Coring: Sampling sediments from the seafloor

There are many scientists from different fields of research on Oden during Arctic Ocean 2016. One benefit of being on the cruise (except getting to collect your own data, of course), is getting to know them and learning about their work.
We attended a tour in the lab of the sediment coring group. Grace Shephard (geologist and post doc at the University of Oslo) and Luz María Mejía (from Universidad de Oviedo, soon to be post doc at the ETH) analyse the seabed sediment cores we have collected during the trip.

Taking cores from the sediments on the seabed can help researchers understand the (distant) past, how the earth looked like back then and how it became the way it is today. The Arctic Ocean is not well mapped, and samples from this area will help a lot in puzzling together the Earths history. In the seabed samples they can find biogenic material (a mix of organic and inorganic materia, like ancient animals, shells or plants), rocks (that can have been dragged with ice from far away, see photo 2) and other things that can tell researchers a lot about the past environmental conditions.

Several seabed cores are collected at different places during the cruise. The cores are sampled from the seabed with a corer, which is deployed from the aft deck (back) of the ship by a team of crew and technicians. Taking a core can take 3-4 hours depending on water depth and ice conditions. Actually, most of the time is spent just waiting for the corer to reach the seabed and taking it back up, since the water can be quite deep (more than 4000 metres). Taking the sample itself on the seabed only takes a few minutes.

The cores on this trip can be up 12 metres long, and they are quite heavy. As you see from the pictures, the seabed sediments include clay, and everyone who has tried lifting clay knows that it can be heavy. The cores come up in plastic cylinders (if you look at the photos you see the white cylinders), which are split into 1.5 metre long units to make carrying and analysing them easier.

They start processing the cores straight away. They have machines to measure sediment properties including temperature, density and magnetic properties, amongst others. (see photo 1). Some core samples are split length-ways for doing analyses and sampling. The researchers observe the core visually, and sketch and note down what they see (lines, patterns, colors, etc). The cores are sampled with small cubes (photo 2), which are frozen and taken home for further analyses (as Grace and Luz Ma are doing in photo 5).

1: Grace showing how pore water are collected from cores with syringes. 2: Close up of a sampled core which has a pebble in it (an added bonus, according to Grace). The square samples that are taken out for paleo-magnetic analysis can easily be seen.
3: Grace demonstrating to Anders Dahlin (student at Aarhus University) and Jon Bjørnø (PhD candidate at the Norwegian University of Science and Technology) how she is sketching what the core looks like.
4: The colours of the sediments are described using charts to make it less subjective.
5: Luz María and Grace at work, sampling sediment cores.


One thought on “Coring: Sampling sediments from the seafloor

  1. Pingback: Dredging: Dragging along the seabed to collect rocks | Runa Skarbø

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s