Paleomagnetic and chronostratigraphic constraints on the middle to late miocene evolution of the transylvanian basin (Romania): Implications for central paratethys stratigraphy and emplacement of the tisza-dacia plate

Arjan De Leeuw*, Sorin Filipescu, Liviu Maţenco, Wout Krijgsman, Klaudia Kuiper, Marius Stoica

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

From the Oligocene onwards, the complex tectonic evolution of the Africa-Eurasia collision zone led to paleogeographic and biogeographic differentiation of theMediterranean and Paratethys, two almost land-locked seas, in the area formerly occupied by the western Tethys Ocean. Episodic isolation of the basins triggered strong faunal endemism leading to the introduction of regional stratigraphic stages for the Paratethys. Chronostratigraphic control on the Paratethys stages remains rudimentary compared to the cyclostratigraphically constrained Mediterranean stages. This lack of chronostratigraphic control restricts the insight in the timing of geodynamic, climatic, and paleobiogeographic events and thereby hinders the identification of their causes and effects. In this paper, we here derive better age constraints on the Badenian, Sarmatian and Pannonian Central Paratethys regional stages through integrated 40Ar/39Ar,magnetostratigraphic, and biostratigraphic research in the Transylvanian Basin. The obtained results help to clarify the regionsMiddleMiocene geodynamic and paleobiogeographic evolution. Six new 40Ar/39Ar ages were determined for tuffs intercalating with the generally deep marine basin infill. Together with data fromprevious studies, there is now a total of 9 radio-isotopically dated horizons in the basin. Thesewere traced along seismic lines into a synthetic seismic stratigraphic column in the basin center and serve as first order tie-points to the astronomically tuned Neogene timescale (ATNTS). Paleomagnetically investigated sections were treated similarly and their polarity in general corroborates the 40Ar/39Ar results. The integrated radio-isotopic and magnetostratigraphic results provide an improved high-resolution time-frame for the sedimentary infill of the Transylvanian Basin. Early Badenian deepwater sedimentation is characterized by accumulation of theDej Tuff Complex in response to a period of intensive volcanism, the onset ofwhich is constrained between the first occurrence (FO) of Orbulina suturalis at 14.56 Ma and 14.38±0.06 Ma. During the subsequent Badenian Salinity Crisis (BSC) up to 300 mof salt accumulate in the basin center. The faunal turnover thatmarks the Badenian-Sarmatian Boundary is dated at 12.80±0.05 Ma. A second phase of intense volcanism occurs at 12.4 Maand leads to deposition of themiddle Sarmatian tuff complex (Ghiriş, Hǎdǎreni, Turda and Câmpia Turzii tuffs). Rates of sediment accumulation strongly diminish in the basin center at the onset of the Pannonian stage coincidentwith an approximately 20° CWtectonic rotation of the Tisza-Dacia plate. Concurrent enhanced uplift in the Eastern a'nd Southern Carpathians leads to the isolation of the Central Paratethys and triggers the transition from marine to freshwater conditions. An additional Pannonian to post-Pannonian 6° of CW rotation is related to the creation of antiform geometries in the Eastern Carpathians which are notably larger in the north than in the south. An 8.4 Ma age is determined for the uppermost Pannonian sediments preserved in the central part of the Transylvanian Basin. Two sections belonging to middle Pannonian Zone D, and the lower part of Zone E (Subzone E1) are found to cover the 10.6-9.9 Ma time-interval.

Original languageEnglish
Pages (from-to)82-98
Number of pages17
JournalGlobal and Planetary Change
Volume103
Issue number1
DOIs
Publication statusPublished - 2013

Keywords

  • Chronostratigraphy
  • Environmental change
  • Magnetostratigraphy
  • Miocene
  • Paleomagnetism
  • Paratethys
  • Sedimentary history
  • Tectonic rotation
  • Transylvanian basin

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