Particle fluxes at sediment traps AU9701, south of Australia

Sediment trap moorings were deployed from September 21, 1997 through February 21, 1998 at three locations south of Australia along 140°E: at -47°S in the central Subantarctic Zone (SAZ) with traps at 1060, 2050, and 3850 m depth, at -51°S in the Subantarctic Front with one trap at 3080 m, and at -54°S in the Polar Frontal Zone (PFZ) with traps at 830 and 1580 m. Particle fluxes were high at all the sites (18-32 g/m**2/yr total mass and 0.5-1.4 g organic carbon/m**2/yr at -1000 m, assuming minimal flux outside the sampled summer period). These values are similar to other Southern Ocean results and to the median estimated for the global ocean by Lampitt and Antia [1997], and emphasize that the Southern Ocean exports considerable carbon to the deep sea despite its 'high-nutrient, low chlorophyll' characteristics. The SAZ site was dominated by carbonate (>50% of total mass) and the PFZ site by biogenic silica (>50% of total mass). Both sites exhibited high export in spring and late summer, with an intervening low flux period in December. For the 153 day collection period, particulate organic carbon export was somewhat higher in all the traps in the SAZ (range 0.57-0.84 gC/m**2) than in the PFZ (range 0.31-0.53), with an intermediate value observed at the SAF (0.60). The fraction of surface organic carbon export (estimated from seasonal nutrient depletion, Lourey and Trull [2001]) reaching 1000 m was indistinguishable in the SAZ and PFZ, despite different algal communities.

Middle Miocene mineralogical events of Marion Plateau, northeast of Australia

Three ODP sites located on the Marion Plateau, Northeast Australian margin, were investigated for clay mineral and bulk mineralogy changes through the early to middle Miocene. Kaolinite to smectite (K/S) ratios, as well as mass accumulation rates of clays, point to a marked decrease in accumulation of smectite associated with an increase in accumulation of kaolinite starting at ~15.6 Ma, followed by a second increase in accumulation of kaolinite at ~13.2 Ma. Both of these increases are correlative to an increase in the calcite to detritus ratio. Comparison of our record with published precipitation proxies from continental Queensland indicates that increases in kaolinite did not correspond to more intense tropical-humid conditions, but instead to periods of greater aridity. Three mechanisms are explored to explain the temporal trends in clay on the Marion Plateau: sea-level changes, changes in oceanic currents, and denudation of the Australian continent followed by reworking and eolian transport of clays. Though low mass accumulation rates of kaolinite are compatible with a possible contribution of eolian material after 14 Ma, when Australia became more arid, the lateral distribution of kaolinite along slope indicates mainly fluvial input for all clays and thus rules out this mechanism as well as oceanic current transport as the main controls behind clay accumulation on the plateau. We propose a model explaining the good correlation between long-term sea-level fall, decrease in smectite accumulation, increase in kaolinite accumulation and increase in carbonate input to the distal slope locations. We hypothesize that during low sea level and thus periods of drier continental climate in Queensland, early Miocene kaolinite-rich lacustrine deposits were being reworked, and that the progradation of the heterozoan carbonate platforms towards the basin center favored input of carbonate to the distal slope sites. The major find of our study is that increase kaolinite fluxes on the Queensland margin during the early and middle Miocene did not reflect the establishment of a tropical climate, and this stresses that care must be taken when reconstructing Australian climate based on deep-sea clay records alone.

Surface in situ measurements of atmospheric CO, CH4, and CO2 combined with selected meteorological measurements at the University of Wollongong, Australia

Wollongong, Australia is an urban site at the intersection of anthropogenic, biomass burning, biogenic and marine sources of atmospheric trace gases. The location offers a valuable opportunity to study drivers of atmospheric composition in the Southern Hemisphere. Here, a record of surface carbon monoxide (CO), methane (CH4) and carbon dioxide (CO2) was measured with an in situ Fourier transform infrared trace gas analyser between April 2011 and August 2014. Clean air was found to arrive at Wollongong in approximately 10% of air masses. Biomass burning influence was evident in the average annual cycle of clean air CO during austral spring. A significant negative short-term trend was found in clean air CO (-1.5 nmol/mol/a), driven by a reduction in northern Australian biomass burning. Significant short-term positive trends in clean air CH4 (5.4 nmol/mol/a) and CO2 (1.9 ?mol/mol/a) were consistent with the long-term global average trends. Polluted Wollongong air was investigated using wind-direction/wind-speed clustering, which revealed major influence from local urban and industrial sources from the south. High values of CH4, with anthropogenic DCH4/DCO2 enhancement ratio signatures, originated from the northwest, in the direction of local coal mining. A pollution climatology was developed for the region using back trajectory analysis and DO3/DCO enhancement ratios. Ozone production environments in austral spring and summer were associated with anticyclonic meteorology on the east coast of Australia, while ozone depletion environments in autumn and winter were associated with continental transport, or fast moving trajectories from southern latitudes. This implies the need to consider meteorological conditions when developing policies for controlling air quality.

Lower Cretaceous dinoflagellate cysts of Exmouth Plateau, Nortwest Australia

Cores from Leg 122, Sites 762 and 763, were sampled at intervals of one sample per 1.5-m section in the Lower Cretaceous sequences. More than 400 samples were studied, most of which contained dinoflagellate cysts, spores, pollen, and various types of palynoclasts. From the entire palynomorph assemblage mainly dinoflagellate cysts were studied to give a stratigraphic outline for the Lower Cretaceous. Stratigraphic units were interpreted in terms of zones in use for the Jurassic and Cretaceous of Australia. At both sites a condensed Valanginian to Aptian sequence and an expanded middle to late Berriasian sequence containing a rich microplankton assemblage were recovered. Sites 762 and 763 can be correlated with each other and with the wells Eendracht-1 and Vinck-1.

Composite of coastal seagrass meadows in Queensland, Australia - November 1984 to June 2010

Approximately 18,400 km**2 of seagrass habitat has been mapped within the coastal waters (<15 m) of Queensland (Australia) between November 1984 and June 2010. The total seagrass meadow distribution was calculated by merging maps from 115 separate mapping surveys (varying locations and dates). Due to tropical seagrass dynamism, meadow distribution can change seasonally and between years, and as a consequence, the composite represents the maximum area of seabed where seagrass has been observed/recorded. Mapping survey methodologies followed standardised global seagrass research methods (McKenzie et al. 2001) where the presence of seagrass was determined from in situ visual assessment of the seabed by either divers or drop cameras at GPS marked positions. Seagrass meadow boundaries were determined based on the positions of survey sites and the presence of seagrass, coupled with depth contours and remote sensing (e.g. aerial photography) where available. The merged meadow boundary accuracy was dependent on the original survey maps and varied from 10-100 m. The resulting composite seagrass distribution was saved as an ArcMap polygon shapefile, and projected to Geocentric Datum of Australia GDA94.