Publication Date:
2022-05-25
Description:
Author Posting. © American Geophysical Union, 2005. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 20 (2005): PA1016, doi:10.1029/2004PA001103.
Description:
Radiocarbon age relationships between co-occurring planktic foraminifera, alkenones and
total organic carbon in sediments from the continental margins of Southern Chile, Northwest
Africa and the South China Sea were compared with published results from the Namibian
margin. Age relationships between the sediment components are site-specific and relatively
constant over time. Similar to the Namibian slope, where alkenones have been reported to be
1000 to 4500 years older than co-occurring foraminifera, alkenones were significantly (~1000
yrs) older than co-occurring foraminifera in the Chilean margin sediments. In contrast,
alkenones and foraminifera were of similar age (within 2σ error or better) in the NW African
and South China Sea sediments. Total-organic-matter and alkenone ages were similar off
Namibia (age difference TOC-alkenones: 200-700 years), Chile (100-450 years), and NW
Africa (360-770 years), suggesting minor contributions of pre-aged terrigenous material. In
the South China Sea total organic carbon is significantly (2000-3000 yrs) older due to greater
inputs of pre-aged terrigenous material.
Age offsets between alkenones and planktic foraminifera are attributed to lateral advection
of organic matter. Physical characteristics of the depositional setting, such as sea-floor
morphology, shelf width, and sediment composition, may control the age of co-occurring
2
sediment components. In particular, offsets between alkenones and foraminifera appear to be
greatest in deposition centers in morphologic depressions. Aging of organic matter is
promoted by transport. Age offsets are correlated with organic richness, suggesting that
formation of organic aggregate is a key process.
Description:
GM and MK acknowledge financial support from the WHOI postdoctoral scholarship program. This work was funded by NSF grant OCE-0327405.
Keywords:
Compound-specific radiocarbon dating
;
Alkenones
;
High accumulation rate sediments
Repository Name:
Woods Hole Open Access Server
Type:
Article
Format:
application/pdf
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