Proposed Programme

The WAVE project was conceived with a view to understanding the volcanic and geochemical evolution of intraplate volcanoes in West Antarctica and to comparing volcanism and lithospheric structure of West Antarctica with documented parallels In the Ross Sea Embayment. The 1989 - 1990 field season specifically targeted the ECR (77° 15′ S, 126° 30′ W - 76° 15′ S, 126° W) for a number of reasons: 1/ ECR contains some of the youngest volcanism in West Antarctica. 2/ The volcanoes are large and, in the case of Mt. Sidley, particularly well exposed. 3/Reconnaissance sampling indicated considerable compositional range (from basalt to phonolite and peralkali rhyolite). 4/ Lithospheric xenoliths had been reported from one volcano (Mt. Cumming) in the range.

For the 1989/90 season the aim was to study all the volcanoes of the ECR (Mts. Waesche, Sidley, Hartigan, Cumming and Hampton) together with a projected visit to the USAS Escarpment. Delays due to availability of logistic support and poor weather led to curtailment of the field programme by approximately 50%. As a result, the field programme concentrated on Mt Waesche and Mt Sidley at the south end of the range. The reasoning behind this decision was simple: The reconnaissance work and radiometric dating studies (see Le Masurier and Rex 1989) indicated that Mt Sidley (at 4181m the highest volcano in Antarctica) and Mt Waesche were relatively young, the latter yielding rocks < 1ma. Consequently we were keen to ascertain whether any were currently active. Furthermore, these volcanoes are relatively close together offered superior exposure to the other volcanoes and showed compositional variation similar to the volcanoes of the Mc Murdo Volcanic Group.

Scientific Endeavours and Achievements

Despite the foreshortened field season the WAVE party can claim to have completed a very successful programme. Detailed geological mapping was completed on Mt Waesche and Mt Sidley and this work supplemented by extensive sampling for geochronological and geochemical study. At Mt Waesche the very young nature of volcanism was confirmed by the discovery of primary tephra layers in blue ice adjacent to the volcano. Eruptions from both Waesche and Sidley appear to have been dominantly subaerial, punctuated, at least on Mt Sidley, by periods of subaqueous or subglacial volcanism, leading to formation of hyaloclastite. The stratigraphic records of both volcanoes contain evidence for explosive and passive effusive volcanism. Both Mt Waesche and Mt Sidley have spectacular calderas (15 km across in N. Waesche and 6-7 km across in Sidley) and measured sections on the north and west caldera walls of Mt Sidley have yielded near vertical sections through 1000m of exposed rock. These sections provide a detailed record of the construction of the volcanoes and indicate evolution through an early effusive phase culminating in explosive volcanism and eruption of pyroclastic flows which accompanied caldera formation. Waning activity on both Sidley and Waesche saw development of small, broadly basaltic, scoria cones peppering the volcanic edifice. The phonolitic lavas which form a large portion of the early succession on Mt Sidley contain phenocrysts (up to 100mm) of anorthoclase and are strikingly similar to those of Mt Erebus. Thus, the observations on the ECR volcanoes may have important implications for the future evolution of active volcanoes such as Mt Erebus in the Ross Sea Embayment.

Lithospheric xenoliths have been recovered from sites on Mt Waesche (3), Mt Sidley (7) and Mt Cumming (1). Of the sites on Waesche, two consist of plutonic blocks (probably of subvolcanic origin) and supracrustal granitoids which arguably comprise basement to ECR, the third site contains a mixture of lower crustal (granulites) and plutonic blocks. No ultramafic materials were recovered from xenolith localities on Mt Waesche. On Mt Sidley, three of the seven localities yielded subvolcanic and supracrustal xenoliths exclusively. The remaining four yielded a variety of granulites ranging from mafic to felsic and presumably of lower crustal origin. Two of these four sites also contained rare peridotites. A partly eroded basalt scoria cone on Mt Cumming yielded a rich assemblage of texturally variable spinel Iherzolites.

Publications

As this is the first season of the WAVE programme, essential laboratory work has not yet commenced. Summaries of the field seasons work will be submitted for publication in "The Antarctic Record" in the U.S. Antarctic Journal and in the equivalent BAS journal.

Environmental Impact

Apart from removal of rock specimens for scientific purposes the impact on the environment is assessed as negligible. All non-burnable rubbish (cans, plastics, etc) was removed to Mc Murdo. Human waste was buried.

Future Research

A follow-up field season for the WAVE project is projected for 1990/91 and a proposal to this effect has been submitted to RDRC. Put-in sites have yet to be finalised between US - BAS - NZARP contingents and we intend to consult with the MBL Tectonics (Bradshaw-Dalziel, etc) parties before finalising these details. At present we identify Mt Murphy and the Flood Range as prime objectives for 1990 - 1991. This may necessitate a mid season move.

Management of Science In the Ross Dependency

The WAVE project incorporated scientists from three national Antarctic research programmes (USAP, BAS and NZARP). My impression of the 1989/90 season was that, apart from the delayed field access, it was a very successful season. The scientific interests of the three groups were complimentary.