Argentina’s Land of the Dinosaurs

San Juan is one of Argentina’s smaller provinces and lies immediately north of Mendoza. It is a two-hour drive from Mendoza City to San Juan City across a broad, flat plain that is mostly desert but is being reclaimed for agricultural land, thanks to water from the Andes. Fruit orchards, olive groves and vineyards dot the landscape. San Juan has long produced wine and in past decades was mostly known for its whites; however, improved techniques mean that both Mendoza and San Juan are increasingly producing both.

San Juan has other attractions, however. It is the home of Domingo Sarmiento, the great 19th century Argentine president who did more than anyone in the Southern Cone to instil the importance of education and contributed mightily to ensuring that Argentines would become, early on, among the most literate people in South America. The house where he was born is the city’s most notable historic site and museum.

San Juan’s real claim to fame, however, is Ischigualasto Park in the west-central part of the province. Arriving via a highway whose dips would make a person prone to mal de mer uncomfortable, Ischigualasto quickly makes one forget the trip. Located four hours northeast of San Juan City and 1300 km. northwest of Buenos Aires, it is one of the world’s greatest Palaeolithic treasures.

There are no accommodations near the park so we overnighted in San Augustin del Valle Fertil (Fertil Valley), 45 minutes to the south. We found a charming, small posada with 5 rooms and a delightful host, Azucena, who plied us with freshly baked scones and homemade jam for breakfast.

We reached the park at 11, in good time for the noon tour. Ischigualasto, or the Valley of the Moon as it is also known, is the only place where two Palaeolithic eras – the Triassic and Mesozoic – are revealed. Access is carefully controlled by park staff who lead caravans of cars and small buses to several points on a dirt trail that winds for 40 kilometres through the park.

Map of the tourist circuit inside Ischigualasto Park. Because of heavy rain we were unable to visit El Hongo (the mushroom) and El Submarino.

The landscape quickly changes from desert with assorted green scrub and cacti to a barren land where plants are few and far between.

Our guide led the caravan along a dirt road. In the distance are the Barrancas Coloradas (Red Gorges) in La Rioja province.
The first stop on the tour is the “gusano” (worm), so named for its long, segmented shape. Best seen from the road as one approaches, the surprise is on a small ledge that forms part of the underbelly of the beast — beautifully preserved small fossils of a fern and other plants that lived 250 million years ago when most of this region was under water. The body of the gusano also reveals two of the stages through which this land has lived. The bottom half is limestone; the top half is sandstone.

The Barrancas Coloradas (Red Gorges) with multi-coloured sandstone hills in foreground.

A couple minutes later the caravan pulls into the second parking area and the guide gathers the crowd to explain the origins of this area. The red layers come from copper, the green from iron. Long before the Andes pushed up from the sea this area was a lush, fertile land where dinosaurs roamed. The major Palaeolithic excavations and discoveries have taken place in this area of the park and continue every spring and fall.

Sandstone rocks eroded by thousands of years of wind and rain.

On to the third and last stop; too much rain has made access to the last two stops impossible so the caravan will retrace its route back to the park entrance from here.

The most interesting has been saved for last. A few steps across a dry creek bed stands “The Sphinx”, a natural rock formation rather than human creation. Everyone wants a photo op with this gift from nature.
The guide takes off down a trail and invites the group to follow. Rock formations, large and small, call attention to themselves from passers-by.

Meanwhile, the guide has stopped in a large flat area covered with smooth, round balls. This is the “Cancha de Bochas” or Ball Field. The balls are fragile sandstone, created much like a pearl, and covered by eons of loose sand. Over time erosion and the wind have blown away the top layers of the mound in which they were buried, exposing them for all to see. Many are completely exposed; others seem to be emerging from the earth; still others are barely visible, awaiting further erosion.

The balls’ fragility means that, once exposed, they are susceptible to the extremes of wind, rain and temperature that can lash this area. In summer the high can reach 35 or 40 C. and then plunge to 5 or 7 at night. In summer this normally dry region is subject to thunderstorms that can dump as much as 10mm of rain. The balls that can be seen today will disintegrate into the sand around them, then be blown away, exposing more balls below.

Ischigualasto brings one surprise after another and in leaving the park provides one more: a lone guanaco regally surveying its realm. He turns his head and stares at the visitor, as if to ask, “What are you doing here?” but doesn’t move. A dozen pictures later, we move on.

Returning to the park entrance, a museum developed by the Natural Sciences Centre of the University of San Juan awaits us. The docent is from the university and presents the findings of various digs with an enthusiasm that engages listeners of all ages. The fossil she is discussing is real but most of the fossils in the museum are resin reconstructions of dinosaurs found during several decades of excavations.

We left the park exhilarated and exhausted — with a five hour drive back to Mendoza ahead of us. The highway kept us awake as we dealt with baldenes – dips in the road — for much of our time in San Juan; fording rivers — La Rioja Province hasn’t discovered culverts; and breathtaking mountain passes.