Geochemical record of the subsurface redox gradient in marine red beds: A case study from the Devonian Prague Basin, Czechia

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00025798%3A_____%2F21%3A00000131" target="_blank" >RIV/00025798:_____/21:00000131 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/67985831:_____/21:00547972 RIV/00216224:14310/21:00119589 RIV/61989592:15310/21:73610769

Výsledek na webu

<a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/sed.12910" target="_blank" >https://onlinelibrary.wiley.com/doi/abs/10.1111/sed.12910</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1111/sed.12910" target="_blank" >10.1111/sed.12910</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Geochemical record of the subsurface redox gradient in marine red beds: A case study from the Devonian Prague Basin, Czechia

Popis výsledku v původním jazyce

Marine red beds are usually interpreted as indicating water column oligotrophy, good bottom-water oxygenation and redox conditions. Lower Devonian successions of the Prague Basin, Czechia,exhibit a distinct centimetre to metre-scale alternation of layers of marine red beds, grey carbonates, marls and black shales. In order to understand why the redox potential fluctuated so rapidly, reflectance spectroscopy, microscopy, elemental geochemistry data, and stable isotopes of Mo have been analysed in this paper. Whilst the grey and black facies only contain goethite, the marine red beds are enriched with synsedimentary and early diagenetic, submicronic hematite, which is present in micrite, skeletal interiors, microstromatolites and oncoids. It was formed by microbially mediated precipitation, the replacement of detrital Fe phyllosilicates, and/or by the oxidation of microbially precipitated Fe-bearing aluminosilicate precursors. The marine red beds are frequently enriched in Fe, depleted in U, V, Mo and Cu, and show negative 98Mo values indicating oxic conditions. Peloidal micrite, microbial coatings and cements with the marine red beds exhibit positive (up to 9) Ce/Ce* anomalies. The non-red facies show opposite patterns. This geochemical variability is probably related to Mn oxyhydroxide cycling and organic matter remineralization along the sediment subsurface redox gradient, particularly by reactions between pore water and various elemental pools. These patterns, combined with the centimetre-scale colour alternation of the sediments, may reflect redox zonation that has been preserved beneath the ancient seafloor. Four zones are recognized: (i) the oxic zone of Fe-oxide precipitation (marine red beds); suboxic zones of (ii) Fe enrichment, and (iii) U-Mo enrichment; and (iv) suboxic–anoxic zone of Cu, V (± Mo) enrichment. The presented model of a marine red bed origin from redox reactions in sediment subsurface contradicts models of the formation of marine red beds through iron enrichment from Fe2+ supersaturated ocean waters following periods of ocean anoxia.

Název v anglickém jazyce

Geochemical record of the subsurface redox gradient in marine red beds: A case study from the Devonian Prague Basin, Czechia

Popis výsledku anglicky

Marine red beds are usually interpreted as indicating water column oligotrophy, good bottom-water oxygenation and redox conditions. Lower Devonian successions of the Prague Basin, Czechia,exhibit a distinct centimetre to metre-scale alternation of layers of marine red beds, grey carbonates, marls and black shales. In order to understand why the redox potential fluctuated so rapidly, reflectance spectroscopy, microscopy, elemental geochemistry data, and stable isotopes of Mo have been analysed in this paper. Whilst the grey and black facies only contain goethite, the marine red beds are enriched with synsedimentary and early diagenetic, submicronic hematite, which is present in micrite, skeletal interiors, microstromatolites and oncoids. It was formed by microbially mediated precipitation, the replacement of detrital Fe phyllosilicates, and/or by the oxidation of microbially precipitated Fe-bearing aluminosilicate precursors. The marine red beds are frequently enriched in Fe, depleted in U, V, Mo and Cu, and show negative 98Mo values indicating oxic conditions. Peloidal micrite, microbial coatings and cements with the marine red beds exhibit positive (up to 9) Ce/Ce* anomalies. The non-red facies show opposite patterns. This geochemical variability is probably related to Mn oxyhydroxide cycling and organic matter remineralization along the sediment subsurface redox gradient, particularly by reactions between pore water and various elemental pools. These patterns, combined with the centimetre-scale colour alternation of the sediments, may reflect redox zonation that has been preserved beneath the ancient seafloor. Four zones are recognized: (i) the oxic zone of Fe-oxide precipitation (marine red beds); suboxic zones of (ii) Fe enrichment, and (iii) U-Mo enrichment; and (iv) suboxic–anoxic zone of Cu, V (± Mo) enrichment. The presented model of a marine red bed origin from redox reactions in sediment subsurface contradicts models of the formation of marine red beds through iron enrichment from Fe2+ supersaturated ocean waters following periods of ocean anoxia.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10505 - Geology

Projekt

<a href="/cs/project/GA19-17435S" target="_blank" >GA19-17435S: Paleoklimatologický význam paleozoických červených pelagických karbonátů: časově specifické facie nebo produkty mikrobiální aktivity?</a><br>

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Rok uplatnění

2021

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Sedimentology

ISSN

0037-0746

e-ISSN

—

Svazek periodika

68

Číslo periodika v rámci svazku

7

Stát vydavatele periodika

GB - Spojené království Velké Británie a Severního Irska

Počet stran výsledku

25

Strana od-do

3523-3548

Kód UT WoS článku

000690458200001

EID výsledku v databázi Scopus

2-s2.0-85113490687