Late Neogene Climates in Australia: Fossil Pollen- and Spore-based Estimates in Retrospect and Prospect

Abstract

Australian sites that are claimed to preserve evidence of fossil spores and pollen for Late Neogene (Late Miocene, Pliocene) climates, mostly lack one or both of the prerequisites, i.e. accurate dating and continuous preservation of plant microfossils. Nevertheless, the available data confirm that climatic gradients closely parallelled those of the present day in direction although not in strength: broad-scale vegetation successions are ecologically consistent with long-term cooling and (middle to high latitudes) drying trends in global climate. Although it is rarely possible to establish precise meteorological values for the individual sites along these gradients, climatic envelopes can be estimated for many localities. For example, during the Late Miocene-Pliocene, mean annual precipitation along the northern margin appear to range from 600 mm to 1500 mm in the Kimberley region of north-western Western Australia to above 2000-3000 mm on the Atherton Tableland, north-eastern Queensland. If these and other estimates are correct, then environments along the northern margin show only gradual (unidirectional?) change or did not fall below biologically critical thresholds during the Late Miocene and Early Pliocene but began to approach modern values during Late Pliocene time. Whether the observation implies that meteorological controls at this time were similar to modern synoptic scale systems is unknown. Climates along the southern margin were more labile. For example, there is unequivocal evidence that Early Pliocene climates in the Bass Strait region were effectively more humid and warmer than at present, possibly resembling conditions now found on the northern New South Wales and southern Queensland coast. This phase was preceded (weak evidence) and succeeded (strong evidence) by less temperate conditions during the Late Miocene and Late Pliocene respectively. Forcing factors appear to include changes in relative sea level, orographic effects and, speculatively, remote events such as the isolation and reconnection of the Mediterranean Sea to the world ocean. One promising direction for future research is provided by a recently located onshore basin in Western Australia which preserves an extraordinarily long (100 m), detailed sequence of Late Neogene palynofloras.

Extensive Phylogeographic and Morphological Diversity in Diporiphora nobbi (Agamidae) Leads to a Taxonomic Review and a New Species Description

“…australis/bilineata lineage occurring at a similar time (between 8 and 19 mya). Due to the similar timing of these events, it is likely that the developing aridity in Australia during the midlate Miocene, leading to dramatic changes in forest types (Bowler, 1976;Macphail, 1997;Kershaw et al, 2003), is associated with diversification of the eastern Australian Diporiphora australis-nobbi lineage. Previous analysis has suggested a northern origin for the D. australis lineage (Edwards and Melville, 2010), which has only recently been present in southern QLD and northern NSW as of the mid-late Pleistocene (Hocknull et al, 2007).…”

“…Both D. australis and D. nobbi currently occupy dry woodland habitats, habitats that rapidly expanded during the mid-late Miocene climate shift (Bowler, 1976;Macphail, 1997;Kershaw et al, 2003). Diporiphora phaeospinosa, in contrast, seems to be restricted to the wetter eucalypt forests in central southern QLD, a region harboring many endemic and relictual species of snail (A. F. Hugall, pers.…”

Biogeography and speciation of a direct developing frog from the coastal arid zone of Western Australia

“…The onset of aridity in Australia became entrenched in the southwest during the Late Miocene and was associated with an overall drop in sea-levels as well as a general drying of the continent (Macphail, 1997;Dodson and Macphail, 2004); consequently, vast new areas of coastal sand habitats formed and dune-building processes began (Hocking et al, 1987). The Pliocene saw a brief retreat of arid conditions (Dodson and Macphail, 2004) then a general trend of increasing fluctuation between wet to arid climates, with arid pulses gradually increasing in intensity across the Australian continent (Bowler, 1976;Kershaw et al, 1991;Macphail, 1997). Pleistocene climate fluctuations were associated with eustatically controlled sea-level transgression/regression cycles leading to massive changes in the occurrence and area of coastal sandplain and sand-dune habitats (Hocking et al, 1987;Mory et al, 2003).…”

A Tortonian (Late Miocene, 11.61–7.25Ma) global vegetation reconstruction

“…Location 212 at Lake Tay predicts this biome to have a 495 MAP of 1375±125 mm (Macphail, 1997), which was an increase of around 1100 mm/yr when 496 compared to modern data. A small area of temperate grassland was present in southeast Australia 497 (Site 214) and BIOME4 predicts coastal warm-temperate evergreen and mixed forest and temperate 498 needleleaf forest along the east coast (Fig.…”