Michael Macphail

Luminescence dating of rock art and past environments using mud-wasp nests in northern Australia

Mud-nesting wasps are found in all of the main biogeographical regions of the world, and construct nests that become petrified after abandonment. Nests built by mud-dauber and potter wasps in rock shelters in northern Australia, often overlie, and occasionally underlie, prehistoric rock paintings. Mud nests contain pollen, spores and phytoliths from which information about local palaeovegetation can be gleaned. Here we report a new application of optical dating, using optically stimulated luminescence (OSL), and accelerator mass spectrometry (AMS) 14C dating of pollen to determine the ages of mud-wasp nests associated with rock paintings in the Kimberley region of Western Australia,. Optical dating of quartz sand (including the analysis of individual grains) embedded in the mud of fossilized nests shows that some anthropomorphic paintings are more than 17,000 years old. Reconstructions of past local environments are also possible from the range of pollen and phytolith types identified. This approach should have widespread application to studies of rock-art dating and late Quaternary environmental change on continents where mud-wasps once lived and other sources of palaeoecological information are absent.

Palynostratigraphy of the murray basin, inland Southeastern Australia

Abstract To date, the only published comprehensive zonation for dating and correlating late Tertiary non‐marine sequences in Australia is that developed in the 1970s for the offshore Gippsland Basin on the extreme southeastern margin of the continent. In this paper an analogous zonation scheme is presented for the Murray Basin, a large intracratonic basin that covers some 300 000 km2 of inland New South Wales, Victoria and South Australia. Major spore and pollen sequences identified within this basin correspond with major periods of marine transgression‐regression, in the middle Eocene to early Oligocene, early Oligocene to middle Miocene and late Miocene to Pliocene. Presence/absence data allow the first two sequences to be subdivided into palynological zones that can be confidently correlated with zones established for the Gippsland Basin, viz., equivalents of the middle to late Eocene lower, middle and upper Nothofagidites asperus zones, and the Oligocene to middle Miocene Proteacidites tuberculatus an...

Age and palaeoenvironmental constraints on the genesis of the Yandi channel iron deposits, Marillana Formation, Pilbara, northwestern Australia*

Fossil pollen and spores preserved in organic‐rich claystones near the base of the palaeochannel hosting the Tertiary Yandi channel iron deposits (CID) provide an in situ constraint on the age of this world‐class orebody. This assemblage also aids understanding of the palaeoenvironment leading to the deposition and preservation of the host Marillana Formation. The provisional Early Oligocene age of claystones links the genesis of the Yandi CID to the profound disruption of global climates and oceanography at the Eocene‐Oligocene transition (Terminal Eocene Event) and provides circumstantial evidence that ore formation was linked to the development of a warm south‐flowing proto‐Leeuwin Current along the Pilbara coast. It is likely that rainfall increased but remained strongly seasonal (monsoonal?) as global climates warmed during the Late Oligocene — Early Miocene. The same fossil evidence indicates that wood fragments, the iron‐oxide‐replaced remains of which are a significant component of cemented goethitic gravel making up CID, came from Casuarinaceae‐ and Myrtaceae‐dominated sclerophyll communities lining the channel banks. Increasingly dry conditions since the late Early Miocene Climatic Optimum are likely to have contributed to the preservation of CID at Yandi.

Eocene Nypa from Regatta Point, Tasmania

A new species of the mangrove palm Nypa, N. australis, is formally described from Lower Eocene sediments from near Strahan, western Tasmania. Fossil material comprises fronds (with cuticle), fruits, and pollen. Coming from a paleolatitude of approximately 65°S, it is the most polar Nypa known.

Polar forests on the edge of extinction: what does the fossil spore and pollen evidence from East Antarctica say?

Diverse pollen and spore assemblages, spanning the Late Eocene preglacial–glacial transition, have been recovered from Ocean Drilling Program cores from Prydz Bay, East Antarctica. These microfloras are mostly in situ and provide an unparalleled record of terrestrial plant communities growing in Antarctica during the earliest stages of ice-cap formation. The evidence provides a basis for assessing the phytogeographic relationships of the Antarctic floras with other high-latitude floras in the southern hemisphere, including possible migration routes for some taxa. Preliminary studies (Macphail and Truswell 2004a) suggested the Late Eocene vegetation at Prydz Bay was floristically impoverished rainforest scrub, similar to Nothofagus–gymnosperm communities found near the climatic treeline in Patagonia and Tasmania. Re-evaluation of the microfloras indicates the diversity of shrubs, especially Proteaceae, was underestimated and the Late Eocene vegetation was a mosaic of dwarfed (krumholtz) trees, scleromorphic shrubs and wetland herbs, analogous to the taiga found in the transition zone between the boreal conifer forest and tundra biomes across the Arctic Circle. Microfloras similar to although much less diverse than the Prydz Bay assemblages occur in coreholes from the Ross Sea region on the opposite side of Antarctica. Interpretation of the latter is complicated by reworking and low yields but the combined evidence points to the collapse of taller woody ecosystems during the Eocene–Oligocene transition and their replacement by tundra-like or fell-field vegetation during the Oligocene and Neogene. This temperature-forced regression seems to have been broadly synchronous across the continent. The high-palaeolatitude location (~70°S) means that the Prydz Bay flora was adapted to several months of winter darkness and short-summer growing seasons. The nearest living relatives of identifiable woody taxa suggest year-round high humidity, with an annual precipitation between ~1200 and 1500 mm. Palaeotemperatures are more difficult to quantify although the inferred humid microtherm climate is consistent with mean annual temperatures less than 12°C and freezing winters.

Glacial climates in the Antarctic region during the late Paleogene: Evidence from northwest Tasmania, Australia

Published data suggest that ice buildup commenced in Antarctica during the late middle Eocene. This predates by 30 m.y. the earliest evidence of Cenozoic glaciation on other fragments of Gondwana, although several of these were at high latitudes during the Paleogene. We provide new evidence for local glacier development during the late Paleogene in Tasmania, then a mountainous peninsula at about lat 55°-63°S projecting into the circum-Antarctic ocean. The date of glaciation is not precisely known, but an earliest Oligocene age is indicated. We suggest that episode may correlate with abrupt cooling of the sea surface surrounding Antarctica during the earliest Oligocene (36 Ma).

A MIDDLE-LATE EOCENE INFLORESCENCE OF CARYOPHYLLACEAE FROM TASMANIA, AUSTRALIA'

A new genus and species (Caryophylloflora paleogenica genus and species nova G. J. Jord. & Macphail) are proposed for a fossil inflorescence found in Middle-Late Eocene sediments at Locharbour, northeastern Tasmania, Australia. A parsimony analysis of 75 extant species of the order Caryophyllales and five outgroups placed the fossil within Caryophyllaceae, either subfamily Alsinoideae or Caryophylloideae. The analysis used molecular (rbcL and/or matK), morphological, and anatomical data for the extant species and morphological data for the fossil. Tests on extant species imply that the placement of the fossil should be convincing. The fossil appears to be of a lineage distinct from any extant Australian Caryophyllaceae. In situ pollen are consistent with the form species, Periporopollenites polyoratus. This relatively simple pollen type first appears in Australia and New Zealand in the Late Cretaceous, the oldest known record of the Caryophyllaceae. The last appearance of P. polyoratus in Australia is in the Oligocene, and extant Australian members of the Caryophyllaceae are best interpreted as having evolved from species that dispersed from elsewhere during the Neogene or Quaternary.

Sedimentology and stratigraphy of an intra-cratonic basin coal seam gas play: Walloon Subgroup of the Surat Basin, eastern Australia

Large gas reserves are trapped in the coals of the Middle Jurassic (Callovian) Walloon Subgroup (lower part of the Injure Creek Group) in the Surat Basin, eastern Australia. The series is divided into the Juandah Coal Measures (upper), Tangalooma Sandstone and Taroom Coal Measures (lower). The upper and lower units are locally further subdivided. These economically important coals were deposited in an alluvial plain setting within an interior basin, which has no recorded contemporaneous marine influence. The coals are typically bituminous, perhydrous and low rank with a high volatile content. Despite individual ply (bench) thicknesses typically less than a metre, series of plies or seams of coals up to 10 m thick have historically been tentatively correlated across the entire play area (over 150 km).

Near-tropical early eocene terrestrial temperatures at the Australo-Antarctic margin, western Tasmania

A worldwide greenhouse warm climate prevailed in the Early Eocene, and nowhere was warming more dramatic than at high latitudes. Sea-surface temperatures of ∼34 °C have been estimated for a site at paleolatitude 65°S on the East Tasman Plateau of the southwest Pacific Ocean, but these estimates require independent validation, including from terrestrial proxies. Here we determine a near-tropical terrestrial mean annual temperature estimate of ∼24 °C at sea level for an Early Eocene site in Tasmania, Australia, using three proxies based on well-dated estuarine plant fossils. This estimate is lower than the nearby sea estimates to the east, but similarly suggests that, as in the southwest Pacific, Early Eocene climates in the eastern Australo-Antarctic region were warmer than inferred elsewhere at high latitudes, including on the Antarctic Peninsula. Such data are essential for improving our understanding of climatic and biotic evolution in the Southern Hemisphere.

Fossil evidence for open, Proteaceae-dominated heathlands and fire in the Late Cretaceous of Australia

PREMISE OF THE STUDY The origin of biomes is of great interest globally. Molecular phylogenetic and pollen evidence suggest that several plant lineages that now characterize open, burnt habitats of the sclerophyll biome, became established during the Late Cretaceous of Australia. However, whether this biome itself dates to that time is problematic, fundamentally because of the near-absence of relevant, appropriately aged, terrestrial plant macro- or mesofossils. METHODS We recovered, identified, and interpreted the ecological significance of fossil pollen, foliar and other remains from a section of core drilled in central Australia, which we dated as Late Campanian-Maastrichtian. KEY RESULTS The sediments contain plant fossils that indicate nutrient-limited, open, sclerophyllous vegetation and abundant charcoal as evidence of fire. Most interestingly, >30 pollen taxa and at least 12 foliage taxa are attributable to the important Gondwanan family Proteaceae, including several minute, amphistomatic, and sclerophyllous foliage forms consistent with subfamily Proteoideae. Microfossils, including an abundance of Sphagnales and other wetland taxa, provided strong evidence of a fenland setting. The local vegetation also included diverse Ericaceae and Liliales, as well as a range of ferns and gymnosperms. CONCLUSIONS The fossils provide strong evidence in support of hypotheses of great antiquity for fire and open vegetation in Australia, point to extraordinary persistence of Proteaceae that are now emblematic of the Mediterranean-type climate southwestern Australian biodiversity hotspot and raise the profile of open habitats as centers of ancient lineages.