Radiocarbon Age Offsets Between Two Surface Dwelling Planktonic Foraminifera Species During Abrupt Climate Events in the SW Iberian Margin

In light of the current rate of anthropogenic climate change, it is becoming increasingly critical to enhance knowledge of past abrupt climate events and subsequent responses of the Earth system. One period that can provide such insight is the last ~28 kyr, with several abrupt changes occurring over the course of the deglaciation. The Portuguese Margin has been an ideal location to study the impacts of these abrupt climate events on marine and terrestrial environments.&#160; The combined effect of the narrow continental shelf and close proximity to the Tagus and Sado rivers, lead to the rapid delivery of a high quantity of sediment, including our pollen and biomarker proxies, to the Tagus Abyssal Plain. Joint terrestrial and palaeoceanographic analyses from the same sediment samples enable an in situ assessment of the relative timing of changes in palaeoceanographic and terrestrial proxies.&#160;Here we document the response of western Iberian vegetation to millennial and centennial-scale changes, particularly changes in moisture availability, over the deglaciation and Holocene, by combining (for the first time at a Portuguese Margin site) pollen and leaf-wax isotopic biomarker records (&#948;13C and &#948;D) from&#160;core&#160;SHAK06-5K. A high-resolution pollen record (every 2cm) and lower-resolution n-alkane &#948;13C and &#948;D records spanning 28kya are compared with high-resolution XRF sediment and planktonic foraminiferal d18O analyses from the same core.&#160; The sequence is supported by high-resolution age control, based on 40 Accelerator mass spectrometry (AMS) 14C dates from monospecific samples of the planktonic foraminifera, Globigerina bulloides.&#160;Our pollen record indicates the rapid response of regional vegetation to centennial changes and millennial-scale climate events, with forest expansion during the warm interglacial/ interstadial B&#248;lling-Aller&#248;d and Holocene, and forest contraction and steppe expansion during cold glacial/ stadial conditions of the Last Glacial Maximum and Younger Dryas. Comparing our pollen and n-alkane biomarker data with the XRF Zr:Sr ratio and&#160;planktonic foraminiferal &#948;18O records, a clear synchroneity can be seen in the timing of millennial-scale changes in all records.&#160;&#160;The millennial-scale changes in our leaf wax n-alkane &#948;D and &#948;13C records can be explained by both vegetation composition and growing season water availability.&#160;

Download Full-text

How well is the deep Tore seamount basin ventilated?

10.5194/egusphere-egu2020-11702 ◽

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

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).Here we analyse benthic (Cibicidoides wellerstorfi) d13C, 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&#176;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.The results for the LGM show similar values around -1.0 &#8240; 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 &#8240;, 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.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.&#160;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 CO2. Core MD13-3473 covers 430 thousands of years, therefore 5 deglacial cycles (Spanish project &#8220;TORE5deglaciations&#8221;, CTM2017-84113-R, 2018-2020).

Download Full-text

Present Status of Radiocarbon Calibration and Comparison Records Based on Polynesian Corals and Iberian Margin Sediments

Radiocarbon ◽

10.1017/s0033822200033087 ◽

2004 ◽

Vol 46 (3) ◽

pp. 1189-1202 ◽

Cited By ~ 46

Author(s):

Edouard Bard ◽

Guillemette Ménot-Combes ◽

Frauke Rostek

Keyword(s):

Present Status ◽

Planktonic Foraminifera ◽

The Other ◽

Data Sets ◽

The Bahamas ◽

Subsequent Addition ◽

Iberian Margin ◽

Radiocarbon Calibration

In this paper, we present updated information and results of the radiocarbon records based on Polynesian corals and on Iberian Margin planktonic foraminifera. The latter record was first published by Bard et al. (2004a,b), with the subsequent addition of some data by Shackleton et al. (2004). These data sets are compared with the IntCal98 record (Stuiver et al. 1998) and with data sets based on other archives, such as varves of Lake Suigetsu (Kitagawa and van der Plicht 1998, 2000), speleothems from the Bahamas (Beck et al. 2001), and Cariaco sediments (Hughen et al. 2004). Up to 26,000 cal BP, the Iberian Margin data agree within the errors of the other records. By contrast, in the interval between 33,000 and 41,000 cal BP, the Iberian Margin record runs between the Lake Suigetsu and Bahamian speleothem data sets, but it agrees with the few IntCal98 coral data and the Cariaco record.

Download Full-text

Radiocarbon calibration beyond 20,000 14C yr B.P. by means of planktonic foraminifera of the Iberian Margin

Quaternary Research ◽

10.1016/j.yqres.2003.11.006 ◽

2004 ◽

Vol 61 (2) ◽

pp. 204-214 ◽

Cited By ~ 107

Author(s):

Edouard Bard ◽

Frauke Rostek ◽

Guillemette Ménot-Combes

Keyword(s):

Planktonic Foraminifera ◽

Data Sets ◽

Last Glacial Period ◽

Polynomial Curve ◽

Abrupt Changes ◽

Image Position ◽

Reservoir Age ◽

Iberian Margin ◽

Good Agreement ◽

The Last Glacial

We present a new set of 14C ages obtained by accelerator mass spectrometry (AMS) on planktonic foraminifera from a deep-sea core collected off the Iberian Margin (MD952042). This site, at 37°N, is distant from the high-latitude zones where 14C reservoir age is large and variable. Many independent proxies — alkenones, magnetic susceptibility, ice-rafted debris, foraminifera stable isotopes, abundances of foraminifera, pollen, and dinoflagellates — show abrupt changes correlative with Dansgaard-Oeschger and Heinrich events of the last glacial period. The good stratigraphic agreement of all proxies — from the fine to the coarse-size fractions — indicates that the foraminifera 14C ages are representative of the different sediment fractions. To obtain reliable 14C ages of foraminifera beyond 20,000 14C yr B.P. we leached the shells prior to carbonate hydrolysis and subsequent analysis. For a calendar age scale, we matched the Iberian Margin profile with that of Greenland Summit δ18O. Both are proxies for temperature, which in models varies synchronously in the two areas. The match creates no spurious jumps in sedimentation rate and requires only a limited number of tie points. Except for ages older than 40,000 14C yr B.P. Greenland's GISP2 and GRIP records yield similar calendars. The 14C and imported calendar ages of the Iberian Margin record are then compared to data — from lacustrine annual varves and from corals and speleothems dated by U–Th — previously used to extend the calibration beyond 20,000 14C yr B.P. The new record follows a smooth pattern between 23,000 and 50,000 cal yr B.P. We find good agreement with the previous data sets between 23,000 and 31,000 cal yr B.P. In the interval between 33,000 and 41,000 cal yr B.P. for which previous records disagree by up to 5000 cal yr, the Iberian Margin record closely follows the polynomial curve that was previously defined by an interpolation of the coral ages and runs between the Lake Suigetsu and the Bahamian speleothem data sets.

Download Full-text

Atlantic sea surface temperatures estimated from planktonic foraminifera off the Iberian Margin over the last 40Ka BP

Marine Geology ◽

10.1016/j.margeo.2015.06.001 ◽

2015 ◽

Vol 367 ◽

pp. 191-201 ◽

Cited By ~ 10

Author(s):

Maria Virgínia Alves Martins ◽

Adriana Rodrigues Perretti ◽

Emilia Salgueiro ◽

Fabrizio Frontalini ◽

João Moreno ◽

...

Keyword(s):

Planktonic Foraminifera ◽

Sea Surface ◽

Sea Surface Temperatures ◽

Surface Temperatures ◽

Iberian Margin

Download Full-text

Radiocarbon Age Profiles and Size Dependency of Mixing in Northeast Atlantic Sediments

Radiocarbon ◽

10.1017/s003382220004159x ◽

2001 ◽

Vol 43 (2B) ◽

pp. 929-937 ◽

Cited By ~ 11

Author(s):

Louise Brown ◽

Gordon T Cook ◽

Angus B MacKenzie ◽

John Thomson

Keyword(s):

Planktonic Foraminifera ◽

Sediment Accumulation ◽

Deep Ocean ◽

Coarse Fraction ◽

Surface Mixed Layer ◽

Radiocarbon Age ◽

Sediment Size ◽

Common Technique ◽

Sediment Component ◽

Selection Of

In recent years, the most common technique for radiocarbon dating of deep-ocean sediments has been accelerator mass spectrometry (AMS) analysis of hand-picked planktonic foraminifera (forams). Some studies have exposed age offsets between different sediment size fractions from the same depth within a core and this has important implications when establishing a chronological framework for palaeoceanographic records associated with a particular sediment component. The mechanisms generating the age offsets are not fully understood, a problem compounded by the fact that the fraction defined as “large” varies between different studies. To explore this problem, we dated samples of hand-picked forams from two Biogeochemical Ocean Flux Study (BOFS) cores, for which the presence of an offset between the bulk carbonate and >150 μm foraminiferal calcite had already been demonstrated. The presence of a constant age offset between bulk carbonate and coarse fraction material at the two BOFS sites has been confirmed, but the magnitude of the offset is dependent on whether a simple size-separation technique or hand-picking of well-preserved forams is applied. This may be explained if the selection of well preserved forams biases the sample towards those specimens that have spent least time in the surface mixed layer (SML) or have undergone less size selective mixing. Modeling of the 14C profiles demonstrates that SML depth and sediment accumulation rates are the same for both the bulk and coarse sediment fractions, which is consistent with the hypothesis that size-selective mixing is responsible for the age offset.

Download Full-text

Depth-habitat reorganization of planktonic foraminifera across the Albian/Cenomanian boundary

Paleobiology ◽

10.1666/09027.1 ◽

2010 ◽

Vol 36 (3) ◽

pp. 357-373 ◽

Cited By ~ 35

Author(s):

Atsushi Ando ◽

Brian T. Huber ◽

Kenneth G. MacLeod

Keyword(s):

Stable Isotope ◽

North Atlantic ◽

Planktonic Foraminifera ◽

Environmental Parameters ◽

Implicit Assumption ◽

Ocean Stratification ◽

Evolutionary Changes ◽

Surface Dwelling ◽

Cooling Trend ◽

Species Specific

New mid-Cretaceous stable isotope (δ18O and δ13C) records of multiple planktonic foraminiferal species and coexisting coccoliths from Blake Nose (western North Atlantic) document a major depth-ecology reorganization of planktonic foraminifera. Across the Albian/Cenomanian boundary, deep-dwellingPraeglobotruncana stephaniandRotalipora globotruncanoidesadapted to living at a shallower depth, while, at the same time, the population of surface-dwellingParacostellagerina libycadeclined. Subsequently, the opportunistic speciesHedbergella delrioensisshifted to a deep environment, and the deep-dwelling formsRotalipora montsalvensisandRotalipora reichelifirst appeared. The primary paleoenvironmental cause of the observed changes in planktonic adaptive strategies is uncertain, yet their coincidence with an earliest Cenomanian cooling trend reported elsewhere implicates the importance of reduced upper-ocean stratification. Although there has been an implicit assumption that the species-specific depth habitats of fossil planktonic foraminifera were invariant through time, planktonic paleoecology is a potential variable. Accordingly, the possibility of evolutionary changes in planktonic foraminiferal depth ecology should be a primary consideration (along with other environmental parameters) in paleoceanographic interpretations of foraminiferal stable isotope data.

Download Full-text

Effects of temperature and salinity on the growth and survival of the planktonic foraminiferGlobigerinoides sacculifer

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315400026643 ◽

1987 ◽

Vol 67 (2) ◽

pp. 323-341 ◽

Cited By ~ 38

Author(s):

David A. Caron ◽

Walter W. Faber ◽

Allan W. H. Bé

Keyword(s):

Planktonic Foraminifera ◽

Species Abundance ◽

Geographic Range ◽

Growth And Survival ◽

Number Of Species ◽

Physical And Chemical Variables ◽

Surface Dwelling ◽

Effects Of Temperature ◽

Geographic Distributions ◽

Physical And Chemical

The geographic distributions of most surface-dwelling species of planktonic Foraminifera are now well-known (Bé, 1959, 1960, 1977; Bé & Hamlin, 1967; Bé, Vilks & Lott, 1971; Bé & Tolderlund, 1971; Tolderlund & Bé, 1971; Bé & Hutson, 1977). These distributions, established from species abundance in plankton net collections, have been used to correlate abundance with physical and chemical variables (primarily temperature and salinity) in an effort to establish the factors which control the geographic range of these shelled protists. Significant correlations have been derived from these comparisons and the temperature and salinity ‘limits’ and ‘optima’ of a number of species have been reported (e.g. Bé & Tolderlund, 1971).

Download Full-text

Are Past Sea-Ice Reconstructions Based on Planktonic Foraminifera Realistic? Study of the Last 50 ka as a Test to Validate Reconstructed Paleohydrography Derived from Transfer Functions Applied to Their Fossil Assemblages

Geosciences ◽

10.3390/geosciences11100409 ◽

2021 ◽

Vol 11 (10) ◽

pp. 409

Author(s):

Frédérique Eynaud ◽

Sébastien Zaragosi ◽

Mélanie Wary ◽

Emilie Woussen ◽

Linda Rossignol ◽

...

Keyword(s):

Transfer Functions ◽

Climatic Variability ◽

Planktonic Foraminifera ◽

Extreme Environments ◽

World Ocean ◽

Last Glacial Period ◽

Degree Of Confidence ◽

World Ocean Atlas ◽

Climate Events ◽

The Last Glacial

Since its existence, paleoceanography has relied on fossilized populations of planktonic foraminifera. Except for some extreme environments, this calcareous protist group composes most of the silty-to-sandy fraction of the marine sediments, i.e., the foraminiferal oozes, and its extraction is probably the simplest among the currently existing set of marine fossil proxies. This tool has provided significant insights in the building of knowledge on past climates based on marine archives, especially with the quantification of past hydrographical variables, which have been a turning point for major comprehensive studies and a step towards the essential junction of modelling and paleodata . In this article, using the modern analog technique and a database compiling modern analogs (n = 1007), we test the reliability of this proxy in reconstructing paleohydrographical data other than the classical sea-surface temperatures, taking advantage of an update regarding a set of extractions from the World Ocean Atlas for transfer functions. Our study focuses on the last glacial period and its high climatic variability, using a set of cores distributed along the European margin, from temperate to subpolar sites. We discuss the significance of the reconstructed parameters regarding abrupt and extreme climate events, such as the well-known Heinrich events. We tested the robustness of the newly obtained paleodata by comparing them with older published reconstructions, especially those based on the complementary dinoflagellate cyst proxy. This study shows that the potential of planktonic foraminifera permits going further in reconstructions, with a good degree of confidence; however, this implies considering ecological forcings in a more holistic perspective, with the corollary to integrate the message of this fossil protist group, i.e., the obtained parameters, in light of a cohort of other data. This article constitutes a first step in this direction.

Download Full-text

Paleoceanographic reconstructions from planktonic foraminifera off the Iberian Margin: Temperature, salinity, and Heinrich events

Paleoceanography ◽

10.1029/1998pa900027 ◽

1999 ◽

Vol 14 (3) ◽

pp. 384-396 ◽

Cited By ~ 94

Author(s):

Olivia Cayre ◽

Yves Lancelot ◽

Edith Vincent ◽

Michael A. Hall

Keyword(s):

Planktonic Foraminifera ◽

Heinrich Events ◽

Iberian Margin

Download Full-text