Modèle cinématique de la zone subandine du coude de Santa Cruz (entre 16°S et 19°S, Bolivie) déduit de la construction de cartes équilibrées

Entre 16°S et 19°S, la zone subandine se caractérise par une évolution latérale rapide de la géométrie des structures chevauchantes et des directions de raccourcissement. A partir de cartes équilibrées, nous proposons un modèle cinématique de cette partie frontale des Andes. La carte équilibrée finale montre que la structuration du coude de Santa Cruz implique le développement de décrochements, sénestres dans sa partie nord, et dextres dans sa partie sud. Ces mouvements transversaux, pratiquement nuls au front de la chaîne, s'intensifient progressivement vers la cordillère où ils peuvent atteindre plusieurs dizaines de kilomètres. (Résumé d'auteur

La napa de Calazaya : una prueba de acortamientos importantes controlados por elementos paleoestructurales en los Andes bolivianos

Una napa tectonica de desplazamiento importante se evidencia en el limite Altiplano-Cordillera Oriental de Bolivia (20° S). Su emplazamiento proviene del transporte hacia el Este de un amplio dominio aloctono en el Oligoceno Superior-Mioceno Inferior. El despegue basal del aloctono se ubica en una unidad estratigrafica cuya geometria en la cuenca controlo la de la deformacion. (Résumé d'auteur

Hydrocarbon generation in relation to thrusting in the sub Andean zone from 18 to 22°S, Bolivia

Formation of the Bolivian eastern cordillera started at the end of the Oligocene and continues to the present day with thrusting affecting the Sub Andean Zone since late Miocene. The "classical" source rock is the Devonian, but the Silurian interval has some potential. Their initial original potential is not high but they are thick (700 m, Los Monos Fm) and may be thicker still due to stacking in thrust duplexes. The three phases of sedimentation during the Tertiary each start with conglomeratic deposits and are discordant over the previous one. Seismic data allow us to correlate these steps with three periods of tectonic accretion : Late Miocene (Tariquia Fm), Pliocene (Guandacay Fm) and Plio-Quaternary (Emborozu Fm). Modelling demonstrates two phases of hydrocarbon generation. A first phase from Devonian to Carboniferous is due to the deepening of the Palaeozoic basin. The second phase of maturation is due to the Tertiary deposits in the foreland and under the piggyback basins. The central aera (Santa Cruz) has never been more deeply buried than during the Palaeozoic and has been a high during the Tertiary. (Résumé d'auteur

Strike-slip faulting, thrusting and related basins in the Cenozoic evolution of the Southern branch of the Bolivian orocline

The evolution of the Cenozoic deformation of the Cordillera Oriental and of the contact zone with the Altiplano in southern Bolivia is well documented in the Tupiza, Nazareno and Estarca basins. The tectonic evolution started at about 29 Ma. The period between 29 and about 22-21 Ma is marked by developement of a pull-apart basin related to N-S trending left-lateral strike-slip faulting. During this period, initial deposition consisted of andesitic lavas and detrital sediments (breccias ; matrix-supported red conglomerats ; sands and silts...) of the Catati and Tupiza Formation, deposited in alluvial fan and flood plain environments. From 21 to 20 Ma, the tectonic setting evolved to N-S oriented thrusts, which had a dextral component. This event caused the Tupiza basin to evolve into a full-ramp basin, and triggered the developement of two piggy-back basins : Nazareno and Estarca. Both basins record detrital deposition (Nazareno Formation) in an alluvial fan environment. At 10-9 Ma, deformation in this area stopped allowing peneplanation during which time the San Juan de Oro erosional surface was formed and the fluvial conglomerates of the Oploca Formation were deposited. This segment of the Andes was then tectonically transported to the east, while uplift due to thrusting continued in the eastern Andean front and in the Subandean zone. (Résumé d'auteur