Late Pleistocene sea-level changes recorded in tidal and fluvial deposits from Itaubal Formation, onshore portion of the Foz do Amazonas Basin, Brazil

Abstract

The Pleistocene deposits exposed in the Amapá Coastal Plain (onshore portion of the Foz do Amazonas Basin, northeastern South America) were previously interpreted as Miocene in age. In this work, they were named as "Itaubal Formation" and were included in the quaternary coastal history of Amazonia. The study, through facies and stratigraphic analyses in combination with optically stimulated luminescence (single and multiple aliquot regeneration), allowed interpreting this unit as Late Pleistocene tidal and fluvial deposits. The Itaubal Formation, which unconformably overlies strongly weathered basement rocks of the Guianas Shield, was subdivided into two progradational units, separated by an unconformity related to sea-level fall, here named as Lower and Upper Units. The Lower Unit yielded ages between 120,600 (± 12,000) and 70,850 (± 6,700) years BP and consists of subtidal flat, tide-influenced meandering stream and floodplain deposits, during highstand conditions. The Upper Unit spans between 69,150 (± 7,200) and 58,150 (± 6,800) years BP and is characterized by braided fluvial deposits incised in the Lower Unit, related to base-level fall; lowstand conditions remained until 23,500 (± 3,000) years BP. The studied region was likely exposed during the Last Glacial Maximum and then during Holocene, covered by tidal deposits influenced by the Amazon River.

Neogene sharks and rays from the Brazilian ‘Blue Amazon’

“…In the Bragantina Platform carbonates were gradually replaced by siliciclastic sediments of the Barreiras Formation, which represent the expressive progradation of continental deposits linked to the last thermal tectonic event in the North to Eastern Brazilian coastal margin during the middle to late Miocene ( Fig 2 ). In contrast, the carbonate platforms in the Western Brazilian Coast, clearly indicate the step-wise hydrographic changes related to the enlargement of the main Amazon drainage system since the Pliocene-Pleistocene (e. g., [ 3 , 5 , 12 – 18 ]). This event also triggered changes in the coastal marine environment together with sea level variation through time [ 19 ].…”

A review of last interglacial sea-level proxies in the western Atlantic and southwestern Caribbean, from Brazil to Honduras

“…In general, the study of the Last Interglacial in Brazil is hindered by the small number of reliable chronological constraints. Therefore, the most recent studies were directed to use radiometric dating techniques (such as OSL or TL) to establish radiometric ages for Pleistocene deposits (Barreto et al, 2002;Buchmann and Tomazelli, 2003;Suguio et al, 2003;Tomazelli and Dillenburg, 2007;Rossetti et al, 2011;Suguio et al, 2011;Bezerra et al, 2015).…”

A review of Last Interglacial sea-level proxies in the Western Atlantic and Southwestern Caribbean, from Brazil to Honduras

“…In general, the study of the Last Interglacial in Brazil is hindered by the small number of reliable chronological constraints. Therefore, the most recent studies were directed to use radiometric dating techniques (such as OSL or TL) to establish radiometric ages for Pleistocene deposits (Barreto et al, 2002;Buchmann and Tomazelli, 2003;Suguio et al, 2003;Tomazelli and Dillenburg, 2007;Rossetti et al, 2011;Suguio et al, 2011;Bezerra et al, 2015).…”

“…In the northernmost states of Brazil, information on Pleistocene marine deposits was generally lacking until the recent work of Bezerra et al (2015) in Amapa State. These authors define the Pleistocene "Itaubal Formation", and subdivide it into two progradational units (Upper and Lower), separated by an unconformity.…”

“…Using OSL ages, the Itaubal Lower Unit was constrained to MIS 5 (120 ka to 71 ka). Detailed facies analysis along several outcrops allowed Bezerra et al (2015) to assert that the Itaubal Lower unit is representative of "subtidal and tide-influenced meandering stream and floodplain deposits".…”