Go with the (core) flow

Howdy folks,

We’ve arrived at our next Site, U1444 in the Bay of Bengal!

Indian Ocean map3

It’s not quite where we were originally planning to be coring, but as Steve said in the last post, nothing ever completely goes to plan at sea and you’ve got to be prepared to be flexible. Looking forward to having more core on deck soon, regardless of the location!

We arrived at 07.30 this morning (while I was still fast asleep), thrusters are down and we’re tripping (lowering) pipe to the seafloor now. We’re in 3000 m of water out here, so the first core on the floor is not anticipated until around 7 pm this evening…

So this seems like a good moment to explain what we call “core flow” to you all. Basically this is the order in which measurements and descriptions are taken from the core as it moves through the core lab – our specialist deck on the JR for handling the precious mud. [We will hear more about the various specialties, like “phys props”, “sedimentology”, “geochem” etc., and the people on board who do these jobs in later “meet the scientist” posts].

CORE FLOW: A beginner’s guide:

  1. After the drill pipe is lowered all the way to the sea floor at the bottom of the ocean, the core is cut from the sediment pile (this is the steel-straw pushing into the mud, if you recall). The mud gets pushed up inside a plastic core liner inside the pipe, which is then pulled all the way back to the surface 3+ km above with a really strong wire. The 9.6 m-long core liner full of precious oozes is then received on the drill floor, before being carried to the “catwalk” where the curator (Chad) and technicians (Chieh, Heather, Colin, Maggie, Aaron etc…) cut the core into more manageable 1.5 m sections. Everything is very carefully labeled using triple-redundancy pens, stickers and laser engraving – the order of the core sections is super-important!

exp353_028

  1. While the cores are still on the catwalk, the “core-catcher” (the sample at the bottom of each 9.6 m core) is sampled and given to the biostratigraphers so they can get to work straight away. They will look at the micro- and nanno- (really tiny!) fossils in the mud, which can tell us how old the oozes are and how deep the seawater was when it was deposited. At the same time our microbiologist John takes some samples and wraps them up tightly in sterile containers (and freezes them) so he can search for cool “deep-biosphere” bugs later. The geochemists also take a few “whole round” samples from the cores, which they will then squeeze in the lab downstairs to sample the “pore waters” that exist within the sediment pile. The leftover bits of mud from this are called “squeeze cakes”, which I rather like. Nom nom nom.

microbiology sampling

  1. The core sections are then given over to the physical properties team (or “phys props”) whose job it is to scan the cores for a variety of parameters like magnetic susceptibility (how magnetic are the minerals in the mud), p-wave (how dense is the mud), gamma ray (how radioactive is the mud (don’t panic, the answer is always “not very at all”- You get more radiation from spending 15 minutes near the Cornish Granites!)).
  1. After scanning, the cores are left to “equilibrate” for a few hours – this means they have time to come up to room temperature (it’s cold down there and warm up here) and do any expanding they are planning on doing (there’s a lot of pressure at the bottom of the sea, and not much up here, so sometimes the cores get bigger while they’re sitting in the lab!). After equilibration, the cores are split in half lengthways using a piano wire – truly high tech stuff. Now we have two halves – the “working half” which people are allowed to take samples from, and the “archive half” which is to be left untouched for future reference. Some extra samples are taken from the working half for geochemistry measurements before it’s put away for the rest of the cruise.

Liping

  1. The sedimentologists now get their grubby hands on the archive half of the cores and can begin the exciting job of describing them. What color are they? (hint they are not always creamy-white like in the photo above!). What are they made of? How big are the grains? Can we see any structures or macrofossils? All of this info is carefully written down in the database so we can make beautiful diagrams and plots of the sediment characteristics later on, while we try to figure out what’s going on.
  1. Last to get the cores are the Paleomagnetists (or “paleo-magicians” as we affectionately call them). These guys measure the ancient magnetic field direction and strength preserved in the magnetic minerals in the mud, which can be really useful for telling where we are in time. [This is pretty complicated, so we’ll let one of the magicians explain it themselves in a later post].
  1. After all this, the cores are boxed up and put in the reefer (the big fridge at the very bottom of the ship), where they will stay until they are unloaded again in Singapore at the end of the expedition, ready to be shipped to our IODP Indian Ocean repository in Kochi, Japan. In about 4 months time, we will all meet up again in Kochi and take our personal samples to do further experiments on the mud – one of the perks of sailing is that you get a 1-year head start on everyone else to do some science on the cores from your expedition, before they are opened up to the whole scientific community. Tick tock…

So that’s about it for core flow. T-minus 4 hours to next core on the floor, so I’d better get back to work!

Next update: meet the (super awesome) sedimentologists…

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