Pages: 411 - 424
Abstract: A quantitative analysis of benthic foraminifera was carried out on a scientific core from the type locality of the Paratethyan stage Badenian (Middle Miocene) and results were compared to stable isotopes (δ18O and δ13C) and magnetic susceptibility. Two approaches were applied to reconstruct the paleoenvironment. First, several indices (inbenthics %, oxyphylic %, foraminiferal numbers, diversity) and paleodepth proxies were calculated, second, multivariate statistics (Detrended Correspondence Analysis, cluster analyses combined with the indicator value method) were carried out. High correlations between environmental indices and core-depth manifest some trends. Five biofacies units were recognized, and the lowermost unit I encompasses a laminated interval coinciding with a biofacies subunit. The most indicative and abundant species is Uvigerina semiornata, a dysoxy tolerant inbenthic. The following unit II can be characterized as a stable period of improved oxygenation and lowered nutrient supply. Unit III is distinguished by Trifarina angulosa preferring well-aerated turbulent bottom water and sandy substrate, while accompanied by some low salinity tolerant species. A non-stratified water column with high terrigenous input is accepted for this unit. Unit IV is characterized by low diversities and the deep inbenthic indicator species Bulimina elongata, Fursenkoina acuta, tolerant of oxygen deficiency and benefiting from unlimited food supply in a well-stratified sea. The high foraminiferal numbers are the consequence of low terrigenous input not diluting the highly productive opportunistic species in the sediment. The indicator species of unit V, the reticulate Bolivina viennensis, has ecological needs similar to the previous unit. Environmental changes from unit IV to V are the increased terrigenous input and oscillation, indicating less stable conditions. The biofacies unit boundaries always coincide with major shifts of the isotope and susceptibility record. It is concluded, that the physical environmental parameters controlling benthic foraminiferal distribution are primarily influenced by proximity to land.
Keywords: Middle Miocene, Paratethys, Vienna Basin, statistics, paleowater proxy, benthic foraminifera, Badenian stratotypeDownload PDF document Show Text Version