Benthic foraminifera and sediment grain size variability at intermediate water depths in the Northeast Atlantic during the late Pliocene–early Pleistocene

2000 ◽  
Vol 170 (3-4) ◽  
pp. 423-441 ◽  
Author(s):  
W.E.N Austin ◽  
J.R Evans
Keyword(s):  
Grain Size ◽  
Benthic Foraminifera ◽  
Early Pleistocene ◽  
Intermediate Water ◽  
Sediment Grain Size ◽  
Late Pliocene ◽  
Northeast Atlantic ◽  
Size Variability ◽  
Water Depths

Mineralogy of agglutinated benthic foraminifera; implications for paleo-environmental reconstructions

2008 ◽  
Vol 179 (6) ◽  
pp. 583-592 ◽  
Author(s):  
Eric Armynot du Chatelet ◽  
Philippe Recourt ◽  
Vincent Chopin
Keyword(s):  
Grain Size ◽  
Benthic Foraminifera ◽  
Tidal Marsh ◽  
Environmental Parameters ◽  
Mineralogical Composition ◽  
Test Construction ◽  
Taxonomic Composition ◽  
Tidal Elevation ◽  
Sediment Grain Size

Abstract Benthic foraminifera of recent salt marsh environments are often dominated by species with an agglutinated test. The grains used for test construction by these foraminifera are collected from their surrounding environment. In this study we investigate the role of sediment grain size and mineralogical composition for richness, population density and taxonomic composition of agglutinating foraminifera. Foraminifera from 15 stations of the tidal marsh of the Canche estuary (Pas-de-Calais, France) were studied. The species richness depends on the grain size of the sediment, whereas the density is not related to sediment grain size. The distribution of foraminifera species throughout the tidal marsh may depend on many environmental parameters such as OM as well as tidal elevation, already largely discussed in literature. The mineralogical composition of the agglutinated grains in Trochammina inflata and Arenoparrella mexicana is very different from that of sediment; the composition of Jadammina macrescens is generally different from that of the sediment with some exceptions, and in Miliammina fusca, Paratrochammina haynesi and Remaneica plicata the mineralogical compositions are similar to those of the sediment. The studied species may be able to select their preferred grains based upon composition even if a particular mineral is scarce in the sediment.

Sediment (grain size and clay mineralogy) and organic matter quality control on living benthic foraminifera

2009 ◽  
Vol 52 (1) ◽  
pp. 75-84 ◽  
Author(s):  
Éric Armynot du Châtelet ◽  
Viviane Bout-Roumazeilles ◽  
Armelle Riboulleau ◽  
Alain Trentesaux
Keyword(s):  
Grain Size ◽  
Quality Control ◽  
Organic Matter ◽  
Benthic Foraminifera ◽  
Clay Mineralogy ◽  
Sediment Grain Size ◽  
Organic Matter Quality

scholarly journals An assessment of the influence of orbital forcing on Late Pliocene global sea-level using a shallow-marine sedimentary record from the Wanganui Basin, New Zealand

2021 ◽  
Author(s):  
◽  
Juliet Perry Sefton
Keyword(s):  
New Zealand ◽  
Sea Level ◽  
Benthic Foraminifera ◽  
Volume Changes ◽  
Shallow Marine ◽  
Late Pliocene ◽  
Ice Volume ◽  
Global Ice Volume ◽  
Global Sea Level ◽  
Water Depths

<p>Classical Milankovitch Theory suggests variance in the orbital cycles of precession (21,000 year) modulated by eccentricity (~100,000 year) and obliquity (41,000 year) should have a profound influence on polar insolation and ice volume. However, the globally-integrated ice volume proxy record (benthic δ¹⁸O) during the Late Pliocene (3.0-2.6 Ma) is dominated by obliquity-paced cycles, and lacks a significant precession component. A number of conceptual hypotheses have been proposed to explain this “41,000 year problem”, but palaeoclimate records independent of the benthic δ¹⁸O record are required to test these hypotheses.  The Wanganui Basin, New Zealand, contains a well-dated, shallow-marine Neogene sedimentary succession that is widely recognised as an important site for examining sea-level/ice volume changes at orbital frequencies. In this study, the shallow-marine Late Pliocene Mangaweka Mudstone is examined at an orbital-scale resolution (~3-5 kyr sampling) along a continuous 672 metre thick (true thickness) outcropping road section on Watershed Road between the Rangitikei and Turakina River valleys.  Two modern analogue-calibrated water depth proxies were used to evaluate palaeobathymetric changes: (i) sediment texture and (ii) benthic foraminifera census data. An overall trend of shallowing to inner-shelf water depths occurs up-section, but is superimposed by higher frequency fluctuations. For the lowermost ~400 metres of the section, in situ benthic foraminifera assemblages indicate water depths >100 metres. As wave-induced sand transport does not occur on the modern Manawatu-Wanganui outer-shelf, and modern wave climates are assumed to be analogous to the Pliocene, it is concluded that the sediment grainsize approach is not an appropriate proxy for reconstruction water depth changes in the lower ~400 metres of section.  An integrated magneto-, bio- and tephrostratigraphy was developed that constrains the outcrop succession to between ~3.0 Ma and 2.58 Ma. Nine distinct cycles spanning ~400,000 years are identified in the grainsize and benthic foraminifera assemblages. Within the uncertainty of the age model, the Mangaweka Mudstone grainsize cycles can be matched one-for-one to the δ¹⁸O glacial-interglacial cycles, as they display a similar pattern in terms of frequency and amplitude. The frequency of the Mangaweka Mudstone cycles (and the corresponding interval in the benthic δ¹⁸O record) are dominated by the ~40,000 year obliquity cycle, but with a subordinate eccentricity component. Therefore, the fluctuations in the grainsize and benthic foraminifera proxies likely represent an indirect response to global sea-level fluctuations via their effect on continental shelf sediment transport mechanisms (non-wave) with the orbitally-paced transgression and regression of the shoreline on a restricted palaeo- continental shelf.  The implications for the orbital theory of the ice ages are that during the Late Pliocene, global ice volume changes responded primarily to obliquity, and the precession influences were either: (i) too low in amplitude to have influenced the grainsize and benthic foraminifera assemblages in the Mangaweka Mudstone depositional environment, or (ii) cancelled-out in global ice volume and sea-level changes because precession forcing is anti-phased between the hemispheres.</p>

scholarly journals A major change in North Atlantic deep water circulation during the Early Pleistocene transition 1.6 million years ago

2013 ◽  
Vol 9 (6) ◽  
pp. 6495-6513 ◽  
Author(s):  
N. Khélifi ◽  
M. Frank
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
Late Quaternary ◽  
Major Change ◽  
Water Circulation ◽  
Water Masses ◽  
Early Pleistocene ◽  
Global Ocean ◽  
Northeast Atlantic ◽  
Water Depths

Abstract. The global ocean-climate system has been highly sensitive to the formation and advection of deep water in the North Atlantic but its evolution over the Pliocene–Pleistocene global cooling is not fully understood. In particular, changes in the sources and mixing of prevailing deep waters are not well constrained. Here we present new records of the bottom-water radiogenic neodymium isotope (&amp;varepsilon;Nd) variability obtained from three DSDP/ODP sites at water depths between 2100 and 5000 m in the Northeast Atlantic to reconstruct changes in deep water circulation over the past 4 million years. Prior to 1.6 million years ago (Ma), we find &amp;varepsilon;Nd values primarily oscillating between −9 and −11 at all sites, consistent with enhanced vertical mixing of water masses. At 1.6 Ma, the &amp;varepsilon;Nd signatures synchronously shifted to less radiogenic values around −12 at different water depths and water mass signatures gradually became more distinct. Since then values and amplitudes of "glacial/interglacial" &amp;varepsilon;Nd oscillations have been similar to the Late Quaternary at each site. This change 1.6 Ma reflects a major reorganization of deep water circulation in the Northeast Atlantic towards a more stratified water column with distinct water masses accompanying the enhanced response of climate to the Earth's obliquity forcing during the Early Pleistocene transition.

Distribution of living benthic foraminifera in relation with environmental variables within the Aiguillon cove (Atlantic coast, France): improving knowledge for paleoecological interpretation

2009 ◽  
Vol 180 (2) ◽  
pp. 131-144 ◽  
Author(s):  
Eric Armynot du Chatelet ◽  
Delphine Degre ◽  
Pierre-Guy Sauriau ◽  
Jean-Pierre Debenay
Keyword(s):  
Grain Size ◽  
Organic Matter ◽  
Chlorophyll A ◽  
Benthic Foraminifera ◽  
Environmental Variables ◽  
Organic Matter Content ◽  
Distribution Patterns ◽  
Tidal Elevation ◽  
Sediment Grain Size ◽  
Organic Matter Quality

Abstract Search for bioindicators in marine environments has provided new tools for monitoring global and local natural changes. Among these tools, benthic foraminifera play a central role. More accurate paleogeographical and paleoecological reconstructions become possible on the basis of the ecology of recent foraminifera. Nevertheless, factors acting on foraminiferal assemblages are still partially understood. The aim of this study is to correlate the distribution patterns of living (stained) benthic foraminifera with environmental variables such as tidal elevation, interstitial pore water salinity, organic matter content of the sediment, pheopigments, chlorophyll a, carbonate contents and grain size distribution of the sediment from 86 samples collected in the Aiguillon cove (France). In this paralic environment, sediment grain size, salinity and tidal elevation are fundamental factors that drive the distribution of the most abundant species i.e. Brizalina variabilis, Cribroelphidium excavatum and Haynesina germanica. Organic matter also influences the distribution patterns of benthic foraminifera: the relative abundance of Ammonia tepida is typically favored by an increase of total organic matter food resources. Chlorophyll a and pheopigments, as indicators of organic matter quality however may not be limiting in the proportion present in the Aiguillon cove. Carbonate proportions do not limit benthic foraminifera of the Aiguillon cove essentially with carbonaceous shells.

scholarly journals An assessment of the influence of orbital forcing on Late Pliocene global sea-level using a shallow-marine sedimentary record from the Wanganui Basin, New Zealand

2021 ◽  
Author(s):  
◽  
Juliet Perry Sefton
Keyword(s):  
New Zealand ◽  
Sea Level ◽  
Benthic Foraminifera ◽  
Volume Changes ◽  
Shallow Marine ◽  
Late Pliocene ◽  
Ice Volume ◽  
Global Ice Volume ◽  
Global Sea Level ◽  
Water Depths

<p>Classical Milankovitch Theory suggests variance in the orbital cycles of precession (21,000 year) modulated by eccentricity (~100,000 year) and obliquity (41,000 year) should have a profound influence on polar insolation and ice volume. However, the globally-integrated ice volume proxy record (benthic δ¹⁸O) during the Late Pliocene (3.0-2.6 Ma) is dominated by obliquity-paced cycles, and lacks a significant precession component. A number of conceptual hypotheses have been proposed to explain this “41,000 year problem”, but palaeoclimate records independent of the benthic δ¹⁸O record are required to test these hypotheses.  The Wanganui Basin, New Zealand, contains a well-dated, shallow-marine Neogene sedimentary succession that is widely recognised as an important site for examining sea-level/ice volume changes at orbital frequencies. In this study, the shallow-marine Late Pliocene Mangaweka Mudstone is examined at an orbital-scale resolution (~3-5 kyr sampling) along a continuous 672 metre thick (true thickness) outcropping road section on Watershed Road between the Rangitikei and Turakina River valleys.  Two modern analogue-calibrated water depth proxies were used to evaluate palaeobathymetric changes: (i) sediment texture and (ii) benthic foraminifera census data. An overall trend of shallowing to inner-shelf water depths occurs up-section, but is superimposed by higher frequency fluctuations. For the lowermost ~400 metres of the section, in situ benthic foraminifera assemblages indicate water depths >100 metres. As wave-induced sand transport does not occur on the modern Manawatu-Wanganui outer-shelf, and modern wave climates are assumed to be analogous to the Pliocene, it is concluded that the sediment grainsize approach is not an appropriate proxy for reconstruction water depth changes in the lower ~400 metres of section.  An integrated magneto-, bio- and tephrostratigraphy was developed that constrains the outcrop succession to between ~3.0 Ma and 2.58 Ma. Nine distinct cycles spanning ~400,000 years are identified in the grainsize and benthic foraminifera assemblages. Within the uncertainty of the age model, the Mangaweka Mudstone grainsize cycles can be matched one-for-one to the δ¹⁸O glacial-interglacial cycles, as they display a similar pattern in terms of frequency and amplitude. The frequency of the Mangaweka Mudstone cycles (and the corresponding interval in the benthic δ¹⁸O record) are dominated by the ~40,000 year obliquity cycle, but with a subordinate eccentricity component. Therefore, the fluctuations in the grainsize and benthic foraminifera proxies likely represent an indirect response to global sea-level fluctuations via their effect on continental shelf sediment transport mechanisms (non-wave) with the orbitally-paced transgression and regression of the shoreline on a restricted palaeo- continental shelf.  The implications for the orbital theory of the ice ages are that during the Late Pliocene, global ice volume changes responded primarily to obliquity, and the precession influences were either: (i) too low in amplitude to have influenced the grainsize and benthic foraminifera assemblages in the Mangaweka Mudstone depositional environment, or (ii) cancelled-out in global ice volume and sea-level changes because precession forcing is anti-phased between the hemispheres.</p>

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