Rapid lateral particle transport in the Argentine Basin : molecular C-14 and Th-230(xs) evidence
McManus, Jerry F.
Muller, Peter J.
Eglinton, Timothy I.
MetadataShow full item record
KeywordSediment transport; Radiocarbon dating; Sea-surface temperatures; Core-top sediments; South Atlantic Ocean; Argentine and Brazil Basins; Brazil-Malvinas Confluence
Recent studies have revealed that lateral transport and focusing of particles strongly influences the depositional patterns of organic matter in marine sediments. Transport can occur in the water column prior to initial deposition or following sediment re-suspension. In both cases, fine-grained particles and organic-rich aggregates are more susceptible to lateral transport than coarse-grained particles (e.g. foraminiferal tests) because of the slower sinking velocities of the former. This may lead to spatial and, in the case of redistribution of resuspended sediments, temporal decoupling of organic matter from coarser sediment constituents. Prior studies from the Argentine Basin have yielded evidence that suspended particles are displaced significant distances (100 - 1000 km) northward and downslope by strong surface and/or bottom currents. These transport processes result in anomalously cold alkenone-derived sea surface temperature (SST) estimates (up to 6°C colder than measured SST) and in the presence of frustules of Antarctic diatom species in surface sediments fromthis area. Here we examine advective transport processes through combined measurements of compound-specific radiocarbon ages of marine phytoplankton derived biomarkers (alkenones) from core-tops and excess 230Th (230Thxs)-derived focusing factors for late Holocene sediments from the Argentine Basin. On the continental slope, we observe 230Thxs-based focusing factors of 1.4 to 3.2 at sites where alkenone-based SST estimates were 4–6°C colder than measured values. In contrast, alkenone radiocarbon data suggest coeval deposition of marine biomarkers and planktic foraminifera, as alkenones in core-tops were younger than, or similar in age to, foraminifera. We therefore infer that the transport processes leading to the lateral displacement of these sediment components are rapid, and hence probably occur in the upper water column (<1500 m).
Author Posting. © Elsevier B.V., 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 53 (2006): 1224-1243, doi:10.1016/j.dsr.2006.05.005.
Showing items related by title, author, creator and subject.
Timescales of lateral sediment transport in the Panama Basin as revealed by radiocarbon ages of alkenones, total organic carbon and foraminifera Kusch, Stephanie; Eglinton, Timothy I.; Mix, Alan C.; Mollenhauer, Gesine (2009-12)Paired radiocarbon measurements on haptophyte biomarkers (alkenones) and on cooccurring tests of planktic foraminifera (Neogloboquadrina dutertrei and Globogerinoides sacculifer) from late glacial to Holocene sediments ...
A moored array along the southern boundary of the Brazil Basin for the Deep Basin Experiment : report on a joint experiment 1991-1992 Tarbell, Susan A.; Meyer, Ralf; Hogg, Nelson G.; Zenk, Walter (Woods Hole Oceanographic Institution, 1994-02)The Deep Basin Experiment (DBE) is an international effort and a part of the World Ocean Circulation Experiment with the principal objective of improving our knowledge of the subthermocline circulation. The DBE fieldwork ...
Kassis, Patricia (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2000-08)With Lagrangian and hydrographic data taken in the deep Brazil Basin, we identify several submesoscale coherent vortices (SCVs). These features contrast with SCV paradigms in that float data indicate approximately equal ...