Groundwater red beds in Holocene fluvial sediments as a product of iron and manganese redox cycling; Morava River, Czechia

نویسندگان

چکیده

Modern fluvial deposits can be affected by early diagenetic element mobilization at redox boundaries between oxygenated, and oxygen free zones near the groundwater level. The visible product of transformation Fe is sediment colour. Distinct red black layers have been studied in eight shallow (<4.2 m depth) sections floodplain Morava River, Czechia. aim was to investigate composition, origin, rates formation stratigraphic significance strata using bulk-rock analytical methods, radiocarbon dating, optical scanning electron microscopy coupled with in-situ (energy-dispersive X-ray laser ablation inductively plasma mass spectrometry) geochemistry. coloured layers, places well cemented, developed permeable sands gravels above water table, close boundary overlying less sandy silts. Their colour due Mn oxyhydroxides (goethite, hematite, todorokite birnessite) coatings framework grains. Black, Mn-rich occur stratigraphically higher than red, Fe-rich ones. are a few-hundred microns thick maximum, often botryoidal, composed alternating laminae enriched As, Mo, Sb, P, Cu U. formed under suboxic conditions oxyhydroxide cycling, driven partly microbial activity, groundwater-related which resulted distinct vertical arrangement layers. Being markedly As bound Fe-oxyhydroxides exposed fluctuating conditions, potentially release represent serious environmental hazards. Radiocarbon ages suggest that groundwater-type beds extremely quickly, over few hundred years. It assumed that, suitable circumstances, this reddening preserved rock record, specific model for development continental beds.

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ژورنال

عنوان ژورنال: Sedimentology

سال: 2023

ISSN: ['1365-3091', '0037-0746']

DOI: https://doi.org/10.1111/sed.13119