|The next adventure was to find the Cretaceous-Tertiary boundary
layer in the hills of Umbria. This boundary layer has been found
to be enriched in Iridium and interpreted as a result of the impact of
an astronomical body with the earth that caused the extinction of the dinosaurs.
The type locality is near Gubbio in Umbrian region of Italy and not far
from Assisi (the pretty home of St. Francis and
a site that any good northern Californian can not pass up!)
The cathedral in Assisi is the resting spot for the remains of St. Francis and an important site for large numbers of pilgrims which is probably the reason that although Assisi was hit by a large earthquake in 1999, the cathedral's seriously damaged frescos have already been restored. There is still evidence of damage in the town, here in the wall of a building, here in the major portal to the city (an example of what kind of damage the frescos were subject to).
There happened to be a exhibit of D'vinci inventions in Assisi while I was there and I found this volcano model rather interesting and need to know more about it. Here is the beginning of the animated model and here is the end product (Perhaps predicting/stimulating Jules Verne's journey?) There was also a model of a mirrored room that shows way too many images of me.
From Assisi, it was a easy drive to Gubbio to find that boundary layer. Gubbio is a pretty little town with a nicely preserved boundary wall. It does appear that the earthquake might have caused damage here as well. The blocks in the wall tell us quite a bit about the region...limestones with layers of red chert here and also blocks of sandstone with indications of turbidity current deposition. They also have a relatively hidden sculpture that looks a lot like Andy Goldsworthy's work and a beautiful terraced park for walking. It was tempting to stay and sample all of the goodies in this store, but it was on to find that layer!
Driving into the canyon east of the city on SS298, I was admiring the tilted layers and wondering just how it would be possible to recognize "the layer" among the thousands, if not millions when I spied a fellow walking in the canyon with a geology pick and other paraphenalia that suggested that he might know something AND if he spoke English this might be another grand opportunity. Well he did and he did...turns out he was a consulting geologist in Gubbio who just happened to be reviewing the geologic sequence for a study he was doing for the regional government (I can't believe that I did not take his picture). We talked a bit and when I asked him if he knew where the boundary layer was, he turned and pointed down the canyon to a bright yellow sign (close up) that was just about where I had left my car and walked towards him. I had walked right passed it! "The layer" which I presume contains the Iridium spike is quite recessed and appears clay rich which might explain the recession but the possibility that it has been heavily sampled, probably by hundreds of pilgrim geologists who have stopped by for a look-see. Sort of like taking a little piece of one of the St. Francis church's frescos home with you?
In the layers above and below the boundary, there are metal plaques indicating the position in the Gubbio paleomagnetic section which is extensively sampled and now has been correlated with sections around the world and from cores taken from the deep-sea. Above the predominately limestone sequence there is a turbidite sequence in which an Italian geologist came to the same conclusions about their origins that Bouma came to studying the Peira Cava area. After comparing the Peira Cava and the Gubbio exposures my hat is certainly off to the abilities of that Italian geologist. There were some better exposures but most that I saw were behind steel netting. There were bottom structures to be seen but they do not begin to compare with spectacular examples in the Digne les-Bains and Peira Cava regions that I have seen on this trip but have not had the time to report on them. Some good examples can be seen in my Rhodes reports from the fall trip.
To complete the journey I had to return by an adjacent canyon(SS452) where a more spectacular section was to be seen in a quarry. But first there was a quite spectacular example of drag folding along the road that connected the two canyon sections.
Leaving the Umbria area was hard...but one last experience was both interesting and disappointing. Near the town of Dunarobba the tourist information said that there was a fossil Sequoia forest...now if that is not a connection with Marin and California...what is? Well there was to be a tour at 11:30 and I got there before then and a couple with their two young boys from Rome had driven up especially to take the tour joined me. We waited, but no tour guide showed up! The one local who spoke some English and tried to call the number on the brochure (no answer) suggested that they probably went to have lunch because hardly anyone ever shows up! The park is understandably fenced and so I did get some pictures from a distance. In this picture, the standing trunks seem to be encased in some light colored matrix and here you can get some idea of the size. I still don't have a clear idea about the preservation although in some plowed ground outside of the fenced region there were lignitic or charcoal-like fragments of a well defined wood fragments (quite similar to a burl we see in our California redwoods that had been burned). And yes, they are still there since it was clearly indicated that taking samples was against the law, even when written in Italian...although the lady from Rome came up to me with a piece of wood and suggested that I take it! Fortunately, it was quite clearly not a fossil sample. (online info re the Dunarobba fossil forest / another source)
One last piece of info from the helpful local was that the trees came to light as a company was excavating clay from former lakebed sediments for making clay pipes and roofing tiles and when they came to a tree they just left them and excavated around them...paleontologists discovered them and given their uniqueness the company now has to go elsewhere to get their clay.
When I have a chance to catch up...I have now spent time in Italy touring the Carrera, Cinque Terra, Tuscany, Venice, Southern Tyrolean Mts in Italy (Now this is the way to study glaciers!), the lake district (Como, Orta) and the Liguria coast where I am as I draft this sequence and am headed for Spain...if I can get past Monaco, Cannes, St Tropez and Marseille where there is reportedly a very interesting geology as well as other sights on the beaches!