Vegetation and climate record across the Carnian Pluvial episode from the Transdanubian Range, Hungary, Western Tethys

Abstract

The Carnian Pluvial Episode (CPE) is one of the most extensively studied Triassic hyperthermal events that triggered biological turnovers both on land and in the marine realm. From a palynological perspective, the CPE is marked by a notable increase in the hygrophytic spore-pollen assemblages compared to the early Late Triassic. In the Transdanubian Range (Western Hungary), Carnian mixed clastic‑carbonate successions indicate a relatively wetter climate and elevated terrestrial input into the basins during the CPE. The quantitative and qualitative palynological data from three borehole successions provided insight into the Julian and early Tuvalian vegetation history of the study area. The new palynostratigraphical data refined the age constraints of the CPE deposits spanning from the late Julian to early Tuvalian correlated to the Duplicisporites continuus zone from the Alpine Realm. Palynological marker taxa characteristic for the middle to late Tuvalian were absent, confirming that the well-documented hiatus between the CPE deposits and the Main Dolomite extends over large parts of the Tuvalian. A complex interplay between regional and global processes influenced the palynological assemblages that responded to both eustatic sea-level changes and climatic fluctuations. The climate change in the Julian 2 was not uniform and seemingly expressed in the palynofloras of the Transdanubian Range with a delay due to transgression, as the palynological assemblage were still predominantly characterized by xerophytic conifer pollen in the pelagic depositional site in the early CPE phase, and even they might point to highly seasonal climate at the onset of the event inferred from the proliferation of the Enzonalasporites group. Hygrophytic vegetation elements such as spores and cycad-bennettite pollen peaked only in the late Julian 2. Variations in the relative abundance of spores, cycad-bennettite pollen and marine palynomorphs showed the combined effects of local sea-level changes and humid climatic episodes in controlling terrestrial influx from the latest Julian 2–Tuvalian onwards. The palynofloras point to aridification from later in the early Tuvalian, indicating the waning of the pluvial phase.