In professional circles, Talampaya & Ischigualasto are known as fossil excavation sites. In the last picture you'll see a grey-whitish sediment, that expands upon contact with water, thereby shielding the layers underneath. This is where many dinosaur fossils have been found. However, as a tourist, you get to see none of the excavation – "for security reasons" – and will have to put up with admiring the canyon's natural beauty.