Holocene millennial to centennial carbonate cyclicity recorded in slope sediments of the Great Bahama Bank and its climatic implications

A 38 m long sediment core (MD992201) retrieved from a water depth of 290 m from the leeward margin of the Great Bahama Bank (GBB; 25degrees53.49'N, 79degrees16.34'W) has been investigated for changes in aragonite content. The core covers the Mid to Late Holocene (the past 7230 yr). Sediment lightness (L*-values) was used as a proxy for aragonite content, based on a high linear correlation (R = 0.93) between the X-ray diffraction derived aragonite content and L*-values. The resulting time resolution of the L*-values derived aragonite content ranges from 1 yr at the base of the core to 4 yr at the top. Detailed time series analysis using Monte Carlo Singular Spectrum Analysis and spectral analysis (Lomb-Scargle Fourier transform) identifies the presence of seven signals with varying amplitudes and wavelengths that could be traced throughout the past 5500 yr. During the first similar to1600 yr of sedimentation the aragonite record is dominated by the initial flooding of the flat-topped GBB. Superimposed on a multimillennial signal, related to Holocene sea-level changes, a millennial-scale fluctuation and five quasi-periodic oscillations were detected (similar to1.3-2 kyr, similar to500-600 yr, similar to380 yr, similar to260 yr, similar to200 yr and similar to100 yr period). Comparisons with other proxies (e.g. tree ring-Delta(14)C, Be-10 and delta(18)O in ice cores) provides information on the origin and dynamics of the individual signals. The analysis shows that the similar to200 yr and similar to100 yr signals can be attributed to solar forcing. The similar to260 yr, similar to380 yr and the similar to500-600 yr quasi-periodic signals are found to be of climatic origin, whereas the millennial scale fluctuations remain enigmatic, although solar forcing mechanisms seem likely. The data show that variability of solar output as well as past oceanographic and atmospheric changes have modulated the Mid to Late Holocene climate, which in turn controlled sediment input variations found in the Holocene wedge leeward of the GBB. Although these periplatform sediments have a rather uniform appearance, they still contain a large variety of subtle sedimentary variations.