Tectonism in paleosoils of Itaqueri Hill (SP): analysis by fault cinematic criteria

Abstract

The Itaqueri Formation, Tertiary, is located in Itaqueri Hill, Southeast of Brazil. It is composed of sediments deposited in an alluvial-fan environment under semi-arid conditions. The study involved recognition and analysis of paleosoils, and tectonic features that affect them, as well as, their relationship. Cenozoic tectonic motions uplifted and lowered the area successively and led to relief inversion, partial destruction of the sediments and paleosoils, and exposures in different altitudes along the area. The NW and NE normal fault zones form horsts and grabens along the Itaqueri Hill. Such displacements are responsible by the completeness of lateritic profile in some places and deep erosion or even absence in others. The analysis of the faults indicates two distinct episodes of extensional tectonic motion in the hill, both affecting the lateritic profile: an episode with 1 NE/subvertical, 3 NW/sub-horizontal and 2 NE/sub-horizontal, followed by other with 1 NW/sub-vertical, 3 NE/sub-horizontal and 2 NW/sub-horizontal. These extensional motions are related to the neotectonic activity of strike-slip regional regime, which occurred preferentially along NE and NW normal faults by reactivation of the pre-existing structures.