Abstract
ABSTRACT: The objective of the present study was to interpret the direction of gravitational sedimentary flows in the turbidite deposits of the Maracangalha Formation (Reconcavo Basin), indicating their source areas. Thus, the indicative deformational structures existing in the formation were analyzed. The structures observed ranged from brittle to highly ductile and viscous states, with a diversity of deformational styles. A total of 284 planar and linear measurements was collected in three distinct subareas, separated according to their degree of deformation. The structures found were separated into four groups according to their formation process: (i) pre-deformation structures; (ii) plastic deformation structures; (iii) intrusion structures (fluidization), related to either early or syn-sedimentation events; and finally (iv) brittle deformation structures, with late sedimentation. Some structures were observed to be good indicators of apparent mass movement direction, which yielded predominantly SSW directions, suggesting a partially confined flow, parallel to the main axes of Reconcavo Basin, towards its depocenter.
Highlights
IntroductionThe overall orientation of this basin is N-S, with an inflexion towards ENE-WSW at its northern limit (Magnavita 1996)
The Recôncavo Basin is located within the RecôncavoTucano-Jatobá Rift System
The present study aimed to evaluate the relationship between gravitational flow patterns and the main tension fields that acted during the tectonic evolution of the Recôncavo Basin
Summary
The overall orientation of this basin is N-S, with an inflexion towards ENE-WSW at its northern limit (Magnavita 1996). The origin of this system is associated with the early stages of the South Atlantic opening and Gondwana rupturing event, and the tension fields responsible for the rifting that were active between the Middle-Jurassic (175 Ma) and EarlyCretaceous (145 Ma) periods (Silva et al 2007, Milhomem et al 2003). According to Guerra & Borgui (2003), the shales of the Maracangalha Formation accommodate two members whose origins are associated with gravitational and deformational facies: the Pitanga and Caruaçu Members. The origin of the Pitanga Member is believed to be associated with the occurrence of slumps, while the origin of the Caruaçu Member has been related to depositional processes associated with turbidity currents
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