A small but nevertheless very important piece of the puzzle in the study of climatic reconstruction of the early history of the earth is Sven Kretschmer's project with his working group from the Alfred Wegener Institute in Bremerhaven. His scientific instruments include the Schwerelot and the multicorer. During the whole of this expedition ANTXXIII/9, it is these drilling instruments that make the ocean floor core drilling project possible. The exact positioning is determined by parasounding equipment.

The concentration of thorium 230 in sediment is particularly interesting to geochemists. This radioactive element is a disintegration product, and in water it is extremely insoluble, so it binds immediately to single minerals or other organic particles. In this way, thorium 230 builds up as a component of the sea floor and can give information about the transport of the sediment in relation to the Earth's history. To be able to make conclusions about just how much material is being deposited at different sites in the ocean, this type of research is critical. The information obtained makes it possible to reconstruct earlier environmental conditions.


Sediment samples in the centrifuge.

The 29 year-old scientist will apply the thorium method later in his laboratory in Bremerhaven, and determine just how widely the informatively rich sediments on the sea floor are distributed. Sven explains that smaller and lighter sediment particles are more easily transported over the sea floor than heavier material. Particle sizes differ, and these can be studied separately by sieving for size. Back in Germany, the research work will begin in earnest. The many samples will most probably provide a rich trove of scientific information that will help the working group find answers to many geochemical questions.


Sven Kretschmer decanting seawater.


Wet sieving in the sediment sieve.


Sediments after the particle size separation

Text and photos: Lars Focke