THE MERCURY CONCENTRATIONS AND BIOCHRONOLOGY OF BOUNDARY EVENTS ACROSS THE CRETACEOUS-PALEOGENE TRANSITION IN SLOVAKIA

The end-Cretaceous mass extinction at the Cretaceous-Paleogene boundary (KPB) is often explained by Chicxulub bolide impact event and/or Deccan trap volcanism. We studied a drilled KPB sequence close to the Žilina city (Slovakia). The Žilina (ZA1) drill core, 75 m long, is located in Western Carpathians transitional sequence of Upper Cretaceous and Paleogene sediments. The micropaleontological research of the ZA1 drill core provides a stratigraphic data ranging from the Late Maastrichtian to Early Ypressian. The light grey Maastrichtian marlstones with rich globotruncanid and heterohelicid microfauna, and the dark grey bioturbated marlstones at the KPB, are preserved. Post KPB formation is impoverished in microfauna (disaster species like Guembelitria, Globoconusa). Marlstones of Lower Danian formations are rich in recovered planktic foraminifers like Parasubbotina, Eoglobigerina and Praemurica. Middle Paleocene formation varies in appearance of large-sized morozovellids, igorinids and globanonalinids.

Mercury enrichments in sediments have been documented across many mass extinction events as well as KPB event (Keller et al., 2020). For the ZA1 Maastrichtian sequence is characteristic high variability in mercury concentrations, exceeding 104 ppb 40 cm prior the KPB. Danian sedimentary sequence provides also wide range of Hg concentrations (from 12 to 111 ppb) with highest value close to end of the P1 biozone. From Selandian to Ypresian, the Hg concentrations show lower and more stable range of values (up to 58 ppb) without any distinct elevations in the late Paleocene. Total Organic Carbon (TOC) concentrations carry lower values in the Maastrichtian (from 0.29% to 0.57%) in comparison to the Paleogene (from 0.57% to 1.58%). Even though the Maastrichtian part of the ZA1 shows lower TOC values, the Hg concentrations are elevated and Deccan volcanic activity could be the explanation for origin of the Hg in the Maastrichtian part of the ZA1 drill core.

The research is supported by grant VEGA 2/0013/20, project APVV-20-0079 and Czech Science Foundation project no. 19-07516S is in accordance with research plan no. RVO67985831.

Keller, G. et al. (2020): Mercury linked to Deccan Traps volcanism, climate change and the end-Cretaceous mass extinction. Glogal and Planetary Change, 194, 103312.