[[:file:applied-paleontology_fig17-29.png|Figure 1]] illustrates a typical oxygen isotope record (expressed as delta oxygen-18 values) for the middle Tertiary, showing standard Oligocene and Miocene isotope stages. | [[:file:applied-paleontology_fig17-29.png|Figure 1]] illustrates a typical oxygen isotope record (expressed as delta oxygen-18 values) for the middle Tertiary, showing standard Oligocene and Miocene isotope stages. |