Abstract

We present a temporal analysis of highresolution geochemical data series obtained from Holocene sediment cores recovered from two lakes in central Chile (Laguna del Maule [LdM: 36ºS, 2200 m] located in an active volcanic field the Andes, and Laguna Vichuquén [VIC: 34°S, 72º 05W, 4 m] on the coast) to study the existence of cycles associated with climatic forcing. Temporal dynamics were established using a spectral analysis (Morlet wavelet power spectrum or MWPS and Lomb-Scargle Fourier Transform or LSFT) and break points methods for quantifying major climate transitions present in the geochemical proxies. Both sequences reveal high periodicity. The MWPS analysis for the LdM sequence shows two periods of minimum variability between ∼13-9 ka and 7-5 ka, which occurred during lower lake levels. The wavelet and LSFT analysis show significant peaks at ca. 5000, 200 (De Vries/Suess oscillation), 80 (Gleissberg cycle), and 60-yrs cycles for LdM and at 1500, 650, 300, 13, 10.5 (11-yr Schwabe cycle), and 5.5-yrs (ENSO) cycles for VIC. During the mid-Holocene, the VIC record shows low-frequency cycles in productivity, clastic input and paleoredox indicators that appear to be driven by the Southern Westerlies (SW) variability at centennial scales. Both records are underlain by a period of minimum variability between ∼74/3 ka that was coeval with aridity at the regional scale prior to 3-4 ka. Bioproductivity began to increase ~4-3 ka in both records as evidenced by the MWPS analysis, which could reflect the onset of modern ENSO dynamics. These cycles are related to the ENSO/PDO though changes in the dynamics of the SW and Hadley Cell circulation. Also, the dominance frequencies in the spectra underestimates the rate of sea-level change during deglaciation but also misrepresents the timing when maximum ice-loads are reached. This study may therefore provide a new view of ice load history in Northern Greenland, and points towards the importance of including marine ice dynamics in models of ice retreat, and, perhaps, better constraints on regional variations of viscosity in GIA ice-models.