We saw several herds of guanacos, which unlike llamas or alpacas, have thin hair except at the scruff of the neck where a little wool gathers. Under the heavy wind that wool gets ruffled, given the heard the aspect of a gang of punk teenagers. The other interesting animal was the choique or lesser rhea, which is a small type of ostrich that is difficult to spot because its curved back mimics so well the rounded shrubbery. We saw two or three groups, and in them there were a lot of babies, locally called choritos. Apparently eggs hatch in November, so the young birds must have been a couple months old.
After following the highway south for 300 km we cut to the west on a dirt road to pass through immigration control by Argentina, got in the bus and went along the same road for another 5 km and went into Chile, and after immigration we were finally ready to come into the Torres del Paine National Park. The massif is an isolated mountain mass, roughly circular in outline. It has a diameter of about 12 km and rises 2,700 m above the level of the surrounding lowlands. There are some large lakes around its perimeter to the east, that for some curious reason don't drain to the sea (to the west the glacier valleys are fjords where the Pacific has encroached into the land). Because they are "closed" lakes they are slightly salty and alkaline, conditions under which water snails cannot live. This has resulted into conditions favorable for the formation of stromatolites (sub-variety trombolites), where cyanobacteria build disorganized mounds of calcium carbonate along the shore.
The rocks around the lakes are thick sequences of black shales, nut unlike the Mesozoic Pierre Shale and the Devonian Marcellus Shale in the United States, where fracking has allowed the development of large natural gas resources. Apparently the South American black shales are found all along the back-arc portion of the Andes, and farther north, near Neuquén, have been fracked to yield large amounts of natural gas.
Ah, there it was, the Torres del Paine in its whole glory, as seen from the east. To the north, the torres are three enormous spires formed by light-colored granite, which are very distinctive because the rocks that surround them are black. Panning to the south you see that the flank is formed by the same black shales I had seen on the way in, and looking even farther south, you see "The Claws", where smaller spires of granite are capped by black jagged rocks. For the rest of the day we circled the massif clockwise (we actually only did one fourth of a circle), and as we did so more exposures came to view and the whole geometry of the massif became clear. I believe that what we have here is a high level intrusion that "ballooned" its way up through the black shales but never broke to the surface. As it intruded it caused contact metamorphism of the shale to transform it into a highly resistant hornfels, so the massif was encased on a hard shell, like an overcooked muffin or a Baked Alaska. Later, as the Andes continued their uplift, erosion of the soft shales around it isolated the hard massif, which during the last glaciation was dissected by glaciers to create the distinctive chiaroscuro landscape of the mountain. Supercool!
