Optimising Sample Preparation for the Investigation of Bottom Current Strengths of the Scotia Sea during the Pliocene

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Anissa Findley
Anissa Findley

Anissa is a rising senior at Wesleyan University. She is an International student from Kingston, Jamaica where she graduated from the Immaculate Conception High School. She is currently a double major in Chemistry and Molecular Biology and Biochemistry. She plans on applying the knowledge she gained at Wesleyan to further her studies in a PhD program, after which she hopes to continue a career in research. Anissa enjoys watching thought-provoking cinematic pieces, singing and appreciating music in an unbiased manner.

Abstract: Seafloor sediment is commonly used to give insight into the climatic history of planet Earth. Seafloor sediment is more suitable for this function than terrestrial sediment because of how dynamic the land on Earth is, and because of natural disasters that periodically affect the Earth’s topographical and geological features. The amount of sediment between 10-63 μm, sortable silt, can be used to infer ocean bottom current strengths and speed. At higher ocean bottom current speeds and strengths, the sortable silt mean size is larger. The samples to be investigated come from cores from the seafloor of the Scotia Sea between South America and Antarctica and date back to the Pliocene (5.3 – 2.6 million years ago). The sediment is wet sieved at 63 μm which is the boundary between sand, the coarse fraction, and silt and clay, the fine fraction. Sample preparation includes removing organic matter and siliceous microfossils from the sediment using 30% hydrogen peroxide and 1.5M sodium hydroxide respectively. Three different methods were used to prepare these samples for analysis to test if changing the sample preparation affects the results of the particle size analysis. The sample preparation methods used involved making the samples dry completely then gently crushing to create a homogenous mixture, keeping the samples wet at all times before beginning the procedure, and completely drying the samples then re-wetting to mix. These reflect the most common sample preparation methods currently applied by other researchers. The grain size analysis was performed using the Beckman Coulter LS 13 320 XR Particle Size Analyser. There was no statistically significant difference observed from the results of each method; however, the dry and re-wet method showed the most consistent sortable silt mean size results.