My main job with the sedimentology team for the last several weeks has been taking photographs in regular light and cross polar light (see the pictures at the bottom of this blog) of magnified smear slides from the core. Brad Field on the night logging crew makes at least one smear slide from each meter of core (we have drilled 1138.54 meters of core = at least 1139 smear slides) and more from some intervals of sediment. A smear slide is made by taking a little scrape of the sediment with a tool (toothpicks and dental tools are both used) and then spreading that sediment sample thinly on a glass microscope slide. A clear fixative is added to the slide to hold the sediment in place and then a cover slip is attached. Each smear slide is labled with the depth in the core from which it was taken.
These smear slides are used initially by the night logging crew to help with the description of the core and to give the initial compositional name to the sediments. The sediment might be mostly terriginous (sediment from the land), or perhaps have more volcanic or biologic origins. The smear slides also give the team some information about grain sizes. This may make the difference in the name given to the sediment in the formation. For example, diamictite vs sand with pebbles. To be true diamictite, the sediment must have all three grain sizes, gravel, sand and mud, without any one of those size classes, that section of rock will have another name. This information is part of Chris Fielding's core summary shared with the whole group every morning.
The photos I'm taking are primarily for archival purposes. There are scientists working with this information all around the world and most will never travel to Florida to view the actual core itself. The images taken by the teams here are placed on a shared computer drive that everyone in the project has access to. This makes sharing the samples much easier than having to physically send the one set of smear slides to different countries....it also means that we only need one set, because everyone can use it, we don't need one set for each scientist. With 1200 smear slides, you don't want to make lots of sets! It is also part of our data set, the information that core description and characterization is based upon needs to be accessible to everyone in the team.
Compare the two pictures of the same microscope view of smear slide (at 10x). What observations can you make about the various grains with the two kinds of different lighting?