Abstract
Abstract. Re-examination of sediment cores from Deep Sea Drilling Project (DSDP) Site 277 on the western margin of the Campbell Plateau (paleolatitude of ~65° S) has identified an intact Paleocene–Eocene (P–E) boundary overlain by a 34 cm thick record of the Paleocene–Eocene Thermal 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 δ13C values over 20 cm, followed by a 14 cm interval in which δ13C is 2 ‰ lighter than uppermost Paleocene values. After accounting for effects of diagenetic alteration, we use δ18O and Mg/Ca values from foraminiferal tests to determine that intermediate and surface waters warmed by ~5–6° at the onset of the PETM prior to the full development of the negative δ13C excursion. After this initial warming, sea temperatures were relatively stable through the PETM but declined abruptly across the horizon that truncates the event at this site. Mg/Ca analysis of foraminiferal tests indicates peak intermediate and surface water temperatures of ~19 and ~32 °C, respectively. These temperatures may be influenced by residual diagenetic factors and changes in ocean circulation, and surface water values may also be biased towards warm-season temperatures.
Highlights
Stable isotope analysis of foraminiferal tests from sediments cored at Deep Sea Drilling Project (DSDP) Site 277 (Shackleton and Kennett, 1975) provided the first paleotemperature record for the Paleogene of the Southern Ocean and laid the foundation for many subsequent studies of the regional paleoclimate and paleoceanography (e.g., Kennett, 1977, 1980; Kennett and Shackleton, 1976; Hornibrook, 1992; Nelson and Cook, 2001)
The 45 m thick studied interval (425–470 mbsf) consists of five cores, with significant gaps due to poor recovery in three of the cores, which extend from middle Paleocene to lower Eocene (Fig. 2)
The sediments are greenish-white to greenish-grey nannofossil chalk, with higher clay content in the upper Paleocene and lowwww.clim-past.net/11/1009/2015/
Summary
Stable isotope analysis of foraminiferal tests from sediments cored at DSDP Site 277 (Shackleton and Kennett, 1975) provided the first paleotemperature record for the Paleogene of the Southern Ocean and laid the foundation for many subsequent studies of the regional paleoclimate and paleoceanography (e.g., Kennett, 1977, 1980; Kennett and Shackleton, 1976; Hornibrook, 1992; Nelson and Cook, 2001). There has been renewed interest in the early Paleogene (66 to 35 Ma) climate history of the Southern Ocean, partly driven by a societal imperative to understand how the Antarctic ice sheet will respond to anthropogenic global warming (e.g., Joughin et al, 2014). One event in particular has been touted as a geological analogue for greenhouse gas-driven global warming: the Paleocene–Eocene Thermal Maximum (PETM, ∼ 56 Ma). This event was a short-lived (∼ 220 kyr) perturbation to the climate and carbon cycle in which global temperatures rose by 4–5 ◦C within a few thousand years
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