Expedition 395C: Reykjanes Ridge planktonic foraminifer biostratigraphy and assemblages

Expedition 395C will recover a series of drill cores from the sea bed on a feature known as the Reykjanes Ridge south of Iceland. The cores will consist of volcanic rocks (the so-called 'basement') overlain by sediments which have accumulated over long periods of time. The cores provide a way of studying the North Atlantic Ocean in the geological past. The oldest sediments recovered are expected to be about 35 million years old at which time climate was much warmer and there was very little ice in the northern hemisphere. The project will reconstruct how climatic conditions have changed in the North Atlantic over this long period and also over shorter term changes such as the ice age cycles. Various ideas about the possible influence of the Iceland volcanic hotspot on North Atlantic sea floor geometry and the direction of ocean currents will be tested.

It is necessary to provide accurate age dating for the sedimentary rocks. This specific project is to study a group of fossil plankton known as foraminifers which produce a hard shell made of calcium carbonate which survives on the sea floor. Because the plankton evolve rapidly it is possible to compare the species in any given sediment sample with reference sites elsewhere to determine the approximate age.

Planktonic foraminifers also respond to climate change. For instance, at the present time it appears that some sub-tropical species are moving further north with warmer surface currents. The very latest sediments will be examined to see if this is happening. Cold and warm climate phases in the geological past will be tracked in the same way by documenting the relative abundance of subtropical and polar species.