Ischigualasto

Ischigualasto Provincial Park in San Juan Province contains an 80-million-year geological sequence so complete — the layers of Triassic grey clay and sandstone exposed across its 60,000 hectares — that palaeontologists have named it the 'cradle of the dinosaurs', and the first true dinosaur (Eoraptor lunensis) was found here in 1991. The grey badlands known as Valle de la Luna (Moon Valley) stretch to every horizon without a single plant — the soil chemistry preventing growth — and the wind-eroded clay balls called the 'giant marbles' roll slowly across the valley floor as the clay beneath them weathers away. The landscape looks geologically recent; it is 230 million years old.

Ischigualasto is a UNESCO World Heritage Site (jointly designated with Talampaya, 80 kilometres south) and one of the world's most important Triassic fossil sites, yielding specimens of Eoraptor lunensis (220 million years old, one of the earliest known dinosaurs), Herrerasaurus ischigualastensis, and dozens of other Triassic species unknown elsewhere. The park's geological sequence spans the full Triassic period from approximately 250 to 200 million years ago — a 50-million-year record of life including the emergence and early diversification of the dinosaur lineage. The tours are vehicular circuits, conducted in convoys with park rangers, stopping at a sequence of geological and fossil features — the circuit takes approximately three hours and covers 40 kilometres of badland terrain. A full-moon night tour, offered monthly when visibility allows, transforms the grey clay landscape under lunar light into a scene sufficiently disorienting to justify the drive from San Juan or La Rioja.