scholarly journals Landscape Mapping, Ichnological and Benthic Foraminifera Trends in a Deep-Water Gateway, Discovery Gap, NE Atlantic

Geosciences ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 474
Author(s):  
Evgenia V. Dorokhova ◽  
Francisco J. Rodríguez-Tovar ◽  
Dmitry V. Dorokhov ◽  
Liubov A. Kuleshova ◽  
Anxo Mena ◽  
...  
Keyword(s):  
Deep Water ◽  
Benthic Foraminifera ◽  
Bottom Water ◽  
Sediment Cores ◽  
Abiotic Factor ◽  
Bottom Water Temperature ◽  
Temporal Differences ◽  
Landscape Mapping ◽  
Position Index ◽  
Macro Benthos

Multidisciplinary studies have allowed us to describe the abiotic landscapes and, thus, reveal the ichnological and benthic foraminifera trends in a deep-water gateway. Mesoscale landscape mapping is presented based on the bathymetric position index, substrate types and near-bottom water temperature. Four sediment cores, retrieved from the entrance, centre and exit of the gap, were subject to computed tomography, ichnological and benthic foraminifera studies. A high diversity of abiotic landscapes in the relatively small area of Discovery Gap is detected and its landscape is characterized by 23 landscape types. The most heterogeneous abiotic factor is a topography that is associated with sediment patchiness and substrate variability. The ichnological and tomographical studies of the sediment cores demonstrate lateral and temporal differences in the macrobenthic tracemaker behaviour. The ichnofossils assemblage of the sediment core can be assigned to the Zoophycos ichnofacies with a higher presence of Zoophycos in the entrance site of the gap and during glacial intervals. Higher benthic foraminifera diversity and species richness during the Holocene are also registered in the southern part of the gap compared to the northern part. The spatial and temporal differences in macro-benthos behavior and benthic foraminifera distribution in the deep-water gateway are proposed to relate to the topographical variations of the Antarctic Bottom Water and its influence on the hydrodynamic regime, nutrient transport, etc.

scholarly journals Glacier and ocean variability in Ata Sund, west Greenland, since 1400 CE

The Holocene ◽  
2020 ◽  
Vol 30 (12) ◽  
pp. 1681-1693
Author(s):  
Fanny Ekblom Johansson ◽  
David J Wangner ◽  
Camilla S Andresen ◽  
Jostein Bakke ◽  
Eivind Nagel Støren ◽  
...  
Keyword(s):  
Large Scale ◽  
Bottom Water ◽  
Sediment Cores ◽  
Ice Age ◽  
Bottom Water Temperature ◽  
Ocean Variability ◽  
The Past ◽  
Period 2 ◽  
Climate Cooling ◽  
Tomography Scan

To improve knowledge of marine-terminating glaciers in western Greenland, marine sediment cores from the Ata Sund fjord system, hosting two outlet glaciers, Eqip Sermia and Kangilerngata Sermia, were investigated. The main objective was to reconstruct glacial activity and paleoceanographic conditions during the past 600 years. Ice-rafted debris (IRD) was quantified by wet-sieving sediment samples and by using a computed tomography scan. Variability in relative bottom water temperatures in the fjord was reconstructed using foraminiferal analysis. On the basis of this, three periods of distinct glacial regimes were identified: Period 1 (1380–1810 CE), which covers the culmination of the Little Ice Age (LIA) and is interpreted as having advanced glaciers with high IRD content. Period 2 (1810–1920 CE), the end of the LIA, which was characterised by a lowering of the glaciers’ calving flux in response to climate cooling. During Period 3 (1920–2014 CE), both glaciers retreated substantially to their present-day extent. The bottom water temperature started to decrease just before Period 2 and remained relatively low until just before the end of Period 3. This is interpreted as a local response to increased glacial meltwater input. Our study was compared with a study in Disko Bay, nearby Jakobshavn Glacier and the result shows that both of these Greenlandic marine-terminating glaciers are responding to large-scale climate change. However, the specific imprint on the glaciers and the different fjord waters in front of them result in contrasting glacial responses and sediment archives in their respective fjords.

scholarly journals Relationships between bottom water carbonate saturation and element/Ca ratios in coretop samples of the benthic foraminifera <i>Oridorsalis umbonatus</i>

2012 ◽  
Vol 9 (2) ◽  
pp. 1483-1510 ◽  
Author(s):  
C. F. Dawber ◽  
A. Tripati
Keyword(s):  
Benthic Foraminifera ◽  
Partition Coefficients ◽  
Bottom Water ◽  
Energetic Cost ◽  
Individual Element ◽  
Fractionation Factor ◽  
Bottom Water Temperature ◽  
Rayleigh Fractionation ◽  
Wide Range ◽  
Water Carbonate

Abstract. Elemental ratios in benthic foraminifera have been used to reconstruct bottom water temperature and carbonate saturation (Δ[CO32−]). We present elemental data for the long-ranging benthic foraminifera Oridorsalis umbonatus from sediment core tops that span a narrow range of temperatures and a wide range of saturation states. B/Ca, Li/Ca, Sr/Ca and Mg/Ca ratios exhibit positive correlations with bottom water carbonate saturation. The sensitivity of individual element/calcium ratios to bottom water Δ [CO32−] varies considerably, with B/Ca being most sensitive and Sr/Ca the least sensitive. The empirically derived sensitivity of B/Ca, Li/Ca, Mg/Ca and Sr/Ca to bottom water Δ [CO32−] are 0.433 ± 0.053 and 0.0561 ± 0.0084 μmol mol−1 per μmol kg−1 and 0.0164 ± 0.0015 and 0.00241 ± 0.0004 μmol mol−1 per μmol kg−1, respectively. To assess the fidelity of these relationships and the possibility of applying these relationships to earlier periods of Earth history, we examine the mechanisms governing elemental incorporation into foraminiferal calcite. Empirical partition coefficients for Li and Sr are consistent with Rayleigh fractionation from an internal pool used for calcification. For O. umbonatus and other benthic species, we show that the fraction of Ca remaining in the pool is a function of bottom water Δ [CO32−], and can be explained by either a growth rate effect and/or the energetic cost of raising vesicle pH at the site of calcification. Empirical partition coefficients for Mg and B may also be controlled by Rayleigh fractionation, but require that either the fractionation factor from the internal pool is smaller than the inorganic partition coefficient and/or additional fractionation mechanisms. O. umbonatus element ratio data may also be consistent with fractionation according to the surface entrapment model and/or the presence of discrete high- and low-Mg calcite phases. However at present we are limited in our ability to assess these mechanisms. The new X/Ca data for O. umbonatus provide constraints to test the role of these mechanisms in the future.

scholarly journals Mg/Ca and Mn/Ca ratios in benthic foraminifera: the potential to reconstruct past variations in temperature and hypoxia in shelf regions

2013 ◽  
Vol 10 (7) ◽  
pp. 5125-5138 ◽  
Author(s):  
J. Groeneveld ◽  
H. L. Filipsson
Keyword(s):  
Dissolved Oxygen ◽  
Trace Metal ◽  
Benthic Foraminifera ◽  
Bottom Water ◽  
Oxygen Depletion ◽  
Open Ocean ◽  
Low Oxygen ◽  
Saturation State ◽  
Bottom Water Temperature ◽  
Fish And Shellfish

Abstract. Shelf and coastal regions are exceptionally important for many countries as they provide the main habitat for many economically important fish and shellfish species. With ongoing climate change and human-induced eutrophication the shelf regions are especially affected, resulting in increased temperatures and stratification as well as oxygen depletion of the bottom waters. In order to be able to predict the magnitude of these changes in the future, it is necessary to study how they varied in the past. Commonly used foraminiferal climate and environmental proxies, e.g., stable isotopes and trace metal/Ca ratios, that are applied in open-ocean settings are not necessarily applicable in shelf regions, either as faunas are significantly different or as conditions can change much faster compared to the open ocean. In this study we explore the use of Mg/Ca as paleothermometer and Mn/Ca as a potential proxy for changing dissolved oxygen conditions in bottom water on the benthic foraminifera Bulimina marginata and Globobulimina turgida. Living specimens were collected from the Skagerrak and the Gullmar Fjord (SW Sweden); the latter is hypoxic for several months a year. As the specimens were alive when collected, we assume it unlikely that any diagenetic coatings have already significantly affected the trace metal/Ca ratios. The Mg/Ca ratios are similar to previously published values but display much larger variation than would be expected from the annual temperature change of less than 2 °C. An additional impact of the difference in the calcite saturation state between the Skagerrak and the Gullmar Fjord could explain the results. Mn/Ca ratios from G. turgida can potentially be related to variations in dissolved oxygen of the habitat where the foraminifera calcify. Samples from the Skagerrak display increased Mn/Ca in specimens that lived deeper in the sediment than those that lived near the surface. G. turgida samples from the low-oxygen Gullmar Fjord showed significantly increased Mn/Ca, being highest when bottom water dissolved oxygen was at a minimum. Our study suggests that trace metal/Ca ratios in benthic foraminifera from shelf regions have the potential to record past variations in bottom water temperature and dissolved oxygen concentrations, but an additional impact of the inorganic carbonate chemistry cannot be excluded.

scholarly journals Exploring the controls on element ratios in middle Eocene samples of the benthic foraminifera <i>Oridorsalis umbonatus</i>

2012 ◽  
Vol 8 (6) ◽  
pp. 1957-1971 ◽  
Author(s):  
C. F. Dawber ◽  
A. K. Tripati
Keyword(s):  
Benthic Foraminifera ◽  
Bottom Water ◽  
Middle Eocene ◽  
Environmental Parameters ◽  
Intermediate Water ◽  
Saturation State ◽  
Bottom Water Temperature ◽  
Elemental Ratios ◽  
Elemental Ratio ◽  
Element Ratios

Abstract. Culturing studies and empirically based core top calibrations have been used to infer that elemental ratios in benthic foraminifera can be used as proxies to reconstruct past variations in bottom water temperature and saturation state (Δ [CO32−]). However the mechanisms linking elemental ratios to these parameters are poorly constrained. Here, we explore the environmental parameters influencing the incorporation of B, Li, Sr and Mg in Oridorsalis umbonatus in early Cenozoic sediments from Ocean Drilling Program Site 1209. We investigate the influence of middle Eocene variations in intermediate water Δ [CO32−] using relationships developed from core top samples. The fidelity of bottom water Δ[CO32−] reconstructions based on single element ratios is assessed by comparing the X/Ca-based reconstructions to each other and to carbon cycle proxy records (benthic foraminifera δ13C, organic carbon content, foraminifera dissolution indices), and a seawater δ18O reconstruction for Site 1209. Discrepancies in the reconstructed Δ[CO32−] values based on these different metal ratios suggest that there are still gaps in our understanding of the parameters influencing X/Ca and demonstrate that caution is required when interpreting palaeo-reconstructions that are derived from a single elemental ratio. The downcore record of O. umbonatus Mg/Ca does not exhibit any similarities with the Li/Ca, B/Ca and Sr/Ca records, suggesting that the environmental parameters influencing Mg/Ca may be different for this species, consistent with temperature as the strongest control on this elemental ratio. This hypothesis is supported by the coefficients of multiple linear regression models on published Mg/Ca data. An incomplete understanding of the controls on elemental incorporation into benthic foraminifera hinders our ability to confidently quantify changes in saturation state using single X/Ca reconstructions over a range of timescales.

Surface- and deep-water response to the Early Aptian OAE 1a in the western Tethys

2021 ◽  
Author(s):  
Cinzia Bottini ◽  
Victor M. Giraldo-Gómez ◽  
Maria Rose Petrizzo ◽  
Elisabetta Erba
Keyword(s):  
Deep Water ◽  
Surface Waters ◽  
Benthic Foraminifera ◽  
Bottom Water ◽  
Black Shales ◽  
Ontong Java Plateau ◽  
Western Tethys ◽  
Organic Carbon Flux ◽  
Water Response ◽  
Matter Flux

&lt;p&gt;The Cretaceous was punctuated by interludes of widespread deposition of organic-rich sediments (black shales) in the oceans and epicontinental seas, named Oceanic Anoxic Events (OAE)s, representing major alterations in the global carbon budget. The early Aptian OAE 1a (ca. 120 Ma) coincided with a global paleoclimatic and paleoenvironmental perturbation which lasted for ca. 1.1 Myrs probably triggered by volcanogenic CO&lt;sub&gt;2&amp;#160;&lt;/sub&gt;emissions associated with the emplacement of the Ontong Java Plateau. To date, there is a comprehensive characterization of OAE 1a paleoceanographic conditions and paleoecology of surface-waters while less information is available for bottom-water evolution. In this regard, benthic foraminifera are ideal to characterize deep-water oxygen levels and the organic carbon flux. We present a high-resolution study of benthic foraminiferal assemblages across OAE 1a in the Cismon Core (western Tethys, Lombardy Basin, Northern Italy). Contrarily to many sites, the Cismon Core yields benthic foraminifera also in the Selli Level thus providing information about deep-water conditions during OAE 1a. Our data are indicative of fluctuations in bottom-water oxygenation and organic-matter flux to the sea-floor prior to, during and after OAE 1a. The integration of the new benthic foraminiferal data with calcareous nannofossil and planktonic foraminiferal datasets is here used to produce a model of surface- to bottom-water paleowater evolution through the latest Barremian-early late Aptian. In particular, the new data show coeval changes in bottom- and surface-waters conditions prior to and at the onset of OAE 1a. Anoxia was reached during the core of the negative carbon isotope anomaly, under maximum warming and higher surface-water fertility. Conversely, the repopulation of benthic foraminifera postponed the plankton recovery. Benthic foraminifera data at Cismon show, for the first time, evidence of a repopulation event during the OAE 1a suggestive for a slight increase in the supply of oxygen to the seafloor during the Selli Level deposition.&lt;/p&gt;

scholarly journals Pliocene three-dimensional global ocean temperature reconstruction

2009 ◽  
Vol 5 (4) ◽  
pp. 769-783 ◽  
Author(s):  
H. J. Dowsett ◽  
M. M. Robinson ◽  
K. M. Foley
Keyword(s):  
Water Temperature ◽  
Deep Water ◽  
Bottom Water ◽  
Thermal Structure ◽  
Three Dimensional ◽  
The Arctic ◽  
Global Ocean ◽  
Validation Data ◽  
Data Set ◽  
Bottom Water Temperature

Abstract. The thermal structure of the mid-Piacenzian ocean is obtained by combining the Pliocene Research, Interpretation and Synoptic Mapping Project (PRISM3) multiproxy sea-surface temperature (SST) reconstruction with bottom water temperature estimates from 27 locations produced using Mg/Ca paleothermometry based upon the ostracod genus Krithe. Deep water temperature estimates are skewed toward the Atlantic Basin (63% of the locations) and represent depths from 1000 m to 4500 m. This reconstruction, meant to serve as a validation data set as well as an initialization for coupled numerical climate models, assumes a Pliocene water mass framework similar to that which exists today, with several important modifications. The area of formation of present day North Atlantic Deep Water (NADW) was expanded and extended further north toward the Arctic Ocean during the mid-Piacenzian relative to today. This, combined with a deeper Greenland-Scotland Ridge, allowed a greater volume of warmer NADW to enter the Atlantic Ocean. In the Southern Ocean, the Polar Front Zone was expanded relative to present day, but shifted closer to the Antarctic continent. This, combined with at least seasonal reduction in sea ice extent, resulted in decreased Antarctic Bottom Water (AABW) production (relative to present day) as well as possible changes in the depth of intermediate waters. The reconstructed mid-Piacenzian three-dimensional ocean was warmer overall than today, and the hypothesized aerial extent of water masses appears to fit the limited stable isotopic data available for this time period.

scholarly journals Relationships between bottom water carbonate saturation and element/Ca ratios in coretop samples of the benthic foraminifera <i>Oridorsalis umbonatus</i>

2012 ◽  
Vol 9 (8) ◽  
pp. 3029-3045 ◽  
Author(s):  
C. F. Dawber ◽  
A. Tripati
Keyword(s):  
Benthic Foraminifera ◽  
Partition Coefficients ◽  
Bottom Water ◽  
Energetic Cost ◽  
Individual Element ◽  
Fractionation Factor ◽  
Bottom Water Temperature ◽  
Rayleigh Fractionation ◽  
Wide Range ◽  
Water Carbonate

Abstract. Elemental ratios in benthic foraminifera have been used to reconstruct bottom water temperature and carbonate saturation (Δ[CO32−]). We present elemental data for the long-ranging benthic foraminifera Oridorsalis umbonatus from sediment core tops that span a narrow range of temperatures and a wide range of saturation states. B/Ca, Li/Ca, Sr/Ca and Mg/Ca ratios exhibit positive correlations with bottom water carbonate saturation. The sensitivity of individual element/calcium ratios to bottom water Δ[CO32−] varies considerably, with B/Ca being most sensitive and Sr/Ca the least sensitive. The empirically derived sensitivity of B/Ca, Li/Ca, Mg/Ca and Sr/Ca to bottom water Δ[CO32−] are 0.433 ± 0.053 and 0.0561 ± 0.0084 μmol mol−1 μmol kg−1 and 0.0164 ± 0.0015 and 0.00241 ± 0.0004 mmol mol−1μmol kg−1, respectively. To assess the fidelity of these relationships and the possibility of applying these relationships to earlier periods of Earth history, we examine the mechanisms governing elemental incorporation into foraminiferal calcite. Empirical partition coefficients for Li and Sr are consistent with Rayleigh fractionation from an internal pool used for calcification. For O. umbonatus and other benthic species, we show that the fraction of Ca remaining in the pool is a function of bottom water Δ[CO32−], and can be explained by either a growth rate effect and/or the energetic cost of raising vesicle pH at the site of calcification. Empirical partition coefficients for Mg and B may also be controlled by Rayleigh fractionation, but require that either the fractionation factor from the internal pool is smaller than the inorganic partition coefficient and/or additional fractionation mechanisms. O. umbonatus element ratio data may also be consistent with fractionation according to the surface entrapment model and/or the presence of discrete high- and low-Mg calcite phases. However, at present we are limited in our ability to assess these mechanisms. The new X/Ca data for O. umbonatus provide constraints to test the role of these mechanisms in the future.

scholarly journals Element/Calcium ratios in middle Eocene samples of <i>Oridorsalis umbonatus</i> from Ocean Drilling Program Site 1209

2011 ◽  
Vol 7 (6) ◽  
pp. 3795-3821 ◽  
Author(s):  
C. F. Dawber ◽  
A. K. Tripati
Keyword(s):  
Benthic Foraminifera ◽  
Bottom Water ◽  
Middle Eocene ◽  
Single Element ◽  
Intermediate Water ◽  
Ocean Drilling Program ◽  
Saturation State ◽  
Bottom Water Temperature ◽  
Elemental Ratios ◽  
Ocean Drilling

Abstract. Culturing studies and empirical-based calibrations suggest that elemental ratios in benthic foraminifera can be used as proxies to reconstruct past variations in bottom water temperature and saturation state (Δ[CO32−]). However the mechanism(s) linking elemental ratios to Δ[CO32−] are poorly constrained. We present middle Eocene records of Oridorsalis umbonatus Li/Ca, B/Ca, Mg/Ca and Sr/Ca from Ocean Drilling Program Site 1209. We apply calibrations developed from core top samples to estimate middle Eocene variations in intermediate water Δ[CO32−]. The fidelity of bottom water Δ[CO32−] reconstructions based on single element ratios are assessed by comparing the X/Ca-based reconstructions to each other and to carbon cycle proxy records (benthic foraminifera δ13C, organic carbon content, foraminifera dissolution indices), and a seawater δ18O reconstruction for Site 1209. Discrepancies in the reconstructed Δ[CO32−] values for the middle Eocene based on these different metal ratios suggests that there are still gaps in our understanding of the parameters influencing X/Ca. The downcore record of O. umbonatus Mg/Ca does not exhibit any similarities with the Li/Ca, B/Ca and Sr/Ca records, suggesting that bottom water Δ[CO32−] is not the dominant influence on Mg/Ca ratios for this species. This hypothesis is supported by the coefficients of multiple linear regression models on new and published Mg/Ca data.

Major Change in Atlantic Deep and Bottom Waters 700,000 yr Ago: Benthonic Foraminiferal Evidence from the South Atlantic

1982 ◽  
Vol 17 (1) ◽  
pp. 26-38 ◽  
Author(s):  
L. C. Peterson ◽  
G. P. Lohmann
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
Bottom Water ◽  
Sediment Cores ◽  
North Atlantic Deep Water ◽  
South Atlantic ◽  
Antarctic Bottom Water ◽  
The South ◽  
Circumpolar Deep Water ◽  
Bottom Waters

AbstractIn the modern South Atlantic the transition between deep water and bottom water is marked by a clear change in the associated benthonic foraminiferal fauna. Uvigerina and Globocassidulina characterize oxygen-poor Circumpolar Deep Water which has long been isolated from the surface. Planulina and miliolids are found associated with the more newly formed, oxygen-rich North Atlantic Deep Water. Antarctic Bottom Water is characterized by “Epistominella” umbonifera. Analysis of the benthonic foraminiferal faunas in two sediment cores recovered from the Vema and Hunter Channels in the western South Atlantic shows that the level of the transition between deep and bottom waters shallowed sharply about 700,000 yr ago. This rise indicates a sharp, sustained increase in the volume of bottom water flowing through the South Atlantic after this time. Prior to about 700,000 yr ago, the amount of Antarctic Bottom Water entering the western South Atlantic was greatly reduced and Circumpolar Deep Water apparently accounted for the bulk of northward flow. Production of southward-flowing North Atlantic Deep Water seems not to have been affected. The timing of this change in circulation regime suggests a possible causal link to similar changes in records of terrestrial and sea-surface climate.

Benthic foraminiferal zonation in deep-water carbonate platform margin environments, northern Little Bahama Bank

1988 ◽  
Vol 62 (01) ◽  
pp. 1-8 ◽  
Author(s):  
Ronald E. Martin
Keyword(s):  
Deep Water ◽  
Benthic Foraminifera ◽  
Carbonate Platform ◽  
Sedimentary Facies ◽  
Depositional Environments ◽  
Near Surface ◽  
Sediment Gravity Flows ◽  
Gravity Flows ◽  
Platform Margin ◽  
Water Carbonate

The utility of benthic foraminifera in bathymetric interpretation of clastic depositional environments is well established. In contrast, bathymetric distribution of benthic foraminifera in deep-water carbonate environments has been largely neglected. Approximately 260 species and morphotypes of benthic foraminifera were identified from 12 piston core tops and grab samples collected along two traverses 25 km apart across the northern windward margin of Little Bahama Bank at depths of 275-1,135 m. Certain species and operational taxonomic groups of benthic foraminifera correspond to major near-surface sedimentary facies of the windward margin of Little Bahama Bank and serve as reliable depth indicators. Globocassidulina subglobosa, Cibicides rugosus, and Cibicides wuellerstorfi are all reliable depth indicators, being most abundant at depths &gt;1,000 m, and are found in lower slope periplatform aprons, which are primarily comprised of sediment gravity flows. Reef-dwelling peneroplids and soritids (suborder Miliolina) and rotaliines (suborder Rotaliina) are most abundant at depths &lt;300 m, reflecting downslope bottom transport in proximity to bank-margin reefs. Small miliolines, rosalinids, and discorbids are abundant in periplatform ooze at depths &lt;300 m and are winnowed from the carbonate platform. Increased variation in assemblage diversity below 900 m reflects mixing of shallow- and deep-water species by sediment gravity flows.

Sign in / Sign up

Export Citation Format

Share Document