A PHOTOGRAPHIC ATLAS OF THE ARCHITECTURE, FLOW GEOMETRY AND MORPHOLOGY, AND FACIES OF SERRA GERAL GROUP (PARANÁ IGNEOUS PROVINCE) IN THE STATE OF PARANÁ, BRAZIL

Abstract

The rocks that make up the Serra Geral Group spread over approximately 100,000 km2 of the State of Parana, which represent about 10% of the Parana Igneous Province. The geologic mapping of the Serra Geral Group in the State of Parana was carried on from 2003 to 2018, and revealed a great diversity of features and facies of basic and acidic lava lows, as well as the presence of interbedded volcaniclastic deposits. This paper presents an inventory of this geodiversity along with brief descriptions, a wealth of photographic documentation, and the georeferenced location of each outcrop, making it easy to access the documented sites, in order to assist the development of scientiic research in this geologic compartment, which occupies nearly half of the Parana territory. The processes responsible for the lithologic features are interpreted in compliance to the knowledge accumulated on the various continental basaltic provinces by many researchers, including the authors of this paper, so to build up a genetic system for the Serra Geral Group more complete and coherent with the paleogeography of Gondwana in its initial breakup stage. In the early Cretaceous, during ca. 1.2 Ma with the paroxysm at 134.7 Ma, a huge magma amount, which is estimated at least in 600,000 km3, lowed over the thick sedimentary Paleozoic sequence of the Parana Basin, stacking up a volcanic sequence. The interaction between the rising magma with the sedimentary sequence up to 7,000 m thick, gave rise also to thousands of intrusive bodies, such as sills and dikes, almost all of a basic nature. Furthermore, the ascending magma interacting with aquifer systems gave rise to explosive volcanism – hydrovolcanism – which produced many maic volcaniclastic deposits MVDs, interbedded to the basic lows. Thus, in South America, during this relatively short lapse of time, basic and acidic lows covered the Parana Basin, being reported in Brazil, Argentina, Paraguay, and Uruguay under diverse names. In the present article, it will be simply referred as Serra Geral Group (SGG). The lithological inventory represented by the present photographic atlas comprises diagnostic features of basalt, andesi-basalt, rhyolite and dacite lava lows, maic volcaniclastic deposits MVDs, and dykes of basic composition.