Fig. 4 | Nature Communications

Fig. 4

From: Burial-induced oxygen-isotope re-equilibration of fossil foraminifera explains ocean paleotemperature paradoxes

Fig. 4

Assessment of the impact of burial-induced O isotope re-equilibration on the planktonic foraminifera O isotope records. a Planktonic foraminifera O isotope data from Pearson et al.17 (Tanzania, Paleolatitude 20° S) and from Wilson and Norris 18 (ODP Site 1052, Paleolatitude 20° N) are shown together with the results from numerical simulations run with a geothermal gradient of 50 °C km−1 and a diffusion activation energy of 90 kJ mol−1, assuming an ice-free ocean (δ 18O = −1‰ VSMOW) and a temperature of 3.5 °C at the water–sediment interface. The curves represent the present-day O isotope compositions of fossil planktonic foraminifera tests formed in equilibrium with seawaters at −2, 2, 7, 13, 20, 25, 27 and 27.5 °C. These temperatures roughly correspond to those of surface waters in the modern ocean at 70, 60, 50, 40, 30, 20, 10 and 0° latitude10. b Latitudinal profiles of the O isotope compositions of the planktonic foraminifera for different simulated burial durations: a latitude gradient similar to the modern one (yellow curve) will flatten substantially after 45 Myr (red curve) and 100 Myr (brown curve) in response to the burial-induced O isotope re-equilibration. Also shown are the Eocene (45 Ma) tropical planktonic foraminifera O isotope data from Pearson et al.17 (red) and the high-latitude planktonic foraminifera O isotope data from Zachos et al. 10 (grey). The temperature conversion is from Anderson and Arthur 3 and assumes an ice-free ocean with a seawater δ 18O = −1 ‰ (VSMOW)

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