Jimmy Van Itterbeeck

Taphonomy and Age Profile of a Latest Cretaceous Dinosaur Bone Bed in Far Eastern Russia

Abstract A large dinosaur bone bed has been investigated in the Udurchukan Formation (?late Maastrichtian) at Blagoveschensk, Far Eastern Russia. The observed mixture of unstratified fine and coarse sediments in the bone bed is typical for sediment-gravity-flow deposits. It is postulated that sediment gravity flows, originating from the uplifted areas at the borders of the Zeya-Bureya Basin, reworked the dinosaur bones and teeth as a monodominant bone bed. Fossils of the lambeosaurine Amurosaurus riabinini form >90% of the recovered material. The low number of associated skeletal elements at Blagoveschensk indicates that the carcasses were disarticulated well before reworking. Although shed theropod teeth have been found in the bone bed, <2% of the bones exhibit potential tooth marks; scavenging activity was therefore limited, or scavengers had an abundance of prey at hand and did not have to actively seek out bones for nutrients. Perthotaxic features are very rare on the bones, implying that they were not exposed subaerially for any significant length of time before reworking and burial. The underrepresentation of light skeletal elements, the dislocation of the dental batteries, and the numerous fractured long bones suggest that most of the fossils were reworked. The random orientation of the elements might indicate a sudden end to transport before stability could be reached. The size-frequency distributions of the femur, tibia, humerus, and dentary elements reveal an overrepresentation of late juveniles and small subadult specimens, indicative of an attritional death profile for the Amurosaurus fossil assemblage. It is tentatively postulated that the absence of fossils attributable to nestling or early juvenile individuals indicates that younger animals were segregated from adults and could join the herd only when they reached half of the adult size.

Cenozoic deformation and exhumation of the Kampot Fold Belt and implications for south Indochina tectonics

Latest Mesozoic to earliest Cenozoic deformation affected SE Asias Sundaland core. The deformation event bridges the Mesozoic SE Asian fusion with the Cenozoic era of rifting, translation, basin formation, and the creation of modern SE Asian oceans. Southern Cambodia and Vietnam are central to this shift, but geological investigations of the region are in their infancy. Based on apatite and zircon fission track analyses (AFTA and ZFTA), stratigraphic and structural observations, seismic data, thermal maturity, and igneous rock dating, the geological evolution of southern Cambodia and Vietnam is investigated. Diverse depositional styles, igneous activity, structural deformation and subsurface unconformities testify to a highly variable Phanerozoic tectonic setting. Major latest Cretaceous to Paleocene thrusting and uplift affected the Kampot Fold Belt and surrounding regions and the associated up to ~11 km exhumation probably exceeds earlier denudation events since at least Permian time. The present relief of the Bokor Mountains rising high above the Kampot Fold Belt represents an artifact after differential erosion and only 2.5–4.5 km of erosion affected this area. The latest Cretaceous to Paleocene orogenesis affected much of greater Indochina probably owing to plate collision along eastern Sundaland or a combination of collisions along both east and west Sundaland. AFTA and ZFTA data document protracted cooling of Cretaceous granites and locally elevated thermal gradients persisting a few tens of million years after their emplacement. The thermal gradient had stabilized by early Miocene time, and Miocene cooling probably reflects a renewed denudation pulse driven by either regional tectonism or climate-enhanced erosion.

Oculobairdoppilata gen. nov. (Ostracoda, Bairdiidae): a new genus from the Paleocene of Tunisia

A new marine ostracod genus, Oculobairdoppilata, belonging to the family Bairdiidae, is described from Paleocene deposits in Tunisia. Its main characteristic is the occurrence of an eye tubercle in the anterodorsal part of the valves. Internally, small denticles and corresponding sockets are present at the terminal parts of the dorsal edge of the right and left valves, respectively. It is the first bairdiid with an external eye structure to be described, although the existence of such a genus was predicted previously.