As I mentioned yesterday, when the whole round core gets split, the working half goes to the sampling table, while the archive half goes on its own journey. Its first stop is to the description table.
While at first glance it may all look like grey mud, upon closer inspection one can see variations in shading, layers of browns and greens, and also inclusions such as rocks or macro fossils (so far just rocks on this expedition). Least appealing to the sedimentologists are the landslides, bioturbations (mixing of sediment by burrowing worms or other marine organisms back in the day), or most frustrating – the expansion or flow-in of sediment within the drill core. These show up as ‘u’ shaped layers in the sediment, and can not really be correlated to any specific age since it is essentially a smear. These cause some of those gaps that stress out the stratigraphic correlators.
Regardless of the quality of the core section, all are processed. The first step on the description table is to clean the surface. The core slicer will also cause smearing, but only localized on the surface. The sedimentologists take a scraper and gently clean off the top thin layer. From the cleaned surface, they will take a small swab at various intervals to look under the microscope. This way they can tell the percent make-up of the sediment – so much clay, some percentage of microfossils, the relative amount of minerals, etc. Other sedimentologists take photos of the core sections, and then measure the reflectivity along its length, again in an attempt to identify the specific make-up (lithology) which can be used in correlating its age as well as sometimes its climatic history.