The Szolnok unit and its probable paleogeographic position

Abstract

In the Szolnok unit, a flysch trough, beneath the Great Hungarian Plain, a more than 1000 m thick clastic sedimentary series has been penetrated by drilling activity in the last few decades. Refering to the non-continous core material this sequence is built up by rhythmic, turbidite-dominated sandstones and shales. Earlier, the flysch series was thought to have been continuously deposited during the Cretaceous and the Paleogene. The detailed study of the available drilling cores proved that only a few Late Cretaceous and Paleogene nannoplankton zones are present in the sequence and there is no positive evidence for the others. Evidence was found for the presence of Campanian-early Maastrichtian, latest Paleocene-Early Eocene, Middle Eocene (Bartonian) and early Priabonian, as well as for most Oligocene nannoplankton zones. The Szolnok unit is thrust and folded into imbricated structures. Micropaleontological investigations suggest evidence for post-Oligocene compressional deformation. This non-continuous stratigraphic built up of the Szolnok sedimentary sequence suggests that it can be correlated with some of the Central (“Inner”) Carpathian flysches and strata correlation with the Outer Carpathian flysch units can be excluded. Taking into account all the lithological and paleontological features of the Szolnok unit succession a gradual change of the depositional environment is proposed from deep-water pelagic to shallower environment during the time of its formation.