Integrated Paleoenvironmental Reconstruction and Taphonomy of a Unique Upper Cretaceous Vertebrate-Bearing Locality (Velaux, Southeastern France)

Abstract

The Velaux-La Bastide Neuve fossil-bearing site (Bouches-du-Rhône, France) has yielded a diverse vertebrate assemblage dominated by dinosaurs, including the titanosaur Atsinganosaurus velauciensis. We here provide a complete inventory of vertebrate fossils collected during two large-scale field campaigns. Numerous crocodilian teeth occur together with complete skulls. Pterosaur, hybodont shark and fish elements are also represented but uncommon. Magnetostratigraphic analyses associated with biostratigraphic data from dinosaur eggshell and charophytes suggest a Late Campanian age for the locality. Lithologic and taphonomic studies, associated with microfacies and palynofacies analyses, indicate a fluvial setting of moderate energy with broad floodplain. Palynomorphs are quite rare; only three taxa of pollen grains occur: a bisaccate taxon, a second form probably belonging to the Normapolles complex, and another tricolporate taxon. Despite the good state of preservation, these taxa are generally difficult to identify, since they are scarce and have a very minute size. Most of the vertebrate remains are well preserved and suggest transport of the carcasses over short distances before accumulation in channel and overbank facies, together with reworked Aptian grains of glauconite, followed by a rapid burial. The bones accumulated in three thin layers that differ by their depositional modes and their taphonomic histories. Numerous calcareous and iron oxides-rich paleosols developed on the floodplain, suggesting an alternating dry and humid climate in the region during the Late Campanian.

The oldest freshwater crabs: claws on dinosaur bones

“…3d), has been extracted from a comparable block, also containing a crocodylomorph skull, a rhabdodontid tooth, as well as a partial titanosaurid dorsal vertebra showing preserved ossified tendons. The freshwater palaeoenvironment of the channel in sequence 2 is strongly supported not only by sedimentological evidence 23 , but also by the most recently collected taxonomic assemblage itself.…”

“…Magnetostratigraphic analysis of the deposits, however, correlates with the normal chron of chron 32 23 , corresponding to an age of 71.6 to 74 Ma 24 . Along with correlations with charophytes and dinosaur eggshell biozones, a late Campanian age for the locality may confidently be proposed 23,[25][26][27] . The fossil site is mostly known for its vertebrate assemblage, recovered from three different sedimentological sequences and corresponding to newly described 110 dinosaur (titanosaurid sauropod 26,28 ; rhabdodontid ornithopod 29 ) and pterosaur (azhdarchid pterosaur 30 ) taxa, as well as eusuchian crocodilians 27 .…”

“…Velaux-La Bastide Neuve is located in the western part of the Aix-en-Provence Basin, Southeastern France. K-Ar dating of the locality was attempted based on glauconites collected from sandstones 23 , but these minerals are clearly reworked from lower Aptian marine limestones and are therefore 105 useless for dating the site 23 . Magnetostratigraphic analysis of the deposits, however, correlates with the normal chron of chron 32 23 , corresponding to an age of 71.6 to 74 Ma 24 .…”

“…K-Ar dating of the locality was attempted based on glauconites collected from sandstones 23 , but these minerals are clearly reworked from lower Aptian marine limestones and are therefore 105 useless for dating the site 23 . Magnetostratigraphic analysis of the deposits, however, correlates with the normal chron of chron 32 23 , corresponding to an age of 71.6 to 74 Ma 24 . Along with correlations with charophytes and dinosaur eggshell biozones, a late Campanian age for the locality may confidently be proposed 23,[25][26][27] .…”

“…The sedimentology of the site together with the fossil assemblage indicates a likely freshwater setting for the deposits. The succession of conglomeratic sandstones, 120 siltstones (including paleosols), mudstones and lacustrine limestone on top of the stratigraphic section indicate sedimentation in, respectively, a low-energy fluvial channel, channel levees, alluvial plain and lake 23 . Given the proximity of Velaux to the paleo-coast during the Late Cretaceous 31,32 , occasional marine incursions are not excluded, even though they were not recorded at Velaux-La Bastide Neuve nor at other fossiliferous localities of the same age in the region 23,25 .…”