End-Cretaceous to middle Eocene events from the Alpine Tethys: Multi-proxy data from a reference section at Kršteňany (Western Carpathians)

Abstract

Early Paleogene events of the Alpine Tethys were considerably upgraded for the Western Carpathians. The Kršteňany KRS-3 core section provides high-resolution data from the Cretaceous-Paleogene (K/Pg) transition to Lutetian/Bartonian boundary. The Upper Cretaceous sequence started from terrestrial red-beds superposed by transgressive sediments with Abathomphalus mayaroensis. The K/Pg transition is inferred in a horizon with reworked Maastrichtian microfossils and earliest Danian species of Globigerinidae. Multiple redeposition with eugubina-rich clasts implies a storm erosion and resuspension of the post K/Pg sequence during P0 - Pα Zones (approx. 300 kyr). The early Danian microfauna was initially impoverished, later enriched by first praemuricids, and after the Latest Danian Event (LDE) diversified to angulate morozovellids, igorinids and fasciculiths. Paleocene bioevents and polarity chrons imply a radiation of planktic foraminifera during transgressive cycles in the late Danian (P1, C28n), Middle Selandian (P3b, C26r/n) and late Thanetian (P4c/P5, C25n/C24r), and vacant P/C zones either in regressive cycles or during unconformities in the early Danian (P1a/C28r), Danian/Selandian transition (P2/P3a, C27r/n) and middle Thanetian (P4b/C25r). The late Thanetian transgression (Th-2) led to replacement of Assilina-rich beds (SBZ 4) by Nummulites-bearing marls (SBZ 5) at the base of Ilerdian (= LFT). The Paleocene – Eocene transition is marked by Acarinina-rich marlstones with densely muricate species (Ac. acarinata) and excursion taxa (Ac. sibaiyaensis, D. araneus), which correspond to the Paleocene-Eocene Thermal Maximum (PETM). This horizon implies a warm-water productivity, eutrophication, humidity and upwelling activity (pteropods, diatoms). The hyperthermal conditions culminated at the beginning of the Early Eocene Climatic Optimum (EECO) with demise of morozovellids, intensification of hydrological cycles and enhanced continental input of siliciclastics, which progressed by accumulation of Ypresian nummulite banks and terminated by pelagic deposition with recovery of hispid morozovellids (E5 – E7 Zones, chron C23n - C22r). The lower Lutetian sequence reveals a post-EECO cooling by predominance of deep-dwelling habitats (subbotinids, turborotaliids, catapsydracids) and appearance of subtile morozovellids (M. gorrondatxensis), earliest globigerinathekids and another marker species of the E7 – E8 Zones (chron 22n - C21r). Late Lutetian warming (LLTM) is indicated by increased plankton productivity of mixed-layer habitats like strongly muricate species of anguloconical acarininids (Ac. topilensis, Ac. medizzai) and gracile species of morozovelloids (M. coronatus). The youngest part of the Kršteňany section belongs to the E11 Zone, indicating prior conditions of Middle Eocene Climatic Optimum (MECO) warming.