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Le mésozoïque du système Subandin de Bolivie : évolution sédimentaire et synthèse du bassin

Abstract : In Bolivia, the Mesozoic is located in the Subandine belt, East of the Andean Cordillera. It is mainly represented by continental sequences described as local formations, without any tentative correlation between the various area. In this work, we show that the Mesozoic characterise two different basins formed in rifting context. The Villamontes basin, located in the Southern part of the Subandine, began its evolution during Middle/Late Triassic and developped during Jurassic times. In the Northern Subandine the Santa Cruz basin was active during Cretaceous.The basal sequence of the Subandine Mesozoic is restricted to the Villamontes basin where the red sediments of the Ipaguazu Fm represent the basal part of the synrift deposits, overlain by tholeiitic basaltic lava flows (Entre Rios Fm) of Toarcian age (181,5 ± 0,90 My by Ar/Ar method). The overlying Tapueca and Castellon Fms characterise a synrift regime contemporaneous to a period of thermal subsidence. The geometry of the various contacts underlines the dissymetry of the basin. Fms Ichoa and Beu represent the prerift deposits in the Northern Subandine, and are overlain by synrift Yantata and Eslabon Fms that underline the Northward migration of the extensional processes during the Mesozoic. In correspondance with the location of the Santa Cruz depocenter, the synrift deposits are represented by the basal sequence of the Cajones Fm ; the upper part of the Cajones Fm and its northern equivalent, the Flora Fm, characterise the final step of the thermal subsidence. In the area of the Boomerang, these formations have been affected by an important erosion, well known as the 'pretertiary unconformity'.
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https://tel.archives-ouvertes.fr/tel-00690400
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Submitted on : Monday, April 23, 2012 - 3:36:30 PM
Last modification on : Friday, March 25, 2022 - 9:40:25 AM
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Maria Elena Kusiak. Le mésozoïque du système Subandin de Bolivie : évolution sédimentaire et synthèse du bassin. Sciences de la Terre. Université de Grenoble, 2008. Français. ⟨tel-00690400⟩

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