Fig. 1.

Comparison of δΔ values between modern (ε = 5.2; n = 43) and fossil (ε = 16.4; n = 95) eggshell organic matrix δ¹³C values vs. eggshell carbonate δ¹³C values. This relationship clearly documents the difference in nutrient routing and thereby supports our contention that eggshell carbonate is not diagenetically altered even though the fossil eggshell ε value differs from the modern eggshell value. In fact, fossil values (r² = 0.25) exhibit a better linear correlation than modern values (r² = 0.13), and the offset (ε) is greater in the fossil material.