Mercury occurrence in basal and top Cretaceous boundary intervals of Carpathian sedimentary sequences
Abstrakt
At least since the past decade, mercury (Hg) chemostratigraphy has been increasingly used as a potential proxy for volcanism in the geological record (e.g., Grasby et al. 2019). While poor or no evidence of extensive volcanic activity was provided for the Jurassic-Cretaceous (J/K) boundary, the timing of the Deccan traps with its Hg signal was set around the Cretaceous-Paleogene (K/Pg) boundary.
Data on Hg concentrations collected from several J/K and K/Pg boundary sections in the Carpathians were correlated with other stratigraphical methods (e.g., magnetostratigraphy, biostratigraphy). At the J/K boundary, comprehensively studied sections such as Kurovice (Czech Republic), Sněžnica (Slovakia), Velykyi Kamianets (Ukraine) and newly investigated sections such as Ropice (Czech Republic) and Goleszów (Poland) cover a wide range of lithologies, as well as different depositional environments with wide palaeobathymetric settings.
Compared to J/K boundary sections, K/Pg boundary sections at Uzgruň (Czech Republic), Bukovec (Czech Republic) and drill core ZA1 (Slovakia) are at most only weakly calcareous. Usually, organic matter, sulphides or clay minerals are listed as the main sedimentary host phase of Hg in such rocks (Shen et al. 2020).
Thus, correlations between total organic carbon, total sulphur and aluminium contents were determined in order to identify anomalous Hg values. Hg contents vary from 0.2 ng/g to 92.8 ng/g in J/K sections and from 4.4 ng/g to 221.1 ng/g in K/Pg sections.
Current research aims to identify differences in Hg deposition during the period of fairly low volcanic emission (J/K) to extensive volcanic emission (K/Pg), as well as to characterise the sedimentary host phase of Hg in various depositional environments. The present research is supported by the Czech Science Foundation, projects nos. 20-10035S and 19-07516S, and is in accordance with research plan no.
RVO67985831. The research was also funded by projects APVV20-0079 and VEGA/0013/20 (to JM, DR, JS).
REFERENCES Grasby, S.E., Them, T.R., Chen, Z., Yin, R. and Ardakani, O.H. 2019. Mercury as a proxy for volcanic emissions in the geologic record.
Earth-Science Reviews, 196, 102880. https://doi. org/10.1016/j.earscirev.2019.102880 Shen, J., Feng, Q., Algeo, T.J., Liu, J., Zhou, C., Wei, W., Liu, J., Them, T.R., Gill, B.C. and Chen, J. 2020. Sedimentary host phases of mercury (Hg) and implications for use of Hg as a volcanic proxy.
Earth and Planetary Science Letters, 543, 116333. https://doi.org/10.1016/j. epsl.2020.116333