Planktic foraminifera of sediment core GeoB1710-3

• Main Authors: Volbers, Andrea N A, Henrich, Rüdiger
• Format: Dataset
• Language: English
• Published: PANGAEA 2002
• Subjects: Benthic foraminifera/planktic foraminifera index; Calculated; see reference(s); Counting >125 µm fraction; DEPTH; sediment/rock; Foraminifera; planktic; fragments; planktic indeterminata; Fragmentation index; planktic foraminifera; GeoB; GeoB1710-3; Geosciences; University of Bremen; Globigerina bulloides dissolution index (Volbers); Globorotalia inflata; Globorotalia minuta; Globorotalia truncatulinoides; Gravity corer (Kiel type); M20/2; Meteor (1986); Namibia continental slope; Neogloboquadrina pachyderma; Orbulina universa; Radiolaria/planktic foraminifera index; SFB261; SL; South Atlantic in Late Quaternary: Reconstruction of Budget and Currents
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.57026; https://doi.org/10.1594/PANGAEA.57026

In this study, we test various parameters in deep-sea sediments (bulk sediment parameters and changes in microfossil abundances and preservation character) which are generally accepted as indicators of calcium carbonate dissolution. We investigate sediment material from station GeoB 1710-3 in the northern Cape Basin (eastern South Atlantic), 280 km away from the Namibian coast, well outside today's coastal upwelling. As northern Benguela upwelling cells were displaced westward and periodically preceded the core location during the past 245 kyr (Volbers et al., submitted), GeoB 1710-3 sediments reflect these changes in upwelling productivity. Results of the most commonly used calcium carbonate dissolution proxies do not only monitor dissolution within these calcareous sediments but also reflect changes in upwelling intensity. Accordingly, these conventional proxy parameters misrepresent, to some extent, the extent of calcium carbonate dissolution. These results were verified by an independent dissolution proxy, the Globigerina bulloides dissolution index (BDX') (Volbers and Henrich, 2002, doi:10.1016/S0025-3227(02)00333-X). The BDX' is based on scanning electronic microscope ultrastructural investigation of planktonic foraminiferal tests and indicates persistent good carbonate preservation throughout the past 245 kyr, with the exception of one pronounced dissolution event at early oxygen isotopic stage (OIS) 6. The early OIS 6 is characterized by calcium carbonate contents, sand contents, and planktonic foraminiferal concentrations all at their lowest levels for the last 245 kyr. At the same time, the ratio of radiolarian to planktonic foraminiferal abundances and the ratio of benthic to planktonic foraminiferal tests are strongly increased, as are the rain ratio, the fragmentation index, and the BDX'. The sedimentary calcite lysocline rose above the core position and GeoB 1710-3 sediments were heavily altered, as attested to by the unusual accumulation of pellets, aggregates, sponge spicules, radiolaria, benthic ...