Origin, transport and deposition of leaf-wax biomarkers in the Amazon Basin and the adjacent Atlantic

Häggi, Christoph; Sawakuchi, André Oliveira; Chiessi, Cristiano Mazur; Mulitza, Stefan; Mollenhauer, Gesine; Sawakuchi, Henrique O.; Baker, Paul A.; Zabel, Matthias; Schefuß, Enno

doi:10.1016/j.gca.2016.07.002

Cited by 60 publications

(82 citation statements)

References 79 publications

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“…This is necessary to constrain the major controls on sedimentation rates and the role of precipitation changes for carbon burial. The TOC concentration in core XC05 varies from 1.77 to 3.35% (average of 2.45%), similar to TOC values measured in bottom sediments collected in the Xingu Ria (average of 2.36%) (Häggi et al, 2016). Irion et al (2006) showed TOC values with low variation in the Tapajós Ria, varying from 2.2 to 2.9% in sediments younger than 7,500 years.…”

Section: Discussionsupporting

confidence: 77%

“…The measured concentrations are similar to values in samples from bottom sediments of the Xingu Ria (Häggi et al, 2016). Values of δ 13 C org range from −31.04 to −27.49‰, and indicate that organic matter from bottom sediments of the Xingu Ria is mainly derived from arboreal C3 vegetation (Table S1).…”

Section: Chronology Magnetic and Geochemistry Data Of Sediment Coressupporting

confidence: 73%

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The Fate of Carbon in Sediments of the Xingu and Tapajós Clearwater Rivers, Eastern Amazon

Bertassoli

Sawakuchi

et al. 2017

Front. Mar. Sci.

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The Xingu and Tapajós rivers in the eastern Amazon are the largest clearwater systems of the Amazon basin. Both rivers have "fluvial rias" (i.e., lake-like channels) in their downstream reaches as they are naturally impounded by the Amazon mainstem. Fluvial rias are widespread in the Amazon landscape and most of the sedimentary load from the major clearwater and blackwater rivers is deposited in these channels. So far, little is known about the role of Amazon rias as a trap and reactor for organic sediments. In this study, we used organic and inorganic geochemistry, magnetic susceptibility, diatom, and pollen analyses in sediments (suspended, riverbed, and downcore) of the Xingu and Tapajós rias to investigate the effects of hydrologic variations on the carbon budget in these clearwater rivers over the Holocene. Ages of sediment deposition (∼100 to 5,500 years) were constrained by optically stimulated luminescence and radiocarbon. Major elements geochemistry and concentration of total organic carbon (TOC) indicate that seasonal hydrologic variations exert a strong influence on riverine productivity and on the input and preservation of organic matter in sediments. Stable carbon isotope data (δ 13 C from −31.04 to −27.49‰) and pollen analysis indicate that most of the carbon buried in rias is derived from forests. In the Xingu River, diatom analysis in bottom sediments revealed 65 infrageneric taxa that are mostly well-adapted to slack oligotrophic and acidic waters. TOC values in sediment cores are similar to values measured in riverbed sediments and indicate suitable conditions for organic matter preservation in sediments of the Xingu and Tapajós rias at least since the mid-Holocene, with carbon burial rates varying from about 84 g m −2 yr −1 to 169 g m −2 yr −1 . However, redox-sensitive elements in sediment core indicate alternation between anoxic/dysoxic and oxic conditions in the water-sediment interface that may be linked to abrupt changes in precipitation. The variation between anoxic/dysoxic and oxic conditions in the water-sediment interface controls organic matter mineralization and methanogenesis. Thus, such changes promoted by hydrological variations significantly affect the capacity of Amazon rias to act either as sources or sinks of carbon.

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Section: Discussionsupporting

confidence: 77%

Section: Chronology Magnetic and Geochemistry Data Of Sediment Coressupporting

confidence: 73%

The Fate of Carbon in Sediments of the Xingu and Tapajós Clearwater Rivers, Eastern Amazon

Bertassoli

Sawakuchi

et al. 2017

Front. Mar. Sci.

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“…The effect of groundwater use on δD C29 is thus apparently minor. The recorded southwest to northeast trend in δD C29 values is particularly visible in marine samples suggesting that river‐mouth deposits reflect an average value of the catchment area (e.g., Häggi et al, ; Hemingway et al, ). The individual catchment and suspension load samples apparently reflect more local and/or short term signals.…”

Section: Resultsmentioning

confidence: 99%

The Provenance of Terrigenous Components in Marine Sediments Along the East Coast of Southern Africa

Hahn

Miller

Andó

et al. 2018

Geochem Geophys Geosyst

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Terrestrial signals in marine sediment archives are often used for paleoclimatic reconstructions. It is therefore important to know the origin of the different terrestrial sedimentary components. The proximity to a river mouth is often the key location to determine the source. Especially in regions with strong ocean currents, such an assumption might, however, lead to considerable misinterpretations. To investigate the source of various terrigenous sediment fractions in southeastern Africa, a region with strong sediment redistribution, we have performed an extensive comparison between terrestrial material (pollen, plant lipids, detrital modes, and heavy minerals as well as bulk inorganic geochemical composition) from potential source regions and the same components in the adjacent coastal and continental shelf sediments. Onshore the proxy‐indicators reflect small‐scale diversity in sampling locations and associated environments (riverbank sediments, flood deposits, suspension loads, and soils). Nevertheless, the overall trends reflect significant environmental gradients along a SW to NE transect. We note a general comparability of the studied parameters between the continental and marine sediments regardless of their specific differences in transport and depositional characteristics. We propose that the influence of the Agulhas Current affects sediment deposition and distribution only seaward of the midshelf and that pockets of sediment remain preserved in the lee of coastal protrusions where they are protected from erosion. This study provides the essential prerequisite to allow the attribution of temporal variations of compositional changes in marine sediment cores to environmental changes in southeastern Africa.

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“…Part of the TOC-stable carbon isotopic composition and Al / Si data were previously published in Häggi et al (2016). Riverbed sediments contain between 0.13 and 3.99 % dry weight (wt) TOC (Table 1, Fig.…”

Section: Toc and Stable Carbon Isotopic Compositionmentioning

confidence: 99%

Origin and processing of terrestrial organic carbon in the Amazon system: lignin phenols in river, shelf, and fan sediments

et al. 2017

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Abstract. The Amazon River transports large amounts of terrestrial organic carbon (OC terr ) from the Andean and Amazon neotropical forests to the Atlantic Ocean. In order to compare the biogeochemical characteristics of OC terr in the fluvial sediments from the Amazon drainage basin and in the adjacent marine sediments, we analysed riverbed sediments from the Amazon mainstream and its main tributaries as well as marine surface sediments from the Amazon shelf and fan for total organic carbon (TOC) content, organic carbon isotopic composition (δ 13 C TOC ), and lignin phenol compositions. TOC and lignin content exhibit positive correlations with Al / Si ratios (indicative of the sediment grain size) implying that the grain size of sediment discharged by the Amazon River plays an important role in the preservation of TOC and leads to preferential preservation of lignin phenols in fine particles. Depleted δ 13 C TOC values (−26.1 to −29.9 ‰) in the main tributaries consistently correspond with the dominance of C3 vegetation. Ratios of syringyl to vanillyl (S / V) and cinnamyl to vanillyl (C / V) lignin phenols suggest that non-woody angiosperm tissues are the dominant source of lignin in the Amazon basin. Although the Amazon basin hosts a rich diversity of vascular plant types, distinct regional lignin compositions are not observed. In the marine sediments, the distribution of δ 13 C TOC and 8 (sum of eight lignin phenols in organic carbon (OC), expressed as mg/100 mg OC) values implies that OC terr discharged by the Amazon River is transported north-westward by the North Brazil Current and mostly deposited on the inner shelf. The lignin compositions in offshore sediments under the influence of the Amazon plume are consistent with the riverbed samples suggesting that processing of OC terr during offshore transport does not change the encoded source information. Therefore, the lignin compositions preserved in these offshore sediments can reliably reflect the vegetation in the Amazon River catchment. In sediments from the Amazon fan, low lignin content, relatively depleted δ 13 C TOC values and high (Ad / Al) V ratios indicating highly degraded lignin imply that a significant fraction of the deposited OC terr is derived from petrogenic (sourced from ancient rocks) sources.

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Origin, transport and deposition of leaf-wax biomarkers in the Amazon Basin and the adjacent Atlantic

Cited by 60 publications

References 79 publications

The Fate of Carbon in Sediments of the Xingu and Tapajós Clearwater Rivers, Eastern Amazon

The Fate of Carbon in Sediments of the Xingu and Tapajós Clearwater Rivers, Eastern Amazon

The Provenance of Terrigenous Components in Marine Sediments Along the East Coast of Southern Africa

Origin and processing of terrestrial organic carbon in the Amazon system: lignin phenols in river, shelf, and fan sediments

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