Palynological evidence for the age of the Brewer Conglomerate, Amadeus Basin, central Australia

An assemblage of spores recovered from the Undandita Member of the Brewer Conglomerate, the uppermost unit of the Pertnjara Group in the Amadeus Basin of central Australia, establishes the age of that formation as Late Devonian. Comparison with spore assemblages from sedimentary basins in Western Australia indicates that the central Australian assemblage is dateable within the post-early Frasnian to pre-late Famennian interval. Fish remains and spores previously described from the Parke Siltstone at the base of the Pertnjara Group are of probable early Frasnian age, so it now appears that the entire group was deposited during the Late Devonian. The Brewer Conglomerate is of synorogenic origin, and was deposited during uplift associated with the Alice Springs Orogeny; the spore data thus indicate that this tectonic event began in the Late Devonian. Isotopic age determinations in the Arltunga Nappe Complex and the Strangways Range of the Arunta Block have yielded Early Carboniferous dates. These possibly reflect a later stage of deformation than that which was responsible for the deformation and folding of the Brewer Conglomerate

Banksia species (Proteaceae) from severely phosphorus-impoverished soils exhibit extremem efficiency in the use and re-mobilization of phosphorus

Banksia species (Proteaceae) occur on some of the most phosphorus (P)-impoverished soils in the world. We hypothesized that Banksia spp. maximize P-use efficiency through high photosynthetic P-use efficiency, long leaf lifespan (P residence time), effective P re-mobilization from senescing leaves, and maximizing seed P concentration. Field and glasshouse experiments were conducted to quantify P-use efficiency in nine Banksia species. Leaf P concentrations for all species were extremely low (0.14–0.32 mg P g−1 DM) compared with leaf P in other species reported and low relative to other plant nutrients in Banksia spp.; however, moderately high rates of photosynthesis (13.8–21.7 µmol CO2 m−2 s−1), were measured. Some of the Banksia spp. had greater P proficiency (i.e. final P concentration in senesced leaves after re-mobilization; range: 27–196 µg P g−1 DM) than values reported for any other species in the literature. Seeds exhibited significantly higher P concentrations (6.6–12.2 mg P g−1 DM) than leaves, and species that sprout after fire (‘re-sprouters’) had significantly greater seed mass and P content than species that are killed by fire and regenerate from seed (‘seeders’). Seeds contained only small amounts of polyphosphate (between 1.3 and 6 µg g−1 DM), and this was not correlated with P concentration or fire response. Based on the evidence in the present study, we conclude that Banksia species are highly efficient in their use of P, explaining, in part, their success on P-impoverished soils, with little variation between species.Matthew D. Denton, Erik J. Veneklaas, Florian M. Freimoser and Hans Lamber