Let’s Split

This entry is written by Debbie Thomas, co-chief scientist of Expedition 378. It comes from her Expedition 378 Odyssey blog, which can be found here.

Each whole-round core section is divided lengthwise into two halves – the working half, from which discrete samples are removed for analyses of all sorts, and the archive half, which is intended for an intact legacy record for future reference. The splitting room features some very clever innovations to split soft sediment and hard rock cores:

A photo of a machine atop a cutting table. There is a grey box with a hole in the bottom center, and aligned with that hole is a white sediment core in its core liner. A long bar holds the core to the cutting table and a tech's blue gloved hand can be seen at the edge of the picture, lightly gripping the table. — The core section is held in place by the triangular metal guide and brace on top, and a trolley just to the left of the brace pulls a piano wire through the core to slice it in half along the black line.

Once split, Nicolette and Susan each take one of the ends, tap the section firmly on the table, and split the core apart, while Aaron starts cleaning the splitter:

Three lab technicians in the cutting room. One is spraying the cutting table from the last photo with a hose, and the other two are holding a freshly split core on the table. All three people have neutral expressions on their faces. — Susan took the archive half to the description table and Nicolette took the working half to the sampling table.

The first stop for the archive half is the first core description table, where the split halves await their turn in the digital imager, and then the color reflectance scanner. Measuring these properties shortly after splitting is critical to capture and record the original color and composition before the sediments begin reacting in the presence of oxygen, light and warmer temperatures.

A shot of the core lab. In front of the camera is a table with U-shaped channels mounted into it and a computer mounted nearby. Most of the channels are holding split cores. There are two more of these stations further back in the shot. At the back of the shot is a woman holding an iPad to take a picture. There is a long instrument on a moving track to her left. — It looks like Claire had the same idea. The digital imager and color reflectance tracks are to Claire’s left.

Next stop is the visual description tables. Ingrid is focusing on documenting the original color of the different sediment features (while Laura escorts the sections to the scanners):

Two scientists are working at the tables from the last picture. The tables have color charts (small cards with color samples and holes punched out beneath them) strewn across the work surface. A lab technician works at a table in the background of the image. — Good grief, did the Munsell color chart explode on the table or did Ingrid hurl it in frustration at the difficulty of identifying the precise white of our cores?

At the final description table, Laura receives the cores from Ingrid and identifies the structures and features apparent in the cores such as burrows or unique layers:

And to round out the sediment description team’s activities, Erika is assessing the sediment composition by swiping a toothpick’s worth of the sediment onto a microscope slide and sealing it with optical adhesive and a cover slip. She has the important task of estimating the relative abundance of the major types of grains that we find in the sediment – microfossils, detrital grains such as dust particles, volcanic glass, mineral grains, and any other minor phases.

A scientist sitting at a microscope. Her hand is holding a pen over a piece of paper, and she is turned to the camera and smiling. There is a computer monitor with several spreadsheets open above her work station.

Here is an example of what she might see under the microscope from one of the JR’s library of teaching slides:

An image taken through a microscope. The background is blue and there are several transparent grains in the field with a few black opaque grains. There is a scale bar at the bottom that indicates 1 millimeter. Most grains look to be between 1/6th and 1/100th of a millimeter. — The black scale bar is at the bottom. Thank you for sharing this, Erika!

We are taking a few samples from the working half of the core during the cruise to help us characterize the composition, paleomagnetic character, and physical properties of the material. Standard analyses such as moisture and density (MAD), carbonate (CARB), x-ray diffraction (XRD), paleomagnetism (PMAG) among a few others are carefully taken from the sections at the sampling table and then the sections are wrapped and slid into containers for storage in the reefer until they are shipped to the Gulf Coast Repository at Texas A&M University.

A scientist standing in front of a core workstation. She is pressing a small black instrument into one of the split cores with a slight smile on her face. — Gabby taking a physical properties measurement, and if you look closely you can see the tops of a few styrofoam plugs in the sections marking the locations of samples already removed for shipboard analysis.

A lab coat hanging from two grey squeeze cake machines. The lab coat has the name "Chang" stitched above the breast pocket. Sitting above the neck hole, as if it was wearing the lab coat, is a blue octopus plushie wearing a hard hat. A fuzzy green plushie, Little Cthulhu, sits on one of the lab coat's arms. — LC was quite taken with Eleni’s Octo dressed as Chang in the chem lab.

A fuzzy green plushie, Little Cthulhu, sitting on a rack next to a mop head. The mop head looks almost like a person's long hair hanging down. LC is positioned so it looks like it's looking at the mop head. — I’m not sure she is into you, LC.

Until the next time,

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