The Jura is an area in the East of France, named after the Jura Mountains, and is one of four departments of the Franche-Comté region and is surrounded by the French departments of Doubs, Haute-Saône, Côte-d’Or, Saône-et-Loire, and Ain. It is easy to bypass on your way to the Mediterranean in summer or the Alps on your way to the Ski slopes – DON’T! It is one of the most beautiful regions I know in France. It offers it all: Mountains, white sandy beaches and some of the most magnificent waterfalls and natural water features you will ever see! In the Jura Mountains, the turquoise lakes, waterfalls and rivers are fighting for attention from the blue of the sky.
Having previously lived in a nearby area, I jumped at the chance to employ my more recently learned geology skills and join the OUGSME trip to the Jura – I cannot lie: The promise of wine and cheese tasting was also a big incentive!
Geology of the Jura: an overview
During the middle and upper Jurassic, (~175 – 154Ma) the Jura region was a shallow continental shelf dotted with islands, undergoing numerous cycles of relative sea-level change, north of the deep Tethys ocean. The tropical climate and low siliciclastic sedimentation provided the perfect environment for the growth of coral reefs, development of oolitic sands and formation of back reef lagoons where carbonate muds accumulated.
Mont Rivel Quarry
We started off the first day with some exciting fossil finds (ammonites and variety of bivalves) within the Oxfordian rock formation on the plateau of Champagnole (Lower part of the Mont Rivel).
This was originally an Outlier – glacier took the surroundings away ~20kya. The (disused) quarry was used in conjunction with a cement factory, and is composed of limestone and marl.
Oxfordian rock formation and dinosaur footprints in Loulle
We spent an afternoon at Loulle looking at a site where dinosaur footprints from 20 to 90 cm in diameter can be found on the base of a quarry. The site was discovered by Jean-François Richard in 2006 and the excavation started in 2007. Excavation ended in 2009 after revealing over 1500 prints on 4 different layers. It covers 3800 m2 and, as such, is called a MEGATRACKSITE.
The rock formation dates back to ~155 mya (Upper Jurassic), when the area was covered with warm, shallow tropical seas and coral reefs when the area lay between 30º and 40º N – about the present day position of Morocco. During periods of temporary low sea levels, large littoral mud plains developed and joined the large islands of the ancient eroded massifs of the Ardennes, Massif Central.
Desiccation cracks and stromatolites are clearly visible on the floor of the quarry.
When you visit you just have to close your eyes and imagine these Herds of Sauropods (like Diplodocus) and Theropods (like T-Rex, below) migrating in search of food. It was even possible to estimate the size of the dinosaurs from their footprints (some nearly 40 meters in height), and individual dinosaurs were distinguishable from the manner in which they walked and left footprints!
It is one of the biggest sites discovered in Europe, similar to those in North America, however due to the nature of the rock in which these prints were found, the prints are eroding rapidly now exposed, and a fight to get them covered and the area to be turned into a museum is on.
In order to raise awareness of this cause, and in cooperation with Jean-François Richard, I am building a website and petition which will be online soon. If you would like to volunteer time and/or services to aid us, please contact me directly on Geology@Cathrene.com.
In the meantime, the quarry is accessible to public, is next to a small car park, and a sign provides explanation about the location.
In a road cutting below the megatracksite, we examined the facies (Beach, Lagoonal (On top of which the dinosaur footprints were found) and Coral Reef). These beds are from the Upper Oxfordian (~155 Ma) and were rife with fossils: Corals, shells, stromatolites and plant fossils.
Folds and faults
This small syncline (below) has a diameter of less than 10m within the Purbekien limestone. The fold has no direct relationship with the major tectonic axes: the small scale folds which we examined along this stretch of road cutting are the result of compressional deformation in the major Chaux-des-Crotnay syncline, which is several kilometers in diameter.
We stopped off at a further Purbeckian outcrop (Baumette, Chaux des Crotenay) where we examined the side slopes of the small anticline represents the top of the classic Purbekien series, which is also dominated by limestone facies, interspersed with marls.
Gorge de la Langouette: Lunch stop
We took a long lazy lunch break in a field next to a bridge with an impressive view of the Gorge de la Langouette.
Morillon (le Rachet)
After lunch we stopped to look at an outcrop of near-vertical bedding which represented the edge of an anticline.
The lake of Chalain
Our next stop, Le lac de Chalain, was the largest natural lake in the Jura, formed in one of many valleys carved out by glaciers, which cut their way into the Upper Jurassic limestone of the Champagnole plateau. The valley of Chalain is a few kilometres in depth, accentuating the contours of the escarpment of the western edge of the plateau. Same altitude as in Arbois, and different levels.
Small villages, some dating back 3000 years, have been preserved below the water in the lake. After 30 years of study, the site has been documented as one of the most extraordinary for the insight it has provided on Neolithic human life. However, today, the lake is a paradise for holiday makers and water sports fans. Visitors can participate in many activities on the water, surrounded by turquoise fresh waters.
At this point we split into two groups – those wishing to enjoy re-joining civilisation and having a dip in the lake, and a second group which headed off to look at a sequence of prograding delta deposits on the edge of the glacial lake in a quarry in nearby Charcier.
The glaciers released their sedimentary load into a lake at the meltwater edge: sloping gravel beds prograded into the centre of the lake (below).
We were lucky enough to enjoy a visit and wine tasting at the Institut du Vin in Arbois, where we attempted to identify various smells in the wine which we tasted…. Needless to say none of us used the spit buckets provided……the experience was fascinating: smelling mini bottles containing scents from the “normal” (lavender) to weird smells which you would never know could be associated with wine, and the wine tasting itself : we all had our own little (private) cabin to taste in isolation and under the experienced eye and taste buds of Elisabeth’s husband, I think we have improved our taste buds somewhat, and extended our knowledge of Jurassian wine. The evening was then concluded with a very fine barbecue at Elisabeth’s own home, with views of the middle Jurassic cliffs (oolitic limestone).
The Osselle cave (Grotte d’Oselle), one of the first caves of its kind to be open to the public at the beginning of the 15th Century, is situated 10 miles from Besancon in the Doubs region of the Franche Comté, although it is so large that half of it is in the Doubs and the other half is in the Jura!
It is the most impressive cave of its kind that I have ever visited: The assortment of stalactites and stalagmites, geological phenomena and prehistoric remains, coupled with its size (the main cave is over 1200 meters) make it a must see! Astonishingly, in addition to the geological features, the Grotte boasts a discovery of 15 complete skeletons of giant bears, making it one of the most important cemeteries of the creatures in the world!
Source du Lison
There are sooo many waterfalls in the Franche-Comte as a result of the geology of the area, rivers split, vanish and re-surface, pouring out of cliff faces in woodland glades; all of them are worth a visit.
We visited the “Source du Lison” – the Source of the river Lison, which is (like the river Loue) partially a resurfacing of the river Doubs from in the depths of a cave. Like any waterfall, it is all the more spectacular after rainfall, or during the spring when the snow is melting. The source du Lison is the second most powerful spring in the Jura, with over 600 litres flowing out of it per second.
The day was concluded with a short walk up Mont Poupet to see the view. Not only did we enjoy breathtaking views of a large area overlooking Salins-Les-Bains – a valley formed in an anticline, cut through by a river, which exposed Triassic evaporates from which the town received its name – in addition to a view across as far as Mont Blanc!
Thanks to Elisabeth d’Eyrames, and her family, for a wonderful weekend!
Links and further information:
- Loulle Dinosaur Footprints: Site à pistes de dinosaures de Loulle
Email : firstname.lastname@example.org
Virtual Tour in pictures : http://www.lieux-insolites.fr/jura/loulle/loulle.htm
http://www.lejurassique.com (in French)
http://www.juramusees.fr/1/musee/musees/histoire_naturelle/-b9eaca2121/site.html (in french)
- The lake of Chalain : http://www.lac-chalain.com/lake-chalain/index.htm
- Grottes d’Oselle: http://grottes.osselle.free.fr/acc_ang.htm