A day in the life of a sedimentologist

By Jin-Sol Lee, University of Melbourne

Although it would be hard to imagine, you couldn’t have seen a more excited group of adults than when a three-metre rectangular block of muddy sediment was pulled onto the ship. This surreal moment is when you realise you’ve fallen into the rabbit hole and entered a whole new world; the world of a sedimentologist.

This image of the stern (back) deck of RV Investigator shows the A-frame almost at its uppermost position as the 4 members of the crew and support staff work to deploy the kasten core off its track from the back of RV Investigator in a submarine canyon off Portland Victoria as part of hands-on marine science training for students on CAPSTAN's 2019 voyage.
Kasten core being pulled up from the depths of the Southern Ocean

This block of muddy sediment is a sediment core taken from the bottom of the ocean and reveals a whole plethora of wonderful and strange stories from Earth’s history. These stories relate to how our planet’s environment, climate, and ocean currents have changed over time. What is truly amazing is that we know so much about the long and dramatic history of our planet despite the fact that we have not been part of that history for very long. This amazement is humbling and is a reminder of the capabilities of the human race, and the responsibilities we have as stewards of the planet.

Once the core is brought into the lab there is a flurry of activity to open the metal casing, which holds the sediment core, and to see what strange and mysterious tales from the ocean depths have been brought to the surface. With the casing removed heads are bent over to observe the colour, structure and composition of the sediments. Quick, sharp remarks are exchanged between the various parties involved before the processing of the core is started without delay. First, the core is logged which involves documenting the major characteristics of the core. This is important because these observations will underpin the majority of the interpretations which brings the whole story together. From here smear slides and small sediment samples are taken along the core to examine the changes which occur from top to bottom.

The sediment lab is full of students and trainers as the kasten core (3 m long steel pipe) is opened on one side and imaged using a DSLR camera.  Students and trainers described the sediments, sampled plankton, and measured seawater properties as part of hands-on marine science training during CAPSTAN's 2019 voyage on RV Investigator.
The big reveal! A hub of activity as the core is brought into the lab and the task of processing and sampling the sediments begins!

Hours will be spent analysing these slides and samples, with more sampling done along areas of interest until the sediment core looks less than pristine. Not to worry however since before the sediment core was scooped, poked and prodded an archive core was taken and stored in the fridge. This archive core is kept with all its structures and features intact as an original record for safekeeping.

Two students and a trainer stand around the lab bench in the sediment lab working to describe the sediments using a Munsell color chart and several microscopes securely fastened to the counter as part of hands-on marine science training during the 2019 CAPSTAN voyage.
Hard at work! Sediment core being logged to describe the major characteristics and sediments being analysed under the microscope.

There is a certain amount of chaos and untidiness in the lab which may be disconcerting to the casual viewer, but there is a method to the madness with great care being taken to systematically record and sample the sediment core. Furthermore, there are efforts to limit contamination across the core (i.e. avoid mixing sediment from one area of the core to another). In fact, it is quite liberating to be able to conduct science in a lab where things are more practical, and improvisation is encouraged. A day in a life of a sedimentologist will surely shake up the perception of the typical scientist in a lab coat conducting experiments in a clean and well organised laboratory.

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