Ischigualasto – The Valley of the Moon

27 November 2010

The name is old – from the native Quechua tribe and it means the place where you put the moon. Ischigualasto is an extraordinary almost off world experience. Geologists have been visiting the valley in Argentina for more than one hundred years. It doesn’t take long to see what attracts them.

There is little vegetation in the place – the climate is hostile with high winds and little water. Yet in the Triassic period more than 230 million years ago it was rather different – and the fossils of the dinosaurs which abound in the valley show that it once must have been a green and fertile place.

The impressive scenery and unspoiled beauty are unique and totally different from other natural areas in Argentina. The mushroom, The submarine, The parrot and Alladin's lamp, are names that have been given to the weird and irregular grey-green rock formations found here. They were created by the constant action of wind erosion which, like some mad artist, sculpted the bizarre shapes over a period of millions of years.

The valley is just over six hundred square miles in size and borders the Pampean Hills in the west. Some of the oldest known dinosaur remains have been found here – the Triassic period is almost completely represented in a sequence of rock deposits. As such the area has been vital in the study of the transition between dinosaurs and the first mammals.

It is easy to see why these bone-dry badlands were called the Valle de la Luna (Valley of the Moon). Around the formations the landscape is other worldly, one where you might imagine yourself on a distant, forsaken planet.

Yet it was not always like this. Although it would still seem foreign to our eyes, petrified tree trunks and the fossils of giant horsetails and ferns have been discovered which show how different the place must have been in the past.

Yet it was not until the 1950s that the place was really rediscovered as a site of such a wealth of information of the fossil record. Although it is not as famous as Chinle Formation in Arizona, North America, the quality and number of its fossil finds outrank the US site. It is effectively the most important place in the world for paleontologists.

Erosion over the millennia unearths the fossils as well as other geological formations such as a host of almost spherical concretions. The wind, inexorable and patient, has pounded the local bedrock for an age. Revealed, the boulders that mudstone – in its original wet form, helped to form look as if giants have been playing marbles.

Ischigualsto is a basin region and although now its rugged and somewhat bizarre terrain give it the name it now has, in the past the place was volcanically active with many rivers and a heavy rainfall.

It may be a surprise to discover that dinosaurs are not the most numerous or the largest of animals to be discovered here. Much more common are the fossils of Rhyncosaurs and cynodonts. This has led to speculation that when dinosaurs first appeared on the planet they were not a desperately successful creature to begin with.

The site, which is a national park and UNESCO World Heritage Site has over forty kilometers of unpaved roads. Despite the richness of the fossil record, these days you are lucky if a small lizard crosses your path.



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