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

Result code in 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>

Alternative codes found

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

Result on the web

<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>

Result language

angličtina

Original language name

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

Original language description

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.

Czech name

—

Czech description

—

Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

10505 - Geology

Project

<a href="/en/project/GA19-17435S" target="_blank" >GA19-17435S: Palaeoclimatologic significance of Palaeozoic red pelagic carbonates: time specific facies or products of microbial activity?</a><br>

Continuities

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

Publication year

2021

Confidentiality

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

Name of the periodical

Sedimentology

ISSN

0037-0746

e-ISSN

—

Volume of the periodical

68

Issue of the periodical within the volume

7

Country of publishing house

GB - UNITED KINGDOM

Number of pages

25

Pages from-to

3523-3548

UT code for WoS article

000690458200001

EID of the result in the Scopus database

2-s2.0-85113490687