Diatoms

In addition to geochemical changes within my lake cores, I am attempting to analyze biological changes within my sediments in the form of diatoms. Diatoms are siliceous algae which can be identified and analyzed under a microscope. These tiny, single-celled organisms are abundant in these lake sediments and different species prefer different aquatic environments. Thus, by identifying different diatom species at different depths in my cores, I hope to develop an additional line of evidence for different depositional environments (freshwater, marine).

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Using the Element Analyzer

After completing initial assessments of my cores, the next step in lab work was sampling each core for analysis in the Element Analyzer. This instrument combusts a small sample of dry sediment, passing the gasses through a series of chambers in order to analyze the gasses for percentages of Carbon, Nitrogen and Sulfur. With these percentage results (in addition to Carbon to Nitrogen ratios), geochemical changes related to changes in depositional environment are often apparent. Sulfur can be particularly useful since it often tracks changes from marine to freshwater inputs, where higher Sulfur levels are likely marine.

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Lab Work: Core logs and Magnetic Susceptibility

As I wrote in my last post, when we returned from field work, I had many cores to process before selecting the cores that I am focusing on for my thesis. Each core we collected in the field had to be split, and we selected one half as a “working half” to be sampled and the other as an “archive” which will be stored for future reference. After splitting each core, I completed a core log, describing the visual properties of the sediment in addition to the length of each core section. This first step, describing changes with depth in the core, is used as a reference for sampling and identifying different units (sections of the core with similar sedimentation history) within the core.

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Field Work: Coring Lakes in Lofoten, Norway

In northern Norway, general trends of sea level lowering throughout the Holocene have been developed, with sea level in this area lowering ~10m over the past 6000 years. However, the details of this lowering are poorly constrained during the late Holocene (the past ~5000 years) (Møller, 1986). For my senior research project, I am studying sediment records from isolation basins (coastal lakes characterized by their past connection to and isolation from the sea due to relative sea level changes) in Lofoten, Norway. Using these sediment cores, I hope to better constrain the rate and magnitude of sea level lowering during the late Holocene in Norway and to understand how these changes may have affected human activity (think: Vikings) in Lofoten.

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Almost done!

Me and a giant wild grape vine

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