Flow processes and sedimentation in contourite channels on the northwestern South China Sea margin: A joint 3D seismic and oceanographic perspective

3D seismic data from the northwestern South China Sea margin, coupled with the quantification of oceanographic processes and morphological results, were used to infer three-dimensional flow processes and in turn sedimentation in contourite channels. Contour currents resulting from the Northern Pacific Deep Water (NPDW-CCs) flowing through the bends of contourite channels around a topographic high lead to an imbalance in the transverse direction, around the bend, between three competing forces (i.e., upslope directed Coriolis forces versus downslope directed centrifugal and pressure-gradient forces). The interface deflection of NPDW-CCs by Coriolis, pressure gradient, and centrifugal forces yields a helical flow cell consisting of upper return flows directed downslope and basal flows orientated upslope. Ekman boundary layers, at the base and flow interface, are also likely present leading to flows in the downslope direction. The helical flow cell in the bulk of contour currents, and Ekman boundary layers, constitute a Coriolis force-induced helical flow circulation, which we suggest promoted asymmetric intra-channel deposition (i.e., downslope deposition versus upslope erosion), forcing contourite channels to consistently migrate in an upslope direction. Such Coriolis force-induced helical flow circulation is evidenced by occurrence of volumetrically significant overbank deposits along downslope margins and by asymmetric channel cross-sections with steepened channel walls and truncation terminations along upslope margins. The Coriolis force-induced helical flow circulation exhibits subcritical flow conditions (represented by internal Froude numbers estimated as 0.04 to 0.19), and is sufficiently deep to spill out of the studied contourite channels, yielding overbank deposits along the downslope flanks of the contourite channels

When and how does continental break-up occur at the Iberia margin: constraints from mapping the 3D distribution of syn-tectonic sedimentary units

International audienc

What controls continental breakup at magma-poor rifted margins?

International audienc

Compressional structures on the West Iberia rifted margin : what controls their distribution ?

International audienc

Heredity of twin births

About 1 per cent. of human births are twin births. However, there are certain families in which the proportion rises to 5, 10, or even 15 per cent. There can be little doubt then that, as in sheep, so in man, there are strains having a special tendency toward the production of twins. It is commonly believed that this tendency toward the production of twins must be wholly a maternal quality, depending upon the inherited tendency to double ovulation. The study of the heredity of twins is accompanied by certain difficulties, such as the fact that the occurrence of twins is frequently isolated, apparently haphazard, occurring perhaps in only one case in a fairly large fraternity, in which other representatives are single births. It will simplify the matter a little if we consider only those cases in which two or more sets of twins have arisen from a given mating. The study of twins is still further complicated by the fact that they are of two types, namely twins derived from a double ovulation and twins derived from a single ovulation, there being a subsequent fission or budding of the fertilized egg. Such single-egg twins are'easily distinguished clinically by being both enveloped in the same chorion. They are also always of the same sex. The statement that the mother alone determines the tendency to twins is not, however, supported by the facts. Of the births giving rise to the fraternities of twin-repeating mothers, 4.5 per cent, are twin births. Of the births giving rise to fraternities of twin-repeating fathers, 4.2 per cent are twin births. These figures depend upon 355 and 289 labors respectively. The sisters of twin-producing fathers have twins in 8.2 per cent. of labors, while the sisters of twin-producing mothers have twins in 5.5 per cent. of labors

Observations from the Alpine Tethys and Iberia/Newfoundland margins pertinent to the interpretation of continental break-up, in Karner, G.D., Manatschal, G., and Pinheiro, L., eds., Imaging, Mapping and Modelling Continental Lithosphere Extension and Breakup.

International audienc

New Crustal Vs Model Along an Array in South‐East China: Seismic Characters and Paleo‐Tethys Continental Amalgamation

The assembly of East Asia was closely linked to the closure of the Tethyan oceans. In south-east China, the closure of the Paleo-Tethys ocean led to a continental collision between the South China and North China blocks (SCB and NCB), forming the world renowned (ultra-) high pressure (UHP) metamorphic belt of the Dabie-Sulu Orogen. The region was subsequently reworked by postorogenic extensional processes. These tectonic processes likely have left lithospheric scars identifiable by seismic imaging techniques. Here we characterize seismic structures across the orogen and analyze processes related to the closure of the Paleo-Tethys. Using cutting-edge tomographic approaches and ambient noise dispersion data, we developed a fine-scale crustal shear-wave velocity model beneath key crustal domains in the region. Distinct crustal scale velocity domains are identified, corresponding to the normal Precambrian crust, slow-velocity suture zones and fault systems, and fast-velocity orogens, suggesting a deep root of the corresponding surface geological features. By combining recent models of active-source, gravity and magnetotellurics, characteristic lithospheric deformation patterns such as crustal thrust systems and lithospheric wedges can be inferred, which are attributed to a northward subduction of the SCB lithosphere and the eventual continental collision after the closure of the Paleo-Tethys Ocean