Abstract
Abstract. Reconstructing the early Palaeogene climate dynamics of terrestrial settings in the high southern latitudes is important to assess the role of high-latitude physical and biogeochemical processes in the global climate system. However, whereas a number of high-quality Palaeogene climate records has become available for the marine realm of the high southern latitudes over the recent past, the long-term evolution of coeval terrestrial climates and ecosystems is yet poorly known. We here explore the climate and vegetation dynamics on Tasmania from the middle Palaeocene to the early Eocene (60.7–54.2 Ma) based on a sporomorph record from Ocean Drilling Program (ODP) Site 1172 on the East Tasman Plateau. Our results show that three distinctly different vegetation types thrived on Tasmania under a high-precipitation regime during the middle Palaeocene to early Eocene, with each type representing different temperature conditions: (i) warm-temperate forests dominated by gymnosperms that were dominant during the middle and late Palaeocene (excluding the middle/late Palaeocene transition); (ii) cool-temperate forests dominated by southern beech (Nothofagus) and araucarians that transiently prevailed across the middle/late Palaeocene transition interval (~ 59.5 to ~ 59.0 Ma); and (iii) paratropical forests rich in ferns that were established during and in the wake of the Palaeocene–Eocene Thermal Maximum (PETM). The transient establishment of cool-temperate forests lacking any frost-sensitive elements (i.e. palms and cycads) across the middle/late Palaeocene transition interval indicates markedly cooler conditions, with the occurrence of frosts in winter, on Tasmania during that time. The integration of our sporomorph data with previously published TEX86-based sea-surface temperatures from ODP Site 1172 documents that the vegetation dynamics on Tasmania were closely linked with the temperature evolution in the Tasman sector of the Southwest Pacific region. Moreover, the comparison of our season-specific climate estimates for the sporomorph assemblages from ODP Site 1172 with the TEX86L- and TEX86H-based temperature data suggests a warm bias of both calibrations for the early Palaeogene of the high southern latitudes.
Highlights
The Southern Ocean is an important region for early Cenozoic (65–34 Ma) climates, being the dominant region for deep-water formation during that time (Thomas et al, 2003; Sijp et al, 2011; Hollis et al, 2012)
Our results show that three distinctly different vegetation types thrived on Tasmania under a high-precipitation regime during the middle Palaeocene to early Eocene, with each type representing different temperature conditions: (i) warm-temperate forests dominated by gymnosperms that were dominant during the middle and late Palaeocene; (ii) cool-temperate forests dominated by southern beech (Nothofagus) and araucarians that transiently prevailed across the middle/late Palaeocene transition interval (∼ 59.5 to ∼ 59.0 Ma); and (iii) paratropical forests rich in ferns that were established during and in the wake of the Palaeocene–Eocene Thermal Maximum (PETM)
During the late Palaeocene and early Eocene, sea-surface temperatures (SSTs) gradually rose to tropical values (> 26 ◦C), with maxima being reached during the Palaeocene–Eocene Thermal Maximum (PETM; Sluijs et al, 2011) and the Eocene Climatic Optimum (EECO) (Bijl et al, 2009; Hollis et al, 2009, 2012)
Summary
The Southern Ocean is an important region for early Cenozoic (65–34 Ma) climates, being the dominant region for deep-water formation during that time (Thomas et al, 2003; Sijp et al, 2011; Hollis et al, 2012). L. Contreras et al.: Southern high-latitude terrestrial climate change sea-surface and global intermediate water temperatures increased from the late Palaeocene to the early Eocene, with maximum warmth during the Early Eocene Climatic Optimum (EECO; 53–51 Ma), followed by a cooling trend during the middle and late Eocene (Zachos et al, 2001, 2008; Bijl et al, 2009; Hollis et al, 2012). Low SSTs are recorded for the high-latitude Southwest Pacific Ocean during the interval spanning the middle/late Palaeocene transition (59.5– 59.0 Ma); TEX86-derived SST decreased by ∼ 3 ◦C during that time (Bijl et al, 2009; Hollis et al, 2012, 2014) Along with this SST drop, lowered sea level and marked bathyal erosion suggest that a transient growth of an Antarctic ice sheet may have occurred (Hollis et al, 2014)
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