DiscussionComment on “Relative bathymetric position of opoka and chalk in the Late Cretaceous European Basin” by M. Machalski and O. Malchyk [Cretaceous Res. 102 (2019) 30–36]
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Acknowledgements
I thank all the reviewers for their critical comments and useful suggestions to improve an earlier version of the manuscript. The work is performed according to the Russian Government Program of Competitive Growth of Kazan Federal University. The work was supported by the Ministry of Science and High Education of the Russian Federation contract No. 14.Y26.31.0029 in the framework of the Resolution No.220 of the Government of the Russian Federation.
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Evolution of Late Cretaceous Si cycling reflected in the formation of siliceous nodules (flints and cherts)
2020, Global and Planetary ChangeCitation Excerpt :However, a hydrothermal/volcanic origin of DSi for the Late Cretaceous siliceous nodules and their abiotic precipitation has not been widely accepted due to a lack of direct evidence (e.g. glass shards, ash, etc.) and geochemical signals enabling the identification of the volcanic/hydrothermal origin. With the increasing distance of magmatic sources, the products of volcanic eruptions are completely dissolved, and since the associations of opal-CT, clinoptilolite, and authigenic clays are no longer indicators (Jurkowska et al., 2019b) of ‘camouflaged pyroclastics’ (but see Zorina et al., 2018; Zorina, 2020 for a contrasting opinion; see also Machalski and Machlyk, 2020) only detailed microtextural studies of silica polymorphs can yet reveal the origin of DSi (Jurkowska et al., 2019b). These are similar to geochemical signals, which can be weakened during long periods of transport (Vogt, 1989).