1,413 research outputs found
Reassessment of the Bivalvia (Mollusca) from the Boom Formation (Rupelian, Oligocene) of Belgium, with description of new species
The bivalve species found in the Boom Formation (Rupelian, Early Oligocene) in Belgium are taxonomically revised. The distribution of the species over the Members and beds of this Formation is detailed. Of the 39 species occurring in the Boom Formation, 11 are recorded for the first time in Belgium, four of which are new to science: Semierycina (Semierycina) kruibekensis nov. sp., Scacchia (Scacchia) dufraingi nov. sp., Thracia (Thracia) vanremoorteli nov. sp. and Cardiomya (sensu lato) annamariae nov. sp. The large majority of the species seems to be endemic to the North Sea Basin. It is attemped to link the distribution of the species to ecological conditions (especially bathymetry) of the different beds
Ecology and evolution of Pliocene bivalves from the Antwerp Basin
The dock construction works in the port of Antwerp at Doel and Kallo (prov. Oost-Vlaanderen, Belgium) have allowed the collection of a rich and diverse Pliocene bivalve fauna. It contains 182 taxa, 178 species and four subspecies. 90 species out of 178 (51%) are extinct. The rate of extinction does not significantly vary between the recognised strata, ranging from Lower to Upper Pliocene. The average longevity of the species is calculated at 10.7 Ma. This long range makes most of these bivalve species unfit for use in Neogene stratigraphy. The bathymetry of the different levels of the Pliocene is assessed, using the species still occurring in the Recent fauna (49% of the total number): it decreases towards the end of the Pliocene
The family Triphoridae in the Neogene of Belgium (Mollusca, Gastropoda)
The taxonomy of the Neogene Triphoridae of Belgium is revised. From the Pliocene, the species Marshallora adverse (MONTAGU, 1803), Triphora radiospirata sp. nov., Triphora antwerpiensis sp. nov., Obesula scaldensis sp. nov., Norephora pliocaenica sp. nov., Subuliphora fritschi (von KOENEN, 1882), Inella vandermarki sp. nov., and Metaxia metaxae (DELLE CHIAJE, 1828) are described from the Kattendijk Formation and the Luchtbal and Oorderen Sand Members. Three Miocene species are studied: Subuliphora fritschi (von KOENEN, 1882), Triphora borealis KAUTSKY, 1925 and Metaxia degrangei (COSSMANN & PEYROT, 1922)
Gaps between jets in double-Pomeron-exchange processes at the LHC
The possibility to measure jet-gap-jet final states in
double-Pomeron-exchange events at the LHC is presented. In the context of the
ATLAS experiment with additional forward physics detectors, cross sections for
different experimental settings and gap definitions are estimated. This is done
in the framework of the Forward Physics Monte Carlo interfaced with a
perturbative QCD model that successfully reproduces standard jet-gap-jet cross
sections at the Tevatron. The extrapolation to LHC energies follows from the
Balitsky-Fadin-Kuraev-Lipatov dynamics, implemented in the model at
next-to-leading logarithmic accuracy.Comment: 8 pages, 5 figures, version to appear in PR
Next-leading BFKL effects in forward-jet production at HERA
We show that next-leading logarithmic (NLL) Balitsky-Fadin-Kuraev-Lipatov
(BFKL) effects can be tested by the forward-jet cross sections recently
measured at HERA. For d\sigma/dx, the NLL corrections are small which confirms
the stability of the BFKL description. The triple differential cross section
d\sigma/dxdk_T^2dQ^2 is sensitive to NLL effects and opens the way for an
experimental test of the full BFKL theoretical framework at NLL accuracy.Comment: 5 pages, 4 figures, NLL-BFKL saddle-point approximation now compared
with exact integration, version to appear in PL
Testing saturation with diffractive jet production in deep inelastic scattering
We analyse the dissociation of a photon in diffractive deep inelastic
scattering in the kinematic regime where the diffractive mass is much bigger
than the photon virtuality. We consider the dominant q\bar{q}g component
keeping track of the transverse momentum of the gluon which can be measured as
a final-state jet. We show that the diffractive gluon-jet production
cross-section is strongly sensitive to unitarity constraints. In particular, in
a model with parton saturation, this cross-section is sensitive to the scale at
which unitarity effects become important, the saturation scale. We argue that
the measurement of diffractive jets at HERA in the limit of high diffractive
mass can provide useful information on the saturation regime of QCD.Comment: 12 pages, 5 figures, misprints corrected, published versio
QCD traveling waves at non-asymptotic energies
Using consistent truncations of the BFKL kernel, we derive analytical
traveling-wave solutions of the Balitsky-Kovchegov saturation equation for both
fixed and running coupling. A universal parametrization of the ``interior'' of
the wave front is obtained and compares well with numerical simulations of the
original Balitsky-Kovchegov equation, even at non-asymptotic energies. Using
this universal parametrization, we find evidence for a traveling-wave pattern
of the dipole amplitude determined from the gluon distribution extracted from
deep inelastic scattering data.Comment: 10 pages, 5 figures, minor revision, version to appear in PL
Stratigraphy of an Early-Middle Miocene sequence near Antwerp in northern Belgium (southern North Sea Basin)
The lithostratigraphy and biostratigraphy of a temporary outcrop in the Antwerp area is described. The deposits can be attributed to the Kiel Sands and the Antwerpen Sands members, both belonging to the Lower and Middle Miocene Berchem Formation. Invertebrate and vertebrate macrofossils are abundantly present. The molluscan fauna compares well to former findings in the Antwerpen Sands Member. It can be concluded that the studied sequence is continuously present in the Antwerp area, and thickens in a northward direction. The study of the marine mammal fauna shows that eurhinodelphinids are the most common fossil odontocete (toothed-bearing cetaceans) in the Antwerpen Sands Member, associated here with kentriodontine, physeteroid, squalodontid, mysticete (baleen whales) and pinniped (seals) fragmentary remains. Both the molluscan fauna and the organic-walled palynomorphs indicate for the Antwerpen Sands Member deposition in a neritic, energetic environment, which shallowed upwards. The dinoflagellate cysts indicate that the Antwerpen Sands Member was deposited during late Burdigalian to Langhian times
- …