unizeit Schriftzug

Kiel nuclear research

An international expedition has pulled drill cores from the seabed of the Gulf of Corinth. Two young female scientists from the CAU are participating in the evaluation. They are being offered insights into the climate and landscape history of the region.

A woman and a machine.
© GSHDL

Joana Seguin equips the X-ray fluorescence scanner with a piece of drill core in order to analyse its chemical composition and draw conclusions about climate history.

The sediment deposits in lakes and seas are archives of a special kind. If you can "read" them, they tell you whether thousands of years ago the waters around the lakes and seas were dry or wet, warm or cold, wooded or grassy, and whether the waters already existed at all. The Gulf of Corinth is particularly interesting because it is located in one of the most seismically active areas in Europe: due to plate movements, it grows by about 15 millimetres per year, which is also reflected in its sediments.

It is this tectonic rift formation, but also other processes such as climate and landscape development, that the members of the "Corinth Active Rift Development" expedition of the International Oceanographic Discovery Programme IODP are interested in. Within the framework of the European Marine Research Drilling Consortium ECORD, the special ship "Fugro Synergy" was deployed in the Gulf of Corinth at the end of 2017 and extracted drill cores from the seabed at three different locations at depths of up to 750 metres. The Kiel doctoral students Aslı Oflaz and Joana Seguin successfully applied to participate in the evaluation of the cores. As members of an international team, they were present in Bremen when the cores were opened.

"Other participants came specially from Australia or the USA, so we had a comparatively short journey", explains Joana Seguin. The geographer is writing her doctoral thesis in the Collaborative Research Center 1266 "Transformational Dimensions" and, like the geoengineer Aslı Oflaz, is a member of the Graduate School Human Development in Landscapes. "We didn't celebrate at the so-called Onshore Science Party in Bremen, however, but worked on the cores in two shifts throughout February", Oflaz reports. The approximately three metre long and six centimetre thick sections of the cores were first cut in half lengthwise. One half went into the archive for later comparative samples, the other half was allowed to be "slaughtered" for the investigations, as it is called in scientific jargon.

"The more different methods lead to the same finding, the more likely it is that the result is correct."

Thus Aslı Oflaz set out to search for traces of foraminifera in the chronologically stratified sediment. These are unicellular aquatic creatures whose calcareous shell can be preserved over millions of years. "If the water in their environment was cold, the foraminifera shells exhibit a different ratio of different oxygen isotopes than at warmer temperatures", explains the geoscientist.

In her doctoral thesis, she reconstructs the climate history of the Holocene, i.e. the current period of the earth's history since the end of the Ice Age about 11,700 years ago, for various regions of the eastern Mediterranean. "In particular, I focus on the occurrence and extent of drought phases in the Middle and Late Holocene as well as their effects on vegetation and human societies", says Oflaz. "What's great is that we, as members of the Onshore Science Party, are allowed to use the data of the other participants before it is available to the entire scientific community in a year's time."

Joana Seguin is particularly interested in aspects of climate change in Greece in the late Holocene. In order to trace changes in a larger area, she examines cores from the Gulf of Corinth as well as cores from surrounding lakes. For her doctoral thesis, Seguin focuses on analyses using X-ray fluorescence scanners, which provide information on the chemical composition of the drill cores. Fluctuating manganese and iron concentrations, for example, indicate changes in the pH content of the water, which in turn can serve as an indicator of rather dry or rather moist phases in the catchment area of the water body under investigation. During the core sampling in Bremen, Joana Seguin was also employed as an organic geochemist to examine the solid material of the drill cores as well as the pore water between the individual sediment particles. "The more different methods lead to the same finding, the more likely it is that the result is correct", says Seguin.

Author: Jirka Niklas Menke