Chile From Within

The Geology of the Cajon del Estero Navarro

Estero Navarro

Estero Navarro is a large stream that joins the Juncal River at Los Hornitos. The upper valleys of Estero Navarro contain a number of excellent examples of rock glaciers. The largest lies in the valley at the foot of Cerro Los Tres Gemelos (photo 13). There are several different subtypes of rock glacier, but basically they are masses of rock and permafrost ice that flow in the same manner as ice glaciers. The Los Tres Gemelos rock glacier is actually a relict rock glacier which has stopped moving because the ice has melted out of it. The empty glacial trough and 100 feet deep and wide lateral moraines that lie above the rock glacier suggest that it probably transitioned into an ice glacier at one time. Several other rock glaciers are located south of Cerro El Yeso, accessed by the smaller north-south valley beginning in the area known as Las Canchitas.

Cerro El Yeso is itself an interesting feature (photo 14). It is another gypsum diapir, far more extensive than the smaller outcrops in Estero Mono de Aguas. Gypsum was mined here in the early twentieth century and there are scattered remains of the mining operations. Another gypsum belt can be seen high up on the west end of the south face of Cerro Los Tres Gemelos.

The area where the north and south forks of Estero Navarro join at Las Canchitas is within the same belt of sedimentary rocks as those which are found in the upper Estero Monos de Agua. The northward extension of the thrust fault in Estero Monos de Agua can be seen high up on the slope of Cordon los Puntones to the southwest (photo 15). Another igneous intrusion similar to Mono Verde, but not as clearly defined, makes up the peaks immediately northwest of Las Canchitas. Colorful red and orange rocks visible along the northern slopes of the lower Estero Navarro canyon are zones of alteration formed by hot groundwater that circulated around this intrusion.

The meadow at Los Canchitas has a beautiful spring known as the Ojo de Agua (photo 16). Groundwater draining the slopes of El Yeso carries enough calcium in solution from disolved gypsum that it has deposited a slightly raised rim around the large spring outlet. Numerous other springs emerge from the talus slope to the east to water this meadow.





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