Towards an astrochronological framework for the eastern Paratethys Mio–Pliocene sedimentary sequences of the Focşani basin (Romania)

Abstract

A reliable geological timescale for the Neogene sedimentary deposits of the Romanian Carpathian foredeep did not exist so far due to the lack of accurate isotopic datings and straightforward magnetostratigraphic correlations. Here we present a new chronology for the Upper Miocene to Pliocene deposits of the westernmost part of the eastern Paratethys based on high-resolution magnetostratigraphic data from the Focşani basin. The thick and continuous river sections of Putna (2.35 km) and Rîmnicu Sărat (7.32 km) yield excellent magnetostratigraphic results and allow an unambiguous correlation to the polarity timescale for the interval between 7 and 2.5 Ma. The new age control permits the calculation of accumulation rates for each polarity zone, which shows a significant increase at approximately 5.8–6 My. The Upper Miocene to Pliocene sedimentary rocks of the Focşani basin display cyclic alternations of sandy units and finer intervals. The calculated values for the average duration of the observed sedimentary cycles are very close to the average duration of precession (21.7 ky), which indicates that the sedimentary cycles from the eastern Carpathian foredeep deposits are astronomically forced. We show that the usage of the unambiguous time-control offered by magnetic polarity stratigraphy would give a more realistic picture of the processes that have taken place in this tectonically active region.