The Quaternary is characterized by two climatic signatures: that of the last 800,000 years (the upper Pleistocene), and that of the period from 900,000 to 1,800,000 years ago (the middle Pleistocene). Glacial cycles within the upper Pleistocene climatic signature are 100,000 years long and contain interglacial periods of 10,000-12,000 years and a "full" glacial period of 20,000-30,000 years. Cycles of the middle Pleistocene climatic signature range from 20,000 to 40,000 years. Analysis of Miocene cores from the Deep Sea Drilling Project reveals eight widespread hiatuses. These hiatuses correspond to intervals of cooling, as indicated by fauna and flora, ¹⁸O anomalies, and low sea levels. The Miocene hiatuses may result from decreased polar temperatures and conc mitant increased bottom-water circulation and corrosiveness. Durations represented by

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both hiatuses and preserved sediments are approximately 1-2 m.y. The inferred Miocene glacial epochs are of the same duration as the glacial epochs of the Pliocene-Pleistocene. Oligocene hiatuses are found in all of the world's oceans, indicating cold bottom-following waters. Evidence (e.g., hiatuses or ice-rafted material) demonstrates the occurrence of Eocene continental glaciers in Antarctica. Interaction between the three planetary orbital parameters of eccentricity, tilt, and precession apparently control much of long-term climate change, with the dominance of eccentricity dictating glacial cycles. Continuity of climate pattern for the Tertiary is indicated, given constancy of planetary motion. Miocene, Frio, and Wilcox hydrocarbon reservoirs in the Gulf Coast should be reviewed n terms of a more subtle climatic model to refine interpretation of known depositional sequences.

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