Response of benthic foraminiferal communities to changes in productivity and watermass conditions in the epicontinental Paratethys during the middle Miocene
Abstrakt
The Langhian epicontinental sea - the Central Paratethys - represented a dynamic environment experiencing many changes, making it an ideal system for testing various geochemical proxies. Here we present a result of a study based on a combination of organic geochemistry (delta C-13(org), n-alkane based indices; TOC/TIC) with benthic foraminiferal stable isotopic (delta C-13; delta O-18) and paleoecological data from the time interval of similar to 14.4 to 14.36 Ma.
Moreover, we evaluated foraminiferal paleoecological data (selected species: Melonis pompilioides; Gyroidinoides spp.; Cibicidoides spp.) together with the delta C-13 and delta O-18 to interpret the paleoecological consequences at the seafloor. Doing so we assessed the problematics regarding the origin of the organic matter together with changes in productivity and subsequent reaction of benthic foraminiferal assemblages at the seafloor.
We used the delta C-13(org) TOC/TIC and the n-alkane based indices to estimate the primary production rate and to determine the origin of the organic matter at the studied locality. The reconstructed paleoenvironment represented an open marine realm without significant freshwater influence, where the primary productivity was generated by marine algae.
A gradual decrease of productivity could be observed, linked with shallowing of the basin towards a more carbonate-dominated environment. Changes in nutrient flux and vertical migration of the less oxygenated zone turned out to be the main phenomena responsible for physicochemical and paleoecological changes in the foraminiferal communities within the sediment.
In addition we tried to characterize the population dynamics of the studied benthic foraminiferal species under a variety of existing conditions at the seafloor.