The Birth of a Connected South Atlantic Ocean: A Magnetostratigraphic Perspective

Abstract

The early Paleogene sedimentary record of the Sao Paulo Plateau holds the key to understanding the timing and mechanisms of the onset of Atlantic oceanic circulation, with implications for ocean-climate feedback systems. The timing and evolution of South Atlantic Ocean connectivity remain poorly understood, hindering a full understanding of modern circulation mechanisms. In this work, we develop an improved magnetostratigraphic age model for the late-Cretaceous to Eocene sedimentary record of Deep-Sea Drilling Project (DSDP) Site 356, located on the São Paulo Plateau at the edge of the Rio Grande Rise. The model constrains the timing of the beginning of Atlantic Ocean circulation, as the last obstacle to a connected Atlantic was removed. We use the age model to quantify sedimentary rates, and correlate with rock magnetic and published geochemical data to explore links between ocean current rearrangement and climatic anomalies. We find that periods characterized by variations in the magnetic properties of sediments and sedimentation anomalies in the Sao Paulo Plateau are reflected in carbon isotope events, supporting a possible link between ocean circulation and hyperthermal events.

Increasing impact of North Atlantic Ocean circulation on sedimentary processes along the passive Galicia Margin (NW Spain) over the past 40 million years

“…While large amounts of sand have accumulated on the outer shelf, fine-grained material has intermittently been stored in a mid-shelf mudbelt (Dias et al, 2002a;2002b;Lantzsch et al, 2009;Oberle et al, 2014a;Zhang et al, 2016a). Resuspension during storm events has been allowed for efficient off-shelf transport in bottom nepheloid layers (Dias et al, 2002b;Oliveira et al, 2002;Vitorino et al, 2002;Oberle et al, 2014b). Sediment deposition at the continental slope and inside GIB has been governed by a succession of hemipelagic deposition, the arrival of ice-rafted debris, phases of contouritic activity, and downslope processes (Hall and McCave, 2000;Bender et al, 2012;Martins et al, 2013;Hanebuth et al, 2015;Zhang et al, 2016b;Plaza-Morlote et al, 2017;Mena et al, 2018;Petrovic et al, 2019).…”

“…Defined deep-and bottom-water masses were limited to the North Atlantic and Tethys Oceans; the oceans were generally poorly ventilated during the outgoing Mesozoic (Roth, 1986;Miller et al, 2009;Straume et al, 2020). Bottom-water ventilation improved with the deepening of the South Atlantic Ocean basin due to an intensification of southern high-latitude deep-water formation in Late Cretaceous times (Robinson and Vance, 2012) and a further intensification of the South Atlantic circulation in the early Paleogene (Palcu et al, 2020). The onset of Northern Component Water (NCW), the ancient equivalent of NADW, represents the initiation of deep-water production at North Atlantic high latitudes at around 35 Ma (Priabonian/latest Eocene), as indicated by an onset of the Southeast Faeroes Drift in the Faeroe-Shetland Basin (Davies et al, 2001;Poore et al, 2006;Langton et al, 2016;Coxall et al, 2018;Hovikoski et al, 2021).…”

Contourite depositional systems offshore Madeira Island: Decoding the deepwater circulation since the Late Cretaceous to the Quaternary in the NE-Central Atlantic

“…In the Campanian (84-72 Ma), the Equatorial Atlantic Gateway was fully opened favoring the progressive and better ventilated circulation between these two basins (Poulsen et al, 2001;Martin et al, 2012;Robinson and Vance et al, 2012;Murphy and Thomas, 2013;Voigt et al, 2013;Granot and Dyment, 2015;Donnadieu et al, 2016;Pérez-Díaz and Eagles, 2017). Therefore, since the Late Campanian-Maastrichtian the ocean circulation involved a more oxygenated deep-water mass sourced in the south ocean, the SCW (MacLeod et al, 2011;Friedrich et al, 2012;Murphy and Thomas, 2013;Sabatino et al, 2018;Ladant et al, 2020;Palcu et al, 2020). This water mass crossed the Equatorial Atlantic Gateway and spread northward bathing the entire Atlantic basin at depths greater than 3000 m (Robinson and Vance, 2012;Donnadieu et al, 2016;Pérez-Díaz and Eagles, 2017;Ladant et al, 2020).…”

Biostratigraphy and Paleoenvironmental Reconstruction at the Gebel Nezzazat (Central Sinai, Egypt): A Paleocene Record for the Southern Tethys

“…It is hypothesized that this interval is the consequence of a revolution of the bottom water conditions following the beginning of a deep-water connection in the South Atlantic Ocean (Figure 1), when the Atlantic Ocean Circulation increasingly substitutes the Tethys circum-equatorial oceanic circulation [16]. Moreover, some studies attributed the sharp climatic anomalies in the early Paleogene to drastic changes in paleocirculation [16].…”

“…It is hypothesized that this interval is the consequence of a revolution of the bottom water conditions following the beginning of a deep-water connection in the South Atlantic Ocean (Figure 1), when the Atlantic Ocean Circulation increasingly substitutes the Tethys circum-equatorial oceanic circulation [16]. Moreover, some studies attributed the sharp climatic anomalies in the early Paleogene to drastic changes in paleocirculation [16]. A hiatus characterized the Selandian Stage at its type locality in Denmark [17]; consequently, intensive efforts have been made to define the GSSP (Global Stratotype Section and Point) for the base of the Selandian that was formally ratified at Itzurun Beach in Zumaia, Basque Country, northern Spain [2,15].…”