The occurrence of driftwood trees or parts of trees, without any signs of anthropogenic association, that is cutting and/or dressing, in southern polar regions has been documented by Lewis Smith (Reference Lewis Smith1985 and references therein). That account related particularly to stranded tree trunks or branches on sub-Antarctic South Georgia (53°58′–54°53′S, 38°01′–35°47′W), and maritime Antarctic islands in the South Sandwich Islands (Candlemas Island 57°04′S, 26°41′W) and South Shetland Islands (61°00′–63°20S, 54°00–62°45′W). All identified timbers were of southern South American provenance and predominantly of species of southern beech (Nothofagus betuloides, N. pumilio and possibly N. obliqua). Subsequently several other Nothofagus trunks have been found embedded in raised beaches in the maritime Antarctic, three of which are reported here.
In January 1987 a branched irregular trunk of a species of Nothofagus, 5.6 m long and ranging from 34 cm to 25 cm diameter, was found emerging from a late snow bank on a raised cobble beach circa 2.5 m above high tide mark in a cove at Williams Point, Livingston Island, South Shetland Islands (62°27′S, 60°09′W). The trunk was worn smooth by the action of water and white in colour. It was abundantly pitted by toredo ‘worm′ holes indicating that it had been in the sea for some considerable time before being washed ashore.
The basal part of two trunks identified as Nothofagus spp. of Fuegian origin were found on the western coast of the Antarctic Peninsula. In 1993 a large piece of the base of a tree trunk emerged from a receding ice cap on Black Island, the southernmost of the Argentine Islands archipelago (65°16′S, 64°17′W), 1200 km south of Tierra del Fuego. Two years later a similar piece of basal tree trunk emerged from a receding icefield at Rothera Point, Adelaide Island (67°34′S, 68°08′W), 1600 km south of Tierra del Fuego. Both were on raised cobble beaches about 2.5 m above sea level. The Black I. specimen was about 15 m from the high water shoreline and the Rothera Point specimen about 50–70 m from the shore.
Of particular interest is determining the provenance of these logs. All previous records of Nothofagus logs found on raised beaches on sub-Antarctic islands and the South Shetland Islands originated from southern South America. Transport by the prevailing ocean currents can easily explain their eastward drift, hence their occurrence on the south-western side of the Falkland Islands, South Georgia, Marion Island, Tasmania and Macquarie Island (Barber and others Reference Barber, Dadswell and Ingle1959; van Zinderen Bakker Reference van Zinderen Bakker, van Zinderen Bakker, Winterbottom and Dyer1971; Lewis Smith Reference Lewis Smith1985). Aided by north-south gales flotsam can cross Drake Passage to reach the shores of the South Shetland Islands. Surprisingly, no logs have been reported from the South Orkney Islands. However, the occurrence of logs far to the south of the South Shetland Islands raises the question of whether their provenance could have been from New Zealand, where Nothofagus is also a widespread genus. Trans-Pacific crossing on the west wind drift seems a logical explanation to transport the logs to the Antarctic Peninsula.
Although identification to species has not been possible their anatomical features are as follows:
Black Island log. Cells diffuse porous; rays mainly uniseriate with a few biseriate; vessels with spiral thickening, mainly in radial multiples of 1–5 (up to 8), tylosed; fibres thin-walled; axial parenchyma apparently absent.
Rothera Point log. Cells semi ring porous; rays 1–2 seriate but sometimes 2–4 seriate; vessels in multiples of 1–8, with spiral thickening, tylosed; fibres occasionally septate; axial parenchyma diffuse.
These details are consistent with both taxa being Nothofagus but they do not fit any of the New Zealand species. A key diagnostic feature is that no New Zealand species has spiral thickening in the vessels (Patel Reference Patel1986), although species from New Caledonia do but the vessels are much wider than in the South American species (J.M. Harris, personal communication, 15 August 1996). The conclusion is that the two Antarctic Peninsula logs are of South American origin, probably from Tierra del Fuego. Here, N. antarctica, N. betuloides and N. pumilio occur to sea level throughout much of the archipelago, but forests dominated by each exhibit an altitudinal succession with N. betuloides at the lower altitudes and N. antarctica at the highest where it also develops a stunted krummholz form at the treeline. The former two extend to the most southerly islands (McQueen Reference McQueen1976; Moore Reference Moore1983). However, the separation of N. betuloides and N. pumilio on the basis of wood anatomy is unreliable. The anatomical characters were inconsistent with N. antarctica, while a fourth species, N. obliqua, occurs predominantly in northern Patagonia.
To date, these specimens represent the most southerly records of naturally transported driftwood that show no sign of human intervention. What remains unknown is whether the Antarctic Peninsula logs moved directly southwards to their present locations possibly during prolonged storms, or whether they could have circumnavigated the Southern Ocean on a slightly southerly trajectory to come ashore on the west side of the Antarctic Peninsula. Even more curious is the circuitous route that the more southerly log would have taken. It must first have reached the waters off the western side of Adelaide Island, drifted around the island's southern tip and then northwards across Marguerite Bay to the east side of Rothera Point on the eastern side of Adelaide Island. It may have been deposited at its present site some distance beyond the shoreline by a storm or glacier-calving surge at a time before the raised beach became buried by an ice field that may have persisted for centuries or even millennia. Unfortunately, radiocarbon dates were not obtained for either log.
Acknowledgements
I am grateful to Dr. John Smellie, formerly of the British Antarctic Survey, Cambridge, who provided the Livingston Island wood sample, and to Peter Stark, also BAS, for providing the Argentine Islands sample. I am indebted to the late Dr. John Harris and Dr. Brian Butterfield, University of Canterbury, Christchurch, for providing the anatomical details of the two Antarctic Peninsula logs, and to them and Dr. D.R. McQueen, personal communication, 12 July 1984, Victoria University of Wellington, for comments on these and other Nothofagus samples.