CYSTRATI: a computer program for spectral analysis of stratigraphic successions

Abstract The spectral analysis of stratigraphic successions represents an objective approach for the detection of periodic components that give the succession its cyclical form, as for example, in the periodicity attributed to climatic changes and related to the Milankovitch cycles or with the decennial cyclicity of solar activity. We present the CYSTRATI program, written in ANSI standard FORTRAN 77, which includes five of the most widely established techniques for spectral analysis in the earth sciences: Blackman-Tukey's classic approach; classic periodogram approach; maximum entropy approach; Thompson multitaper approach for continuous variables; and finally Walsh's spectral analysis that lets us investigate cyclicity rhythms for binary variables (for example the alternation of limestone-marl). Another important characteristic is the program's versatility in providing different ways of processing experimental data (windowing, tapering, smoothing) in order to better estimate the power spectrum. Obviously any one-dimensional (1-D) succession can be analyzed with CYSTRATI, but for stratigraphic successions the possibility of adopting a previous, more exhaustive treatment has been included, a treatment in which the lithology and the type of contact between the strata can be included. The estimated results of the power spectrum in two different temporal successions will be provided, the first corresponding to lacustrine varves and the second to the Wolfer number of sunspots: such results can be used to check the program's implementation.