Figure 10. Spectral analysis periodograms with red noise levels (RN), as well as 90% and 95% non-randomness confidence levels (see text for details) for anchovy (a), herring (b), and sediment gray-scale value data (c), for the interval from 287-920 cm depth. Periods in years are based on a constant sedimentation rate of 0.23cm/year. Standard error for bandwidth of cycles due to standard error of ¹⁴C data is ±7 percent. Black bars mark bandwidth error for each period. d-f: Cross-spectral analysis utilizing a 5-point-lag Hamming window for gray-scale value data with anchovy and herring scale abundances: squared coherency (bottom) and phase spectrum (+ to - ) at top: horizontal gray bars mark in-phase (+) or inverse (–) cross-correlation. Dotted vertical lines mark periods that are cross-correlated. Dotted horizontal lines mark 90% and 95% confidence level (calculated from the F-distribution). Note that most of the significant periods in (d) have negatively cross-correlated amplitudes and are phase shifted (i.e., they are not directly correlated in time) except for the 56-57, 74, and 77 year periods. These intervals show an in-phase correlation between bright sediments and herring and a negative cross correlation (+/– ) between herring and anchovy and gray-scale values and anchovy. Note that the strong decrease in power with decreasing period is primarily the result of non-equidistant sampling with the fish data.