Alex R. Pyne

Downwasting of the Tasman Glacier, South Island, New Zealand: Changes in the terminus region between 1971 and 1993

Abstract Downwasting has altered the morphology of the terminus region of the Tasman Glacier between 1971 and 1993. Rapid melting began in the late 1960s in a few isolated melt ponds in the centre and in a small elongated lakelet at the eastern lateral moraine. These ponds and lakes grew rapidly in size during the 1970s and coalesced to form a large melt lake by about 1990. This melting has led to a disintegration of the entire terminus region, and now occurs as far as 3 km upstream from the old terminus. The main front of the glacier has retreated c. 1.5 km since 1982. The breaking up of the glacier has been accelerated by the onset of iceberg calving—a process which probably started in 1991. The icebergs can have volumes of several millions of cubic metres before they break up into smaller ice masses that melt slowly during the summer. A temperature survey has shown that the melt lake is almost isothermal (0.3–0.5°C). A poorly understood convection mechanism prevents suspended silt from settling and cau...

Antarctic Drilling Recovers Stratigraphic Records From the Continental Margin

The Antarctic Geological Drilling (ANDRILL) program—a collaboration between Germany, Italy, New Zealand, and the United States that is one of the larger programs endorsed by the International Polar Year (IPY; http://www.ipy.org)—successfully completed the drilling phase of the Southern McMurdo Sound (SMS) Project in December 2007. This second drill core of the programs campaign in the western Ross Sea, Antarctica, complements the results of the first drilling season [Naish et al., 2007] by penetrating deeper into the stratigraphic section in the Victoria Land Basin and extending the recovered time interval back to approximately 20 million years ago.

Observations of sea-level variability in Ross Sea, Antarctica

Abstract Data from a new sea‐level recorder station at Scott Base on Ross Island and from a long‐established sea‐level recorder at Cape Roberts are analysed for tides and storm surge. Tides are primarily diurnal and their amplitude reduces to almost zero every 13.66 days, corresponding to the Moons crossing of the equator. Global tide models are shown to give a poor fit with observations in Ross Sea, and although a local tide model gives a better fit for phase, the amplitudes are still not accurate. The only atmospheric tide that is significant is the semidiurnal solar tide whose amplitude is much larger than empirical models predict. Storm surge can be largely explained by changes in atmospheric pressure. Significant storm surge events are infrequent compared to locations at lower latitudes.

Bedrock geology of DFDP-2B, central Alpine Fault, New Zealand

ABSTRACT During the second phase of the Alpine Fault, Deep Fault Drilling Project (DFDP) in the Whataroa River, South Westland, New Zealand, bedrock was encountered in the DFDP-2B borehole from 238.5–893.2 m Measured Depth (MD). Continuous sampling and meso- to microscale characterisation of whole rock cuttings established that, in sequence, the borehole sampled amphibolite facies, Torlesse Composite Terrane-derived schists, protomylonites and mylonites, terminating 200–400 m above an Alpine Fault Principal Slip Zone (PSZ) with a maximum dip of 62°. The most diagnostic structural features of increasing PSZ proximity were the occurrence of shear bands and reduction in mean quartz grain sizes. A change in composition to greater mica:quartz + feldspar, most markedly below c. 700 m MD, is inferred to result from either heterogeneous sampling or a change in lithology related to alteration. Major oxide variations suggest the fault-proximal Alpine Fault alteration zone, as previously defined in DFDP-1 core, was not sampled.

Antarctic Cenozoic climate history from sedimentary records: ANDRILL and beyond.

Mounting evidence from models and geological data implies that the Antarctic Ice Sheet may behave in an unstable manner and retreat rapidly in response to a warming climate, which is a key factor motivating efforts to improve estimates of Antarctic ice volume contributions to future sea-level rise. Here, we review Antarctic cooling history since peak temperatures of the Middle Eocene Climatic Optimum (approx. 50 Ma) to provide a framework for future initiatives to recover sediment cores from subglacial lakes and sedimentary basins in Antarcticas continental interior. While the existing inventory of cores has yielded important insights into the biotic and climatic evolution of Antarctica, strata have numerous and often lengthy time breaks, providing a framework of ‘snapshots’ through time. Further cores, and more work on existing cores, are needed to reconcile Antarctic records with the more continuous ‘far-field’ records documenting the evolution of global ice volume and deep-sea temperature. To achieve this, we argue for an integrated portfolio of drilling and coring missions that encompasses existing methodologies using ship- and sea-ice-/ice-shelf-based drilling platforms as well as recently developed seafloor-based drilling and subglacial access systems. We conclude by reviewing key technological issues that will need to be overcome.

Geology of the Mt Fleming area, South Victoria Land, Antarctica

Abstract Abstract The Mt Fleming area has extensive exposures of strata of the Beacon Supergroun (Devonian-Late Triassic) and Ferrar Dolente (Early-Middle Jurassic) which dip 3-6° northwest. The area is crossed by a vertical northeast-striking fault which has a maximum throw of 270 m at the eastern end of Mt Fleming.The throw decreases southwestwards, reaching zero vertical displacement at Horseshoe Mountain. Drag folding associated with the fault has locally tilted strata to produce dips of up to 45°. The fault is considered to result from intrusion of a dolerite sill, at least 270 m thick, into lower Beacon Heights Ortho-quartzite,which is not exposed at Mt Fleming but forms bluffs in the Airdevronsix Icefalls 3 km to the east.The increase of throw northeastwards along the fault indicates intrusion of the sill from the NNE.