The Alto Chiascio Geosites
The extinction of the dinosaurs is a mystery that has stimulated the imagination of scientists for decades. At the end of the 1970s, a team of scientists from the University of California at Serkeley, composed of physicist Luis Alvarez, his son Walter, a geologist, and nuclear chemists Helen Michel and Frank Asaro, made a shocking discovery.
They were studying a thin clay layer of the Scaglia Rossa formation outcropping along the Bottaccione Gorge, near Gubbio, in Umbria. This clay layer marks the boundary between the Cretaceous and the Tertiary Penods (the so-called K/T boundary. In these rocks of marine origin, the K/T boundary is defined by a drastic and sudden change of fossil microfauna. The discovery consisted in an anomalous concentration of indium which is very rare in terrestrial rocks but more abundant in extraterrestrial rock asteroids, and the rocky nuclei of comets The Alvarez hypothesis is that the anomalous concentration of iridium found in the thin clay layer of Gubbio is the result of an immense natural catastrophe, induced by the collision of a gigantic body (such as an asteroid or the nucleus of a comet) with the Earth, causing the mass extinction at the end of the Cretaceous Period of the Mesozoic Era, the era of the Reptiles. The animal and plant species which survived the disaster became the ancestors of new forms of life. These repopulated the Earth in the following Tertiary Period, at the beginning of the new Cenozoic Era, the era of Mammals.
In the sedimentary rocks of many parts of the world containing the K/T boundary, and in particular in the Scaglia Rossa formation of the Bottaccione section, near Gubbio, it is possible to see the hints of catastrophe that caused the extinction not only of the dinosaurs but also of numerous other life forms, including those of the microscopic marine plankton which, in fact, constitute these pink limestones.
Saturday 7" July 2007
h. 11:15 am Prof. Alessandro Montanari Lecture on 'Impacts and Extinctions'
h. 12:15 am Prof. Paco Lanciano Presentation of the 'Umbria Geo' project
h. 01:30 am Tasting of typical products
h 02:30 pm Guided visit to the Bottaccione Gorge
h 03:30 pm Guided visit to the Historical town centre of Gubbio