Coccoliths and carbonate grain-size compositions in sediment samples from the Mid-Atlantic Ridge

DOI

This study presents a differentiated carbonate budget for marine surface sediments from the Mid-Atlantic Ridge of the South Atlantic, with results based on carbonate grain-size composition. Upon separation into sand, silt, and clay sub-fractions, the silt grain-size distribution was measured using a SediGraph 5100. We found regionally characteristic grain-size distributions with an overall minimum at 8 µm equivalent spherical diameter (ESD). SEM observations reveal that the coarse particles (>8 µm ESD) are attributed to planktic foraminifers and their fragments, and the fine particles (<8 µm ESD) to coccoliths. On the basis of this division, the regional variation of the contribution of foraminifers and coccoliths to the carbonate budget of the sediments are calculated. Foraminifer carbonate dominates the sediments in mesotropic regions whereas coccoliths contribute most carbonate in oligotrophic regions. The grain size of the coccolith share is constant over water depth, indicating a lower susceptibility for carbonate dissolution compared to foraminifers. Finally, the characteristic grain-size distribution in fine silt ( 4 µm). Smaller species (length < 4 µm) belong to the clay fraction (<2 µm ESD). The average length of most frequent coccolith species is connected to prominent peaks in grain-size distributions (ESD) with a shape factor. The area below Gaussian distributions fitted to these peaks is suggested as a way to quantitatively estimate the carbonate contribution of single coccolith species more precisely compared to conventional volume estimates.The quantitative division of carbonate into the fraction produced by coccoliths and that secreted by foraminifers enables a more precise estimate for source/sink relations of consumed and released CO2 in the carbon cycle. The allocation of coccolith length and grain size (ESD) suggests size windows for the separation or accumulation of distinct coccolith species in investigations that depend on non to slightly-mixed signals (e.g., isotopic studies).

Supplement to: Frenz, Michael; Baumann, Karl-Heinz; Boeckel, Babette; Höppner, René; Henrich, Rüdiger (2005): Quantification of foraminifer and coccolith carbonate in South Atlantic surface sediments by means of carbonate grain-size distributions. Journal of Sedimentary Research, 75(3), 446-475

Identifier
DOI https://doi.org/10.1594/PANGAEA.779778
Related Identifier IsSupplementTo https://doi.org/10.2110/jsr.2005.036
Related Identifier References https://nbn-resolving.org/urn:nbn:de:gbv:46-ep000103333
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.779778
Provenance
Creator Frenz, Michael; Baumann, Karl-Heinz; Boeckel, Babette; Höppner, René; Henrich, Rüdiger
Publisher PANGAEA
Publication Year 2005
Rights Creative Commons Attribution 3.0 Unported; https://creativecommons.org/licenses/by/3.0/
OpenAccess true
Representation
Resource Type Supplementary Publication Series of Datasets; Collection
Format application/zip
Size 7 datasets
Discipline Geosciences; Natural Sciences
Spatial Coverage (-24.248W, -44.517S, 0.875E, 1.790N); Walvis Ridge; Equatorial Atlantic; Guinea Basin; Northern Guinea Basin; West Angola Basin; Mid Atlantic Ridge; East Brazil Basin; Brazil Basin; Western Equatorial Atlantic; Ascencion Island; Mid-Atlantic Ridge; Angola Basin; Central South Atlantic
Temporal Coverage Begin 1988-03-10T00:00:00Z
Temporal Coverage End 2000-03-04T02:21:00Z