A morfologia superficial da estrutura circular de São Miguel do Tapuio (Piauí-BR) e casos similares no território brasileiro

Abstract

The circular structure of São Miguel do Tapuio (ECSMT) is a striking geomorphological feature noted in the Mesopaleozoic sandstones of Parnaiba basin (Piaui-BR). In this work the morphological characterization of ECSMT surface was mainly provided using SRTM topographic data. Such characterization allowed us to outline a 20 Km diameter and define the following: the circular structural pattern distinguished in its relief, the high symmetrical degree, the presence of borders and core topographically uplifted, as well as the correlation of relief features with deformed and thermal transformed compartments described according to field surveys and petrographic studies. The features of the main circular and semi-circular structures of endogenous source (ECSCOEN) and exogenous source (ECSCOEX) found in the Brazilian territory allow us to establish that the ECSCOEN with diameters from 8 to 38 Km barely have perfect circular morphology, they are associated directly or indirectly to Mesozoic igneous complex; the ECSCOEX presents perfect circular morphology with diameters from 4.5 to 40 Km and they are highly coplex impact structures. The morphological characteristics of ECSMT surface are compatible with the ones shown by the ECSCOEX. Despite the structural and textural features found in the ECSMT may be only suggestive to classify them as an ECSCOEX type, in the other hand, the lack of identification of the outcropping and/or subsurface igneous rock does not allow us to classify it as an ECSCOEN type.