Petrography and detrital zircon U-Pb geochronology of sedimentary rocks of the Campo Alegre Basin, Southern Brazil: implications for Gondwana assembly

Abstract

The Campo Alegre Basin is a volcano-sedimentary sequence covering an area of about 500 km 2 , located at the northeast portion of Santa Catarina state (Brazil), and formed during the late stages of the Neoproterozoic era. Three main stratigraphic units compose this basin, the lowermost of which is the Bateias Formation, corresponding to the pre-volcanic stage. It is characterized by the fanglomeratic sediments at the basin's northern boundary, which were deposited in a fluvial environment and progressively replaced by fluvial sandstones towards the south. Poorly sorted conglomerates and breccias compound the fanglomeratic facies, which comprises angular to subrounded fragments in a matrix ranging from sand fractions to fragments larger than gravel. The ubiquitous presence of volcanogenic and metamorphic fragments in the fanglomeratic facies strongly suggests that the Piên Magmatic Arc and a volcanic manifestation coeval with the earlier stages of the basin formation were important source areas, as well as the basin basement (the Luís Alves Terrane). In this sense, geological, petrographic, and detrital zircon geochronology data are combined in order to interpret the mechanisms that had acted during the deposition of these sedimentary rocks and to constraint the maximum depositional ages of Bateias Formation at ca. ~606 Ma.

Zircon U-Pb geochronology and Hf isotopes of the Luís Alves Terrane: Archean to Paleoproterozoic evolution and Neoproterozoic overprint

“…The biggest of these sequences, the Campo Alegre Basin, was deposited between ca. 605 and 585 Ma (Citroni et al 2001;Quiroz-Valle et al 2019;Lino et al in review).…”

“…Along the northern portion of the LAT, the Campo Alegre, Corupá and Guaratubinha basins share similar lithological associations, and are therefore considered remnants of the same volcanosedimentary cover (Basei et al 1998b). They mostly comprise terrigenous sediments covered by thick pyroclastic and volcanic sequences (Citroni et al 2001;Quiroz-Valle et al 2019), the onset of deposition of the lowermost unit of the Campo Alegre was constrained to ~606-590 Ma (Quiroz-Valle et al 2019). Together with the A-type magmatism of the Serra do Mar Suite, these basins represent an important extensional phase after in the final stages of the Brasiliano/Pan-African orogenic cycle (Campos Neto and Figueiredo 1995;Campos Neto 2000;Almeida et al 2010).…”

“…230km long and 50km wide is located in southern Brazil and is surrounded by orogenic belts formed during the Brasiliano / Panafrican orogenic cycle at the end of the Neoproterozoic and Cambrian (Basei et al 1998a(Basei et al , 2009aPassarelli et al 2018;Siegesmund et al 2018). Nonetheless, Neoproterozoic-Cambrian activity in the LAT was restricted to the emplacement of intrusive rocks (Kaul 1984;Gualda and Vlach 2007 a,b) and the development of (volcano-) sedimentary basins (Basei et al 1998b;Rostirolla et al 1999;Citroni et al 2001;Guadagnin et al 2010;Basei et al 2011b;Quiroz-Valle et al 2019) while the crystalline basement, the Santa Catarina Granulitic Complex (SCGC), remained largely unaffected (Hartmann et al 1979(Hartmann et al , 2000Basei et al 1992Basei et al , 1998a2009b, Siga Jr. 1995Harara et al, 2003;Passarelli et al 2018). All hightemperature geochronological data of the SCGC yield Paleoproterozoic and Archean ages (Basei 1985;Siga Jr 1995;Hartmann et al 2000;Harara 2001;Basei et al 2009 a,b) and the only signs of reactivation of the basement during the Brasiliano orogenic cycle are ~ 600 Ma old K-Ar ages in shear zones (Siga Jr 1995).…”