Comment on 'Decadal to millennial variations in water column parameters in pelagic marine environments of the Western Tethys (Carpathian realm) during Middle-Late Jurassic - Evidence from the radiolarian record' by M. Bak, K. Bak and M. Michalik

摘要

Bak (et al. (2018) presented a model of global palaeoclimatic changes during the Bajocian-Oxfordian based on an analysis of millimetre-thick microlaminae in the radiolarian-bearing deposits of the Fatricum Domain exposed in the Filipka Valley in the Tatra Mountains, southern Poland. The authors claim that changes in microfacies and microfossil assemblages recorded in such microlaminae are a proxy for climatic changes and for decadal- to millennial-scale fluctuations of nutrient level in the upper water column. Major shortcomings of this study include: (1) a sparse and poorly documented field database; (2) ignoring of the potential effects of sediment bioturbation; (3) over-interpretation of radiolarian abundances and incorrect taxonomical determination of some microfossils; (4) imprecise stratigraphic framework, unsuitable for a high-resolution modelling of oceanic circulation and climatic changes; (5) improperly calculated duration of hypothetical cycles with a formidably high resolution; and (6) non-objective selecting of references. This comment is a cautionary warning against an uncritical use of the model presented in the disputed paper.