Some field photos from a two-week field campaign to the upper Río Yeso with geology students of the Universidad de Chile, April 2018.
The field area is located upriver from the more well-known Embalse el Yeso in the Región Metropolitana of Central Chile, about a three-hour drive from Santiago. The uppermost reaches of the basin lie within the private Parque Valle del Yeso. We camped at the warm springs of Termas del Plomo, just shy of 3,000 m (9,800 ft), and spent all of our time above this altitude--clean, if thin, air.
The place is rad as all get-out, geologically speaking. The zone was first studied by Charles Darwin, where he demonstrated his nose for geology, as well as his inability to cook a potato. The bedrock is a sequence of marine and continental back-arc basin sediments dating from the Jurassic to the Cretaceous, which have been heavily deformed (in some areas overturned). The area is classically considered part of the Aconcagua Fold-and-Thrust Belt (Giambiagi et al. 2003). Interestingly, the modern volcanic arc exists within this tectonic domain, having migrated progressively eastward during the Neogene--the arc now straddles the Chile-Argentina border. Diapiric gypsum is common in the area (yeso = gypsum). On top of all that, late Quaternary glaciation, volcanism, and mass movements have left a spectacular geomorphologic history in the valley (sorry for the pun).
It's a fantastic place to study...but with all this complexity, I'm sure glad I didn't do field camp here.