IODP-expedition 381, site 79A. Palaeoceanographic evolution of the Corinth gulf during the MIS5, based on the downhole distribution of foraminiferal assemblages
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Αντωνίου, Δήμητρα
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Abstract
As an early continental rift with high strain rates, the Gulf of Corinth has mainly attracted many geoscientists due to its preservation of the synrift succession both onshore and offshore. This feature was recognized by the International Ocean Discovery Program (IODP) when marine scientists proposed Corinth Gulf as a study area in European Consortium for Ocean Research Drilling during the program “Exploring the Earth under the sea”. One of the expedition objectives was the generation of a new high-resolution record of the Quaternary paleoclimate. Throughout this expedition three different sites (Site M0078, M0079, M0080) in the Corinth Gulf were drilled, cored and logged. After this phase, the holes were submitted to many and different methods and techniques whereby new data and information for lithostratigraphy, structural geology, geochemistry and micropaleontology of the sediments were arisen. Regarding the micropaleontology, preliminary results of the holes showed that there were temporal intervals when Gulf of Corinth was connected with the open sea and isolated from it.
To reinforce the previous results, in the terms of the master thesis, 58 sediment samples from hole M0079 studied in 125μm and 63μm fractions for the existence of planktonic and benthic foraminifers. The present master thesis aims to study the environmental conditions which contributed to the formation of Corinth Gulf throughout the SU3 deposition (149.2-183.87 mbsf; meter below sea floor) and the upper part of SU4 (186.37-201.01 mbsf). The distribution of foraminifers during the deposition of SU3 sediments shows a high variety and quantity of planktonic and benthic foraminifers with the former be more abundant. Below SU3, foraminifers are significantly decreased. These results in conjunction with the curves of global sea-level fluctuations signify that during SU3 deposition the distribution of planktonic foraminifers along the hole coincides with the substages of Marine Isotope Stage 5 (5a, b, c, d, e) when the rift was connected with the open sea. Finally, the transition from the SU3 to SU4 is characterized by the rapid depletion of foraminifers indicating the onset of MIS 6 when the rift was an isolated/semi-isolated environment.
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Foraminifers, Corinth gulf, MIS5, Marine phase, Isolated/semi-isolated, Tephra, IODP-381, Palaeoevironment