HR: 1340h
AN: T23C-1530 [Abstracts]
TI: Isotopic tracers of Nile sediment sources
AU: Padoan, M
EM: marta.pomi@libero.it
AF: Universita di Milano Bicocca, piazza della Scienza 4, Milano, 20126, Italy
AU: Galbusera, M
EM: eduardo.garzanti@unimib.it
AF: Universita di Milano Bicocca, piazza della Scienza 4, Milano, 20126, Italy
AU: Quistini, S
EM: yankov@libero.it
AF: Universita di Milano Bicocca, piazza della Scienza 4, Milano, 20126, Italy
AU: * Villa, I M
EM: igor@geo.unibe.ch
AF: Universita di Milano Bicocca, piazza della Scienza 4, Milano, 20126, Italy
AU: * Villa, I M
EM: igor@geo.unibe.ch
AF: Universitat Bern, Baltzerstrasse 3, Bern, 3012, Switzerland
AU: Garzanti, E
EM: eduardo.garzanti@unimib.it
AF: Universita di Milano Bicocca, piazza della Scienza 4, Milano, 20126, Italy
AB:
We analyzed Sr and Nd isotopes in sediments of the Nile river and its major Sudanese branches (Blue Nile,
White Nile, Atbara), focusing on the cohesive mud fraction (< 0.04 mm). In one sample for each branch, the
0.125-0.180 mm sand fraction was also analysed.
Marked variations in Sr and Nd isotopic records were expected between White Nile sediments, mostly derived
from cratonic sources, and Blue Nile and Atbara sediments, chiefly derived from Tertiary Ethiopian volcanic
highlands.
Epsilon Nd values, eps(Nd), range between –8.8 ± 0.1 and +3.2 ± 0.1. Nd model ages (tDM) range from 0.8 to 1.6
Ga, duplicating the eps(Nd) trend. Eps(Nd) of main Nile sediments decreases sharply upstream Khartoum,
indicating that the Nile sediments are predominantly contributed by the Blue Nile.
The Sr isotopic ratios range between 0.70402 ± 2 and 0.72128 ± 2, in anticorrelation with eps(Nd), and reproduce
the dichotomy between White and Blue Nile sources.
Results from sand samples are more heterogeneous with respect to mud samples. This may be explained by
the variable mechanical strength of the main Nd carriers and the petrographic observation of their differential
preservation as a function of grain size.
DE: 0744 Rivers (0483, 1856)
DE: 1040 Radiogenic isotope geochemistry
DE: 1051 Sedimentary geochemistry
DE: 1862 Sediment transport (4558)
DE: 4924 Geochemical tracers
SC: Tectonophysics [T]
MN: 2007 Fall Meeting