by Edward S. Grew and Christopher J. Carson Monday, December 29, 2014
It was late November 2003 and not quite summer in Antarctica. As the Squirrel helicopter lifted off after delivering its last load, we set about putting up our two tents and making camp on Stornes Peninsula. The peninsula, which would serve as our home and base for fieldwork for the next two months, is part of the Larsemann Hills, a 40-square-kilometer region of rocky islands and promontories on the eastern shore of Prydz Bay, some 120 kilometers southwest of one of Australia’s Antarctic bases, Davis Station. Our only contacts with the outside world were twice-daily radio calls and an occasional helicopter flight to refurbish our larder and take out our samples. No telephone, no Internet.
What brought us to the Larsemann Hills? Boron and phosphorus. These elements are rarely found in more than trace amounts in highly deformed and metamorphosed rocks such as the granulite-facies metamorphic rocks (rocks subjected to temperatures in excess of 700 degrees Celsius) exposed in the Larsemann Hills, yet previous studies had suggested that both elements could be found in abundance here. The objective of our research program, which was supported by the U.S. National Science Foundation and the Australian Antarctic Division, was to determine just how abundant boron and phosphorus were, and to suggest an explanation for why there might be exceptional enrichment.
In the course of carrying out our research, we made many discoveries, which showed just how unusually diverse the minerals in the Larsemann Hills are. One result of our work turned out to be a project that was a decade in the making: In 2014, Stornes Peninsula within the Larsemann Hills was declared an Antarctic Specially Protected Area for its significant mineral diversity. Stornes Peninsula thus became only the fifth location in Antarctica with geologic features deemed sufficiently precious enough to the geologic community to receive this high level of protection.
Our camp was set up on a snow field and we had to chop lake ice to melt for our water supply. But once summer set in, the place became downright pleasant. The southeast coast of Prydz Bay has a reputation for fine weather with plenty of sun and relatively mild temperatures, with daytime averages ranging from about 1 degree Celsius in late November to 4 to 5 degrees Celsius in December and January. And we were not disappointed. Once the wind died down in the morning, working on outcrops was a delight. At 69 degrees South latitude, the “white nights” in midsummer can be lovely, making for serene scenes in low light. We celebrated Christmas with dinner al fresco.
The price for these pleasant conditions was wading at least knee-deep through snow softened by the intense sunlight, and unpleasant surprises such as finding our camp threatened by rising lake waters. (Mercifully, the lake receded before it engulfed us.) We did not have mechanized transport with which to reach distant exposures and haul our samples; all our traverses were on foot. Some outcrops were conveniently at our doorstep; others entailed trudging up to 10 kilometers over sea ice, which was often covered in soft snow, or across hummocky terrain of rock and snow. The Larsemann Hills top out at the 162-meter-tall Blundell Peak, but this modest height belies a rugged landscape with many ups and downs to negotiate.
By the time we were picked up by helicopter in late January for our return home, the snow had largely disappeared from the area around our camp, and the nearby lakes had melted enough so we could simply scoop up lake water to meet our needs.
Once we returned home, our work involved years of analyzing the mineral samples we had collected.
The Larsemann Hil"s were first noted in 1935 by members of a Norwegian whaling expedition. A few expeditions"studied the area’s geology between the 1950s and the 1970s; one of us (Ed Grew) visited an offshore island with the Soviet Antarctic Expedition in 1973. However, detailed geological investigations only commenced in the late 1980s.
One of the first “finds” in the hills consisted of large, abundant prisms of a black mineral reported to be “tourmaline,” a relatively common borosilicate mineral familiar to amateur and professional mineralogists alike. Several years later, Chinese and Australian geologists (including Chris Carson) showed that the large prisms were actually prismatine — another silicate mineral containing boron as an essential constituent, but far more limited in occurrence. Correcting the mineral identification resulted in the renaming of Tourmaline Peak to Prismatine Peak, the official name for the prominent hill on central Stornes Peninsula where prismatine spectacularly occurs.
Prismatine was only the first unusual boron mineral to be found in abundance. Numerous other boron and phosphorus minerals were also found over the next few decades. Our fieldwork in 2003–2004 showed that prismatine and other minerals such as grandidierite and tourmaline were not limited to isolated outcrops, but instead were enriched in several stratigraphic units. The rocks exposed in the Larsemann Hills had sedimentary precursors unusually enriched in boron; this boron had not been driven off and lost during high-temperature metamorphism as is usually the case in such metamorphic complexes.
And the unusual boron mineralogy was not limited to the vicinity’s metasedimentary rocks. Granitic pegmatites formed by partial melting of the metasediments also featured spectacular development of borosilicates, many of which have only been found in Antarctica and perhaps one or two other locations around the world.
Our fieldwork also revealed a surprising abundance of phosphate minerals, including three new species, two of which have never been seen outside of the Stornes Peninsula. Between those and the new boron mineral, we found four new minerals for which Stornes Peninsula is the type locality (see sidebar). And the new boron mineral is recognizable in hand specimens — exceedingly rare for recently discovered minerals. Most modern mineral discoveries are based on microscopic occurrences and observations.
The unusual minerals in this small area, in addition to their rarity and visual appeal, have provided us with glimpses into the geological evolution of the Larsemann Hills area; the unique mineral diversity resulted from distinctive aspects in its geologic history. On the basis of whole-rock geochemical and mineral boron isotope data, we attribute the enrichment of the sedimentary precursors in boron and phosphorus to hydrothermal alteration prior to metamorphism. The precursor rocks included sandy and clayey sediments mixed with volcanic ash (tuff) and boron-rich salts resulting from evaporation, in a nonmarine basin.
Based on our investigations, it appears these rocks were deposited in a rift basin, in which circulating hydrothermal fluids leached boron from the evaporitic deposits and transported it to the interbedded sandy and clayey sediments. These later recrystallized to form the gneisses and granulites that compose the metasedimentary complex exposed in the Larsemann Hills. We think that the rifted basin was 400 to 500 kilometers landward of a 1-billion-year-old continental arc, which was active along the leading edge of a craton comprising the most ancient rocks now found in southern India and a part of Antarctica. Collision with small terranes 990 million to 900 million years ago resulted in burial and metamorphism of these sediments. Then, about 530 million years ago, this craton (plus the accreted terranes) collided with another craton comprising parts of Australia and Antarctica to form the supercontinent Gondwana. Along the collision zone the sediments were again heated and deformed under conditions that allowed the boron to remain in the rocks as they recrystallized and melted, giving us the distinctive borosilicate minerals we find in the Larsemann Hills, but rarely elsewhere.
As the new and rare minerals came to light during our study of samples in the first two or three years after returning from the field in 2004, we raised the possibility of protecting this region with the Australian Antarctic Division, which acknowledged the importance of the area. Australia took the lead, working with China and the Russian Federation as all three have bases on the next peninsula to the east of Stornes, called the Broknes Peninsula, also in the Larsemann Hills. They prepared a management plan to designate the Larsemann Hills an Antarctic Specially Managed Area and presented it before the Committee for Environmental Protection under the Antarctic Treaty System. This designation establishes a formal framework to ensure close collaboration and cooperation in science, operations and environmental protection. In 2007, the management plan for the Larsemann Hills was endorsed by the 10th meeting of the Antarctic Treaty’s Committee for Environmental Protection, in conjunction with the 30th Antarctic Treaty Consultative Meeting.
The next step was a proposal for the Stornes Peninsula to be made an Antarctic Specially Protected Area (ASPA-174) — the highest level of environmental protection under the Antarctic Treaty’s Protocol on Environmental Protection. This level of protection is used to safeguard outstanding environmental, scientific, historic, aesthetic or wilderness values, any combination of those, or ongoing or planned scientific research. Again, Australia took the lead in preparing and presenting the proposal to the treaty parties; the motion was jointly sponsored by other nations with geological research programs in the Larsemann Hills, including China, India and the Russian Federation. The proposal was adopted at the 37th Antarctic Treaty Consultative Meeting in 2014. Through all of this we contributed to the geological case for protection in the management plans.
The main aim of the protection designation, as specified in the Management Plan for ASPA-174, is to avoid degradation of the protected area by preventing human disturbance and inappropriate collection of rocks and minerals. Scientific research is allowed if justified by compelling reasons, such as the impossibility of carrying out similar research elsewhere; however, a permit is required. Samples can be collected in moderation and if properly documented; and in permit reports, scientists must provide the GPS locations of collection sites, the amounts of material collected at each, and information about the repository where samples are deposited.
There were several factors involved in selecting the Larsemann Hills for protection. The primary factor was the significance of the region for the mineralogical sciences. Four new minerals were found here, and Stornes is noteworthy for the unique abundance and spectacular development of other minerals whose beauty can be appreciated in outcrop and hand specimens with the naked eye. These minerals are rare globally, and, more often than not, they occur only as microscopic crystals at other localities.
There were also nonmineralogical factors that contributed to the case for Stornes Peninsula being declared an ASPA. One was the presence of 4-million-year-old sediments containing abundant and well-preserved foraminifera, diatoms and mollusks that provide information on Antarctica’s paleoenvironment at a time when ice volume was reduced relative to today. It is one of only two such sites of this age in East Antarctica. The sediments are thin and disintegrate easily, and thus require protection from human disturbance.
The ice sheet on Stornes, which is small and has almost no connection with the main Antarctic ice sheet, could respond rapidly to climate change. Studies of this site are important. Stornes has been infrequently visited and is minimally impacted by human activities; it thus also serves as a reference site for comparison with other peninsulas in the Larsemann Hills — notably the Broknes Peninsula, which has been significantly altered as a result of the research stations operating there.
Another consideration is the area’s vulnerability. For all its remoteness, the Larsemann Hills is rather populated by Antarctic standards. Although abundant icebergs and sea ice remain close to land late into the austral summer, neither is a deterrent to icebreakers that service the stations during the brief Antarctic summer. Consequently, the Larsemanns have been “occupied” since 1986, with five nations having set up field huts or established research bases at some point between then and now.
A final consideration is aesthetics. Unlike Broknes Peninsula, Stornes Peninsula has not been subject to year-round occupation. The closest winter-over station is an Indian station on nearby Grovnes Peninsula. The beautiful scenery and unique geology of Stornes Peninsula should be kept pristine. And now, thanks to the efforts of many scientists and policymakers from several countries, it may remain so.
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