Living Planktonic Foraminifera in South Atlantic: ABSTRACT

AAPG Bulletin ◽  
1966 ◽  
Vol 50 ◽  
Author(s):  
Allan W. H. Be
Keyword(s):  
Planktonic Foraminifera ◽  
South Atlantic

How well is the deep Tore seamount basin ventilated?

2020 ◽  
Author(s):  
Laura Antón ◽  
Susana Lebreiro ◽  
Silvia Nave ◽  
Luke Skinner ◽  
Elizabeth Michel ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Water Depth ◽  
Deep Water ◽  
Planktonic Foraminifera ◽  
Deep Ocean ◽  
South Atlantic ◽  
Age Difference ◽  
The South ◽  
Deep Basin ◽  
Iberian Margin

<p>The Last Glacial Maximum (LGM) was characterized by increased carbon storage in the deep ocean, as well as extremely poorly ventilated southern-sourced deep water (AABW) compared to northern-sourced deep water (NADW).</p><p>Here we analyse benthic (Cibicidoides wellerstorfi) d<sup>13</sup>C, and compare 3 sites sitting on the deep floor at 5 km water depth: MD13-3473 in the Tore inside basin; MD03-2698 in the Iberian margin; and TN057-21 in the South Atlantic. The Tore Seamount is a geological structure 300 km off the West Iberian margin at 40°N latitude. It has a crater-like morphology with a 5500 m deep basin in its middle, where calypso core MD13-3473 was collected, confined from the open ocean by a summit rim at 2200 m water depth (wd). The only connection between the deepest Tore Seamount basin and the Atlantic circulation is a NE gateway down to 4300 mwd.</p><p>The results for the LGM show similar values around -1.0 ‰ for the South Atlantic and the Iberian margin, in other words these sites were both bathed by AABW. However, the Tore basin record exhibits values around 0 ‰, similarly to open sites in the Iberian margin at 3.5 km depth. This seems to indicate a remarkable isolation of the Tore inside basin from the Atlantic deep bottom waters influence.</p><p>Among other things, we plan to examine the residence time of the Tore basin bottom water by measuring the radiocarbon age difference between benthic and planktonic foraminifera. </p><p>Our results confer to this enclosed environment the status of an in-situ deep ocean laboratory where to test hypotheses of past ocean circulation changes like the role of deep waters in sequestering glacial CO<sub>2</sub>. Core MD13-3473 covers 430 thousands of years, therefore 5 deglacial cycles (Spanish project “TORE5deglaciations”, CTM2017-84113-R, 2018-2020).</p>

Foraminiferal Solubility Rankings: a Contribution To the Search For Consensus

2018 ◽  
Vol 48 (4) ◽  
pp. 301-313 ◽  
Author(s):  
Sandro M. Petró ◽  
María A. G. Pivel ◽  
João C. Coimbra
Keyword(s):  
Planktonic Foraminifera ◽  
Differential Resistance ◽  
South Atlantic ◽  
Neogloboquadrina Pachyderma ◽  
Resistant Species ◽  
Oxygen Isotopic ◽  
Orbulina Universa ◽  
Moderately Resistant ◽  
Mg Content ◽  
Isotopic Signal

Abstract Factors intrinsic to foraminiferal tests result in different degrees of susceptibility to dissolution. Differential resistance to dissolution among planktonic foraminifera has been studied in several regions, but no previous work has been reported for the western South Atlantic. The goal of this research was to develop a dissolution susceptibility ranking for planktonic foraminifera from the western South Atlantic Ocean, to compare the solubility between benthic and planktonic foraminifera, and to evaluate changes in the oxygen isotopic signal (δ18O) associated with dissolution. Two experiments were carried out by immersing tests in acetic acid or distilled water for 200 days. Our comparison revealed that tests of planktonic foraminifera were more resistant to dissolution than the benthic species tested, which has implications for use of the planktonic/benthic ratio (P/B) as a preservation proxy. Solubility of tests is directly proportional to the Mg content in the calcite structure, which varies widely across benthic taxa but is consistently low in planktonics. The δ18O increased during dissolution, probably due to the preferential dissolution of the internal chambers, making the remaining calcite progressively reflect the composition of the last chambers. Our solubility ranking for planktonic foraminifera agreed in part with rankings for foraminifera from other regions. Neogloboquadrina pachyderma and Globorotalia inflata proved to be resistant species; Globigerinella calida, Globigerinella siphonifera, Globorotalia hirsuta, Candeina nitida, and Trilobatus trilobus were moderately resistant; and Globorotalia fimbriata and Orbulina universa were most susceptible to dissolution. Presence and condition of benthic genera such as Quinqueloculina, Hoeglundina and Bulimina, and the planktonic species O. universa can be used to indicate limited dissolution in paleoceanographic studies. Small variations in the dissolution index may also reflect oceanographic changes that influence the composition of the tests, indicating the importance of regional solubility rankings, such as this study for the western South Atlantic.

scholarly journals Menardiiform planktonic foraminifera stratigraphy from Middle Pleistocene to Holocene in the Western South Atlantic

2018 ◽  
Vol 21 (3) ◽  
pp. 225-237
Author(s):  
Karen Badaraco Costa ◽  
Edmundo Camillo Jr ◽  
Ana Cláudia Aoki Santarosa ◽  
Fabiane Sayuri Iwai ◽  
Juliana Pereira de Quadros ◽  
...  
Keyword(s):  
Planktonic Foraminifera ◽  
South Atlantic ◽  
Middle Pleistocene

scholarly journals Contrasting late-glacial paleoceanographic evolution between the upper and lower continental slope of the western South Atlantic

2020 ◽  
Vol 16 (4) ◽  
pp. 1245-1261
Author(s):  
Leticia G. Luz ◽  
Thiago P. Santos ◽  
Timothy I. Eglinton ◽  
Daniel Montluçon ◽  
Blanca Ausin ◽  
...  
Keyword(s):  
Rio De Janeiro ◽  
Planktonic Foraminifera ◽  
South Atlantic ◽  
Meridional Overturning Circulation ◽  
Coastal Current ◽  
Limited Information ◽  
Last Deglaciation ◽  
Glacial Cycle ◽  
Last Glacial ◽  
The Last Glacial

Abstract. The number of sedimentary records collected along the Brazilian continental margin has increased significantly in recent years, but relatively few are located in shallow waters and register paleoceanographic processes in the outer shelf–middle slope prior to 10–15 ka. For instance, the northward flow up to 23–24∘ S of cold and fresh shelf waters sourced from the Subantarctic region is an important feature of current hydrodynamics in the subtropical western South Atlantic Ocean, and yet limited information is available for the long-term changes of this system. Herein, we considered a suite of organic and inorganic proxies – alkenones-derived sea surface temperature (SST), δD-alkenones, δ18O of planktonic foraminifera, and ice-volume free seawater δ18OIVF−SW – in sediment from two cores (RJ-1501 and RJ-1502) collected off the Rio de Janeiro Shelf (SE Brazilian continental shelf) to shed light on SST patterns and relative salinity variations since the end of the last glacial cycle in the region and the implications of these processes over a broader spatial scale. The data indicate that, despite the proximity (∼40 km apart) of both cores, apparently contradictory climatic evolution occurred at the two sites, with the shallower (deeper) core RJ-1501 (RJ-1502) showing consistently cold (warm) and fresh (salt) conditions toward the Last Glacial Maximum (LGM) and last deglaciation. This can be reconciled by considering that the RJ-1501 core registered a signal from mid- to high latitudes on the upper slope off Rio de Janeiro represented by the influence of the cold and fresh waters composed of Subantarctic Shelf Water and La Plata Plume Water transported northward by the Brazilian Coastal Current (BCC). The data from core RJ-1502 and previous information for deep-cores from the same region support this interpretation. In addition, alkenone-derived SST and δ18OIVF−SW suggest a steep thermal and density gradient formed between the BCC and Brazil Current (BC) during the last climate transition which, in turn, may have generated perturbations in the air–sea heat flux with consequences for the regional climate of SE South America. In a scenario of future weakening of the Atlantic Meridional Overturning Circulation, the reconstructed gradient may become a prominent feature of the region.

Planktonic Foraminiferal Endemism at Southern High Latitudes Following the Terminal Cretaceous Extinction

2020 ◽  
Vol 50 (4) ◽  
pp. 382-402
Author(s):  
Brian T. Huber ◽  
Maria Rose Petrizzo ◽  
Kenneth G. MacLeod
Keyword(s):  
Indian Ocean ◽  
High Latitude ◽  
Planktonic Foraminifera ◽  
South Atlantic ◽  
Weddell Sea ◽  
Southern Indian Ocean ◽  
Ocean Drilling Program ◽  
Ocean Drilling ◽  
Mode Of Life ◽  
Southern High Latitude

Abstract Austral planktonic foraminiferal assemblages from immediately above the Cretaceous/Paleogene (K/Pg) boundary at Ocean Drilling Program Hole 690C (Maud Rise, Weddell Sea) and International Ocean Drilling Program Hole U1514C (southeast Indian Ocean) show a much different record of post-extinction recovery than anywhere outside the circum-Antarctic region. Species of Woodringina and Parvularugoglobigerina, genera with well-documented evolutionary successions within the early Danian P0 and Pα biozones at tropical/subtropical and mid-latitude localities, are absent from southern high latitude sequences. This study proposes new criteria for biostratigraphic correlation of the lowermost Danian Antarctic Paleocene AP0 and AP1 Zones using stratophenetic observations from Scanning Electron Microscope images of lower Danian planktonic foraminifera at deep-sea sites in the southern South Atlantic and southern Indian Ocean. The small but distinctive species Turborotalita nikolasi (Koutsoukos) is a highly reliable index species for the lowermost Danian as it consistently occurs immediately above the K/Pg boundary at multiple southern high latitude sites, which is consistent with its distribution at middle and low latitudes. Also useful for cross-latitude correlation is Parasubbotina neanika n. sp., which first appears within the lowermost Danian worldwide. The geographic distribution of the New Zealand species Antarcticella pauciloculata (Jenkins) and Zeauvigerina waiparaensis (Jenkins), as well as Eoglobigerina maudrisensis n. sp. from just above the K/Pg in the southern South Atlantic and southern Indian Ocean, helps define the extent of the Austral Biogeographic Province and provides evidence for marine communication via marine seaways across Antarctica. While An. pauciloculata was previously considered a benthic species, new stable isotope evidence demonstrates that it lived a planktonic mode of life. It is possible this species evolved from a benthic ancestor and that the benthic to planktonic transition occurred through an intermediate tychopelagic lifestyle at a time when calcareous plankton were less abundant as a result of the terminal Cretaceous mass extinction.

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