Sediment Provenance in the Baker-Martínez Fjord System (Chile, 48°S) Indicated by Magnetic Susceptibility and Inorganic Geochemistry

Troch, Matthias; Bertrand, Sébastien; Amann, Benjamin; Liu, Dawei; Placencia, J. A.; Lange, Carina B.

doi:10.3389/fmars.2021.612309

Cited by 4 publications

(3 citation statements)

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“…The BMFC generally has a two‐layered water mass structure: the upper layer (top 20–30 m depth) consists of estuarine water that is formed from a mix of continental freshwater and seawater, while the lower layer is composed of Subantarctic water that flows in from the Pacific Ocean through the Gulf of Penas (Quiroga et al., 2016 ). The major freshwater and terrestrial inputs into the fjord complex are the Baker River, the Huemules River, the Pascua River, and Jorge Montt Glacier (Troch et al., 2021 ). Glacier meltwater is a significant contributor to the runoff of these rivers (Amann et al., 2022 ; Pryer, Hawkings, et al., 2020 ).…”

Section: Methodsmentioning

confidence: 99%

Benthic Dissolved Silicon and Iron Cycling at Glaciated Patagonian Fjord Heads

Hawkings

Bertrand

et al. 2022

Global Biogeochemical Cycles

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Glacier meltwater supplies silicon (Si) and iron (Fe) sourced from weathered bedrock to downstream ecosystems. However, the extent to which these nutrients reach the ocean is regulated by the nature of the benthic cycling of dissolved Si and Fe within fjord systems, given the rapid deposition of reactive particulate fractions at fjord heads. Here, we examine the benthic cycling of the two nutrients at four Patagonian fjord heads through geochemical analyses of sediment pore waters, including Si and Fe isotopes (δ30Si and δ56Fe), and reaction‐transport modeling for Si. A high diffusive flux of dissolved Fe from the fjord sediments (up to 0.02 mmol m−2 day−1) compared to open ocean sediments (typically <0.001 mmol m−2 day−1) is supported by both reductive and non‐reductive dissolution of glacially‐sourced reactive Fe phases, as reflected by the range of pore water δ56Fe (−2.7 to +0.8‰). In contrast, the diffusive flux of dissolved Si from the fjord sediments (0.02–0.05 mmol m−2 day−1) is relatively low (typical ocean values are >0.1 mmol m−2 day−1). High pore water δ30Si (up to +3.3‰) observed near the Fe(II)‐Fe(III) redox boundary is likely associated with the removal of dissolved Si by Fe(III) mineral phases, which, together with high sedimentation rates, contribute to the low diffusive flux of Si at the sampled sites. Our results suggest that early diagenesis promotes the release of dissolved Fe, yet suppresses the release of dissolved Si at glaciated fjord heads, which has significant implications for understanding the downstream transport of these nutrients along fjord systems.

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Section: Methodsmentioning

confidence: 99%

Benthic Dissolved Silicon and Iron Cycling at Glaciated Patagonian Fjord Heads

Hawkings

Bertrand

et al. 2022

Global Biogeochemical Cycles

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“…The BMFC generally has a two-layered water mass structure: the upper layer (top 20-30 m depth) consists of estuarine water that is formed from a mix of continental freshwater and seawater, while the lower layer is composed of Subantarctic water that flows in from the Pacific Ocean through the Gulf of Penas (Quiroga et al, 2016). The major freshwater and terrestrial inputs into the fjord complex are the Baker River, the Huemules River, the Pascua River, and Jorge Montt Glacier (Troch et al, 2021). Glacier meltwater is a significant contributor to the runoff of these rivers (Amann et al, 2022;.…”

Section: Study Sitesmentioning

confidence: 99%

Benthic dissolved silicon and iron cycling at glaciated Patagonian fjord heads

Hendry

Hawkings

et al. 2023

Preprint

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Glacier meltwater supplies a significant amount of silicon (Si) and iron (Fe) sourced from weathered bedrock to downstream ecosystems. However, the extent to which these essential nutrients reach the ocean is regulated by the processes occurring within fjords, which act as conduits from glacial rivers and subglacial discharge and the ocean. One key &#8211; but understudied &#8211; component of biogeochemistry within fjords is benthic cycling, especially in regions of rapid deposition of reactive particulates at fjord heads. Here, we explore the benthic cycling of Si and Fe at four Patagonian fjord heads through geochemical analyses of sediment pore waters, including stable Si and Fe isotopes (&#948;30Si and &#948;56Fe respectively), and novel reaction-transport modelling for Si. A high diffusive flux of dissolved Fe from the fjord sediments compared to open ocean sediments is supported by both reductive and non-reductive dissolution of glacially-sourced reactive Fe phases, as reflected by the range of pore water stable Fe isotopes (&#948;56Fe from -2.7 to +0.8&#8240;). In contrast, the diffusive flux of dissolved Si from the fjord sediments is relatively low. High pore water &#948;30Si (up to +3.3&#8240;) observed near the Fe(II)-Fe(III) redox boundary is likely associated with the removal of dissolved Si by Fe(III) mineral phases, which, together with high sedimentation rates, contribute to the low diffusive flux of Si at the sampled sites. Our results suggest that early diagenesis promotes the release of dissolved Fe but suppresses the release of dissolved Si at glaciated fjord heads. The redox sensitive coupling of Si and Fe has significant implications for our understanding of how essential nutrients are transport along fjord systems.

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“…Easy detection of geological and hydrodynamic processes by magnetic methods makes magnetic minerals, an exemplary proxy to gain vital insights into the dynamics of magnetic particles in sedimentary systems (Hatfield, 2014; Kulgemeyer et al., 2017). Magnetic methods have been increasingly used to study the estuarine and coastal systems for example, to decipher the origin, and dynamics of heavy (magnetic) minerals (Gallaway et al., 2012; Hatfield et al., 2010; Kulgemeyer et al., 2017), identify the sediment accretion and erosion sites (Franke et al., 2020; Hatfield et al., 2010; Kayvantash et al., 2017; Wang et al., 2011), track changes in sediment provenance, transport pathways, and depositional system (Booth et al., 2005; Hatfield, 2014; Maher et al., 2009; Prizomwala et al., 2013), map the heavy (magnetic) mineral deposits (Badesab et al., 2012; Troch et al., 2021), reconstruct the pollution history (Blaha et al., 2011), characterize the sedimentary environment and littoral drift system (Chaparro et al., 2017; Hatfield & Maher, 2008, 2009; Kulgemeyer et al., 2016), and investigate the magnetic mineral diagenesis (Ahn et al., 2021; Zhang et al., 2001).…”

Section: Introductionmentioning

confidence: 99%

Control of Source‐To‐Sink Processes on the Dispersal, Fractionation, and Deposition of Magnetic Minerals in a Tropical Mesotidal Estuarine System

Badesab,

Kadam,

Gullapalli

et al. 2023

Geochem Geophys Geosyst

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This study aims to elucidate the control of source‐to‐sink processes on the sediment dynamics of a complex mesotidal tropical estuarine system using rock magnetic, sedimentological, mineralogical, and geochemical methods. Integration of multiproxy data of catchment rocks, riverbank and hinterland soils, and bedload sediments from various depositional environment of Mandovi estuary revealed a marked change in the magnetic mineral composition and accumulation pattern. The magnetic mineralogy mainly comprised ferri‐ (magnetite, titanomagnetite) and antiferromagnetic (hematite, goethite) minerals. Higher accumulation of coarser magnetic particles in the catchment area followed by a systematic trend of progressive fining of magnetic grain size in the down reaches of the estuary can be attributed to the decrease in transport energy. Enhanced accumulation of coarser magnetic particles in the estuarine region can be reconciled with the strong tidal and wave‐induced bottom currents, which preferentially favored mineral‐density selective fractionation resulting in higher deposition of heavy (magnetic) particles. A clear trend of loss of fluvial‐derived fine silt‐size clastic sediments and selective retention of coarser and heavy magnetic particles within the estuary can be attributed to the hydrodynamic driven sediment partitioning regime, which inhibited the permanent settling of fine sediment fraction and are therefore frequently flushed out to the sea. A marked drop in S‐ratio in different zones of the estuary can be linked to the increased input of high coercive magnetic particles derived from pedogenic soils along eroding riverbanks. We further demonstrate that the S‐ratio is an effective parameter to track the riverbank erosion in an estuarine system.

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Sediment Provenance in the Baker-Martínez Fjord System (Chile, 48°S) Indicated by Magnetic Susceptibility and Inorganic Geochemistry

Cited by 4 publications

References 76 publications

Benthic Dissolved Silicon and Iron Cycling at Glaciated Patagonian Fjord Heads

Benthic Dissolved Silicon and Iron Cycling at Glaciated Patagonian Fjord Heads

Benthic dissolved silicon and iron cycling at glaciated Patagonian fjord heads

Control of Source‐To‐Sink Processes on the Dispersal, Fractionation, and Deposition of Magnetic Minerals in a Tropical Mesotidal Estuarine System

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