Sampling Tasman Sea Sediment Cores

Adriane here-

One of the rooms in the College Station, TX core repository. Cores are stacked from the floor to the ceiling. The cores that are loaded onto the carts are waiting to be sampled. Cores that were drilled in the 1960’s as recently as this year are stored in this facility!

Back in January, I was in College Station, Texas on a trip related to the scientific ocean drilling expedition I was on last summer (see my previous posts about ship life and my responsibilities on the ship as a biostratigrapher). Part of the trip was dedicated to editing the scientific reports we wrote while sailing in the Tasman Sea, and the other part of the trip was spent taking samples from the sediment cores we drilled.

While we were sailing in the Tasman Sea, our expedition drilled a total of 6 sites: some in shallow waters in the northern part of the Tasman, and some in deeper waters towards the southern end of the sea. In total, we recovered 2506.4 meters of sediment (8223 feet, or 1.55 miles) in 410 cores.

The cores were first shipped to College Station, Texas from the port in Hobart, Tasmania. Eventually, they will all be stored at the core repository in Kochi, Japan. While they were in Texas, several of the scientists from the expedition met up to take samples from the cores for their own research into Earth’s climate in geologic time.

Here, we are taking samples from sediments that are more firm. We’re using 10 cubic centimeter (cc) plastic scoops, which is one of the standard sample sizes for paleoceanographic studies.

I requested samples from two of the six sites we drilled in the Tasman Sea. All of my samples are younger than about 18 million years old, in the period of geologic time called the Neogene. All in all, I requested about 800 sediment samples! Not all of these samples will be used for one project. Instead, they will be used in several different projects, such as to determine evolutionary events of planktic foraminifera in the Tasman Sea and investigate changes in sea surface temperatures during major climate change events of the past.

Another team of researchers working on an older section of a core. In general, the older (deeper below the seafloor) the sediments, the harder and more compacted they are. The sediments in this core are so compacted, we had to use hammers and chisels to get out samples.

To begin sampling, students who work at the College Station core respository set up cores at each workstation. There were 6 workstations: one for each site that we drilled. A team of 3-4 scientists were assigned to each station to sample the cores. We had approximately 1 week to take ~14,000 samples! Luckily, I was able to sample one of the cores from which I requested samples from!

Every workstation had all the materials that we need to sample: gloves, paper towels, various tools (small and large spatulas, rubber hammers, and various sizes of plastic scoops). In addition, each station was also given a list of all the samples every researcher had requested for a specific site. This way, we could cross the samples off the list as we took and bagged them.

My team, which consisted of two other scientists that I sailed with, Yu-Hyeon and May, began sampling the youngest part of our assigned site. Because these sediments were located right at or below the seafloor, they were very soupy! As we moved through the cores (back into time), the sediments became less soupy, and eventually pretty hard. We never encountered sediments that were so hard we had to use a hammer and chisel to get out the samples, but other teams did.

From left to right: Yu-Hyeon, May, and I holding up one of our cores from the Tasman Sea.

After scooping/hammering out the samples, we then put the samples into a small plastic bag. These bags were then labeled with a sticker with information that includes what site the samples came from, the core from which is came from, the specific section in the core, and the two-centimeter interval in that section. This way, the scientists know exactly at what depth (meters below sea floor) the sample came from. It is crucial to know the depth at what each sample was taken, as depth will be later converted to age using various methods (for one using fossils as a proxy for age, see my post about biostratigraphy)

Because the sediments my team and I sampled in were so soft, and we had requested a lot of samples from the core we were working with, we were able to quickly take a lot of samples! I could only stay and sample for two days (I had to fly back to UMass to teach), but in that time, my team and I took so many samples, we broke a record! We currently hold the record for most sediment samples taken in one day at the Gulf Coast Repository in College Station!






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