Our exploration of Bolivia continues and we chose to stay some time in the elegant city of Sucre, the official capital of Bolivia. The downtown of this small city is well preserved with magnificent buildings from the colonial time all painted in white. On the top of this architecture, we really enjoyed here the much better weather conditions and celebrated the absence of negative temperature by night.
We had another reason than the dolce vita to come to Sucre. Bolivia is famous in one specific scientific field: Palaeontology.
Several sites showing dinosaur tracks can be found all around the capital. We visited a first site that has left its mark on me, the site of Niñu Mayu. After a short hike in magnificent landscapes, I could walk next to the very well outlined footprints of several dinosaur species. It is definitively a quick way to feel extremely insignificant. By the way, if you are curious about what a scientific publication in paleontology looks like you can find one concerning a footprint site very close from Niñu Mayu site here.
Bolivia was really pushed into the limelight of paleontology when another site: the Cal Orcko track site was discovered and studied. This site is localized in an open pit mine of a cement plant. It is the world largest track site discovered so far and thanks to the footprints, an amazing number of different dinosaur species was inventoried here.
But if you go at Cal Orcko, do not look for the tracks on the ground, you will not find them. In fact, the past will be in front of your eyes. You may even have to look up. It is on a 1.2 km long cliff dipping 72° on average, that you can see the dinosaur footprints.
The paleontology is intimately linked to geology. It helps us to understand how these footprints can be so well conserved and in this unusual positioning. Cretaceous era started 140 million years ago1 and ended 66 million years ago with a mass extinction. At that time this region was next to a huge lake. The dinosaur feet sank into the soft shoreline in warm damp weather. The marks were solidified by later period of drought. When the wet weather returned it sealed the prints below sediments and mud. The presence of multiple layers of prints is due to the repetition of the wet-dry pattern. Further, the plate tectonics transformed this flat area in the cliff we can see now. As a consequence, million years of earth movement rise in front of us.
The story spread in front of us is worth Jurassic Park movie. The footprints of 293 species appear on the cliff and it is the life of animals from another time that we could imagine. There are life and death stories we can figure like hunting scenes, feeding or escaping. So many behaviors we can only presume from the famous giants as well as the often ignored smallest of the dinosaurs. Importantly this diversity gives precious information about the massive extinction of the dinosaurs at the end of the Cretaceous. It demonstrates the absence of a gradual decline in dinosaur diversity toward the Cretaceous. This fact favors a drastic Cretaceous-Paleogene extinction event and not a slow transition2.
The site is not preserved by man all the opposite. The local mining adds its effect to the erosion. Therefore the site is constantly changing. Tracks disappear, new ones emerge. Paradoxically the increasing tourism may counterbalance a little the effect of other human activities by attracting more conservation projects. But when I left this incredible site I had the feeling that nothing will stop the wheel of time.
1 New constraints on the Jurassic–Cretaceous boundary in the High Andes using high-precision U–Pb data. Vennari, Verónica V.; Lescano, Marina; Naipauer, Maximiliano; Aguirre-Urreta, Beatriz; Concheyro, Andrea; Schaltegger, Urs; Armstrong, Richard; Pimentel, Marcio; Ramos, Victor A. (2014). Gondwana Research. 26: 374–385.
2 The Late Cretaceous vertebrate ichnofacies of Bolivia – facts and implications. CA. Meyer; D. Hippler and M.G. Lockley. Asociación Paleontológica Argentina. Publicación Especial 7 VII International Symposium on Mesozoic Terrestrial Ecosystems: 133-138. Buenos Aires, 30-6-2001