Reconstruction of the unusual Middle Miocene (Badenian) paleoenvironment of the Carpathian Foredeep (Lomnice/Tišnov denudational relict, Czech Republic)
Abstract
Multiproxy sedimentological, gamma-spectrometric, foraminiferal, calcareous nannoplankton, and otolith data were used for the reconstruction of the Badenian (Middle Miocene) history of the Moravian part of the Carpathian Foredeep. The study material originated from the new borehole LOM-1, which drilled >20 metres of monotonous clayey siltstones with exceptionally rich and well-preserved microfossil assemblages.
Distal parts of the Carpathian Foredeep (a forebulge depozone) are exposed in this succession. Generally, a quiet environment of outer shelf to upper bathyal of monotonous clayey silts was interpreted, which is typical for the proximal parts of a peripheral foreland basin.
The section studied can be subdivided into six intervals, confirming the cyclical character of Middle Miocene sedimentation in the Central Paratethys. Interannual oscillations of nutrient content, temperature and/or salinity are interpreted based on the oscillations of geochemical as well as palaeobiological data.
The turn over connected with the initiation of the Middle Miocene Climatic Transition is recorded above the LO (last oc currence) of Helicosphaera waltrans in agreement with previous observations in the Carpathian Foredeep. The changes include cooling, a decrease in nutrients, a probable increase of the salinity of surface water, and increase of seasonality.
Seasonality was man i fested by an alternation of mixed and stratified water columns with a seasonal in put of nutrients. Concerning nutrients, sources of sea sonal riverine in put or sea sonal upwelling are both possible.