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Enregistrements sédimentaire et structural de l'évolution géodynamique des Andes équatoriennes au cours du Néogène : étude des bassins d'avant-arc et bilans de masse

Abstract : The neogene geodynamic evolution of the Ecuadorian Andes is recorded in the syn-orogenic sedimentary sequences that had been deposited in the forearc basins on the Pacific coast, in the intramontane basins on the chain axis as weil as in the foreland basin on the Amazonian side. Based on seismic sections, wells and field data, we performed a stratigraphic and structural analysis and estimated sedimentary mass accumulation rates in these basins. The Neogene evolution can be divided in four stages: 1) During the Lower Miocene (23-21 to 14-12 My), clay sedimentary fluxes are supplying the Manabi and Progreso forearc basins. The tectonic activity and geometry of these basins are mainly controlled by dextral shear related to the obliquity of subduction at the Ecuadorian margin. No basins exist at the chain axis. The Amazonian foreland basin is supplied by major fluxes coming from the Guyana shield and the oriental cordillera. 2) During the upper Middle Miocene (14-12 to 10-9 My), dextral transtension results in the opening of intramontane basins. Throughout the forearc, sedimentary fluxes are decreasing and the deposits are coarsening. 3) During the Upper Miocene (10-9 to 5,3 My) the occidental and oriental cordilleras are uplifted. Dextral transpression causes the inversion and closing of the intramontane basins. The Amazonian basin records flexural subsidence. 4) The Pliocene to Present day is the major orogenic stage in the Ecuadorian chain. Erosion becomes prominent in the intramontane area. The Subandean area is compressed, and uplifted, allowing definitive establishment of the present Amazonian drainage system. Subduction of the Carnegie ridge results in the emersion of Manabi and Progreso forearc basins. The Gulf of Guayaquil basin opened and records the highest neogene mass accumulation rates at this stage.
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Submitted on : Monday, August 13, 2012 - 9:04:45 AM
Last modification on : Friday, March 25, 2022 - 11:10:22 AM
Long-term archiving on: : Friday, December 16, 2016 - 6:14:02 AM

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  • HAL Id : tel-00723692, version 1

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Yann Deniaud. Enregistrements sédimentaire et structural de l'évolution géodynamique des Andes équatoriennes au cours du Néogène : étude des bassins d'avant-arc et bilans de masse. Tectonique. Université Joseph-Fourier - Grenoble I, 2000. Français. ⟨NNT : ⟩. ⟨tel-00723692⟩

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