@article {2567,
	title = {Implications for chloro- and pheopigment synthesis and preservation from combined compound-specific δ13C, δ15N, and Δ14C analysis},
	journal = {Biogeosciences},
	volume = {7},
	year = {2010},
	month = {Jan-01-2010},
	pages = {4105 - 4118},
	abstract = {Chloropigments and their derivative pheopigments preserved in sediments can directly be linked to photosynthesis. Their carbon and nitrogen stable isotopic compositions have been shown to be a good recorder of recent and past surface ocean environmental conditions tracing the carbon and nitrogen sources and dominant assimilation processes of the phytoplanktonic community. In this study we report results from combined compound-specific radiocarbon and stable carbon and nitrogen isotope analysis to examine the time-scales of synthesis and fate of chlorophyll-a and its degradation products pheophytin-a, pyropheophytin-a, and 132,173-cyclopheophorbide-a-enol until burial in Black Sea core-top sediments. The pigments are mainly of marine phytoplanktonic origin as implied by their stable isotopic compositions. Pigment delta15N values indicate nitrate as the major uptake substrate but 15N-depletion towards the open marine setting indicates either contribution from N2-fixation or direct uptake of ammonium from deeper waters. Radiocarbon concentrations translate into minimum and maximum pigment ages of approximately 40 to 1200 years. This implies that protective mechanisms against decomposition such as association with minerals, storage in deltaic anoxic environments, or eutrophication-induced hypoxia and light limitation are much more efficient than previously thought. Moreover, seasonal variations of nutrient source, growth period, and habitat and their associated isotopic variability are likely at least as strong as long-term trends. Combined triple isotope analysis of sedimentary chlorophyll and its primary derivatives is a powerful tool to delineate biogeochemical and diagenetic processes in the surface water and sediments, and to assess their precise time-scales. 

},
	doi = {10.5194/bg-7-4105-201010.5194/bg-7-4105-2010-supplement},
	url = {http://www.biogeosciences.net/7/4105/2010},
	author = {Kusch, S. and Kashiyama, Y. and Ogawa, N. O. and Altabet, M. and Butzin, M. and Friedrich, J. and Ohkouchi, N. and Mollenhauer, G.}
}
@article {352,
	title = {Compound-specific radiocarbon analysis {\textendash} analytical challenges and applications},
	journal = {IOP conference proceedings: Earth and Environmental Sciences},
	volume = {5},
	year = {2009},
	note = {id: 884Y},
	doi = {10.1088/1755-1707/1/012006},
	author = {Mollenhauer, G. and Rethemeyer, Janet}
}
@article {457,
	title = {A radiocarbon-based assessment of the preservation characteristics of crenarchaeol and alkenones from continental margin sediments},
	journal = {Organic Geochemistry},
	volume = {39},
	year = {2008},
	note = {id: 883; 344AQ Times Cited:11 Cited References Count:33Y},
	pages = {1039-1045},
	abstract = {Crenarchaeotal glycerol dibiphytanyl glycerol tetraether (GDGT) lipids and alkenones are two types of biomarkers, derived from planktonic marine microorganisms, which are used for reconstruction of sea surface temperature. We determined the radiocarbon contents of the archaeal GDGT crenarchaeol and of alkenones isolated from continental margin sediments. Systematic differences were found between the two biomarkers, with higher radiocarbon content in crenarchaeol than in the phytoplankton-derived alkenones. These differences can be explained by variable contributions of pre-aged, laterally-advected material to the core sites. Crenarchaeol appears to be more efficiently degraded during transport in oxygen-replete environments than alkenones. Whether this reflects the influence of chemical structure or mode of protection (e.g., particle association) is not known. (C) 2008 Elsevier Ltd. All rights reserved.},
	issn = {0146-6380},
	doi = {10.1016/J.Orggeochem.2008.02.006},
	author = {Mollenhauer, G. and Eglinton, T. I. and HopmanSd, E. C. and Damste, J. S. S.}
}
@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 {1899,
	title = {Diagenetic and sedimentological controls on the composition of organic matter preserved in California Borderland Basin sediments},
	journal = {Limnology and Oceanography},
	volume = {52},
	year = {2007},
	note = {149kgTimes Cited:43
Cited References Count:67
},
	month = {Mar},
	pages = {558-576},
	abstract = {Compound-specific radiocarbon (C-14) contents, stable carbon isotopes, and abundances of phytoplankton and vascular plant derived lipid biomarkers (alkenones and fatty acids) were obtained from Santa Barbara Basin and Santa Monica Basin sediments, along with radiocarbon contents of planktic foraminifera and total organic carbon. We investigated core-top and prebomb sediment intervals at sites from the flanks and depocenters of the basins deposited under contrasting bottom water oxygen concentrations. Bulk organic matter generally has the lowest radiocarbon levels of all sediment constituents measured, whereas planktic foraminifera tend to be the most radiocarbon enriched. Alkenones are systematically depleted in radiocarbon with respect to foraminifera. Short-chain (C-14, C-16, C-18) fatty acids decrease rapidly in absolute abundance and relative to longer-chain (> C-24) homologues from core-top to prebomb samples. The loss of short-chain fatty acids with depth is associated with C-13 depletion of short-chain fatty acids, indicating preferential preservation of terrestrially derived fatty acids. Short-chain fatty acids tend to be more C-14-enriched relative to alkenones in core-top sediments, whereas longer-chain homologues are generally the most radiocarbon depleted of the lipids studied here. Less refractory compounds (e.g., short-chain fatty acids) are thus enriched in radiocarbon with respect to more recalcitrant biomarkers (alkenones, long-chain fatty acids). The lower C-14 content of more refractory compounds reflects a larger proportion of laterally supplied, preaged material. Greater preservation of labile organic compounds observed at the depocenters than in flank sediments results in the presence of "younger" biomarkers, underlining the important influence of selective degradation of labile compounds on their radiocarbon ages.},
	keywords = {c-14 measurements, compound-specific radiocarbon, continental-margin, fatty-acids, marine-sediments, monica basin, oxic degradation, oxygen exposure time, santa-barbara basin, surface sediments},
	isbn = {0024-3590},
	doi = {10.4319/lo.2007.52.2.0558},
	author = {Mollenhauer, G. and Eglinton, T. I.}
}
@article {1980,
	title = {Radiocarbon dating of alkenones from marine sediments: II. Assessment of carbon process blanks},
	journal = {Radiocarbon},
	volume = {47},
	year = {2005},
	note = {993nkTimes Cited:13
Cited References Count:20
},
	month = {2005},
	pages = {413-424},
	abstract = {We evaluate potential process blanks associated with radiocarbon measurement of microgram to milligram quantities of alkenones at the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility. Two strategies to constrain the contribution of blanks to alkenone C-14 dates were followed: 1) dating of samples of known age and 2) multiple measurements of identical samples. We show that the potential contamination associated with the procedure does not lead to a systematic bias of the results of alkenone dating to either younger or older ages. Our results indicate that alkenones record Delta(14)C of ambient DIC with an accuracy of approximately 10 parts per thousand. A conservative estimate of measurement precision is 17 parts per thousand for modern samples. Alkenone C-14 ages are expected to be reliable within 500 yr for samples younger than 10,500 C-14 yr.},
	keywords = {c-14 ams, organic-compounds, records, samples, system, tool},
	isbn = {0033-8222},
	author = {Mollenhauer, G. and Montlucon, D. and Eglinton, T. I.}
}
@article {960,
	title = {On the sedimentological origin of downcore variations of bulk sedimentary nitrogen isotope ratios},
	journal = {Paleoceanography},
	volume = {20},
	year = {2005},
	note = {id: 1066},
	pages = {1-13},
	abstract = {The bulk sedimentary nitrogen isotopic composition of two cores from nearby sites on the northern slope of the South China Sea (Site 17940 and Ocean Drilling Program (ODP) Site 1144) differs by up to >2{\textperthousand} during the last glacial period. Given their close proximity, both core sites are located in the same biogeographic zone and nutrient regime, and it is thus unlikely that this offset is due to a true gradient in surface ocean conditions. In an attempt to resolve this offset, we have investigated the possible effects of two sedimentological parameters that can affect bulk sedimentary δ15N, namely, the variable contribution of inorganic N to bulk N in the sediment and the grain-size dependence of bulk δ15N. We find that neither effect, singly or in combination, is sufficient to explain the significant δ15N offset between the two down-core records. By elimination the most likely explanation for the observed discrepancy is a different origin of both the organic and inorganic nitrogen at each site. This study adds to the growing body of evidence highlighting the complex nature and origin of the sedimentary components in sediment drifts, such as ODP Site 1144.},
	doi = {10.1029/2004PA001081},
	author = {Kienast, M. and Higginson, M. J. and Mollenhauer, G. and Eglinton, T. I. and Chen, M. T. and Calvert, S. E.}
}
