TRIP TO THE PYRENEES (MAY-JUNE, 2004)

 

“Hasta luego”- that's how we said ‘goodbye' at the Barcelona airport, after eight days of traveling through Catalonia and the Spanish Pyrenees. This European trip was co-sponsored by funds from the Department of Geological Sciences and from the University of Michigan International Institute and allowed fifteen students and three faculty to visit one of the best exposed and well-studied orogenic belts. The Pyrenean range is a fold and thrust belt that developed during the Tertiary, as the Iberian block converged towards the European Plate. Its metamorphic core marks the border between France and Spain, with foreland structures verging into both countries.
  Geologic map of the Pyrenees (http://www.ija.csic.es/gt/gdl/Gdl/Pyrenees-2004/Pyrenees.htm)  

Our trip, designed to recognize the deformed Mesozoic and Tertiary cover, started on May 28, when the group arrived at Barcelona from Detroit. After checking in the Spanish Council Residence (CSIC), most of us went to explore downtown Barcelona. A few landmarks could be seen in the hours before we had our group dinner (who can to skip dinner in Spain!). The Cathedral, Gothic Square and Gaudi architecture were among the visited spots by our students. Paella, gazpacho and oviparous salads were the choice selection at our first dinner in Spain, a preview of what would come in the next several days.

The geologic part of the trip begun the day after, about 150 km north of Barcelona, next to the famed Costa Brava (Girona). We enjoyed visiting the Cap de Creus area (inspiration point and home of the Catalan painter Salvador Dali), where a set of ductile shear zones in the Paleozoic basement is marvelously exposed. Professor E. Druguet (Universitat Autonoma) kindly guided us through the area.
 

Shear zones in Cap de Creus (eastern Pyrenees)

 

On the way to Cala Prona ...

 

The following day we headed west, across the Ebro Basin, the southern Foreland Basin of the Pyrenees, towards the town of Jaca. We visited the southern Pyrenean deformation front in the Ebro Basin, including progressive unconformities, syntectonic deposits and thrusts of Mesozoic units on Tertiary conglomeratic sandstones (molasses) . We spent the night in Jaca, in a small "fonda" in front of the Cathedral.  The church was built in 1077-1130, right after the Christian re-conquest of the town, which had been taken by the muslins years earlier.

 

Synorogenic conglomerates in Riglos

 

Folds in the Hecho Group near Jaca

 

Jaca is located in a large ~E-W trending synform that developed during the Paleogene as a piggyback basin ahead of the evolving Pyrenees. Driving east, we looked at several structures related to the Central Pyrenean Unit thrust sheets, as they were emplaced toward the south. These structures include N-S trending anticlines, almost perpendicular to the main Pyrenean thrust faults, which were probably related to lateral ramps of the southern Pyrenean frontal thrust. The following two days we stay ed in Ainsa, a lovely medieval town, which we all enjoyed . The Monte Perdido National Park, north of Ainsa, is probably one of the most spectacular and vibrant parks in the country. We hiked in the park to visit the famous “Gavarnie nappe”, possibly the first thrust described in any orogenic belt (L. Ramond, in 1801, noticed Cretaceous limestones beneath Paleozoic rocks, a feature that was difficult to reconcile with the prevailing idea of "neptunism" of that time!).
 

La Larri tectonic window- Gavarnie thrust

 

 

View from the Rio Real Valley (Ordesa-Monte Perdido)

 

Our next destination was Tremp, in the Central Pyrenees. The Tremp-Graus piggy-back basin forms an E-W trending synform that contains Eocene platform and continental sediments. In the footwall of the upper thrust sheets, these sediments grade into deeper marine turbidite and prodelta marls. Like the ( earlier visited) Ainsa Basin, the Graus-Tremp Basin was incorporated into the Southern Pyrenean thrust system, where new piggy-back basins developed. During these days we joined a group of students from the University of Barcelona, led by Prof. J.A. Muñoz, who were exploring the cover structures along the ECORS profile. The ECORS ( short for Étude Continentale et Océanique par Réflexion et Réfraction Sismique) is a 250 km long deep - seismic survey from the Aquitane Basin to the Ebro Basin (N and S foreland basins of the Pyrenees) across the Pyrenean fold-and-thrust belt that was co-sponsored by Spanish and French institutions and oil companies.
 

ECORS cross-section

 

 

Ann Arbor and Barcelona students in a discussion of a cross-section in the field

 

Michigan and Barcelona students and faculty shared views and field discuss ions for the next couple of days, which was a geologically as well as culturally enriching experience. We stayed just south of Tremp, in a summer camp facility. Great food there too (nothing new at that point!). Along with the Spanish group we visited the south segment of the ECORS profile, from Balaguer (southernmost Pyrenean deformation front) to Pobla de Segur, where we studied Paleozoic rocks that were involved in antiformal stacks.

 

Sharing more discussions in the field

 

Trip to the La Pineta Valley (Ordesa-Monte Perdido)

 

Not without some sadness, we returned to Barcelona on Thursday, June 3. On the way back, we took some time to look at Montserrat, an impressive massif made up of Paleogene fan delta conglomerates that were  deposited in the Southern margin of the Ebro Basin, while the Pyrenean thrust were being emplaced in the North. We spent the last night again at the CSIC Residence, in downtown Barcelona, capped with a pleasant group dinner. Overall, the trip to the Pyrenees was a great experience for both students and faculty , based on informal feedback. We believe that such international experiences will become a regular dish on the University of Michigan's geology menu.

More pictures here ...