Making Jurassic Tracks in the Jura

by Naomi Lubick
Tuesday, June 12, 2018

Just to the north of the Swiss Alps, the gently sloping, lower-elevation Jura Mountains — namesake of the Jurassic — sprawl across the French-Swiss border and into Germany to the east. Composed of limestone and karst deposits, the low-lying mountains harbor caves and eroded cliffs, mountain chalets, Swiss watch factories — and dinosaur tracks.

The footprints buried here came to light nearly a decade ago, when construction on the Transjurane Highway, meant to join Switzerland and France, unearthed layer upon layer of fossilized footprints. The Courtedoux tracksite, one of the first track-bearing layers uncovered in 2002, contains imprints made by multiple species of sauropods and tridactyls (three-digit bipeds, some of which are thought to be theropods), including herbivores and carnivores both large and small. Eventually, geologists identified more than 280 trackways, with footprints ranging from several centimeters to about a meter long that number in the thousands. Results from a conference on the Jura trackways will be reported in an upcoming issue of the Swiss Journal of Geosciences.

A partnership between the local Swiss cantonal government and its French equivalent set up the “Paléontologie A16” project to preserve the tracks while highway construction continued. Some trackways now run beneath highway overpasses and are covered with sand to protect them from erosion and possible vandalism or other human interactions. But sometimes, these sites are open for tourists.

Daniel Marty, a paleobiologist on the project for the Swiss canton of Jura, cautions that while interest in the sites has been high, the trackways generally are closed except for on special exhibition days. Check ahead with the project (www.jura.ch/DFCS/OCC/Paleojura.html) to find out if the dinosaur trackways are open during your visit.

Either way, the local museum housing some fossils and other items of interest from the Paléontologie A16 project is in the quaint old city of Porrentruy, about a kilometer’s walk from the town’s main train station. Check the schedule before you go, as the museum’s short hours in the afternoon could determine your schedule for the rest of your day; the cost is about $3.

Even if the Jurassic tracksites are closed during your visit, another kind of highway that traverses the Jura mountain range, from Zürich to Geneva, could make for a lovely walk. The Jura Hoehenwege, or the Jura Crest Trail, at 310 kilometers long, takes about two weeks to traverse on foot.

But you don’t have to walk the whole thing. Gentle walking, with some gondelbahn rides (basically ski lifts) to negotiate especially steep places, will take you through several larger cities, with stops along the way at mountain restaurants. Generally, hiking in the Jura is best in spring and summer, but be prepared for thunderstorms.

Going on foot may be the best way to see the geologic strata of the range. If you only have a day or two to spare, consider taking one of the many geologic trails in the region. One day-long hike marked with placards describing where you are standing in geologic time starts in the historic town of Solothurn: Take the Swiss Post Bus from the main train station to Oberbalmberg, the end of the line, and follow the geologic trail marked with explanatory plaques from the Kurhaus Balmberg hotel. Near the top of the Wanderweg (German for “walking trail”), at about 1,300 meters in elevation, stop at the Kurhaus Weissenstein hotel for a drink and gipfeli (Switzerland’s version of a croissant). Get a local hiking book for a good map of the region; this walk covers about 12 kilometers and 700 meters in elevation.