PALAEONTOLOGY / EXCAVATIONS AND RESEARCH ALONG THE FUTURE TRANSJURANE HIGHWAY A16 JURA / SWITZERLAND

EXCAVATIONS AND RESEARCH ALONG THE FUTURE TRANSJURANE HIGHWAY A16 JURA / SWITZERLAND

RESEARCH

GENERAL

RESEARCH

ABOUT US

A new project called Palaeontology A16 (Paléontogie A16) was established in February 2000, thanks to the construction of the Transjurane highway A16 (northwestern Switzerland). This project is integrated in the “Section d’archéologie et paléontologie” of the “Office de la culture” of the Canton Jura.

Our mission is the safeguarding of the geological and palaeontological heritage along the future highway course. This comprises excavations, preservation, research and promotion. One of our main goals is to document and promote the natural history of the Jura Mountains. We aim to reconstruct the palaeoecology, the palaeoclimatology and the palaeogeography of the research area during the last 160 My. Our main research topics are focused on Mesozoic tetrapods, dinosaur ichnology, Cenozoic mammals, shallow marine invertebrates and microfossils. Additionally, we use sedimentological, mineralogical and biogeochemical analytical methods (e.g. sequence stratigraphy, clay minerals, stable isotopes).

The Transjurane highway A16 crossing the Canton Jura (rose parts: excavation area Paléontogie A16).

We collaborate with researchers from universities and natural history museums in Switzerland and abroad, participate in projects of the Swiss National Science Foundation and co-supervise bachelor, master and PhD studies.

RESEARCH

MESOZOIC

STRATIGRAPHY

For a long time, the stratigraphy of the Late Jurassic of the Ajoie district has only insufficiently been understood. The main reasons were the bad outcrop conditions due to the flat plateau morphology, where outcrops can only be found in quarries or street and railway outcrops. In the framework of the construction of the Transjurane highway A16, numerous outcrops from the Upper Jurassic were available in the Ajoie region (Canton Jura, northwestern Switzerland). Palaeontological excavations (by the Palaeontology A16), highway construction, opening of new quarries and realisation of core drillings led to an important geological documentation. This set of new data, both from field and laboratory observations, allows proposing new lithostratigraphic subdivision and to precise the lateral evolution of facies within the Late Jurassic carbonate platform.

<<PDF : Litho- and Biostratigraphy of the Late Jurassic in the Ajoie region.

The biostratigraphic frame has only been poorly known and since the excavations of the Palaeontology A16 started, many ammonites have been discovered. These ammonites allowed establishing a well-defined biostratigraphical frame for the upper Reuchenette Formation of northwestern Switzerland. The ammonite zonation currently used are the one of Cariou et al. (1997) for the Oxfordian, and the one of Hantzpergue et al. (1997) for the Kimmeridgian. The Kimmeridgian is marked through an increased provincialism with three domains: the “Domaine Téthysien”, the “Domaine Boréal” and the “Biome Franco-Germanique” which lies in between and comprises the study area.

DINOSAUR TRACKSITES

Since 2002, the Palaeontology A16 systematically excavates and documents dinosaur tracksites prior to the construction of the Swiss federal Transjurane highway A16. Four Late Jurassic (Kimmeridgian) intervals, three of which are laminites with several superimposed track-bearing levels, were excavated level-by-level on six tracksites situated on the future course of the highway.
So far, this revealed 59 ichnoassemblages with 13’475 tracks including 256 sauropod trackways and 405 trackways of tridactyl bipedal dinosaurs, mainly attributed to theropods. The tracks are documented with standard ichnological and state-of-the-art 3D imaging technologies (laserscanning, close-range photogrammetry).

Courtedoux-Bois de Sylleux tracksite, overview of level 1050. Besides large to huge sauropod (diameter of pes impressions up to 1.2 m) and tridactyl (pes length up to 75 cm) tracks, numerous trackways of small theropods were also found. Tracks are artificially coloured in black, man for scale.

Courtedoux-Sur Combe Ronde tracksite, laser scan of the main track level. Crossroads of three sauropod trackways. The oval pes impressions have a diameter around 40 cm. These were the first trackways discovered and excavated in 2002 on the future course of the highway A16.

Courtedoux-Tchâfouè tracksite, desiccation-cracked level 1055. Narrow-gauge sauropod trackway S4 with well-defined semi-circular manus and oval pes impressions, the latter exhibiting digit impressions. Hammer for scale..

Sauropod and tridactyl tracks both vary from very small (10 cm pes length for sauropods; 6 cm for tridactyl tracks) to huge (115 cm for sauropods; 75 cm for tridactyl tracks), and different size classes and morphotypes are commonly associated on single ichnoassemblages. Trackways are up to 115 m long exhibiting different patterns and configurations, also along single trackways. These rich dinosaur ichnoassemblages give important insights into the otherwise poorly-known Late Jurassic dinosaur fauna of the Jura carbonate platform.

Chevenez-Combe Ronde tracksite, main track level. Tridactyl right track R2 with metatarsal impression of trackway T30, possibly left by a small theropod dinosaur. Note small displacement rims around the third digit. Track is filled with water and total track length is approximately 20 cm.

The tracksites are today recognized as an important part of the natural, palaeontological heritage of Switzerland, and so far, one tracksite was protected by the construction of an additional highway bridge. Discussions concerning the future (covering-up or protection by an additional highway bridge) of another site are currently under way at federal level.
A new project of the Canton Jura called paléojura >>> aims at the valorization of the tracksites and the palaeontological heritage in general in terms of sciences, education, and tourism.

VERTEBRATES

Beside dinosaur footprints, bones and teeth of vertebrates reveal a rich and diverse Kimmeridgian coeval fauna, living in a coastal marine environment. The non-dinosaurian assemblage includes bony fishes, sharks, rays, turtles, crocodilians, and some rare remains of sauropterygians and pterosaurs (flying reptiles), deposited in the shallow subtidal setting of the Virgula marls.

Carapace of the coastal marine turtle Plesiochelys, from Courtedoux-Tchâfoué.

Among reptiles, the main fossil group is that of coastal marine turtles, represented by more than 90 carapaces and thousands of isolated bones, belonging to several genera of "Plesiochelyidae" (Plesiochelys, Craspedochelys, Tropidemys, Thalassemys). At the Western Europe scale, Courtedoux appears as a new key locality for Late Jurassic chelonians. Along with the famous Solothurn Turtle Limestone, Switzerland counts now two key Kimmeridgian localities to study basal Eucryptodires.

The other significant reptilian group is that of thalattosuchian crocodilians, with both Teleosauridae (Steneosaurus, Machimosaurus) and Metriorhynchidae (Metriorhynchus, Dakosaurus). Hundreds of isolated teeth and bones, several mandibules and two disarticulated but associated skeletons of Steneosaurus and Metriorhynchus have been found. So far, it is the first recognized occurrence of Metriorhynchus in Switzerland.

Skeleton of the marine crocodilian Metriorhynchus, from Courtedoux–Bois de Sylleux.
Scale bar is 30 cm

This new margino-littoral assemblage of vertebrates can be compared with those from the Late Jurassic of Western Europe, notably Solothurn (Switzerland), Nusplingen and Solnhofen (Germany), Cerin and Canjuers (France).

Woody axis of the conifer Protocupressinoxylon, from Courtedoux–Sur Combe Ronde.
Scale bar is 20 cm

Along with vertebrates, a lot of woody axes of a conifer (Protocupressinoxylon purbeckensis) are common in the Virgula marls, attesting the proximity of the emerged “dino” land.

TAXONOMY AND PALAEOECOLOGY OF UPPER JURASSIC BIVALVES

During the excavations along the future course of the Transjurane highway A16 the research group PAL A16 discovered and collected more than 20000 invertebrate fossils between 2000 and 2011 in the Upper Jurassic of Northwestern Switzerland, the majority comes from the Reuchenette Formation. Bivalves are the dominant invertebrate group in the sediments of a shallow marine carbonate platform, which occupies the Helvetic Shelf in Upper Jurassic times. In several horizons bivalves occur in high frequencies, sometimes they are enriched in mass accumulations, e.g. lumachelles and shell beds in the Banné-Marls (Cymodoce Zone) or in the Virgula-Marls (Eudoxus Zone). The diversity is rather high and approximately 100 species of bivalves can be found at least by close examinations of the Kimmeridgian successions. The preservation of bivalves is different, epibentic forms e.g. in the Banné-Marls, with a stabil calcitic shell like Trichites, Isognomon or Pectinids, are often very well preserved as bivalved specimens. But the majority of the infaunal bivalves (Heterodonta, Anomalodesmata and Palaeotaxodonta) are frequently found as internal moulds, because of the dissolution of the primary aragonitic shell during early diagenesis.

Actinostreon gregareum (J. Sowerby 1815) and Nanogyra nana (J. Sowerby 1822), VTT001-1704, coll. Pal. A16, Lower Kimmeridgian, Cymodoce Zone, Banné-Marls, Reuchenette Formation, Vâ Tche Tchâ near Courtedoux (Ajoie, Canton Jura); group of 3 specimen of A. gregareum (2 complete individuals, 1 left valve) attached on a right valve of Costigervillia sp. (picture on the right), several small left valves of Nanogyra nana attached somewhat later on all specimens of Actinostreon, note the well preserved isolated right valve of N. nana (left side, center); specimens whitened with ammonium chloride.

The first research on the rich bivalve faunas in the Swiss Jura was done in the 19th century by the well-known local geologist and palaeontologist Jules Thurmann (1804-1855). His work on the fossil remains in the Upper Jurassic of the Jura bernois in the neighbourhood of Porrentruy was interrupted by his earlier death, but A. Etallon published the results of his work posthumously. The famous monograph “Lethaea Bruntrutana” of Thurmann & Etallon (1861-64) and the important research done by Contejean (1859), about the geology and palaeontology of the adjacent Jura in the region of Montbéliard (France), are the basis for the taxonomic revision of the bivalve fauna in the Kimmerdigian of the Canton Jura and adjacent France.
The results of the taxonomic work on the new collected material of the Palaeontology A16 and the reevaluation of the historical collections stored in the Cuvier Museum in Montbéliard and the Jura Museum of Natural Sciences in Porrentruy will be published in the next future.

CRINOIDS

Excavations during the Transjurane highway A16 work near Boncourt allowed the discovery of a reef consisting of oysters at its base (hard substrat) and crinoid remains. The documentation of this reef was only possible thanks to the importance of the highway construction and represents an exceptional opportunity. Blocks collected in Boncourt will permit to understand how to build an oyster reef and his colonization by crinoids. In addition, the study of sediment layers deposited at that time will give us indications about the chronology of past events (growth-settlement-"destruction").

Well preserved and articulated crinoid calyx.

Indeed, most of the remains of crinoids are associated with tempestite deposits. The system “oyster bioconstructions + crinoidal tempestites” is sealed at the top by a sandy layer. The removal of the oyster reef with crinoids will be a remarkable scientific and museographic object. The material is exceptional both in terms of quantity and quality for these levels.

RESEARCH

CENOZOIC

TERRESTRIAL PALAEOECOLOGICAL EVOLUTION

What did coastal plains, tropical forests, savannahs, and tundra-steppe look like in the distant geologic past? In which ways were these past environments different from today? How did the mammal communities react to paleogeographic and climatic changes? These are the questions that intrigue the Cenozoic Research Group.

RESEARCH

Landscape reconstruction of the Vâ Tche Tchâ valley during the latest Middle Pleniglacial (NW Switzerland) (T. Yilmaz – ©OCC/SAP)

The research interests of the Cenozoic Research Group are in the mammal palaeobiogeography, palaeobiology and evolution, the mammal systematics, the Late Pleistocene mammals, and the litho-biostratigraphy and palaeogeography of the Molasse Basin deposits. Projects cover topics as post-“Grande Coupure” faunal recolonisation, Jura Molasse stratigraphy, Late Pleistocene environments, Megafauna extinction in Western Europe as well as doline-fills and karstogenesis. Rhinocerotoid and anthracotheriid systematics, small mammal biostratigraphy, and Quaternary malacology accompany the research effort.