Records of geomagnetic reversals from volcanic islands of French Polynesia : 1. Paleomagnetic study of a polarity transition in a lava sequence from the island of Huahine

Présentation d'une étude paléomagnétique concernant une transition du champ magnétique terrestre enregistrée par les laves de l'île de Huahin

Paleointensity of the earth's magnetic field during the Laschamp excursion and its geomagnetic implications

L'étude des données paléomagnétiques des coulées de Laschamp et d'Olby met en évidence que les directions paléomagnétiques enrégistrées ne sont pas liées à une inversion stable de la polarité mais plutôt à une "tentative" d'inversion ou à une inversion "avortée

Records of geomagnetic reversals from volcanic islands of French Polynesia : 2. Paleomagnetic study of a flow sequence (1.2-0.6 Ma) from the island of Tahiti and discussion of reversal models

Une séquence volcanique de 700 m d'épaisseur a été échantillonée dans la vallée du Punaruu (Tahiti). Les résultats de l'étude paléomagnétique montrent que la séquence a enregistré 4 inversions du champ magnétique terrestre. Les données géochronologiques (K/Ar) indiquent que l'inversion plus récente correspond à la transition de Matuyama-Brunhes, que les 2 intermédiaires correspondent à la transition Saramillo et que la plus ancienne, identifiée à la base de la séquence, correspond à la transition Cobb Mountai

Paleogene building of the Bolivian Orocline: Tectonic restoration of the central Andes in 2-D map view

International audienceUsing available information on the magnitude and age of tectonic shortening, as well as paleomagnetically determined tectonic rotations, we have run a series of 2-D map view restorations of the central Andes. Neogene shortening in the foreland belt induced only slight orogenic curvature of the central Andes. The constraints on the ages of the large observed fore-arc rotations (average of 37° counterclockwise in southern Peru and 29° clockwise in northern Chile) indicate that the Bolivian Orocline formed during the Eocene-Oligocene as a consequence of differential shortening focused in the Eastern Cordillera. To minimize local block rotations along the fore arc, the restoration that best fits the central Andean rotation pattern requires about 400 km of total (Paleogene plus Neogene) shortening near the Arica bend. This value corresponds to the upper bound of estimates of maximum horizontal shortening for the central Andes. Along-strike variations in horizontal shortening in the back arc induced bending of the continental margin, block rotations with fore-arc along-strike extension, and/or orogen-parallel transport of upper crustal material toward the symmetry axis of the orocline

Horizontal subduction zones, convergence velocity and the building of the Andes

We discuss the relationships between Andean shortening, plate velocities at the trench, and slab geometry beneath South America. Although some correlation exists between the convergence velocity and the westward motion of South America on the one hand, and the shortening of the continental plate on the other hand, plate kinematics neither gives a satisfactory explanation to the Andean segmentation in general, nor explains the development of the Bolivian orocline in Paleogene times. We discuss the Cenozoic history of horizontal slab segments below South America, arguing that they result from the subduction of oceanic plateaus whose effect is to switch the buoyancy of the young subducting plate to positive. We argue that the existence of horizontal slab segments, below the Central Andes during Eocene-Oligocene times, and below Peru and North-Central Chile since Pliocene, resulted (1) in the shortening of the continental plate interiors at a large distance from the trench, (2) in stronger interplate coupling and ultimately, (3) in a decrease of the trenchward velocity of the oceanic plate. Present-day horizontal slab segments may thus explain the diminution of the convergence velocity between the Nazca and South American plates since Late Miocene

L'Occident équatorien : un terrain océanique pacifique accolé au continent sud-américain

Cet article présente les principaux traits géologiques de la partie occidentale de l'Equateur et les premiers résultats d'une étude paléomagnétique entreprise dans cette région en 1985. Selon les auteurs, la partie occidentale de l'Equateur se serait formée dans le Pacifique, puis elle serait venue se coller au vieux continent sud-américain sous la forme d'un terrain exotique semblable à ceux connus ailleurs, notamment dans les chaînes péripacifique

Activation peptide of the coagulation factor XIII (AP-F13A1) as a new biomarker for the screening of colorectal cancer

International audienceBackground: Colorectal cancer (CRC) remains a major cause of cancer fatalities in developed countries. The risk of death is correlated to the stage of CRC during the primary diagnosis. Early diagnosis is closely associated with enhanced survival rate. We therefore investigated the AP-F13A1 as a potential protein marker of CRC. Methods: The protein expression of FXIII in 40 serum samples was evaluated by enzyme-linked immunosorbent assays. Additionally, targeted proteomic assays (LC-PRM) were used to evaluate the expression of the activation peptide of F13A1 (AP-F13A1) in a further 113 serum samples. Results were analyzed by the Wilcoxon test and receiver operating characteristic curves generated to assess statistical differences and diagnostic factors between CRC patients and controls. Results: AP-F13A1 was quantified in human serum samples using calibration curves with excellent linearity. AP-F13A1 was reduced in CRC patients using PRM assays from two distinct biobanks. The AUC for AP-F13A1 were 0.95 and 0.93. Sensitivity/specificity values for the two sets of patients were 75%/95% and 71%/95% respectively. Conclusion: We have presented the proof of principle that in vivo release of AP-F13A1 can be measured by PRM-based strategies in CRC serum samples. AP-F13A1 may be an effective serological biomarker as part of a screening program of CRC detection

An accreted continental terrane in Northwestern Peru

Cet article présente une étude paléomagnétique des échantillons de plusieurs formations du bassin de Lancones (province de Piura). Les auteurs formulent l'hypothèse de l'accrétion d'une terrane sur la marge péruvienne au cours du Néocomien. Un régime de cisaillement aurait également produit des rotations in situ. L'évolution géodynamique du nord du Pérou est donc comparable aux processus observés sur les Andes septentrionales, en Equateu