A series of ecostratigraphic events across the Langhian/Serravallian boundary in an epicontinental setting: the northern Pannonian Basin

Abstract

The SO-1 core situated in the NE part of the Pannonian Basin represents a parastratotype of the Badenian stage (regional Central Paratethys stage corresponding to the Langhian and Serravallian). A 150-m-thick succession was deposited between ~ 14.2 and 13.5 Ma (dated by the last common occurrence of Helicosphaera waltrans to the last occurrence of Sphenolithus heteromorphus) and spans the Langhian/Serravallian boundary. The section was subdivided into four units: (1) A transgressive carbonate–siliciclastic complex (core depth ~ 150–122 m) deposited in an inner to mid carbonate ramp setting. Carbonate deposition was episodically interrupted by the input of terrigenous phytodetritus as a result of increased precipitation. (2) Tuffaceous siltstone (core depth ~ 122–48 m) corresponding to a sea-level highstand. This unit starts with a Pteropoda immigration event (14.5–14.2 Ma), which could be related to the closing of the Indian-Mediterranean corridor that triggered a change from Indian- to Atlantic-controlled surface circulation in the Mediterranean-Paratethys basin system. An enhanced proportion of high-nutrient markers and a decreased abundance of warm-water plankton might be indicative of eutrophication and cooling of Paratethyan waters at this time. (3) Lowstand sandstone (core depth ~ 48–26 m) indicating stabilization of sea-grass meadows with eutrophic and hypoxic conditions within their root system. A sea-level fall at this time is correlated with the Ser 1 event. (4) A Serravallian transgressive event (core depth ~ 26–5 m) associated with an increase in diversity of benthic assemblages and stabilization of stenohaline assemblages.