Abstract
Abstract. A brief (~150 kyr) period of widespread global average surface warming marks the transition between the Paleocene and Eocene epochs, ~56 million years ago. This so-called "Paleocene-Eocene thermal maximum" (PETM) is associated with the massive injection of 13C-depleted carbon, reflected in a negative carbon isotope excursion (CIE). Biotic responses include a global abundance peak (acme) of the subtropical dinoflagellate Apectodinium. Here we identify the PETM in a marine sedimentary sequence deposited on the East Tasman Plateau at Ocean Drilling Program (ODP) Site 1172 and show, based on the organic paleothermometer TEX86, that southwest Pacific sea surface temperatures increased from ~26 °C to ~33°C during the PETM. Such temperatures before, during and after the PETM are >10 °C warmer than predicted by paleoclimate model simulations for this latitude. In part, this discrepancy may be explained by potential seasonal biases in the TEX86 proxy in polar oceans. Additionally, the data suggest that not only Arctic, but also Antarctic temperatures may be underestimated in simulations of ancient greenhouse climates by current generation fully coupled climate models. An early influx of abundant Apectodinium confirms that environmental change preceded the CIE on a global scale. Organic dinoflagellate cyst assemblages suggest a local decrease in the amount of river run off reaching the core site during the PETM, possibly in concert with eustatic rise. Moreover, the assemblages suggest changes in seasonality of the regional hydrological system and storm activity. Finally, significant variation in dinoflagellate cyst assemblages during the PETM indicates that southwest Pacific climates varied significantly over time scales of 103 – 104 years during this event, a finding comparable to similar studies of PETM successions from the New Jersey Shelf.
Highlights
Gradual widespread warming initiated in the late Paleocene (∼59 Ma) and culminated in the Early Eocene Climatic Optimum (EECO; 52–50 Ma) (e.g., Adams et al, 1990; Zachos et al, 2001; Bijl et al, 2009)
The onset of Eocene Thermal Maximum 2 occurred ∼150 kyrs prior to the reversal of Chron C24r to C24n.3n, which is inconsistent with the location of the recorded carbon isotope excursion (CIE)
A relatively complete Paleocene-Eocene thermal maximum” (PETM) record was identified in sediments recovered from the East Tasman Plateau during Ocean Drilling Program (ODP) Leg 189, deposited at a paleolatitude of ∼65◦ S
Summary
Gradual widespread warming initiated in the late Paleocene (∼59 Ma) and culminated in the Early Eocene Climatic Optimum (EECO; 52–50 Ma) (e.g., Adams et al, 1990; Zachos et al, 2001; Bijl et al, 2009). Superimposed on this longterm warming trend, at least four “hyperthermals” occurred, which represent relatively brief (
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