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Weijers, Johan W H; Schouten, Stefan; Schefuß, Enno; Schneider, Ralph R; Sinninghe Damsté, Jaap S (2009): Bulk and molecular proxies of sediment core GeoB6518-1. PANGAEA,, Supplement to: Weijers, JWH et al. (2009): Disentangling marine, soil and plant organic carbon contributions to continental margin sediments: A multi-proxy approach in a 20,000 year sediment record from the Congo deep-sea fan. Geochimica et Cosmochimica Acta, 73(1), 119-132,

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A 20 kyr long sediment sequence from the Congo deep sea fan (core GeoB 6518-1), one of the world's largest deep sea river fans, has been analysed for bulk and molecular proxies in order to reconstruct the marine, soil and plant organic carbon (OC) contributions to these sediments since the last glacial maximum. The bulk proxies applied, C/N ratio and d13Corg, ranged from 10 to 12.5 and from -24.5 to -21 per mill VPDB, respectively. As molecular proxies, concentrations of marine derived alkenones and terrestrial derived odd-numbered n-alkanes were used, which varied between 0.2 and 4 µg/g dry weight sediment. In addition, the branched vs. isoprenoid tetraether (BIT) index, a proxy for soil organic matter input, was used, which varied from 0.3 to 0.5 in this core.
Application of binary mixing models, based on the different individual proxies, showed estimates for terrestrial OC input varying by up to 50% due to the heterogeneous nature of the OC. Application of a three end-member mixing model using the d13Corg content, the C/N ratio and the BIT index, enabled the distinction of soil and plant organic matter as separate contributors to the sedimentary OC pool. The results show that marine OC accounts for 20% to 40% of the total OC present in the deep sea fan sediments over the last 20 kyr and that soil OC accounts for about half (45% on average) of the OC present. This suggests that soil OC represents the majority of the terrestrial OC delivered to the fan sediments.
Accumulation rates of the plant and soil OC fractions over the last 20 kyr varied by a factor of up to 5, and are strongly related to sediment accumulation rates. They showed an increase starting at ca. 17 kyr BP, a decline during the Younger Dryas, peak values during the early Holocene and lower values in the late Holocene. This pattern matches with reconstructions of past central African humidity and Congo River discharge from the same core and revealed that central African precipitation patterns exert a dominant control on terrestrial OC deposition in the Congo deep sea fan. Marine OC accumulation rates are only weakly related to sediment accumulation rates and vary only little over time compared to the terrigenous fractions. These variations are likely a result of enhanced preservation during times of higher sedimentation rates and of relative small fluctuations in primary production due to wind-driven upwelling.
Latitude: -5.588300 * Longitude: 11.221700
Date/Time Start: 2000-06-20T15:23:00 * Date/Time End: 2000-06-20T15:23:00
Minimum Elevation: -962.0 m * Maximum Elevation: -962.0 m
GeoB6518-1 * Latitude: -5.588300 * Longitude: 11.221700 * Date/Time: 2000-06-20T15:23:00 * Elevation: -962.0 m * Recovery: 7.41 m * Location: Congo Fan * Campaign: M47/3 * Basis: Meteor (1986) * Method/Device: Gravity corer (Kiel type) (SL) * Comment: CC: olive mud
See also Schefuss et al. (2005) dataset: doi:10.1594/PANGAEA.738200
#NameShort NameUnitPrincipal InvestigatorMethod/DeviceComment
1AGEAgeka BPGeocode
2Carbon, organic, totalTOC%Schefuß, EnnoElement analyser CHN-O Rapid, Heraeus
3Carbon/Nitrogen ratioC/NSchefuß, EnnoCalculated, see reference(s)
4Nitrogen/Carbon ratioN/CSchefuß, EnnoCalculated, see reference(s)
5δ13C, organic carbonδ13C Corg‰ PDBSchefuß, EnnoMass spectrometer Finnigan Delta-E
6Sum odd numbered n-alkanes C25-C35A odd (25-35)µg/gSchefuß, Ennosee reference(s)
7C37:2-, C37:3-AlkenoneC37:2, C37:3µg/gSchefuß, Ennosee reference(s)
8Accumulation rate, odd n-alkanesAcc rate A oddmg/m2/aSchefuß, Ennosee reference(s)
9Accumulation rate, alkenone C37Acc rate C37mg/m2/aSchefuß, Ennosee reference(s)
10Alkane/C37-Alkenone ratioAlkane/C37-AlkSchefuß, Ennosee reference(s)
11Alkane/C37-Alkenone indexAlkanes/C37-Alk indSchefuß, Ennosee reference(s)
12CrenarchaeolCrenµg/gSchefuß, Ennosee reference(s)
13Accumulation rate, crenarchaeol per yearAcc rate Crenmg/m2/aSchefuß, Ennosee reference(s)
14Branched glycerol dialkyl glycerol tetraetherbrGDGTµg/gSchefuß, Ennosee reference(s)total
15Accumulation rate, branched glycerol dialkyl glycerol tetraether per yearAcc rate brGDGTmg/m2/aSchefuß, Ennosee reference(s)
16Branched and isoprenoid tetraether indexBITSchefuß, EnnoCalculated, see reference(s)
17δ18O, waterδ18O H2O‰ SMOWSchefuß, Ennosee reference(s)
18n-Alkane C29, δ13CC29 δ13C‰ PDBSchefuß, Ennosee reference(s)
19n-Alkane C29, δDC29 δD‰ SMOWSchefuß, Ennosee reference(s)
20Carbon/Nitrogen ratioC/NSchefuß, EnnoCalculated, see reference(s)% TOM
21Carbon/Nitrogen ratioC/NSchefuß, EnnoCalculated, see reference(s)7-15
22Nitrogen/Carbon ratioN/CSchefuß, EnnoCalculated, see reference(s)7-20
23Nitrogen/Carbon ratioN/CSchefuß, EnnoCalculated, see reference(s)7-15
24δ13C, organic carbonδ13C Corg‰ PDBSchefuß, EnnoMass spectrometer Finnigan Delta-E% TOM
25Branched and isoprenoid tetraether indexBITSchefuß, Ennosee reference(s)% TOM
26Alkane/C37-Alkenone indexAlkanes/C37-Alk ind%Schefuß, Ennosee reference(s)% TOM
27Sedimentation rateSed ratecm/kaSchefuß, Ennosee reference(s)
28Accumulation rate, sediment, meanMARg/cm2/kaSchefuß, Ennosee reference(s)
29Accumulation rate, total organic carbonAcc rate TOCg/cm2/kaSchefuß, Ennosee reference(s)
30Age modelAge modelkaSchefuß, Ennosee reference(s)
4117 data points

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