Late Cretaceous–Paleogene palaeoclimate reconstruction of the Gippsland Basin, SE Australia

Abstract

The Cretaceous–Paleogene palaeovegetation and palaeoclimate in the Gippsland Basin was reconstructed using vascular plant-derived biomarkers, and are consistent with other proxy evidence for palaeoclimate (e.g. spore-pollen assemblages and plankton foraminifera oxygen isotopes). Variation in the higher plant-derived aliphatic and aromatic sesquiterpenoids, diterpenoids and triterpenoids resulted from vegetation succession, and is different in the T. lilliei, F. longus, L. balmei, M. diversus, P. asperopolus and N. asperus palynological biozones. Analyses of the oleanane index, the higher plant parameter, the higher plant index, the higher plant fingerprint, and various aliphatic and aromatic angiosperm/gymnosperm indices indicate the late Cretaceous–Paleogene (ca. 80–40 Ma) palaeoclimate in the Gippsland Basin was initially warm (Campanian T. lilliei Biozone), and then changed in this way: → cool (Maastrichtian upper F. longus Biozone), → warm (Paleocene L. balmei Biozone), → hot (early Eocene M. diversus and P. asperopolus Biozones), → warm and then cool (middle Eocene N. asperus Biozone). This changing climate trend is mostly consistent with global climate changes. In comparison to the analogous Taranaki Basin (western New Zealand), the Gippsland Basin is inferred to have had a less gymnosperm-dominated rainforest and a warmer climate in the late Cretaceous. During the Paleogene the palaeoclimate was similar in the two basins, as deduced from the angiosperm/gymnosperm indices of the sedimentary rocks.