Structural evolution of Lavinia Planitia, Venus: Implications for the tectonics of the lowland plains (original) (raw)

Quantitative characterization of the small-scale fracture patterns on the plains of Venus

1995

The objectives of this research project were to (1) compile a comprehensive database of the occurrence of regularly spaced kilometer scale lineations on the volcanic plains of Venus in an effort to verify the effectiveness of the shear-lag model developed by Banerdt and Sammis (1992), and (2) develop a model for the formation of irregular kilometer scale lineations such as typified in the gridded plains region of Guinevere Planitia. Attached to this report is the paper 'A Tectonic Model for the Formation of the Gridded Plains on Guinevere Planitia, Venus, and Implications for the Elastic Thickness of the Lithosphere'.

Transpressional deformation in northwestern Sardinia (Italy): insights on the tectonic evolution of the Variscan Belt

– Structural investigations in northwestern Sardinia highlight the occurrence of a regional D2 transpressional deformation related both to NNE–SSW direction of compression and to a NW–SE shear displacement. The deformation is continuous and heterogeneous, showing a northward strain increase, indicated by progressively tighter folds and occurrence of F2 sheath folds. D2 transpression is characterised by the presence of a crustal-scale shear deformation overprinting previous D1 structures, related to nappe stacking and top-to-the-south and southwest thrusting. The L2 prominent stretching lineation points to an orogen-parallel extension and to a change in the tectonic transport from D1 to D2. It is attributed to the position of Sardinia close to the northeastern part of the Cantabrian indenter during the progressive evolution of the Ibero-Armorican Arc. D1 phase developed during initial frontal collision, whereas D2 deformation characterised the progressive effect of horizontal displacement during the increasing curvature of the arc. To cite this article: R. Carosi, G. Oggiano, C. R. Geoscience 334 (2002) 287–294.  2002 Académie des sciences / Éditions scientifiques et médicales Elsevier SAS tectonics / transpression / Variscan Belt / folds / stretching lineations / Sardinia Résumé – Déformation transpressive dans le Nord-Ouest de la Sardaigne (Italie) : considérations sur l'évolution tectonique de la chaîne Varisque. L'analyse structurale a mis en évidence dans le Nord-Ouest de la Sardaigne une déformation D2 transpressive, continue et hétérogène, qui augmente d'intensité vers le nord. Elle se superpose aux structures précédentes D1, liées à la mise en place des nappes vers le sud et le sud-ouest. La linéation d'allongement L2 met en évidence une extension parallèle à la chaîne et un changement net, de la phase D1 à la phase D2, de la direction du transport tectonique. La phase D1 s'est développée durant la collision frontale initiale, alors que la déformation D2 est due à l'augmentation progressive de la composante en décrochement pendant le développement de l'arc Ibéro-Armoricain. Pour citer cet article : R. Carosi, G. Oggiano, C. R. Geoscience 334 (2002) 287–294.  2002 Académie des sciences / Éditions scientifiques et médicales Elsevier SAS tectonique / transpression / chaîne Varisque / plis / linéations d'allongement / Sardaigne