Late Paleocene - Early Eocene long and short term environment and climate change in Southeast Australia

Abstract

The Late Paleocene and Early Eocene are characterized by greenhouse climates, culminating in the early Eocene climate optimum (EECO; 53-50 Ma), the warmest period of the last 65 Myr. Especially the high polar temperature estimates are poorly understood from a climate dynamics perspective; climate modelling studies cannot reproduce the temperatures from proxy data in these areas. In recent years, near tropical temperatures were reconstructed for the Antarctic margin and Tasmania, at a paleolatitude of 60° S, supported by spore and pollen data which suggest vegetation indicative for tropical settings in these areas. This study uses biomarker data (TEX86) proxies, dinoflagellate cyst assemblages, and spores and pollen assemblages to reconstruct terrestrial and marginal marine paleoenvironmental conditions during the Late Paleocene and Early Eocene (~5751.5 Ma) of the Latrobe-1 core on the coast of southeast Australia (paleolatitude ~55° S), with special focus on the Paleocene-Eocene Thermal Maximum (PETM; ~56 Ma). A stratigraphic framework for the sedimentary record was developed using biostratigraphic constraints from dinocysts and terrestrial palynology and bulk organic stable carbon isotope stratigraphy. The TEX86H SST record shows high temperatures (up to 32 °C) in the PETM and EECO, although data suggests an influence of land-derived isoprenoid GDGTs. The abundant tropical pollen and spores and abundance of tropical dinocyst species Apectodinium suggest high air and sea surface temperatures during the PETM and towards the EECO. Paleovegetation shows a shift from Late Paleocene rainforest gymnosperm taxa to angiosperm dominated forests towards the EECO, with the introduction of several angiosperm lineages during the PETM and following hyperthermals. These results support the near-tropical temperatures recorded at the Antarctic margin. The paleoceanographic configuration at this location gives an opportunity to assess influence of low latitude surface waters on high latitude climate.