Redox geochemistry of the red ‘orthoceratite limestone’ of Baltoscandia: Possible linkage to mid-Ordovician palaeoceanographic changes

0542527 - GLÚ 2022 RIV NL eng J - Článek v odborném periodiku
Bábek, O. - Kumpan, T. - Calner, M. - Šimíček, D. - Frýda, J. - Holá, M. - Ackerman, Lukáš - Kolková, K.
Redox geochemistry of the red ‘orthoceratite limestone’ of Baltoscandia: Possible linkage to mid-Ordovician palaeoceanographic changes.
Sedimentary geology. Roč. 420, July 2021 (2021), č. článku 105934. ISSN 0037-0738. E-ISSN 1879-0968
Institucionální podpora: RVO:67985831
Klíčová slova: Marine red beds * Early diagenesis * Redox gradients * Laser ablation ICP-MS * Sea-level changes * Carbon isotope geochemistry
Obor OECD: Geology
Impakt faktor: 3.329, rok: 2021
Způsob publikování: Omezený přístup
https://www.sciencedirect.com/science/article/pii/S0037073821000865

The orthoceratite limestone of the Ordovician epicontinental sea of Baltoscandia is one of the oldest Phanerozoicexamples of pelagic marine red beds (MRBs). Being enriched in authigenic haematite, MRBs are considered to besensitive palaeoceanographic redox indicators. In this paper, the origin of the reddening of the Ordovician MRBsand its timing and redox conditions were addressed at two sections, and in a drill core in the Kinnekulle area, Sweden, through the application of diffuse reflectance spectroscopy, sedimentary petrology (microfacies andelectron microprobe), bulk-rock and in-situ element geochemistry (laser-ablation ICP-MS) and molybdenumstable isotope systematics. Enrichment in haematite (up to ~0.05 wt%) occurred during very early diagenesisunder low sedimentation rates (~5 mm/kyr), which is comparable to several examples of Phanerozoic MRBs.The reddening was associated with the mm-scale, in-situ mobility of Fe, Mn, As, Mo and U, due to Fe–Mnredox cycling between primary and secondary minerals and pore water under oxic and suboxic to anoxic condi-tions, it was not related to significant changes in seawater chemistry. Stratigraphic red-to-grey transitions likelycoincided with two mid-Darriwilian global regressions (the so-called Täljsten and at the base of the GullhögenFormation), likely due to the effects of changing sedimentation rates and sub-bottom redox potentials. The Ordo-vician MRBs coincided with a positiveδ13C excursion during the middle Darriwilian, which is different to MRBexamples cited from the Devonian to the Cretaceous age, which frequently coincide with shifts to lower valuesofδ13C. Although MRBs are believed to show a time-specific occurrence in greenhouse or transitionalgreenhouse-to-icehouse climatic modes by several authors, our study suggests that causal links between MRBsand global carbon cycle remain unclear.
Trvalý link: http://hdl.handle.net/11104/0320798