Contexto tectono-sedimentar das depressões tectônicas na zona de confluência dos rios Negro e Solimões, Amazônia Central

Abstract

Great part of the Quaternary sedimentation of the confluence zone of the Negro and Solimões rivers is confined in 04 tectonic depressions, general direction NW-SE. These deposits hold records of the main sedimentary and tectonic processes that influenced the dynamics of these rivers in the Pleistocene-Holocene. The use of SRTM images allowed the delimitation of the depressions and the understanding of the associated depositional processes, with the definition of the depositional morphology of accretion bars with migration direction towards N-NE. The integration of this information with absolute data obtained by Luminescence of Crystals, allowed to define a deposition interval between 303,900 to 1,340 years, influenced by the dynamics of the Negro, Solimões and Ariaú rivers in this period. In the last decade, this geochronological method has contributed to the tectono-sedimentary understanding of stretches of the Negro and Solimões rivers, which includes the deposition processes in the depressions under study. The internal definition of the thickness of the deposits and their relationship of contact with the underlying substratum used surface data (outcrops) and, mainly, unpublished subsurface data (rotary sounding and geophysical surveys). The proven N-NE inclination of the substrates of the depressions, which reaches up to 60 meters in depth, supports the definition of hemigraben, whose origin is associated with the reactivation of tectonic faults and the action of extensional efforts in a general NE-SW direction, which occurred in the Neomiocene-Pliocene. Keyword: Tectonic Depressions; Optically St