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@article{1688496,
author = {Simicek, Daniel and Babek, Ondřej and Famera, Martin and Kalvoda, Jiří},
article_location = {Amsterdam},
article_number = {JUN 2020},
doi = {http://dx.doi.org/10.1016/j.sedgeo.2020.105651},
keywords = {Devonian; Palaeoceanography; Palaeoclimatology; Rare earth elements; Mesotrophic; Oligotrophic conditions},
language = {eng},
issn = {0037-0738},
journal = {Sedimentary Geology},
title = {Million-year secular variations in the elemental geochemistry of Devonian marine records and a link to global climate and bioevents: Prague Basin, Czechia},
url = {https://doi.org/10.1016/j.sedgeo.2020.105651},
volume = {402},
year = {2020}
}
TY - JOUR
ID - 1688496
AU - Simicek, Daniel - Babek, Ondřej - Famera, Martin - Kalvoda, Jiří
PY - 2020
TI - Million-year secular variations in the elemental geochemistry of Devonian marine records and a link to global climate and bioevents: Prague Basin, Czechia
JF - Sedimentary Geology
VL - 402
IS - JUN 2020
SP - 1-17
EP - 1-17
PB - Elsevier Science
SN - 00370738
KW - Devonian
KW - Palaeoceanography
KW - Palaeoclimatology
KW - Rare earth elements
KW - Mesotrophic
KW - Oligotrophic conditions
UR - https://doi.org/10.1016/j.sedgeo.2020.105651
L2 - https://doi.org/10.1016/j.sedgeo.2020.105651
N2 - The sedimentary record is affected by periodic and/or random variations in Earth's near-surface conditions, such as the Milankovitch band variations, which are responsible for small-scale cyclicity in distal marine settings. However, the controlling factors of normal field-scale sedimentary cycles operating on Myr-scale that dominate the stratigraphic record remain largely enigmatic. The Lower to Middle Devonian succession (Lochkovian to Givetian) of the Prague Basin, Czechia, is represented by an alternation of largely deep-marine carbonates and shales with typical duration of similar to 5-7 Myr. We studied the elemental geochemistry of bulk rock samples supported by XRD mineralogy and TOC concentrations. Stratigraphic distribution of the organic-productivity proxies, redox proxies, Ce/Ce* and Pr/Pr* anomalies, and TOC, supported by lithology, allochem composition and field gamma-ray spectrometry, indicates that the Prague Basin was governed by two alternating depositional modes. The oligotrophic mode is characterised by low values of productivity proxies and U/Th ratios, good bottom water oxygenation, heterotrophic skeletal producers, and facies typical of homoclinal ramp settings. The mesotrophic mode is characterised by high U/Th, elevated organic productivity, less oxic bottom conditions, relatively abundant autotrophic skeletal producers and deposition on a distally steepened ramp. The modes were in phase with the Devonian climatically driven environmental changes. We assume that the elevated silicate weathering rates during warmer periods, as previously reported, resulted in higher nutrient input to the seas setting the marine system into the mesotrophic mode. Cooler periods led to oligotrophic water conditions. The global Devonian bioevents show recurrence intervals of the same order as the trophic modes but they typically coincided with the transition between the modes. It is suggested that marine biotic assemblages and the associated carbonate production became unstable during perturbations of the carbon cycle.
ER -
SIMICEK, Daniel, Ondřej BABEK, Martin FAMERA a Jiří KALVODA. Million-year secular variations in the elemental geochemistry of Devonian marine records and a link to global climate and bioevents: Prague Basin, Czechia. \textit{Sedimentary Geology}. Amsterdam: Elsevier Science, 2020, roč.~402, JUN 2020, s.~1-17. ISSN~0037-0738. Dostupné z: https://dx.doi.org/10.1016/j.sedgeo.2020.105651.
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