by Bianca Harrison (University of Cape Town)
Micropalaeontology opens up a whole new world to be observed that is not visible with the naked eye. These are fossils of mainly single-celled organisms smaller than 1mm which is smaller than a pin head! When searching for these tiny fossils underneath the microscope, a sense of awe overcomes you as you realise that YOU are the first person to observe what the rock has hidden away for millions or even billions of years. But I am getting ahead of myself…
I am a first year MSc student in South Africa and had the opportunity to travel to Uppsala, Sweden to work with Malgorzata Moczydlowska-Vidal at Uppsala University. This was a tremendous opportunity to learn how to process rock samples for microfossils in a world-renowned scientist’s lab. This training was extremely vital as I plan to compare microfossils of the Vanrhynsdorp Group, South Africa and the Vestertana Group, Finnmark, northern Norway. These Groups are of significance as they span the Ediacaran-Cambrian boundary (~541 million years ago). The study will contribute to understanding the nature, behavior and diversity of microorganisms before and during the “Cambrian explosion” – a geologically sudden event when complex marine organisms become abundant for the first time. Microfossils are useful as biostratigraphic markers as the presence of different species at different intervals can pinpoint time periods and correlate rock formations from different locations around the world.
With all this in mind, I embarked on a week long journey in Malgorzata’s lab where we dissolved rock samples from South Africa. The fun side of lab work are the cool outfits you get to wear! Safety is of utmost importance but whoever said you can’t look good while doing it?
On a more serious note, hydrofluoric (HF) acid is used as it dissolves silica (a large component in rocks) whereas organic compounds are resistant and do not dissolve. However, HF acid is also capable of dissolving glass and human tissue, so extreme care is used when handling the acid. In light of this, a small disclaimer is needed – do not try this at home! Scientists have special labs and equipment that allow them to work with these dangerous chemicals. However, the exciting part begins once the rock is dissolved and this can take ~2 days.
Once the sample is dissolved, the moment of truth arrives. The bottom-line: the darker the residue, the higher the organic content in the rock and the higher the chance of fossils. From there, the samples are washed thoroughly, boiled in hydrochloric acid to dissolve other minerals, filtered and mounted onto microscope slides. Identifying microfossils underneath the microscope can be tricky but there are a few key things to look out for: 1) sharp boundary of the object, 2) shape, and 3) colour. Depending on the age of the rocks and the species of microfossils, the specimens can range from looking like wrinkled blobs to beautifully complex structures. Regardless, the information they can reveal is invaluable. At the moment, I am still in the preliminary stages and learning all I can about microfossil work before I find any of my own specimens! Wish me luck as I embark into this ‘small’ and exciting world!