Abstract: A method for identifying the boundaries between sequences of rocks laid down in different depositional regimes. The approach used is to search, in well logs or seismic data, for a statistic characteristic of such regimes, and for breaks in that statistic. The preferred statistic used in the method of the present invention is the first moment of the power spectrum of the wavenumber of a suitable physical property as a function of depth. This statistic is calculated rapidly and with excellent depth resolution from the complex-valued autocorrelation function at its zero and unit lag values, respectively, and displayed as a single variable in black-and-white or color. The method of the present invention further includes manipulations that achieve the approximate conversion of the scale (and corresponding display) from its initial dependence on depth to one that is displayed as a function of geologic time.