Publication Date:
2022-05-25
Description:
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.
Description:
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).
Description:
This work was funded by NSF grant #OCE-0327405 and a WHOI-NOSAMS postdoctoral scholarship to GM, and by support from NSF and the Gary Comer Science and Education Foundation to JFM.
Keywords:
Sediment transport
;
Radiocarbon dating
;
Sea-surface temperatures
;
Core-top sediments
;
South Atlantic Ocean
;
Argentine and Brazil Basins
;
Brazil-Malvinas Confluence
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
Format:
1583514 bytes
Format:
application/pdf
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