Tectonic control on the palaeogeographical evolution of the Miocene seaway along the Western Alpine foreland basin

The Miocene of the Western Alpine foreland basin were deposited in a North-South seaway along the active alpine orogenic front. In the subalpine massifs and the southern Jura mountains, the revised Miocene stratigraphy documents a detailed chronology of thrust propagation at the western alpine front, where tectonic activity had a primary influence on seaway palaeogeographical evolution. Here we propose nine palaeogeographical maps during the Miocene, the first of which depicts the initial Miocene transgression at ∼21.0 Ma. Between ∼18.05 Ma and ∼12.0 Ma, a westward retreat of the Miocene Sea occurred in response to the activation of the basal thrust of the Belledonne massif, which in turn triggered successive fault zones from east to west. At ∼10.0 Ma, a major uplift phase intervened and induced a rapid southward retreat of the Miocene Sea. The reconstructed palaeogeographical maps outline the main controls on the foreland basin seaway evolution: (i) the timing of the main thrusts, (ii) the inherited palaeotopography and (iii) eustatic sea-level changes during the Miocene. These reconstructions are integrated at the basin scale, highlighting the southward to westward-directed seaway migration in response to the Belledonne thrust activity that deeply shaped the palaeogeographical evolution during the early to middle Miocene.

New insights on the Early Cretaceous (Hauterivian–Barremian) Urgonian lithostratigraphic units in the Jura Mountains (France and Switzerland): the Gorges de l’Orbe and the Rocher des Hirondelles formations

The Hauterivian–Barremian series of the Jura Mountains were measured over more than 60 sections along a 200 km long transect between Aix-les-Bains (Savoie Department, France) and Bienne (Bern Canton, Switzerland), which prompted the need for a revision and improvement of the current lithostratigraphic scheme for this stratigraphic interval. A new formation, the Rocher des Hirondelles Formation, is proposed in replacement of the unsuitable Vallorbe Formation, while the Gorges de l'Orbe Formation is formally described. The Gorges de l'Orbe Formation, equivalent to the well-known “Urgonien jaune” facies, consists of two members, namely Montcherand Member and Bôle Member. The Rocher des Hirondelles Formation, equivalent to the “Urgonien blanc” facies, consists of three members, i.e. Fort de l'Écluse Member, Rivière Member and Vallorbe Member. The marly Rivière and Bôle members appear to present time-equivalent lithostratigraphic units, recording a major sedimentological event affecting contemporarily both formations. This study proposes a new sedimentary model opening a new point of view on the long-living controversies about the age of the Urgonian series from the Jura Mountains. The data point to strong diachronic ages of lithostratigraphic units with a late Hauterivian to early Barremian occurrence of the “Urgonian blanc” facies in the Meridional Jura area versus a latest Barremian age in the Central Jura area, reflecting a general progradation of the Urgonian shallow-water carbonate platform from the present-day Meridional Jura area toward external deeper-water shelf environments of the present-day Central Jura area and Molasse basin.

A reevaluation of the Late Jurassic dinosaur tracksite Barkhausen (Wiehengebirge, Northern Germany)

A restudy of the Barkhausen dinosaur tracksite shows that the track-bearing surface reveals considerably more detail than previously indicated, and a new map is presented, showing the trackways of nine sauropods, traveling north, possibly as a group. These are among the smallest sauropod tracks recorded in Europe. There is also evidence of two large theropods crossing the area, one moving to the south and the other to the west. Evidence of at least three other sauropods is registered in the form of isolated manus traces that represent larger individuals. Previous interpretations inferred that sauropod trackways trended south, and therefore suggested a predator chasing its prey as in the purported but controversial attack scenario claimed for the famous Paluxy River site in Texas. Based on the present study, this scenario is no longer tenable for the Barkhausen tracksite. The description of Elephantopoides barkhausensis (Kaever and Lapparent, 1974) shows that it represents a moderately wide gauge, but small manus sauropod and can be assigned under the ichnofamily label Parabrontopodidae. E. barkhausensis as originally defined was a nomen dubium, but it has since been re-described semi-formally, without renaming, we emend the description and assigned them to the ichnotaxon Parabrontopodus barkhausensis comb. nov. These tracks could have been produced by the small sauropod dinosaur taxon Europasaurus. The problematic ichnotaxon Megalosauropus teutonicus (Kaever and Lapparent, 1974), which represents a large three-toed theropod, is assigned to the recently described ichnogenus Jurabrontes from the Late Kimmeridgian of the Swiss Jura mountains as Jurabrontes teutonicus comb. nov. Furthermore, we attribute the theropod tracks from the time equivalent Langenberg quarry to the same ichnotaxon.