@article { ISI:000286640400038,
	title = {Radiocarbon and Th-230 data reveal rapid redistribution and temporal changes in sediment focussing at a North Atlantic drift},
	journal = {EARTH AND PLANETARY SCIENCE LETTERS},
	volume = {301},
	number = {{1-2}},
	year = {2011},
	month = {JAN 3},
	pages = {373-381},
	type = {Article},
	abstract = {In locations of rapid sediment accumulation receiving substantial amounts of laterally transported material the timescales of transport and accurate quantification of the transported material are at the focus of intense research. Here we present radiocarbon data obtained on co-occurring planktic foraminifera, marine haptophyte biomarkers (alkenones) and total organic carbon (TOC) coupled with excess Thorium-230 (Th-230(xs)) measurements on four sediment cores retrieved in 1649-2879 m water depth from two such high accumulation drift deposits in the Northeast Atlantic, Bjorn and Gardar Drifts. While Th-230(xs), inventories imply strong sediment focussing, no age offsets are observed between planktic foraminifera and alkenones, suggesting that redistribution of sediments is rapid and occurs soon after formation of marine organic matter, or that transported material contains negligible amounts of alkenones. An isotopic mass balance calculation based on radiocarbon concentrations of co-occurring sediment components leads us to estimate that transported sediment components contain up to 12\% of fossil organic matter that is free of or very poor in alkenones, but nevertheless appears to consist of a mixture of fresh and eroded fossil material. Considering all available constraints to characterize transported material, our results show that although focussing factors calculated from bulk sediment Th-230(xs) inventories may allow useful approximations of bulk redeposition, they do not provide a unique estimate of the amount of each laterally transported sediment component. Furthermore, our findings provide evidence that the occurrence of lateral sediment redistribution alone does not always hinder the use of multiple proxies but that individual sediment fractions are affected to variable extents by sediment focussing. (C) 2010 Elsevier B.V. All rights reserved.},
	keywords = {alkenones, compound-specific radiocarbon dating, drift sediments, focussing factors, Th-230(xs)},
	issn = {0012-821X},
	doi = {10.1016/j.epsl.2010.11.022},
	author = {Mollenhauer, Gesine and McManus, Jerry F. and Wagner, Thomas and McCave, I. Nick and Eglinton, Timothy I.}
}
@article {1897,
	title = {Aging of marine organic matter during cross-shelf lateral transport in the Benguela upwelling system revealed by compound-specific radiocarbon dating},
	journal = {Geochemistry Geophysics Geosystems},
	volume = {8},
	year = {2007},
	note = {213qvTimes Cited:3
Cited References Count:60
},
	month = {Sep 18},
	abstract = {Organic matter accumulation and burial on the Namibian shelf and upper slope are spatially heterogeneous and strongly controlled by lateral transport in subsurface nepheloid layers. Much of the material deposited in depo-centers on the slope ultimately derives from the shelf. Supply of organic matter from the shelf involves selective transport of organic matter. We studied these selective transport processes by analyzing the radiocarbon content of co-occurring sediment fractions. Here we present radiocarbon data for total organic carbon as well as three tracers of surface ocean productivity (phytoplankton-derived alkenones, membrane lipids of pelagic crenarchaeota (crenarchaeol), and calcareous microfossils of planktic foraminifera) in core-top and near-surface sediment samples. The samples were collected on the Namibian margin along a shelf-slope transect (85 to 1040 m) at 24 degrees S and from the upper slope depo-center at 25.5 degrees S. In core-top sediments, alkenone ages gradually increased from modern to 3490 radiocarbon years with distance from shore and with water depth. Crenarchaeol, while younger than alkenones, also increased in age with distance offshore. It was concluded that the observed ages were a consequence of cross-shelf transport and associated aging of organic matter. Radiocarbon ages of preserved lipid biomarkers in sediments thus at least partially depend on the relative amount of laterally supplied, pre-aged material present in a sample, highlighting the importance of nepheloid transport for the sedimentation of organic matter over the Namibian margin.},
	keywords = {alkenones, atlantic-ocean, burial, carbon accumulation, coastal, compound-specific radiocarbon dating, continental-margin, ionization mass-spectrometry, membrane-lipids, namibia, sea sediments, Sediment transport},
	isbn = {1525-2027},
	doi = {10.1029/2007GC001603},
	author = {Mollenhauer, G. and Inthorn, M. and Vogt, T. and Zabel, M. and Damste, J. S. S. and Eglinton, T. I.}
}
@article {2147,
	title = {Effects of biosynthesis and physiology on relative abundances and isotopic compositions of alkenones},
	journal = {Geochemistry Geophysics Geosystems},
	volume = {2},
	year = {2001},
	note = {458kdTimes Cited:6
Cited References Count:39
},
	month = {Jan 29},
	pages = {art. no.-2000GC000052},
	abstract = {The number of double bonds in long-chain, unsaturated ketones (alkenones) produced by some members of the Haptophyceae is correlated with the ambient temperature at the time of synthesis. For these same organisms the depletion of carbon-13 in biosynthetic products relative to dissolved inorganic carbon is related directly to the specific growth rate and inversely to the concentration of dissolved carbon dioxide. This report summarizes issues relating to the physiology, metabolism, and biochemistry of alkenone producers and how they affect the abundances and isotopic compositions of alkenones. These considerations show that an understanding of cellular responses to parameters governing uptake of inorganic carbon (C-i), isotopic fractionation, growth under diverse nutrient conditions, and genetic variability, both in the field and in culture, is necessary for developing a conceptual understanding of the biological significance of the epsilonp and U-37(K{\textquoteright}) indices. Emiliana huxleyi is the best known alkenone producer and can serve as a model organism for these studies. This report identifies knowledge gaps and appropriate objectives for both field- and laboratory-based research.},
	keywords = {algae, alkenones, anhydrase, biogeochemical processes, biosynthesis, calcification, carbon-13, emiliania-huxleyi prymnesiophyceae, fractionation, Haptophytes, inorganic carbon utilization, instruments and techniques, isoprenoid biosynthesis, marine diatom, paleoceanography, photosynthesis, physiology, phytoplankton, sea surface temperature},
	isbn = {1525-2027},
	doi = {10.1029/2000GC000052},
	author = {Gonzalez, E. L. and Riebesell, U. and Hayes, J. M. and Laws, E. A.}
}
