Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

The Natural Variability Sub-program of the Co-operative Research Centre for Antarctic and Southern Ocean Environments aims to study past environmental change by examining ice core and sedimentary records in Antarctica and the Southern Ocean. As the first stage in marine sedimentological studies, Voyage 7 of the Australian National Antarctic Research Expeditions (ANARE) 1992/1993 shipping season included a geoscience program comprising echo sounder traverses, gravity coring and grab sampling of the Antarctic continental shelf and slope on the Mac. Robertson Shelf and in Prydz Bay. This record describes the preliminary results of the voyage and presents location information for core and grab samples and preliminary descriptions of grab samples and lists of subsamples taken by associated research programs.

Mawson is an Australian National Antarctic Research Expedition base on the Antarctic mainland managed by the Australian Antarctic Division. Geomagnetic and seismological recording and processing equipment was maintained and calibrated by an observer provided by the Australian Geological Survey Organisation (AGSO) during 1994. Earthquake phase data was reported weekly to AGSO and to the National Earthquake Information Service (Boulder, Colorado) via email. Magnetic results were reported monthly to AGSO, and to the French Department de Geomanetisme et Paleomagnetism for use in the Oersted magnetic satellite project. Magnetic results indicate the secular variation of the field at Mawson was relatively unchanged over the year, with a three nanoteslas decrease in total intensity and a 5.5 minute increase in westerly declination. Magnetic data recorded at the Casey and Davis Antarctic bases was processed by the Mawson observer and indicated similar relative stability.

This report describes both the geomagnetic and seismological observatories at Mawson. On the geomagnetic side, the routine of absolute field measurements and the variometer system are described; final geomagnetic data are also included. The seismological recording systems and procedures make up the bulk of the seismological report. Observatory timing, power supplies, and buildings are also described. The Australian Antarctic Division provided logistic support. The geomagnetic observatory was operated as part of project 27 and the seismological observatories as part of project 10.

An integrated analysis of biological and geoscientific data collected from the nearshore marine environment of the Vestfold Hills was used to identify benthic habitats and associated communities and examine relationships between benthic community composition and environmental characteristics. A 48 km2 area was surveyed using a multibeam echosounder system (MBES) to produce high-resolution bathymetry and backscatter intensity maps of the seabed. Epibenthic community data and in situ observations of substrate composition and seafloor bedforms and features were obtained from towed underwater video. A comparison of top-down and bottom-up approaches to defining benthic habitats was used to improve understanding of the applicability of mapping methodologies. On a broad scale, both approaches produced habitat classes distinguished largely by geomorphic features, with substrate and depth identified as the main controls of benthic community composition, however, the relationship between benthic community composition and environmental characteristics is complex with many variables contributing to differences in community composition. The top-down approach was based on geomorphic units defined using abiotic characteristics and the assemblages identified within the geomorphic were very broad did not always show clear distinction between assemblages. Conversely, the bottom-up approach generated additional habitat classes, identified clear defining taxa for each class, greater distinction between the benthic communities, and allowed identification of additional environmental factors (i.e. sea ice cover) that influence benthic community distribution that are not discernible from geomorphic information alone. The habitat types identified and mapped using the bottom-up approach include shallow boulder fields and exposed bedrock which are dominated by dense macroalgae communities, and steep slopes, muddy basins and sandy plains which are dominated by invertebrate communities. The results indicate that a bottom-up approach is preferable for benthic habitat mapping, however, where detailed information is not available, geomorphic information provides a reasonable indication of the distribution of benthic habitats and communities. This study highlights the utility of multibeam sonar for interpretation of sea floor morphology and substrate and the multibeam data provide a physical framework for understanding benthic habitats and the distribution of benthic communities. This research provides the scientific context and spatial framework for managing the Vestfold Hills nearshore marine environment and provides a baseline for assessing environmental change.