A 260,000-year continuous, annual geoclimatic time series has been compiled from the varved Permian Castile and Bell Canyon Formations of the Delaware Basin, southeastern New Mexico, and southwestern Texas. The last 200,000 years of the record was obtained from calcite-laminated anhydrite and anhydrite-laminated halite, which formed as a result of seasonal and annual deposition in the evaporite basin. The time series is based on measured thickness of individual varves. Analyses of calcium sulfate, calcium carbonate, and organic matter were made on 50-year intervals in the evaporite part of the sequence. Time series of the major components were examined by using smoothed graphic plots, variance spectra, and moving correlation coefficients. The longest oscillation recorded in the series that may be of climatic origin has a period of about 100,000 years. The calcium sulfate record contains 9-11 distinct oscillations with an average period of about 20,000 years. The strongest oscillation has a preferred spectral period of 2700 years and is recorded throughout the series as thickness changes in calcium sulfate, as events controlling halite deposition, and as episodes of basin freshening. A broad spectral response near a period of about 200 years reflects changes in sulfate, carbonate, and halite thickness. Shorter periods do not have consistent spectra. The time series contains no preferred periods that have not already been identified in previously described records. The climatic changes appear to be the result of a deterministic response to orbital effects at the longer periods and stochastic processes at the shorter periods. An unusually strong response near 2700 years is associated with episodic freshening of the basin. This period has been well established in the Holocene paleoclimatic record, and its presence in the Permian suggests a deterministic origin. |