The Edinburgh Geologist
Issue no 41

Fossils from the South Atlantic
the geological legacy of the Scottish National Antarctic Expedition, 19O2-19O5

by Phil Stone


It was the chance discovery of some unusual fossils in the Falkland Islands that set me to researching the results of the Scottish National Antarctic Expedition during its centenary year. Late in 1902 and led by Dr. William Speirs Bruce, that intrepid team sailed from Troon aboard a barque-rigged, ex-whaling ship, renamed Scotia, to make a generally unrecognized contribution to the 'heroic' era of polar exploration. Recent publicity surrounding the expedition's centenary has gone some way to redress the previous neglect, but it's still hard to imagine that on 22nd July 1904, thousands of people welcomed the Scotia back to the Clyde, where Dr. Bruce received a telegram of congratulations from King Edward VII.

The main emphasis of the expedition's scientific work was on biology, meteorology and oceanographic surveying. The latter aspect has provided the most prominent memorial to the Scotia following the discovery and naming of the eponymous submarine ridge that links South America and the Antarctic Peninsula via the islands of the 'Scotia Arc' and encloses the 'Scotia Sea'. Geology was the responsibility of Dr. J. H. H. Pirie, who was also the expedition's medical officer and carried out bacteriological research. They established a base in the South Orkney Islands, which were virtually unknown at the time, and Pirie carried out some pioneering geological reconnaissance work. Sadly, one of the least successful observations is also one of the best known - the misidentification of graptolites that confused regional interpretations for decades. This story has been told by Ian Dalziel in an early edition of The Edinburgh Geologist.

Not that Pirie should take all the blame. Although his 'graptolites' turned out to be Triassic plant material, they were inspected by no lesser authorities than Ben Peach and Gertrude Elles; the latter, the doyenne of British graptolithologists, went so far as to pronounce them as species of Pleurograptus. Pirie's subsequent paper based on all this was communicated on his behalf to the Royal Society of Edinburgh by another well-respected figure, John Horne. But then, maybe we shouldn't be too surprised since Pirie found his fossils in a greywacke-shale sequence which, as every Scottish geologist of that time would have believed, were invariably Lower Palaeozoic in age.

My interest was not aroused by the non-graptolites however, but by the Expedition's associations with the Falkland Islands, one direct and one rather tenuous. The Scotia put into Stanley in early January, 1903, and the next three weeks were spent taking on stores. During that time the expedition's scientists were entertained by the Governor, Mr (later Sir) William Grey-Wilson, who presented Bruce with a collection of local Falklands fossils. It included various species of Devonian brachiopods, crinoid ossicles, and two small fragments of trilobite thorax, all contained in a brown, micaceous sandstone. Bruce also acquired one other specimen of sandstone with crinoid impressions from a poorly-defined locality in the far west of the Falklands archipelago. These specimens are now housed in the Royal Museum, Chambers Street, Edinburgh, and from a modern perspective seem pretty unremarkable. However, in 1904 they were only the third set of Falklands fossils to be brought to Britain. The two previous collections were by Charles Darwin in 1833-34, and by members of Sir Wyville Thomson's Challenger expedition in 1876, so Bruce and Pirie were keeping pretty good scientific company. All three collections even came from the same place - Port Louis Harbour, East Falkland - with the sole exception of Bruce's West Falkland sample. The latter provided the first evidence for the more widespread outcrop of fossiliferous strata that modern survey work has subsequently confirmed.

The 'Scottish' Falklands specimens were fully described by E. T. Newton in a paper published in the Proceedings of the Royal Physical Society of Edinburgh in 1906. Newton remarked on the great similarity between the Falklands brachiopods and those then being discovered in South Africa and South America. We now recognise this faunal assemblage as defining a 'Malvinokaffric Realm' spanning the margins of the Palaeozoic supercontinent of Gondwana. As Gondwana broke up and the southern hemisphere continents drifted to their present locations they each carried with them a portion of the originally continuous faunal province. Although they didn't know it at the time, the Scottish National Antarctic Expeditioners contributed to our present understanding of plate tectonics and continental drift.

The expedition's Malvinokaffric fossil collection provided the direct link with the Falkland Islands, but rather more interesting from my point of view was the less direct link, also involving fossils but this time of Cambrian age. Now, the oldest in situ fossils in the Falkland Islands are from the Devonian, Malvinokaffric assemblage as presented to Bruce by the Governor. However, stratigraphically above the Devonian sequence is a tillite, a glaciogenic unit dating from the extensive Permo-Carboniferous glaciation of southern Gondwana. As you might expect, the tillite contains a wide variety of exotic clasts and recently a few of them have been identified as Cambrian limestone. We know the limestone is Cambrian because it contains fossil archaeocyathids, an extinct and exclusively Cambrian phylum related to sponges. A couple of examples are illustrated here.

Where though does the Scottish National Antarctic Expedition come in? Well, in 1903 archaeocyathids were very poorly known with very few records (actually, over most of the world, things haven't changed much in 100 years). Australia had provided most examples, and it must have caused some surprise on the Scotia when a lump of archaeocyathid-bearing limestone was dredged from the bed of the Weddell Sea, to the east of the South Orkneys and at a depth of 1775 fathoms. Maybe they didn't fully realize what they had found because the specimen was not passed on to W. T. Gordon for description until 1913; with the distraction of the First World War his paper in the Transactions of the Royal Society of Edinburgh did not appear until 1920.

In the meantime, Shackleton's British Antarctic Expedition (1907-09) had discovered archaeocyathid limestones on the opposite, Ross Sea, side of Antarctica; the first record from that continent. Gordon was thus able to compare the Weddell Sea specimen with other archaeocyathids described from Antarctica and Australia. He rightly deduced that the dredged limestone block had most probably been carried northwards by ice from a source in Antarctica, and commented on the striking similarities between the Australian and Antarctic faunas. Once again, a hesitant step was taken along the intellectual pathway that was eventually to lead to a re-assembly of Gondwana from the southern hemisphere continents.

That same path also winds back towards the Falklands archaeocyathids. They link with similar examples in Permo-Carboniferous tillites from South Africa and the Antarctic to provide more evidence for the previous juxtaposition of those regions in Gondwana. We take that kind of reconstruction for granted these days but can only speculate as to whether Bruce, Pirie, Newton or Gordon glimpsed the wider implications of their work in the development from 1912 onwards of Alfred Wegener's hypothesis of continental drift. Nevertheless, from that starting point, the discoveries of the Scottish National Antarctic Expedition can be seen to have contributed small clues that, with many others, eventually led to our modern theory of plate tectonics. I'm sure that the expedition's members, and their scientific collaborators, would have been delighted by that outcome. It certainly provides them with a far more fitting geological epitaph than that unfortunate business with the graptolites.

A good general account of the Scottish National Antarctic Expedition was published recently in History Scotland:

Duncan, Allison. 2002. Science for a talisman and Scotland on the flag. The Scottish National Antarctic Expedition 1902-1904. History Scotland, Volume 2, No. 5 (Sept/Oct), pp. 24-31.

Scientific bibliography

Dalziel, I. W. D. 1979. The mythical graptolites of the South Orkney Islands. The Edinburgh Geologist, Issue no 6, pp. 2-9.

Gordon, W. T. 1920. Scottish National Antarctic Expedition, 1902-1904: Cambrian organic remains from a dredging in the Weddell Sea. Transactions of  the Royal Society of Edinburgh, Volume 52, pp. 681-714.

Newton, E. T. 1906. Notes on fossils from the Falkland Islands brought home by the Scottish National Antarctic Expedition in 1904. Proceedings of the Royal Physical Society of Edinburgh, Volume 16, pp. 248-257.

Pirie, J. H. H. 1905. On the graptolite-bearing rocks of the South Orkneys. Proceedings of the Royal Society of Edinburgh, Volume 25, pp. 463-470.

Stone, P. and Thomson, M. R. A. in press. An archaeocyathid-bearing limestone block of likely Antarctic origin in Gondwanan tillite from the Falkland Islands.
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Phil Stone is a long-time contributor to this magazine. He works for the British Geological Survey in Murchison House, mainly on rocks of the Southern Uplands of Scotland and northern England. He also acts as geological advisor to the Falklands Islands Government's Department of Mineral Resources.
 
 

Figures
Figure 1 Fitzroy Tillite Formation

Archaeocyathids from a limestone cobble in the Fitzroy Tillite Formation, Port Purvis - cross sections showing circular structure of the double perimeter wass enclosing a central cavity; at least two different species are present.The Falklands 2-pence piece is 2.5 cm in diameter.


Figure 2 Fitzroy Tillite Formation

Archaeocyathids from a limestone cobble in the Fitzroy Tillite Formation, Port Purvis - lateral section showing detail of structure within the perimeter wall. The Falklands 2-pence piece is 2.5 cm in diameter



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