Serra Sul diamictite of the Carajás Basin (Brazil): A Paleoproterozoic glaciation on the Amazonian craton

Raphael Araújo,Afonso Nogueira

doi:10.1130/g46923.1

Abstract

Abstract This paper reports the discovery of glacial deposits of likely Siderian–Rhyacian age (2.58–2.06 Ga) in South America (Carajás Basin, Brazil), thereby expanding the potential reach of Paleoproterozoic glaciations to the Amazonian craton for the first time. Glacially derived diamictites are stacked within a hitherto unrecognized ∼600-m-thick siliciclastic succession, here named the Serra Sul Formation. Well-preserved textures, with evidence of glaciotectonism and ice rafting, indicate deposition in a coastal subglacial to glacial-fed submarine fan system, in which the immediately underlying units (banded iron formation and volcanic rock) were the main source and bedrock. The Serra Sul diamictite may be correlated with any of the known Paleoproterozoic glaciations, or with none of them.

Highlights

Paleoproterozoic glaciations are recorded in almost every continent, but they have not yet been reported in South America
Ga; Rasmussen et al, 2013) are recorded in almost every continent, but they have not yet been reported in South America. These glaciations, called the Huronian Glaciation Event (Tang and Chen, 2013), occurred at the time of the Great Oxidation Event (GOE), and it is suggested that they were triggered by the supercontinent breakups at the end of the Archean (Aspler and Chiarenzelli, 1998; Bleeker, 2003; Strand, 2012)
In the Carajás Basin, Amazonian craton (Brazil), intervals of matrix-supported breccia were previously reported as a particular rock of the Serra Sul succession, and considered a Neoarchean magnetite-rich breccia of the lowermost banded iron formation (BIF) unit (Cabral et al, 2013)

Summary

Introduction

Paleoproterozoic glaciations (ca. 2.45–2.22Ga; Rasmussen et al, 2013) are recorded in almost every continent, but they have not yet been reported in South America. In the Carajás Basin, Amazonian craton (Brazil), intervals of matrix-supported breccia were previously reported as a particular rock of the Serra Sul succession, and considered a Neoarchean magnetite-rich breccia of the lowermost banded iron formation (BIF) unit (Cabral et al, 2013). These rocks were never described in the Neoarchean succession (Grão-Pará Group), which is generally docu-. This formation unconformably overlies the Neoarchean units and unconformably underlies the siliciclastic deposits of the Águas Claras Formation of ca. 2.06 Ga (Mougeot et al, 1996), suggesting Paleoproterozoic (2.58–2.06 Ga) age constraints (Fig. 1)

Methods

Results

Discussion

Conclusion