@article{fdi:010063114,
  title = {{E}vidence for the control of the geochemistry of {A}mazonian floodplain sediments by stratification of suspended sediments in the {A}mazon},
  author = {{R}oddaz, {M}. and {V}iers, {J}. and {M}oreira {T}urcq, {P}atricia and {B}londel, {C}. and {S}ondag, {F}rancis and {G}uyot, {J}ean-{L}oup and {M}oreira, {L}.},
  editor = {},
  language = {{ENG}},
  abstract = {{H}olocene and historical {A}mazonian floodplain deposits collected from two cores of the "{V}arzea do {C}uruai" flooded area ({B}razil) were analysed for major and trace element geochemistry as well as {N}d-{S}r isotopic compositions (21 samples). {T}he {TA}11 and {TA}14 cores (110 cm and 270 cm in depth, respectively) were collected at different locations in the {V}arzea, near a channel inlet connecting the {A}mazon {R}iver to the {V}arzea and at the centre of the {V}arzea, respectively. {T}he two cores represent records of sedimentation on different time-scales, with {TA}11 covering the last 100 years and {TA}14 extending back to 5600 years cal {BP}. {A}lthough the sediments are generally coarser in {TA}11 than in {TA}14, the major and trace element concentrations, {C}r/{T}h and {T}h/{S}c and {E}u anomalies and {N}d-{S}r isotopic compositions in both cores fail to show any clear variations with depth. {H}owever, there are chemical differences between the two analysed cores. {T}he {TA}14 sediments have higher {A}l/{S}i and {C}hemical {I}ndex of {A}lteration ({CIA}) values than those of {TA}11. {T}he {TA}14 sediments are enriched in {T}h, {U}, {Y}, {N}b, {REE}, {C}s, {R}b, {V} and {N}i but show slightly depleted {M}g{O}, {C}a{O} and {S}r and more strongly depleted {N}a2{O}, {Z}r and {H}f compared to {TA}11. {I}n addition, the {N}d-{S}r isotopic compositions of the {TA}11 sediment core are on the whole similar to the {S}olimoes suspended particulate matter ({SPM}), whereas {TA}14 has a similar {N}d-{S}r isotopic composition compared with the {SPM} of the {A}mazon {R}iver at {O}bidos. {T}hese differences are best explained by chemical stratification of the {SPM} of the {A}mazon {R}iver. {D}uring flooding of the {A}mazon {R}iver, coarser grained particulates supplied by the {S}olimoes {R}iver are deposited in the deepest environments near the channel inlet, as recorded in the {TA}11 sediment core. {B}y contrast, finer grained suspended sediments derived from the {M}adeira {R}iver are transported into the shallower environments of the {V}arzea system and deposited as a result of flow expansion and loss of carrying power, as recorded in the {TA}14 sediment core. {U}sing the {N}d isotopic compositions and concentrations of each sediment core, we calculate between similar to 20 and similar to 85% of the sediment input to the {TA}14 core site is derived from the {M}adeira {R}iver, while between 52% and 100% of the sediment input to the {TA}11 core sample is supplied by the {S}olimoes {R}iver. {S}imilar calculation using the {S}r isotopic compositions and concentrations of {TA}11 and {TA}14 sediments gave similar results with between similar to 32% and similar to 49% of {TA}14 sediments deriving from the {S}olimoes {R}iver while between similar to 70% and similar to 100% of {TA}11 sediments originate from the {S}olimoes {R}iver. {F}inally, our findings lead us to question whether particular {A}mazon deposits that do not integrate the entire range of {SPM} present in the river are representative of the overall sediment load provided today and in the past by global rivers.},
  keywords = {{M}ajor and trace elements ; {N}d-{S}r isotopes ; {P}rovenance ; {F}loodplain sediments ; {A}mazon {R}iver ; {B}razil ; {BRESIL} ; {AMAZONE} {BASSIN}},
  booktitle = {},
  journal = {{C}hemical {G}eology},
  volume = {387},
  numero = {},
  pages = {101--110},
  ISSN = {0009-2541},
  year = {2014},
  DOI = {10.1016/j.chemgeo.2014.07.022},
  URL = {https://www.documentation.ird.fr/hor/fdi:010063114},
}