Stratigraphy and palaeoceanography of a topography-controlled contourite drift in the Pen Duick area, southern Gulf of Cádiz

The northern part of the Gulf of Cádiz has and still is receiving a lot of attention from the scientific community due to (amongst others) the recent IODP Expedition 339. In contrast, its southern part, or the Moroccan margin has received far less attention, although mud volcanoes, diapiric ridges and cold-water corals are present in this region. The El Arraiche mud volcano field is characterized by a compressive regime creating several ridges and assisting the migration of hydrocarbon fluids towards the seabed surface. This study presents seismic and multibeam evidence for the existence of a contourite drift at water depths between 550 and 650 meters along the southwestern flank of the Pen Duick Escarpment and Gemini Mud Volcano, within the El Arraiche Mud Volcano field. From the onset of the Quaternary, when the escarpment started to lift and the local mud volcanism initiated, contouritic deposition was initiated as well at the foot of both topographic obstacles. Initially, fairly low-velocity bottom currents gave rise to sheeted drift deposits, affected by the uplift of the escarpment or mud extrusion. From the Middle Pleistocene onwards, separated mounded drift deposits were formed due to intensified bottom currents. An Antarctic Intermediate Water origin is inferred as driving mechanism for the drift development, although glacial conditions are not yet well constrained. The influence of Mediterranean Outflow Water (MOW) cannot be substantiated here. Moreover, the changes recorded within this contourite drift differ from the MOW-dominated contourite depositional system in the northern Gulf of Cádiz, as drift deposits only occur as early as the base of the Quaternary (compared to the Early Pliocene for the north) and mounded drift deposits only occur from the Middle Pleistocene onwards (compared to the Early Pleistocene). Cold-water coral mounds have been observed within and on top of the sedimentary sequence at the foot of the Pen Duick Escarpment. This implies that environmental conditions in which cold-water corals thrive were not necessarily restricted to the top of the Pen Duick Escarpment

Hopfield neural network for stereo matching

ln this paper, we present an algorithm designed for the stereovision matching problem and 3D identification. We use a simulated Hopfield neural network to solve the problem of matching a pair of stereoscopic images. This mode1 is helpful in optimization and it can be implemented on parallel machines easily.Nous nous intéressons au problème d'appariement de primitives entre deux images. Notre domaine d'application est la mise en correspondance d'un couple d'images stéréoscopiques ou l'identification des parties d'un modèle dans une image observée. Nous proposons dans ce papier une approche utilisant un modèle de réseau de neurones pour résoudre le problème. Nous avons choisi le modèle de Hopfield d'une part parce qu'il est souple et ouvert, d'autre part parce qu'il peut s'implanter aisément sur des calculateurs massivement parallèles

Deep-water depositional characteristics and relationship with bottom currents at the intersection of Xi’sha Trough and Northwest Sub-Basin, South China Sea

Simulated flow field characteristics at 2000m depth, at the intersection of the Xi’sha Trough and the Northwest Sub-Basin, show a major anticyclonic gyre. These westward flowing deep currents sweep the South China Sea northern margins until they encounter the Xi’sha Trough and the Xi’sha Uplift. Some of them flow into the Xi’sha Trough and continue going westwards; others change their heading towards to the south and sweep the Xi’sha Uplift eastern margins. In the eastern margins, current velocities could exceed 2cm.s-1 as a result of bottom current intensification (after being deflected by the uplifted morphology). Hydrodynamics over the remaining parts of the Xi’sha Uplift zone (south of the Xi’sha Trough) are complex. Fortunately, high-resolution 2D seismic data enable to reveal the depositional characteristics of bottom currents below 1800m depth in this area, whereas marginal troughs and confined drifts are recognized in the vicinity of the obstacle terrains. Major troughs formed north of those obstacles, indicating mainly westward flowing bottom currents in this area. This study focuses on the analysis of deep-water depositional products, created by bottom currents and the relationship with the South China Sea Deep Water Circulation

Quantitative characterisation of contourite deposits using medical CT

Five sediment cores, retrieved from four different depositional contouritic morphological settings (a sheeted drift, a confined mounded drift, a mounded elongated drift and a plastered drift) from the Northern Gulf of Cadiz and the Alboran Sea have been analysed using medical X-ray computed tomography (medical CT). A quantitative approach has been used, resulting in a workflow that delineates several radio-density ranges based on the Hounsfield Unit (HU) histogram of each core and tracks these ranges throughout the cores. In order to derive the geological significance, the radio-density ranges of all cores have been compared to non-destructive, continuous chemical and physical proxies as well as grain size measurements. The highest correlations occurred between high HU and proxies indicating elevated bottom currents, such as Zr/Al and sortable silt. Additionally, a continuous increase in average HU and inferred bottom current velocities, needed for the creation of the specific contourite setting, could be observed throughout the five cores. Despite imperfections and the requirement of additional research, promising results have been obtained which could improve the detection of diagnostic criteria for contourites. Moreover, the CT data can give more conclusive evidence on the nature of the (contourite) sedimentary sequence boundaries

IONS FOR LHC: STATUS OF THE INJECTOR CHAIN

The LHC will, in addition to proton runs, be operated with Pb ions and provide collisions at energies of 5.5 TeV per nucleon pair, i.e. more than 1.1 PeV per event, to experiments. The transformation of CERN's ion injector complex (Linac3-LEIR-PS-SPS) to allow collision of ions in LHC in 2008 is well under way. The status of these modifications and the latest results of commissioning will be presented. The remaining challenges are reviewed

First Results for the Beam Commissioning of the CERN Multi-Turn Extraction

The Multi-Turn Extraction (MTE), a new type of extraction based on beam trapping inside stable islands in horizontal phase space, has been commissioned during the 2008 run of the CERN Proton Synchrotron. Both singleand multi-bunch beams with a total intensity up to 1.4 1013 protons have been extracted with efficiencies up to 98%. Furthermore, injection tests in the CERN Super Proton Synchrotron were performed, with the beam then accelerated and extracted to produce neutrinos for the CERN Neutrino-to-Gran Sasso experiments. The results of the extensive measurement campaign are presented and discussed in detail

Ions for LHC: Towards Completion of the Injector Chain

The commissioning of CERN's ion injector complex [1] to allow 1.1 PeV collisions of ions in LHC is well under way. After the Low Energy Ion Ring (LEIR) in 2005 [2] and the Proton Synchrotron (PS) in 2006 [3], the Super Proton Synchrotron (SPS) has now been commissioned with the 'Early' ion beam, which should give a luminosity of $5×10^{25}cm^{-2}s^{-1}$ in the LHC. This paper summarizes the operation in 2007 of all the machines involved in the ion injection chain