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

J 2021

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

BÁBEK, Ondřej, Stanislava VODRÁŽKOVÁ, Tomáš KUMPAN, Jiří KALVODA, Markéta HOLÁ et. al.

Basic information

Original name

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

Authors

BÁBEK, Ondřej (guarantor), Stanislava VODRÁŽKOVÁ, Tomáš KUMPAN (203 Czech Republic, belonging to the institution), Jiří KALVODA (203 Czech Republic, belonging to the institution), Markéta HOLÁ (203 Czech Republic, belonging to the institution) and Lukáš ACKERMAN

Edition

Sedimentology, Wiley, 2021, 0037-0746

Other information

Language

English

Type of outcome

Článek v odborném periodiku

Field of Study

10505 Geology

Country of publisher

United States of America

Confidentiality degree

není předmětem státního či obchodního tajemství

References:

URL

Impact factor

Impact factor: 3.810

RIV identification code

RIV/00216224:14310/21:00119589

Organization unit

Faculty of Science

DOI

http://dx.doi.org/10.1111/sed.12910

UT WoS

000690458200001

Keywords in English

Diagenesis; diffuse reflectance spectroscopy; geochemistry; palaeoceanography; sedimentary petrology; stable isotopes of Mo

Abstract

V originále

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 δ98Mo 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 the sediment subsurface contradicts models of the formation of marine red beds through iron enrichment from Fe2+ supersaturated ocean waters following periods of ocean anoxia.

Links

GA19-17435S, research and development project

Name: Paleoklimatologický význam paleozoických červených pelagických karbonátů: časově specifické facie nebo produkty mikrobiální aktivity?

Investor: Czech Science Foundation

Citovat

BÁBEK, Ondřej, Stanislava VODRÁŽKOVÁ, Tomáš KUMPAN, Jiří KALVODA, Markéta HOLÁ and Lukáš ACKERMAN. Geochemical record of the subsurface redox gradient in marine red beds: A case study from the Devonian Prague Basin, Czechia. Sedimentology. Wiley, 2021, vol. 68, No 7, p. 3523-3548. ISSN 0037-0746. Available from: https://dx.doi.org/10.1111/sed.12910.

@article{1822931,
   author = {Bábek, Ondřej and Vodrážková, Stanislava and Kumpan, Tomáš and Kalvoda, Jiří and Holá, Markéta and Ackerman, Lukáš},
   article_number = {7},
   doi = {http://dx.doi.org/10.1111/sed.12910},
   keywords = {Diagenesis; diffuse reflectance spectroscopy; geochemistry; palaeoceanography; sedimentary petrology; stable isotopes of Mo},
   language = {eng},
   issn = {0037-0746},
   journal = {Sedimentology},
   title = {Geochemical record of the subsurface redox gradient in marine red beds: A case study from the Devonian Prague Basin, Czechia},
   url = {https://onlinelibrary.wiley.com/doi/10.1111/sed.12910},
   volume = {68},
   year = {2021}
}

TY  - JOUR
ID  - 1822931
AU  - Bábek, Ondřej - Vodrážková, Stanislava - Kumpan, Tomáš - Kalvoda, Jiří - Holá, Markéta - Ackerman, Lukáš
PY  - 2021
TI  - Geochemical record of the subsurface redox gradient in marine red beds: A case study from the Devonian Prague Basin, Czechia
JF  - Sedimentology
VL  - 68
IS  - 7
SP  - 3523-3548
EP  - 3523-3548
PB  - Wiley
SN  - 00370746
KW  - Diagenesis
KW  - diffuse reflectance spectroscopy
KW  - geochemistry
KW  - palaeoceanography
KW  - sedimentary petrology
KW  - stable isotopes of Mo
UR  - https://onlinelibrary.wiley.com/doi/10.1111/sed.12910
N2  - 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 δ98Mo 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 the sediment subsurface contradicts models of the formation of marine red beds through iron enrichment from Fe2+ supersaturated ocean waters following periods of ocean anoxia.
ER  -

BÁBEK, Ondřej, Stanislava VODRÁŽKOVÁ, Tomáš KUMPAN, Jiří KALVODA, Markéta HOLÁ and Lukáš ACKERMAN. Geochemical record of the subsurface redox gradient in marine red beds: A case study from the Devonian Prague Basin, Czechia. \textit{Sedimentology}. Wiley, 2021, vol.~68, No~7, p.~3523-3548. ISSN~0037-0746. Available from: https://dx.doi.org/10.1111/sed.12910.

Detailed Information on Publication Record