Week One!

Ah, a day off! The last five days have been a flurry of travel, field work, late dinners, and what I have come to fondly refer to as “sink laundry.” After spending one night in Punta Arenas, we collected our field equipment and drove east, hopping on a ferry and crossing the Strait of Magellan to the island of Tierra del Fuego. Based from the hub of Cerro Sombrero, Chile, we spent two days along some truly spectacular cliffs lining the Atlantic coast just south of the strait. These are cliffs that the Patagonia Field Crew 2011 visited this past May. We returned so that Justine could collect samples for luminescence dating from sand wedges that cut into some lovely, ancient, weathered gravel that lie at the northern part of the section. We parked at the coast at the edges of Estancia Shangri-La, just at the shores of a windswept pond where two hardy flamingoes fed amongst a sea of thirsty, shaggy sheep. Justine, Rachel and Olav spent much of their time at the lower bluffs to the north photographing and sampling the sand wedges, while John and I headed south to get a second look at the high cliffs that provide a dramatic cross section of glacial sediments estimated to be about one million years old.

These sediments are the remnants of a large sheet of ice that extended out of the Andes, traveling hundreds of kilometres across the plains to the east, past the modern coast, terminating in what is now covered by the southern Atlantic. The imagination runs wild, standing beneath these thick deposits and trying to comprehend the mass of ice that was grinding and flowing above, in what is really (geologically speaking) not that long ago. It is at the spot last May that eight earth scientists trekked along the beach, our backs to the ocean and our eyes and minds focused on the stratigraphy in the cliffs. After spending a few hours making careful notes and geofantasizing about the events that led to the layers of till and gravel, someone turned around and pointed out that the water level was rising quickly, and would be at our feet in not too much time. This is the nature of the geologist…always looking down at the ground or up at the outcrops, sometimes forgetting to turn around and appreciate the vistas (or rising tides!). There was clearly not enough time to walk back to our car. Part of the group suggested we take refuge on a high shelf of bedrock in the cliff, and part of the group wanted to walk a few hundred metres south to the lighthouse that marks the boundary between Chile and Argentina to see if there was a way up to the top of the cliffs. After standing around discussing our options, the tide forced our decision, and we spent the next six hours on the bedrock shelf, warily watching the rising waters around us. Believe me, we made some REALLY good notes that afternoon.

Geologizing while waiting out the tide in May 2011

Now, nine months later, John and I walked past our perch toward the lighthouse, this time making sure to shift our gaze from the rocks in front of us to the ocean behind. Once again, the tide began to come in, and we decided to walk a bit farther before turning around. We came close to the lighthouse, where we saw an exciting exposure of rusty colored gravels that suggest an important relationship between these deposits and those of the low bluffs where the luminescence crew were spending their afternoon. Walking a bit farther to get a view of these gravels, we reached a gully dissecting partway down the cliff. The gully was too far up from the beach to climb up to, but wouldn’t you know it…someone had fixed a rope leading from the upper surface to the sand. It was ratty but sturdy, and we hoisted ourselves up. It sounds as though we could have climbed to safety last year after all!

After two days of work in this area, we re-crossed the strait and spent an afternoon at Cabo Virgenes, the southernmost location on the continent of South America, where the Atlantic Ocean and the northeastern corner of the strait meet. There is something romantic about standing on this windy point, not only imagining the ice extending from here to Tierra del Fuego across the waters, but thinking about the history that shaped humankind’s knowledge of our planet’s geography. According to the omniscient Wikipedia, on October 21, 1520, after sailing along the Atlantic coast of South America for nearly 10 months, Ferdinand Magellan made a right hand turn at Cabo Virgenes into a passage that took him between the continent of South America and the Isle of Tierra del Fuego to the Pacific Ocean, where he continued sailing for over a year before reaching Asia. That passage was later named for him, and when we looked out at the rough waters, we expressed a great appreciation for those men making such a large voyage on their tiny wooden vessel. Very cool. At the end of the day, we took a short drive to the pinguineria at the gravelly mouth of the strait. Here, we were treated to visiting with hundreds of Magellanic penguins. We took a path through their nesting grounds, where the chicks were bedded down with one parent while the other was out collecting food from the sea. In March, both baby and parent will leave the rookery and swim north for winter, so the chicks had already lost most of their fluffy down. They were pretty loud and active, many of them waddling in long lines from the nesting grounds on their well-worn paths to the beach. After such a long day of work and another long drive to Rio Gallegos ahead of us, these goofy little critters left lingering smiles on our faces.

Getting a stare-down from a Magellanes penguin.

We are now in Rio Gallegos, Argentina, and will be based out of this town until Wave One leaves on the 15^th. We’ve hooked up with some local geologists, Jorge Rabassa and Bettina Ercolano, who have been taking us to key sites, sharing their incredible wealth of knowledge of the local geology. Yesterday we got our first taste of the field season of the Pali Aike volcanic field, where lava flows that date from roughly three million to ten thousand years old lay above and within beds of glacial sediments. These basalts will hopefully allow me to provide ages that constrain the timing of these old and large glaciations, so the next few weeks will involve many drives out into the volcanic field. I feel a sense of crossing a hurdle, where I have transitioned from travel and re-orientation into true field work mode. Every day prompts ten more questions for each one that it answers. 

Laguna Potrok Aike west of Rio Gallegos, Argentina, in the Pali Aike volcanic field. This lake rests within the depression left by a volcanic maar, and has been drilled for sediment cores. It's blue color is striking against the dry brown landscape.

Wave One at the rookery at Cabo Virgenes, Argentina, with cliffs of the Cabo Virgenes Drift behind us. Penguins are coming in from collecting food from the ocean at the sea shore. Left to right: Olav Lian, Justine Cullen, me, Bettina Ercolano, Jorge Rabassa, Rachel Chapman.