Patagonian Orocline Expedition—1967-68
Patagonian Orocline Expedition—1967-68
Kerry Burns, Unaffiliated
IN 1967 AND 1968, MIKE RICKARD AND I, had the chance to explore one of the worlds’s most uncharted regions in the name of science.
Our trip really began in 1954 when the English physicist P.M.S. Blackett proved that magnetic properties of rock samples could be used to measure the drift of continents. Later, Australian geologist S.W. Carey hypothesized that an adjunct to continental drift was the bending of mountain ranges. He gave the name “orocline” to a mountain range that was once straight, then bent, and he postulated that the Pyrenees, Appenines, Baluchistan, Alaskan Rockies and Ural Mountains were oroclines. Mike Rickard and I believed the orocline hypothesis could be evaluated by sampling magnetic rocks from a curved mountain range. We selected the southern Andes as a test location because the rocks are less weathered in high latitudes, and because the Andes make a dramatic bend from north-south to east-west in Tierra del Fuego.
Under Carey’s hypothesis, the rocks should show bending that increases with age, from Tertiary to Cretaceous to Jurassic; and with distance around the arc, from Patagonia to the Straits of Magellan to Cape Horn. Accordingly, the aim became sampling of Jurassic, Cretaceous and Tertiary rocks, to see if the amount of bending varied as predicted. We selected sites north of the bend, at Lago San Martín; within the bend, at Peninsula Brunswick, Peninsula Buckland and Peninsula Seymour; and east of the bend, in Sierra Valdivieso and Navarino Island. In 1967, we obtained a grant of $5000 Australian to test the idea and flew to South America.
Lago San Martín, December 13-26, 1967. The Lago San Martín area, 60 kilometers northeast of Fitz Roy, provided rocks that would become a benchmark against which to measure the rotation of the cordillera to the south. Arriving there, we obtained rock specimens. Rickard and Eduardo Espisur climbed Cerro Kach Eike and Cerro Moro, eroded stumps of igneous plugs.
Peninsula Brunswick Traverses, January 11–23, 1968. Peninsula Brunswick is a mountainous landmass northwest of the Straits of Magellan. On the voyage from Punta Arenas, we landed on Isla Charles and collected specimens of the basalt. We selected Monte Muela, a large spire of Jurassic volcanic rock on the western side of the peninsula. On January 11, Lientur Silva, Rickard and I reached Puerto Cutter on the peninsula and, after examining the rocks underground at the copper mine, climbed the nearby hills to determine a route into the Monte Muela massif. On January 13, we began an attempt on the summit but were unsuccessful due to the weather. We retreated on January 16 in a blinding snowstorm by the route on which we had come. Remarkably, we were accorded a hero’s welcome by the citizens of Puerto Cutter as no one had previously explored the inland portions of the peninsula. They met us on the beach and carried us on their shoulders back to the settlement. We mounted a second attempt on Muela, from the north, but bad weather forced another retreat. For interested climbers, the best approach to Muela is by our second escape route, from the east. We did map from the Cretaceous shale sierra south to the glaciers on Muela. The spires are of Jurassic volcanics, quite different from the well-known granite spires of southern Patagonia. Monte Muela is possibly the greatest unclimbed spire in the southern Andes.
Isla Navarino, January 26–29, 1968. Isla Navarino is an island south of the Beagle Canal, overlooking the Drake Passage into the Scotia Sea. Dolerite layers on the island, running east-west, have been eroded into pinnacles, the Dientes de Navarino. Alvaro Tobar, Rickard and I flew from Punta Arenas to Navarino Island and hiked from Puerto Williams to the Dientes. On January 27, Rickard climbed several hundred feet up the north face of Pico de Navarino, the highest of the Dientes, but retreated. On January 28, Tobar and I attained the ridge of the Pico by an easy scramble up the west face but were stopped short of the summit by loose, slippery rock.
Peninsula Buckland, February 5–9, 1968. Peninsula Buckland is south of the Straits of Magellan and is the northwesternmost extremity of the southern part of Tierra del Fuego. On February 6, we mapped the northern side of the Seno Keats. Tobar and I made the first ascent of Cerro Rudolfy, an easy scramble, reaching the western summit (960 meters) in heavy rain.
We then committed ourselves to our wild plan to traverse the peninsula. It called for the boat to drop us off on the west side and then sail around to pick us up on the east side. The traverse had immense geological value but was a scary proposal as the cutter had to travel more than 300 kilometers through heavy seas. If it encountered a storm in the straits and could not make the rendezvous, we would be stranded on the Peninsula Buckland—one of the world’s remotest places—with little hope of rescue. We put ashore at the head of the Bahía Groth Hansen on Seno Hyatt and walked for two days. Our descent to Bahía Filton proved difficult. Recent warm weather had melted the glacier we walked along and flooded the bay with fresh water.
Previously, our rendezvous had been a shoreline on the map, but, because of the flood, that meeting point had disappeared underwater. Even our route to the rendezvous was under three feet of water. We waded five miles down the outwash plain in chest-high water, making camp on the way. When we reached the rendezvous, there was no sign of the boat. Nervously, we began collecting timber for a raft. However, the cutter had been sheltering in an inlet. It arrived in the early afternoon and, much to our relief, took us off.
For mountaineering, the high peaks of Peninsula Buckland are difficult to approach because of cliffs of Cretaceous shale capped by ice. The easiest approaches are from our traverse route on the south, at Bahía Groth Hansen or from the beaches further north in Bahía Filton.
Peninsula Seymour, February 10–12, 1968. Peninsula Seymour lies between Bahía Broken and Bahía Ainsworth on the north side of the southern part of Tierra del Fuego. Bahía Broken was the start of Shipton’s route into the Cordillera Darwin in 1962. On February 10, we landed two parties on the east side of Bahía Broken. Ivan Galay and I made the first ascent of a peak to the north. The eastern summit overlooks Puerto Demonia and Ventisquero Marti- nelli at the head of Bahía Ainsworth. We named the peak Monte Skemp after a famous Tasmanian naturalist. On the 12th, we were landed in Bahía Ainsworth. Tobar and I mapped the northern part of Monte Skemp while Galay and Rickard mapped the east side of the fjord and made the first ascent of Cerro Señoret. We named the 1250-meter peak standing over Puerto Vuelta Monte Carey after the geologist responsible for the orocline concept.
Sierra Valdivieso, February 14–26, 1968. Twin Mountain ranges run east- and-west in southern Tierra del Fuego, between Lago Fagnano on the north and Canal Beagle on the south. The southernmost is the Sierra Valdivieso. It starts near the Chilean border and runs east through Argentina into the Scotia Sea near Puerto Harberton. It was made famous by the writer E. Lucas Bridges as The Uttermost Part of the Earth (Dutton, 1949). We planned to traverse Tierra del Fuego from Lago Fagnano to Canal Beagle, sampling the eastern end of the Cordillera Darwin and the western end of the Sierra Valdivieso. Rickard and I disembarked at Aserradero Almirantazgo on February 14. On the 15th, we set off east to Lago Fagnano. We hired pack horses, driven by Renaldo Catalán Oporto. At Lago Fagnano, we rested briefly at Renaldo’s slab hut in the forest. Renaldo’s lifestyle was based on meat for food, skins for soft furnishings and wood for artifacts. Continuing east, Renaldo showed us an intricate route across the Río Verde on beaver dams. There, Renaldo turned back, leaving Rickard and me facing a long crossing from Lago Fagnano to Canal Beagle along the Chilean-Argentine border. We hoped to sample the granite of the Cordillera Darwin at its eastern end, on Cerro Svea. We had planned our crossing from aerial photographs and had made two food drops across the island.
On February 16, we climbed from Lago Fagnano to the island’s permanent snow line. On the 17th, I climbed Cerro Verde to obtain rock samples. Our next camp was just below the summit of Cerro El Castillo. I found two bags of food near the peak. This was an easy-to-find drop. The food gave us the endurance to attempt Svea and continue on. On February 18, we set out for Cerro Svea with rain and mist low on the mountain. We reached a granite outcrop 50 meters below the summit. A howling gale and blowing snow made it difficult to collect the specimens, and when we had finished, we deemed it out of the question to continue to the summit. This was a good route up the mountain, but unfortunately we could not wait for the weather to clear for a second attempt.
We climbed over El Castillo and reached Lago Lovenberg on February 19 and Lago de Gasperi on the 20th. Then, on February 21, we climbed a mountain northwest of Lago de Gasperi, which we named Cerro Pintado from the color of the rocks. On February 22, we loaded up and left for Ushuaia. We had to trim the rock samples because of the weight. We made high crossings over the western end of the Sierra Valdivieso and over Cerro Tonelli and descended into the forest. On February 24, we reached open country near Monte Susana, 14 kilometers west of Ushuaia, and walked into town. Rickard finished in grand style, but my boots had been giving me hell the whole trip and I hobbled into town in bare feet. We duly reported the border crossing to the gendarmerie, who were highly amused by our passports, which read, “Not valid for North Vietnam.”
At Punta Arenas, we split the rock samples into three groups. Rickard took one lot via Santiago to Sydney, Australia. Another lot was shipped by coaster to Valparaiso and then by sheep freighter to Sydney. The third lot, shipped via Buenos Aires and Hamburg, took two years to arrive in Sydney! The results of measurements of the magnetic properties of the samples were reported in the journal Tectonophysics in 1980. The results were plain: the Cordillera Darwin once continued south from Patagonia into the Scotia Sea, but it has since been rotated to its present orientation running east-west through Tierra del Fuego. The center of the orocline is not in Patagonia, but in the Magallanes province of Chile, at Peninsula Buckland.
[Editor’s Note: Although this expedition was primarily scientific, it is included because the geologists explored much new mountainous terrain and made a number of first ascents in the course of their work. However, many interesting mountains, such as Monte Muela, Monte Buckland and Pico de Navarino, still await their first ascent.]