Last week we opened two of our Myanmar sediment sequences, described the sediments and sub-sampled one sequence. The first preliminary analyses will be made in January/February and will give us a good idea of where to focus further investigations. It is always exciting to open new sediment cores, and especially from a lake where no one has ever before obtained any sediments. Hopefully we will also get first radiocarbon dates within a few months so that we will know how old the sediments are and how much time the sequences contain. This is important because it will enable us to compare our new findings to our ongoing research in Thailand and to other records in monsoonal Asia.
Studying lake sediment cores is for me probably one of the most exciting things. Imagine that lakes collect and save environmental and climatic information in their sediments over thousands and thousands of years. As such they are excellent recorders of how environmental conditions may have changed in response to climate and/or human activities in their catchment.
Each year remains of dead plants and animals that have been living in the lake fall to the bottom of the lake. Remains of plants and animals living around the lake may also be transported into the lake by waves, wind or small streams. Some of these remains become embedded and preserved in the sediments, or covered by more plant material. This creates oxygen-free conditions, which in turn rescues the organic remains from being eaten up by other organisms. Streams or heavy rains also occasionally flush sediments into the lake. These sediments become mixed with the organic matter or appear as discrete layers.
More and more sediment gradually accumulates on top of each other containing information on when and how the environment around and in the lake has changed over time. Then at some point in this process, we come across and sample a lake sediment sequence. By using all types of different analytical techniques we then try to travel back in time, hundreds and thousands of years. If we are lucky, and most of the time we are lucky, the sediments tell us a story and let us decipher their secrets.