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

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.

A paleoenvironmental study of early to middle Pleistocene foraminifera of the Santa Barbara Formation at Santa Barbara, California

1990 ◽  
Vol 64 (1) ◽  
pp. 1-25 ◽  
Author(s):  
R. Timothy Patterson ◽  
Charlotte A. Brunner ◽  
Rosemary Capo ◽  
Jeremy Dahl
Keyword(s):  
Cluster Analysis ◽  
Water Depth ◽  
Benthic Foraminifera ◽  
Planktonic Foraminifera ◽  
Middle Pleistocene ◽  
Santa Barbara ◽  
Neogloboquadrina Pachyderma ◽  
California Borderland ◽  
History Of ◽  
Age Range

An interval of the Early to Middle Pleistocene history of the California Borderland was assessed using multivariate analysis of foraminifera from the Santa Barbara Formation at Bathhouse Beach, Santa Barbara, California. A census of 93 species of benthic foraminifera and nine species of planktonic foraminifera was compiled from 11 samples from the shelly marls, silts, and sands of the lower member. Most species of benthic foraminifera are rare and only 38 species comprise one percent or more of the population in one or more samples.Paleoenvironment of the sea floor was determined based on benthic foraminifera. R-mode cluster analysis defined five associations which are similar to those of the present-day banks and terraces of the California Borderland. Q-mode cluster analysis grouped samples into four biofacies which characterize shallow banks near 50 meters water depth and off-shore ridges and deep banks averaging 150 meters water depth. The stratigraphic succession of biofacies indicates two transgressive cycles separated by an apparent disconformity between 7.5 and 8.9 meters above the base of the section (between samples 3 and 4).Paleoceanography of surficial waters was interpreted from planktonic foraminifera. Paleotemperature was assessed from the proportion of sinistral to dextral morphs and from the proportion of encrusted, compact morphs to reticulate, globular morphs of Neogloboquadrina pachyderma. The coiling morphs show a warm interval from the base of the section to about 12 meters (between samples 5 and 6), and a cooler interval from about 12 meters to about 24 meters (between samples 10 and 11), and an interval of intermediate paleotemperature in the topmost sample of the section. Changes in the planktonic assemblage do not coincide with the transgressive cycles inferred from the benthic biofacies.The Bathhouse Beach section can be placed chronostratigraphically based on planktonic foraminiferal coiling shifts and strontium isotopic data. The isotopic age range of 400 to 900 Kyr brackets the 600 Kyr age assigned by Lagoe and Thompson (1988) to the Neogloboquadrina pachyderma coiling dominance interval CD9/CD8 boundary which occurs midway in the section, between samples 5 and 6.

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