Identification of sedimentary cycles through Fourier analysis of geochemical data

Abstract

Trace elements are sensitive to slight shifts in the chemical equilibrium of a body of water, and as a result they can be expected to reflect cyclical events in the earth's history. Geochemical data from a section of Upper Jurassic (Kimmeridgian) bituminous sediments in Great Britain, 20 m thick, have been examined by single Fourier series analysis, thereby permitting an objective assessment of sedimentary cycles. Subjectivity only enters into the final interpretative stage. Assumptions made as to the rate of deposition of these sediments have indicated several superimposed periodicities with respective durations of (?) 200,000, 100,000, 40,000, 14,000, and 11,000 years. Comparison is made with long-term cyclic durations estimated by other workers. Several of these periods are coincident with the duration of astronomical phenomena which could cause climatic fluctuations.