Sedimentology

As I mentioned two days ago (internet failure yesterday, sorry), when the whole round core gets split, the working half goes to the sampling table, and the archive half goes on its own journey.photo-15

Its first stop is 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 or 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 they are essentially smears.  These cause some of those gaps that stress out the stratigraphic correlators.P1020673

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 also causes some smearing, but only localized at the cut edges.  The sedimentologists take a scraper and gently clean the top.  From the cleaned surface they will take a small swab at various intervals to look at 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 all in an attempt to identify the specific make-up (lithology), which can be used in correlating its age and sometimes its climatic history.P1020639P1020106