Abstract
The Parana basin is one of the major morphotectures of the South American continent. Although its tectono-sedimentary evolution has been widely studied and fairly well understood, this paper aims to fill a gap in knowledge comprising the tectonic evolution after the end of its last sedimentary cycle, in the Upper Cretaceous. In this context, the Jordan River watershed, situated in the surroundings of Guarapuava municipality, south central region of Parana State, was selected for structural and morphometric analysis where the Cretaceous volcanic rocks of Serra Geral Formation are exposed. The Jordan River watershed was studied for the influence exerted by Taxaquara Fault Zone on its morphologic evolution, since Taxaquara Fault Zone is associated to the Brazilian cycle and extends eastwards to the Ribeira belt in the state of Sao Paulo. The morphometric analysis consisted in the interpretation of the Jordan River watershed drainage network and relief elements, considering the distribution of existing knickpoints in the water courses. Structural analysis was based on the calculation of the stress fields responsible for the activation of local fault zones, which were determined by their spatial arrangement and the statistical and mechanical treatments of structural data. During the Oligocene and Miocene, erosional processes developed a planing surface which marks the relief in the central region of the Jordan River watershed and serves as a stratigraphic marker for the associated deformational events. Three events that contributed to the morphological framework of the Jordan River watershed were defined: an oldest one, probably active before the development of the Jordan pediplane in the Paleogene, by a NE-SW maximum horizontal stress (SHmax); and two more recent ones, being one of Plio-Pleistocene age, with a N05W SHmax, and a still active event of transtensive nature showing a N75W SHmax. The paleostress analysis points to a similarity between the Cenozoic evolution of Parana Basin and the tafrogenic basins of southeast Brazil, revealing the amplitude of the deformation events associated to the studied period and ensuring the importance of further studies on the morphotectonic evolutions of intracratonic regions of the South American plate and their correlation to the Andean tectonic cycle.
Highlights
Located inside the South American plate, Paraná Basin was subjected to deformations caused by tectonic forces from the plate margins in association with its sedimentary history between the Ordovician and the Cretaceous (Milani & Ramos 1998) and the reactivation of large fault zones (Zalán et al 1990, Artur & Soares 2002)
The Jordão River catchment is affected by three tectonic episodes, intercalated by a period of tectonic stability associated with the development of a planning surface during the Oligocene-Miocene
The maximum horizontal main stress would have varied from NE-SW, dominant throughout the Paleogene, to WNW-ESE, which corresponds to the current stress field on the South American plate, considered as neotectonic
Summary
Located inside the South American plate, Paraná Basin was subjected to deformations caused by tectonic forces from the plate margins (mainly the Andean) in association with its sedimentary history between the Ordovician and the Cretaceous (Milani & Ramos 1998) and the reactivation of large fault zones (Zalán et al 1990, Artur & Soares 2002). It was necessary to proceed with a more detailed investigation of the faults and their related structures, correlating them whenever possible with the studies accomplished in the tafrogenic basins of southern Brazil (Campanha et al 1985, Riccomini, 1989, 1995b, Salamuni et al 2004), where most of the works on both the Cenozoic and Neotectonic periods are concentrated. The age limit for the Neotectonic period was established according to the last tectonic reorganization of the landscape (Mörner 1989) and defined as 23 Ma for the South American intraplate region (Hasui 1990)
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