Abundant lagoonal oncoids occur in the Late Oxfordian Hauptmumienbank Member of the Swiss Jura Mountains. Four oncoid types are observed in the studied sections and classiWed according to the oncoid surface morphology, the structure and composition of the cortex, and the texture and fauna of the encasing sediment. Micritedominated oncoids (types 1 and 2) have a smooth surface. Type 1 has a rather homogeneous cortex and occurs in moderate-energy environments. Type 2 presents continuous or discontinuous micritic laminae. It is associated with a low-diversity fauna and occurs in high-energy facies. Bacinella and Lithocodium oncoids (types 3 and 4) display a lobate surface. They are dominated by microencrusters (Bacinella irregularis and Lithocodium aggregatum) and are found in low-energy facies. The stratigraphic and spatial distribution of these oncoid types shows a correlation with the sequence-stratigraphic evolution of the studied interval, and thus with relative sea-level Xuctuations. It can be shown that these sea-level Xuctuations were controlled by orbital cycles with 100-and 20-kyr periodicities. At the scale of 100-and 20-kyr sequences, types 1 and 2 oncoids are preferentially found around sequence boundaries and in transgressive deposits, while types 3 and 4 oncoids are preferentially found around maximum Xoodings and in highstand deposits. This implies that changes of water energy and water depth were direct controlling factors.Discrepancies in oncoid distribution point to additional controlling factors. Platform morphology deWnes the distribution and type of the lagoon where the oncoids Xourished. A low accumulation rate is required for oncoid growth. Additionally, humidity changes in the hinterland act on the terrigenous inXux, which modiWes water transparency and trophic level and thus plays a role in the biotic composition and diversity in the oncoid cortex.

Characteristic fabrics such as micrite envelopes, calcified filaments and micritic grain‐to‐grain bridges are observed in a modern subtidal firmground (Wood Cay, Bahamas) and in a variety of firm‐ and hardgrounds of Lower Cretaceous and Upper Jurassic platform carbonates (Swiss and French Jura Mountains). Their similarity to microbial fabrics described in grapestones and in intertidal to continental vadose environments suggests that microbial activity played an important role in the initial stabilization and cementation of carbonate sands. ‘Meniscus‐type cements’ (to distinguish them from vadose meniscus cements), which clearly formed in subtidal environments, are related to filament calcification, trapping of percolating micrite and microbially induced carbonate formation. Such meniscus‐type cements are commonly micritic, but meniscus‐shaped precipitation of fibrous aragonite or sparitic calcite around organic filaments is also observed. Therefore, an interpretation of vadose early diagenesis should not be based on meniscus cements alone. Similarly, subtidally formed filamentous structures can strongly resemble alveolar septal structures and be interpreted incorrectly as related to subaerial exposure.

The origin of third‐order depositional sequences remains debatable, and in many cases it is not clear whether they were controlled by tectonic activity and/or by eustatic sea‐level changes. In Oxfordian and Berriasian–Valanginian carbonate‐dominated sections of Switzerland, France, Germany and Spain, high‐resolution sequence‐stratigraphic and cyclostratigraphic analyses show that the sedimentary record reflects Milankovitch cyclicity. Orbitally induced insolation changes translated into sea‐level fluctuations, which in turn controlled accommodation changes. Beds and bedsets formed in rhythm with the precession and 100‐kyr eccentricity cycles, whereas the 400‐kyr eccentricity cycle contributed to the creation of major depositional sequences. Biostratigraphical data allow the correlation of many of the 400‐kyr sequence boundaries with third‐order sequence boundaries recognized in European basins. This implies that climatically controlled sea‐level changes contributed to the formation of third‐order sequences. Furthermore, this cyclostratigraphical approach improves the relative dating of stratigraphic intervals.

In 2002 a new dinosaur tracksite was discovered in calcareous laminites of early Late Kimmeridgian age along the future course of the "Transjurane" highway in Courtedoux, Canton Jura, Northern Switzerland. The site has an extraordinary scientific potential, as the laminites, which have been deposited in an intertidal to supratidal environment, contain at least 6 track-bearing levels in a total thickness of about 1 m. The laminites are being systematically excavated by the "Section de paléontologie" over an area of approximately 1500 m 2 . So far the main track level has been uncovered over an area of about 650 m 2 , which reveals 2 trackways of theropods and 17 trackways of sauropods. The sauropod tracks are the smallest known in the Kimmeridgian so far, and the trackways belong to the ichnogenus Parabrontopodus, which has been revealed for the first time in Switzerland. The tracksite belongs to the "Middle Kimmeridgian megatracksite" sensu Meyer (2000), and represents the most important dinosaur tracksite in Switzerland, perhaps with the potential for development into one of the world's largest sauropod tracksites. It will be protected in situ underneath an especially constructed highway-bridge, thus offering opportunities for future research and the development of an interpretative center for education and tourism.

No abstract

Located in the distal part of the Swiss Molasse Basin and in the southern extension of the Rhine Graben, the conglomeratic deposits belonging to the Gompholithes & Conglomérats stratigraphic group have been the object of detailed sedimentological and paleontological studies. The great number of outcrops that came into sight during the building works of the Transjurane highway in the vicinity of Porrentruy (Swiss Jura) lead to a better understanding of Rupelian paleoenvironments (Early Oligocene).The sedimentological and paleontological studies reveal the existence of coastal environments with Mesozoic limestone cliffs notched by canyons with torrential rivers. Those rivers eroding the Mesozoic series create pebbles deposits forming marine deltas prograding towards North. In protected areas, some lacustrine environments can develop.These conglomeratic deposits are strongly bound to the Rupelian tectonic activity. The rhenish distension and the activity of the transform faults located between the Rhine Graben and the Bresse basin divide the Mesozoic blocks in horst and graben structures, thus allowing the erosion of sediments in higher regions (horst) and their transport in lower zones (graben).The discovery of rare pebbles made of endogene and effusive rocks in those conglomeratic deposits shows a transport coming from the Vosges massifs towards south to the Porrentruy region, probably with the support of a littoral drift. Although the surrection of the Vosges and Schwarzwald massifs (and the beginning of their erosion) is normally attributed to the base of the Miocene, the presence of those pebbles attests the existence of faults putting the basement of the Vosges massif to erosion since the base of Rupelian. RESUME Situés dans la partie la plus distale du bassin molassique suisse et dans le prolongement sud du fossé rhénan, les dépôts conglomératiques appartenant au groupe stratigraphique des Gompholithes & Conglomérats ont fait l'objet d'une étude sédimentologique et paléontologique détaillée. La multitude des affleurements réalisés lors des travaux de construction de l'autoroute Transjurane dans la région de Porrentruy (Jura), permet d'appréhender ces paléoen-vironnements rupéliens (Oligocène inférieur).Les études sédimentologiques et paléontologiques révèlent l'existence d'environnements côtiers avec des falaises de calcaires mésozoïques entaillées par des canyons où se trouvent des rivières au régime torrentiel. Ces rivières qui érodent les couches du Mésozoïque créent des galets qui sont déposés sous la forme de deltas marins progradant vers le nord. A l'abri des exutoires des canyons se développent quelques environnements lacustres.Ces dépôts conglomératiques sont fortement liés à l'activité tectonique rupélienne. La distension rhénane et l'activité de la faille transformante située entre le fossé rhénan et le bassin de la Bresse subdivisent les différents blocs mésozoïques en horsts et grabens, permettant ainsi l'érosion des sédiments dans les parties hautes (horst) et leur transport dans les zones basses...

No abstract

No abstract