1992 WAMET/EUROMET Joint Expedition to Search for Meteorites in the Nullarbor Region, Western Australia

The Nullarbor Region is a limestone desert in the south of Australia. It forms part of the larger Eucla Basin, which straddles the border between South Australia and Western Australia. The portion of the Eucla Basin lying in Westem Australia covers an area of about 104,000 km^2 (Bevan and Binns, 1989) and meteorites have been recovered from this region since 1971, new material being deposited at the Western Australia Museum. Between 21/3/92 and 6/4/92 a joint expedition between the Western Australia Museum and EUROMET recovered approximately 440 specimens of meteorites (total mass 13206 g) and 297 tektites. The expedition, whose members were Claude Perron (Paris), Christian Koeberl (Vienna), Georg Delisle (BGR Hannover), Gian- Paolo Sighinolfi (Modena), and Andrew Morse (OU) for Euromet, together with Wayne Smith (Australian Army) and Tom Smith (Perth Astronomical Observatory), was led by Dr Alex Bevan of the Western Australia Museum. Searching was carried out on foot with the participants spread out in a line with a 10-m spacing, walking along a compass bearing for approximately 10 km and back each day. Eight collecting regions were used, with a stop of about 2 days at each camp. Half of the searching was done near known strewn fields in order that the team become practised. Thus the expedition collected material at the following known sites. Camel Donga, Eucrite: The initial recovery was made in 1984 (Cleverly et al., 1986). The strewn field is about 8 km by 2-3 km at coordinates 30 degrees 19'S, 126 degrees 37'E. This expedition recovered 65 stones weighing a total of 2456 g, plus one stone of 4.8 g that was clearly chondritic in hand specimen. Mulga (north), H6: The initial recovery was made in 1964 (McCall, 1968). The strewn field is 8 km by 2 km at coordinates 30 degrees 11'S, 126 degrees 22'E and on this expedition 5 stones were recovered with a weight of 548 g. Also 110 stones (total mass 1535 g) that are certainly not H6 were found within a 100-m radius of coordinates 30 degrees 10'S, 126 degrees 24'E but could be paired with Billygoat Donga, an L6 ordinary chondrite (McCall and Cleverly, 1968). Three other specimens may possibly be part of the Mulga (west) or Mulga (south) strewn fields, or may be new meteorites. Mundrabilla, Anomalous Iron (de Laeter, 1972): 171 fragments were found, weighing a total of 7450 g in the vicinity of coordinates 30 degrees 46'S, 127 degrees 50'E. Eighty five other meteorite specimens were recovered from previously unsearched locations with a total weight of 1217 g. As no concentration/movement mechanism is involved, pairing is much easier than for the Antarctic and from a total of 89 new stones various estimates suggest between 20-40 new meteorites. The Nullarbor Region has proved to be a prolific collecting region and with the specimens collected in this expedition, is second only to Antarctica in terms of productivity for the recovery of meteorites. At present, all the specimens recovered, excluding tektites, are on loan from the Western Australian Museum to EUROMET and are held at the curatorial facility at The Open University for purposes of classification. Forty of the most promising stones are being prepared as PTSs, hopefully in time for identification to be announced at the conference. Acknowledgment: EUROMET is supported by the EC through its SCIENCE (Twinning and operations) programme; contract no.: SCI* - CT91- 0618(SSMA). References: Bevan A. W. R. and Binns R. A. (1989) Meteoritics 24, 127-133. Cleverly W. H., Jarosewich E. and Mason B. (1986) Meteoritics 21, 263-269. de Laeter J. R. (1972) Meteoritics 7, 285-294. McCall G. J. H. (1968) First Suppl. West. Austr. Mus. Spec. Publ. 3, 12. McCall G. J. H. and Cleverly W. H. (1968) Mineralog. Mag. 36, 691-716.