Onset of the Paleocene–Eocene Thermal Maximum in the southern Pacific Ocean (DSDP Site 277, Campbell Plateau)

Abstract

Re-examination of a sediment core collected by the Deep Sea Drilling Project (DSDP Site 277) on the western margin of the Campbell Plateau, Southwest Pacific Ocean (paleolatitude of ∼ 65 • S), has identified an intact Paleocene–Eocene (P–E) boundary overlain by a 34 cm-thick record of the initial phase of the Paleocene–Eocene Thermal 5 Maximum (PETM) within nannofossil chalk. The upper part of the PETM is truncated, either due to drilling disturbance or a sedimentary hiatus. An intact record of the onset of the PETM is indicated by a gradual decrease in δ 13 C values over 20 cm, followed by a 14 cm interval in which δ 13 C is 2 ‰ lighter than uppermost Paleocene values. After accounting for effects of diagenetic alteration, we use δ 18 O and Mg/Ca values from 10 foraminiferal tests to determine that intermediate and surface waters warmed by ∼ 6 • at the onset of the PETM prior to the full development of the negative δ 13 C excursion. After this initial warming, sea temperatures were relatively stable through the PETM, but declined abruptly across the unconformity that truncates the event at this site. Mg/Ca analysis of foraminiferal tests indicate peak intermediate and surface water 15 temperatures of ∼ 19 and ∼ 32 • C, respectively. These temperatures may be influenced by enhanced poleward ocean heat transport during the PETM and surface water values may also be biased towards warm season temperatures.