Temperature and isotopic composition of seawater in the epicontinental sea (Central Paratethys) during the Middle Miocene Climate Transition based on Mg/Ca, delta O-18 and delta C-13 from foraminiferal tests
Abstrakt
Details regarding seawater temperature and isotopic composition of seawater in the Central Paratethys, during the Miocene epoch, are not well known. Here we present an insight based on results from a combination of Mg/Ca, delta O-18 and delta C-13 on foraminifera from the shallow core (LOM-1) representing the time interval of similar to 14.4 to 14.36 Ma.
Globigerinoides trilobus, Globigerina bulloides, Cibicidoides spp. and Melonis pompiliaides were chosen for analysis due to their variable ecological preferences within the water column and on the sea floor. We assessed problems concerning diagenetic alteration of foraminiferal calcite by using a single test approach when analysing delta O-18 and delta C-13.
Paleotemperature ranges turned out to be comparable with modern subtropical regions with no cooling trend as was expected at this period following the Middle Miocene Climatic Optimum. However, we find an interesting offset between the benthic species temperature response that is likely related to the different life-strategies of those species.
Based on a combination of mentioned proxies it was possible to partly reconstruct delta O-18(seawater) for the studied locality and compare it with Mg/Ca derived temperature to obtain a possible correlation between temperature and salinity. We also investigated differences in surface and bottom water hydrography in comparison with the Mediterranean, and distinguish their different hydrographies.
In addition, it was possible to identify dissimilar origins of surface and bottom water masses based on comparison of their isotopic composition.