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

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.

Stratigraphy and geochronological constraints of the Serra Sul Formation (Carajás Basin, Amazonian Craton, Brazil)

“…Different stratigraphic subdivisions have been proposed (e.g., Araujo and Nogueira, 2019;Klein and Ladeira, 2002;Machado et al, 1991;Tavares et al, 2018;Trendall et al, 1998).…”

“…The lack of accurate stratigraphic framework for the Carajás Basin has caused several units to be neglected or misinterpreted and new stratigraphic subdivisions are regularly proposed to account for new discoveries and better understanding of the stratigraphy of the basin. The last stratigraphic subdivision proposed by Araujo and Nogueira (2019) is adopted in this work and is outlined in Figure 2. Relevant time constraints are presented in Figure 4 and Table 1.…”

“…2, Araújo and Nogueira, 2019). The arguments for a glaciogenic origin rely on the occurrence of foliated to massive diamictites, sandstone with micro-striated quartz grains, sometimes exhibiting outsized clasts and rhythmites made up of even parallel laminations (Araujo and Nogueira, 2019). Sedimentary rocks of the Serra Sul Formation are deformed and slightly metamorphosed, as testified by the occurrence of steep dipping beds, pressure shadows and foliation (Araujo and Nogueira, 2019).…”

“…1A; Tavares et al, 2018) and the stratigraphy of the Carajás Basin, located to the east of the craton (Fig. 1B; Araújo Filho et al, 2020;Araujo and Nogueira, 2019), the overall Neoarchean to early Paleoproterozoic geodynamic context of the eastern Amazonian Craton remains poorly constrained. For instance, glaciogenic sediments have recently been reported in the Serra Sul Formation (Fig.…”

“…For instance, glaciogenic sediments have recently been reported in the Serra Sul Formation (Fig. 2; Araujo and Nogueira, 2019), but little stratigraphic description have been provided for this formation. No age constraint is available for the Serra Sul Formation, while such data are critical for correlations with other sedimentary units across the world.…”