Luminescence dated Late Pleistocene wave-built terraces in northeastern Brazil

Abstract

This study presents field and chronological investigations along the coast of northeastern Brazil from ∼4 • S to 9 • S latitude, which corresponds to ∼700 km of coastline under a semi-diurnal mesotidal regime. We investigated wave-built terrace deposits and dated sediments using the optically stimulated luminescence and thermoluminescence methods on quartz grains. The wave-built terraces yielded two main age groups: 200-230 ka and 100-130 ka, which we interpreted as depositional ages. We correlated these age groups with oxygen-isotope stages 7c and 5e, respectively. These events correspond to the antepenultimate and penultimate transgressions along the Brazilian coast. The deposits occur mainly in patches on low-lying flat plateaus along the littoral zone and incision valleys that cut across coastal tablelands. The altitude of the base of the 200-230 ka terraces ranges from 10 m above mean sea level (asl) to -2m asl, whereas the base of the 100-130 ka varies from 12 m asl to -2 m asl. Both terraces were deposited in the foreshore and upper shoreface zones. We noted a coincidence between sea-level highstand chronologies in northeastern Brazil and those in the Bahamas and Bermuda.

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

“…While some data indicate that the sea level during that interval did not reach amplitudes comparable to present mean sea-level (Dutton et al 2009, Bard et al 2002, Schellmann and Radtke 2004, other records indicate sea levels equal or slightly above the present one (Bezerra et al 1998, Vesica et al 2000. This variability is likely to be caused by different dating methods employed (U/ Th series, ESR), by differences among dated materials (corals, vermetids, shells, sediments) and by the tectonic history of each site, as is the case for Holocene deposits in northeastern Brazil (Barreto et al 2002, Suguio et al 2011). Moreover, it shows that it is not possible to establish a single global sea-level curve for any specific time interval based solely on stratigraphic records.…”

“…Other records, however, correlate the highest peak to the event 7.3 (MIS 7c, Barreto et al 2002, Waelbroeck et al 2002, Suguio et al 2011 or to the event 7.1 (MIS 7a, Gallup et al 1994, Hearty and Kindler 1995, Goy et al 2006. The ESR age of ~226 ka BP from a tooth of the extinct mammal Toxodon collected from a Type 1 fluvial facies at the marine-terrestrial transition exposed along Chuí Creek (Lopes et al 2010) indicates that sea-level was already falling around this time, which would be consistent with the end of MIS 7e, around 228 ka BP (Robinson et al 2002).…”

“…Besides the Barrier System II in Rio Grande do Sul, the only other unit recognized as representing the MIS 7 transgressive event on the basis of absolute ages are the aforementioned deposits from northeastern Brazil dated by Barreto et al (2002) and Suguio et al (2011) that belong to the Barra de Tabatinga Formation, and provided TL and OSL ages between 215 and 220 ka (MIS 7c).…”

“…Good records of the transgression correlated to MIS 5 are found in some areas (Poupeau et al 1988 but the situation is complex for older transgressive events; so far, only the northeastern Brazilian coast has provided features recognized as having been formed by the marine transgression during MIS 7 (Barreto et al 2002, Suguio et al 2011). In the Coastal Plain of the state Rio Grande do Sul (CPRS), in southern Brazil, records of sea level oscillations prior to MIS 5 were reported from microfossils in drilling cores (Closs 1970, Carreño et al 1999) and geomorphological features (Poupeau et al 1988, Villwock and Tomazelli 1995, Tomazelli et al 2000.…”

Evolução tectono-sedimentar da porção central emersa da Bacia Paraíba, nordeste do Brasil

“…A large number of publications based on these structures have supported the hypothesis that the passive margin of South America was not as passive as originally perceived (e.g., Bezerra et al, 2008Bezerra et al, , 2011Bezerra et al, , 2014Moura−Lima et al, 2011;Japsen et al, 2012;Gurgel et al, 2013). More importantly, tectonic deformation is also recorded in sedimentary units of Late Pleistocene−Holocene age (e.g., Nogueira et al 2010;Rossetti et al 2011aRossetti et al , 2012Suguio et al, 2011;Ochoa et al, 2013). It may have even continued up to the Present, as suggested by the widespread documentation of seismogenic activity in several areas of northeastern Brazil (e.g., Ferreira et al, 2008).…”