Paleoecology of benthic foraminifera of the Baden-Sooss section (Badenian, Middle Miocene, Vienna Basin, Austria)

摘要

A quantitative analysis of benthic foraminifera was carried out on a scientific core from the type locality of theParatethyan stage Badenian (Middle Miocene) and results were compared to stable isotopes (5180 and 813C) and magneticsusceptibility. 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. Highcorrelations 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 andabundant species is Uvigerina semiornata, a dysoxy tolerant inbenthic. The following unit II can be characterized as astable period of improved oxygenation and lowered nutrient supply. Unit III is distinguished by Trifarina angulosa pre-ferring 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 lowdiversities and the deep inbenthic indicator species Bulimina elongata, Fursenkoina acuta, tolerant of oxygen deficiencyand benefiting from unlimited food supply in a well-stratified sea. The high foraminiferal numbers are the consequence oflow 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 IVto V are the increased terrigenous input and oscillation, indicating less stable conditions. The biofacies unit boundariesalways coincide with major shifts of the isotope and susceptibility record. It is concluded, that the physical environmentalparameters controlling benthic foraminiferal distribution are primarily influenced by proximity to land.