Caracterização e proveniência de litoclastos silicosos associados a depósitos de cascalheira da serra do corpo seco, Ituiutaba, Minas Gerais

Abstract

The Corpo Seco hill, located about six kilometers SSW of Ituiutaba in western Minas Gerais, is a tabular relief macroform inserted in the Tijuco River basin. The mountain is mainly composed of sandstones and conglomerates from the Marília Formation (Bauru Group), Upper Cretaceous of the Paraná Basin. Near the summit is a gravel deposit (terrace) composed of siliceous lithoclasts with dimensions between granular and pebbly, immersed in a pelitic sand matrix. The sedimentological characteristics of the gravel suggest the action of mechanisms of transport and accumulation of sediments with high energy and high viscosity, such as debris flows. The macro- and microscopic characteristics of the fossil pebbles containing stromatolites, oncoliths, and oolites strongly suggest that the primary origin of these lithoclasts is the Irati and Teresina formations of the Passa Dois Group of the Paraná Basin. However, it is unlikely that the paleoheadwaters and paleodrainage system of the Rio Tijuco basin eroded the above formations, since their outcrop area during the Quaternary extends from Rio Grande do Sul to São Paulo on the eastern margin of the Paraná basin. In this work, it is proposed that the lithoclasts were first eroded from the Passa Dois Group and deposited in the Bauru Group during the uplift of the Alto Paranaíba Arch in the Late Cretaceous. During the Plio-Pleistocene, the uplift of the South American platform was accompanied by erosional and depositional processes of the so-called “Velhas" cycle. In this context, terraces, and gravels, such as those in the Serra do Corpo Seco, were deposited on the banks of the great rivers and their tributaries.