Search results for "Cretaceou"
showing 10 items of 184 documents
Ancient or recent? Insights into the temporal evolution of the Bruniaceae
2008
AbstractThe Bruniaceae are a South African plant family endemic to the Cape Floristic Region with one geographic outlier (Raspalia trigyna) in the Natal Province. Recent molecular phylogenetic analyses have cast new light upon inter- and intra-generic relationships within the family. The present work uses those data to gain insights into the temporal evolution of Bruniaceae by inferring a molecular clock. For calibration, the inferred age of Berzelia cordifolia (3–5My) was used, based on its distribution restricted to the geologically young limestone area around Bredasdorp. The results are consistent with the purported Cretaceous age of the family (‘palaeoendemics’), but also suggest that m…
Zonation by ammonites and foraminifers of the Vraconnian-Turonian interval: A comparison of the Boreal and Tethyan domains (NW Europe / Central Tunis…
2008
International audience; Since the end of the 19th century the interval comprising the uppermost Upper Albian, the Cenomamian, the Turonian and the basal Coniacian has been subdivided, first into ammonite zones, then, beginning in the middle of the 20th century, into zones of planktonic foraminifera. These two groups, one macrofossil, the other microfossil, are particularly effective for bio-chronostratigraphy thanks to their rapid rates of evolution. But differences in the faunal makeup between the Boreal domain (northwestern Europe) and the Tethyan domain (Mediterranean) have for a long time hindered precise correlation of the two domains. Today, in a time interval covering about 16 millio…
Morphometry of micrite particles in cretaceous microporous limestones of the Middle East: influence on reservoir properties.
2011
24 pages; International audience; Microporosity may account for a significant part of the total porosity of Cretaceous limestone reservoirs of the Middle East. In these microporous facies porosity is moderate to excellent (up to 35%) while permeability is poor to moderate (up to 190 mD). Micritic limestones also may form dense layers with very low porosity and permeability values. Micritic samples were collected from three fields of the Habshan and Mishrif Formations, to examine the spatial relationship with their porosity, permeability and pore throat radius distributions. Two key parameters of the micritic particles are studied using scanning electron microscopy: their morphology (shape a…
Paleobiology and paleobiogeography of sclerorhynchid sawfishes (Chondrichthyes, Batomorphii)
2021
Sclerorhynchid sawfishes are a monophyletic group of Cretaceous selachians. They resemble modern sawfishes in the outer morphology and by having a hypertrophic rostral cartilage armed with lateral rows of spines. Generally, sclerorhynchid sawfishes were inhabitants of warm, shallow tropical and subtropical marine environments. Teeth of the oldest sclerorhynchid sawfishes from Spain are presented. They belong to Onchopristis Stromer and come from the lower Barrernian of eastern Spain. The paleobiology and paleogeographic pattern of sclerorhynchid sawfishes is reviewed and discussed.
Record of latest Barremian-Cenomanian environmental change in tectonically controlled depressions from the Jura-Burgundy threshold (Jura Mountains, e…
2019
The area of the western Jura Mountains constitutes the former Jura-Burgundy threshold between the Tethys Ocean and the epicontinental Paris Basin Sea. During the Barremian, the area was covered by a shallow-water Urgonian carbonate platform. Tectonic processes influenced the architecture of the Urgonian platform and were notably responsible for the formation of fault-related depressions on top of the Urgonian series, which were subsequently transformed into incised valleys and then to marine depocenters. Their sedimentary infills are mostly represented by the Perte-du-Rhône Formation and record stepwise environmental change on the innermost platform, which was strongly influenced by the nea…
Evolution de la circulation oécanique profonde durant le Crétacé : apport des isotopes du néodyme
2014
The Cretaceous is depicted as the warmest period of the last 300 Ma. The oceanic circulation and location of the source zones of deep-waters are essential to understand the role of oceans in the evolution of the climate during the Cretaceous, yet they remain unclear for this period. The neodymium (Nd) isotopes are used to track oceanic circulation and exchanges between water masses, in both past and modern oceans. The Nd isotope composition (εNd) in the ocean is related to the nature of the surrounding continental landmasses. The oceanic currents transport this isotopic signature, thus every oceanic basin acquires a singular εNd. Unequivocal interpretations of the Cretaceous seawater εNd va…
Isotopic ordering in eggshells reflects body temperatures and suggests differing thermophysiology in two Cretaceous dinosaurs
2015
International audience; Our understanding of the evolutionary transitions leading to the modern endothermic state of birds and mammals is incomplete, partly because tools available to study the thermo-physiology of extinct vertebrates are limited. Here we show that clumped isotope analysis of eggshells can be used to determine body temperatures of females during periods of ovulation. Late Cretaceous titanosaurid eggshells yield temperatures similar to large modern endo-therms. In contrast, oviraptorid eggshells yield temperatures lower than most modern endotherms but B6 °C higher than co-occurring abiogenic carbonates, implying that this taxon did not have thermoregulation comparable to mod…
L’élongation des loges chez les foraminifères planctoniques du Crétacé inférieur: une adaptation à la sous-oxygénation des eaux?
1998
Abstract Planktic foraminifera with radially elongated chambers appeared on four occasions in the early Cretaceous of the Vocontian Basin (SE France). These appearances coincided with or followed the deposition of organic rich levels which are evidence of hypoxic to anoxic conditions at the sea-floor. In addition, oxygen deficient surface waters are inferred from the occasional presence of Hedbergellas with deformed (insufficiently calcified) walls. It is suggested that the elongation of the chambers of these foraminifera was an adaptive response to the low oxygen content of surface waters, the increased surface area of the test allowing better gas exchange with sea water and the intake of …
Chemostratigraphy, magnetostratigraphy, chronology, palaeoenvironments and correlations.
2013
4 pages
Characterization of coelacanth scales from the Early Cretaceous freshwater locality of Las Hoyas, upper Barremian (Cuenca, Spain)
2020
Coelacanths are rare, mostly marine fishes, but the species from the Lower Cretaceous Spanish locality of Las Hoyas (Barremian) is a freshwater form and we know almost nothing about it. The Las Hoyas specimens are very rare and relatively incomplete, but there are still many things we can learn from the isolated skeletons and scales. First, the coelacanth scales were distinguished from other superficially similar scales (i.e., other “amioid” scales). Coelacanth scales are distinguished by the presence of a smooth central surface, a particular pattern of arrangement of concentric growth cessation marks, and mainly a relatively short posterior field with thick elongated ridges. Only a few art…