Morphostructural aspects of the sandstone karst in Northeastern Brazil: Example from Serra da Capivara – PI

Abstract

This work analyses morphostructural aspects and their influence on the development of the karst relief
of Serra da Capivara (State of Piauí, northeastern Brazil). For this purpose, structural data derived from lineament
extraction, sedimentary bed geometry, karstification degree of the layer, and analysis of the karst morphology
were performed. Structural lineament data showed a NE-SW orientation trend, coinciding with the orientation
of the Transbrasiliano Lineament. The reactivation of the brittle structures can be related to the orientation, scarp
retreat, direction, and incision of the main valleys. From the analysis of the fracture array (NE-SW) and bedding
planes, we suggest that the fracture connectivity of these structures resulted in conduit formation, which evolved
to form subterranean galleries. Thus, the expansion of the karst system led to the formation of valleys, which are
situated in higher deformed zones, such as fold hinges. These valleys currently constitute the most advanced
stage of karstification, with the development of the tributary drainages as the most recent stage. The structural directions show a NE-SW trend, represented by larger valleys, and subordinated to this, an NW-SE trend, where
headwaters of low-order channels are located.