The sea-level highstand correlated to marine isotope stage (MIS) 7 in the coastal plain of the state of Rio Grande do Sul, Brazil

Abstract

The coastal plain of the state of Rio Grande do Sul, in southern Brazil, includes four barrier-lagoon depositional systems formed by successive Quaternary sea-level highstands that were correlated to marine isotope stages (MIS) 11, 9, 5 and 1, despite the scarcity of absolute ages. This study describes a sea-level highstand older than MIS 5, based on the stratigraphy, ages and fossils of the shallow marine facies found in coastal barrier (Barrier II). This facies outcrops along the banks of Chuí Creek, it is composed of fine, well-sorted quartz sand and contains ichnofossils Ophiomorpha nodosa and Rosselia sp., and molluscan shells. The sedimentary record indicates coastal aggradation followed by sea-level fall and progradation of the coastline. Thermoluminescence (TL) and electron spin resonance (ESR) ages from sediments and fossil shells point to an age of ~220 ka for the end of this marine transgression, thus correlating it to MIS 7 (substage 7e). Altimetric data point to a maximum amplitude of about 10 meters above present-day mean sea-level, but tectonic processes may be involved. Paleoceanographic conditions at the time of the highstand and correlations with other deposits in the Brazilian coasts are also discussed.

Cordão Formation: loess deposits in the southern coastal plain of the state of Rio Grande do Sul, Brazil

“…These results are consistent with thermoluminescence (TL) ages from sediments and electron spin resonance (ESR) ages of fossil teeth from the underlying Santa Vitória Formation, with ages ranging from ~214 to 34 kyrs (Lopes et al 2010(Lopes et al , 2014.…”

“…The presence of a silt-rich layer, probably of loessic origin, was reported by Gomes et al (1987) from an outcrop of the Barrier III exposed on the coastline. Although a distinct loess layer was not Lopes et al (2010Lopes et al ( , 2013 and (c) TL ages from Lopes et al (2014). observed in the Barrier II, Gomes et al (1987) described the existence of small deflation basins filled with silt on top of this barrier.…”

“…The Barrier II would have been formed by the sea-level highstand that reached its maximum around 220 kyrs ago, correlated to the marine isotope stage (MIS) 7e, according to electron spin resonance (ESR) datings on fossil shells and luminescence ages from sediments of the marine facies (Lopes et al , 2014. The Barrier III was formed by the sea-level highstand of ~125 kyrs ago (MIS 5, Tomazelli andDillenburg 2007, Lopes et al 2015), whereas the Holocene barrier (IV) comprises the present-day coastline, developed in the last 10 kyrs (Caron 2007, 2014, Lima et al 2013.…”

“…The lowermost two meters belong to the marine facies of the Barrier System II (Rosa 2012, Lopes et al 2013), and consist of fine, wellsorted quartz sand with heavy minerals, cross and parallel stratifications, fossil molluscan shells and ichnofossils Ophiomorpha nodosa and Rosselia sp. (Lopes et al 2014).…”

Dating of fossil human teeth and shells from Toca do Enoque site at Serra das Confusões National Park, Brazil

“…ESR dating has been well established for teeth, and some models of radioisotope uptake have been computationally implemented in programs such as ROSY (Brennan et al 1999) and DATA (Grün 2009). ESR has also been used to date shells (Kinoshita et al 2002, Lopes et al 2014a, b, Mascarenhas et al 1982, Blackwell et al 2010 Figure 1 -(a) Photograph of the collective sepulcher (Burial 2) with many skeletons and shells found during excavation at Toca do Enoque, located in Serra das Confusões National Park (Brazil). North direction is indicated by an arrow, and a scale with 1 cm marks is shown.…”