Literature
Kienast S. S., Kienast M., Mix A. C., Calvert S. E., and Francois R. (2007) Thorium-230 normalized particle flux and sediment focusing in the Panama Basin region during the last 30,000 years. PALEOCEANOGRAPHY 22.
Lonsdale P. (1977) Inflow of bottom water to the Panama Basin. Deep Sea Research 24(12), 1065-1094.
DISCUSSION & CONCLUSION
The age-relationships between foraminifera and alkenones do not imply significant contributions of pre-aged material. This sug- gests that lateral sediment transport of pre-aged material did not substantially affect the core locations of Y69-71 and ME0005-24JC. However, considering the 230Th data from KIENAST et al. (2007) which show focusing factors of up to Ψ=3.5 for core Y69-71 and up to Ψ=7.5 for core ME0005-24JC, we deduce that laterally supplied material has not been eroded elsewhere but rather is transported by bottom currents rapidly after particle formation.
ACKNOWLEDGEMENTS
This study was funded by the Helmholtz-University Young Inves- tigators Group „Application of mo- lecular 14C analysis for the study of
sedimentation processes and carbon cycling in marine sedi-
ments“ and a WHOI-NOSAMS post- doctoral scholarship to GM.
COMPOUND-SPECIFIC RADIOCARBON AGES OF ALKENONES REVEAL RAPID BOTTOM CURRENT INDUCED LATERAL
SEDIMENT TRANSPORT IN THE PANAMA BASIN
Stephanie KUSCH
1,2*, Timothy I. EGLINTON
3, Alan MIX
4, Gesine MOLLENHAUER
1,2*Stephanie.Kusch@awi.de
1 Alfred-Wegener-Institut für Polar- und Meeresforschung, Am Handelshafen 12, 27570 Bremerhaven 2 Fachbereich Geowissenschaften, Universität Bremen, Klagenfurter Str., 28359 Bremen 3 Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA 4 College of Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331
Y69-71
Radiocarbon data for core Y69-71 are less conclusive (Figure 4). In the deglacial section, ages of all dated sediment constituents agree rather well. In particular, good agreement is observed between TOC and alke- nones. Alkenone dates from the top of the core (Holocene) are less reli- able due to small sample size.
Therefore we suggest no age offset between the analysed sediment constituents are prominent.
Figure 5: Focusing factors for the time in- tervals from the core top to 9.5, 9.5–13.4, 13.4 to 21, and 21–27 ka (KIENAST et al.
2007, modified).
The 230Th-analysis for core Y69-71 of KIENAST
et al. (2007) show fo- cusing factors of up to Ψ=3.5 for OIS 2 and as high as Ψ=2.5 for the Holocene (Figure 5), implying addition of large amounts of la-
terally supplied sedi- ment.
Figure 4: Fraction modern carbon and conventional radiocarbon ages of alkeno- nes, foraminifera (N. dutertrei and G. sacculifer) and Total Organic Carbon (TOC) for core Y69-71 and the age-offsets of alkenones and TOC related to the foramini- fera radiocarbon ages..
ME0005-24JC
(Figure 3, KIENAST et al. 2007) are as high as Ψ=7.5 for the de- glaciation and amount up to Ψ=4 for the Ho- locene, therefore imp- lying significant cont-
ribution of laterally supplied sediment to this specific location.
The supplied material is likely to have been transported by bottom currents.
INTRODUCTION
We present 14C data of phytoplankton derived biomarkers (alkenones) and co-occurring foraminifer-tests as well as total organic carbon (TOC) to investigate possible input of (pre-aged) laterally advected material - resulting in apparent age-offsets of the sediment constituents - to our study sites Y69-71 and ME0005-24JC in the SW Panama Basin. For our study Holocene and late glacial samples were analysed.
14
Figure 1: Map of the Panama Basin showing the core locations of Y69-71 (orange) and ME0005-24JC (pink), and bottom currents.
Arrows are paths of bottom water circulation inferred from distributi- on of water properties (after LONSDALE 1977).
STUDY AREA PANAMA BASIN
The study area is located in the SW Panama Basin just north of the Carnegie Ridge. Core Y69-71 was recovered at 0°06‘N, 86°29‘W (2740m) and ME0005-24JC was retrieved at 0°01.302‘N, 86°27.788‘W (2941m).
For the Panama Basin the principal inflow of bottom currents originating from the Peru Basin is the Ecuador Trench channel. A further inflow-passage is given across the central saddle of the Carnegie Ridge located between 85 and 86°W. This passage is influenced by episodic spillover of fast bottom currents rather than by perennial exchange with Peru Basin waters (LONSDALE 1977).
Figure 3: Focusing factors for the time in- tervals from the core top to 9.5, 9.5–13.4, 13.4 to 21, and 21–27 ka (KIENAST et al.
2007, modified).
OIS 2
Figure 2: Fraction modern carbon and conventional radiocarbon ages of alkeno- nes, foraminifera (N. dutertrei) and Total Organic Carbon (TOC) for core ME0005- 24JC and the age-offsets of alkenones and TOC related to the foraminifera radio- carbon ages.
-95˚
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0˚ 0˚
5˚ 5˚
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0 200 400
km
Galapagos
Colon Balboa
Quito
Medellin
Y69-71 Cocos
Ridge
ME0005-24JC
Carnegie Ridge
...please ask!
Figure 2 shows no significant age-offsets between the planktonic fo- raminifera and alkenones as well as TOC. The good agreement bet- ween TOC and foram ages suggests that advection of pre-aged orga- nic matter is negligible at this site. Likewise there is no evidence for lateral advection of pre-aged alkenones.
Independent proxies for sediment transport processes provide additi- onal evidence. 230Th-based focusing factors for core ME0005-24JC
0 50 100 150 200 250 300
core depth Y69-71 [cm]
0 5000 10000 15000 20000 25000 30000
Conventional14 C age [yrs BP]
-4000 0 4000 8000 Age offset [yrs]
0 50 100 150 200 250 300
1 0.8 0.6 0.4 0.2 0
fMC
*TOC
&Alkenones
/N. dutertrei 1G. sacculifer
AForams-TOC
,Forams-Alkenones
0 50 100 150 200 250 300
*TOC
&Alkenones
/N. dutertrei 1G. sacculifer
? ?
?
?
?
sample am
ount <30µg sample amount <30µg
?
0 50 100 150 200 250 300 350 400
core depth ME0005-24JC [cm]
0 4000 8000 12000 16000 20000
Conventional 14 C age [yrs BP]
-1000 -500 0 500 1000 1500 Age offset [yrs]
0 50 100 150 200 250 300 350 400
1 0.8 0.6 0.4 0.2 0
fMC
*TOC
&Alkenones
/N. dutertrei 1G.sacculifer
AForams-TOC
,Forams-Alkenones
0 50 100 150 200 250 300 350 400
*TOC
&Alkenones
/N. dutertrei 1G.sacculifer
