Figure 3

δ¹⁵N of modern and fossil corals plotted with δ¹⁵N values of the regional N source. Fossil data are compared to the δ¹⁵N values of modern corals from different locations, and the δ¹⁵N of their regional nitrogen source^{10, 24, 25} displaying the typical ~7‰ offset¹⁰. Early Miocene (18–20Ma) corals (orange and yellow squares) from adjacent sites in Indonesia (note the offset of the Z-like and AZ-like corals) and Triassic corals from Turkey (green rhombi) are plotted outside of the box as the δ¹⁵N of their regional N source is unknown. The δ¹⁵N values of Miocene, zooxanthellate coral Acropora papillare (yellow squares) and azooxanthellate coral Caryophyllia sp. (orange squares) indicate that the δ¹⁵N of their regional N source was approximately 2.5‰ (arrow), indicative of oligotrophic waters^{25 .}