1 ka.