Core on Deck

A core being carried onto the catwalk by IODP technicians during Expedition 374

This is the phrase that participating scientists on IODP expeditions love to hear. When a new core is brought up to the rig floor of the JOIDES Resolution (the JR) from beneath the seafloor, the driller’s announcement of “core on deck” comes through the speakers in all the labs. At this point, multiple people leap into action and prepare for the new core. The IODP technicians get ready to accept the (hopefully full) 9.5 meter (~30 ft) long core. The drilling crew lays the core down horizontally on the drill floor, with the base of the core facing the ‘catwalk’, and a technician will get small piece from the base of the core (called the core catcher) and hand it off to one of the paleontologists.

The paleontology lab will immediately start to process the sediment to isolate and identify microscopic fossils and fossil fragments that will provide information about the age of the deposits (an application of paleontology called biostratigraphy). The rest of the core is put on a rack on the catwalk at which point the IODP curator will measure, assign identification to the core, and prepare it to be cut into 1.5 m long sections. Once the sections are created they are carried into the lab and put on a rack to equilibrate to surface temperatures (~4 hours).

The whole-round core sections will then go through a series of measurements (natural gamma radiation, magnetic susceptibility, P-wave velocity, bulk density) that aid the science party in characterizing the sediments even before they are split. The IODP techs will then split the cores, creating a ‘working’ half and an ‘archive’ half. The working half is sampled for additional measurements (density, moisture content, porosity, paleomagnetics, geochemistry, paleontology) and the archive half is thoroughly described. By the time any single core makes it through this process, the biostratigraphy lab team will have a preliminary age for that core. (In some cases, they have an age within 10 minutes of getting the core catcher!) The paleomagnetism lab team will also generate an age model based on magnetostratigraphy, which can be compared with the paleontology team. After ~24 hours of that core coming on deck, the geochemistry lab team will have initial results about general composition (e.g., % of calcium carbonate). This shipboard characterization provides the foundation for research that is done several years or even decades after the expedition.

Photo from a drone during Exp 374 taken by IODP photographer and imaging specialist Bill Crawford

The JOIDES Resolution (JR) is a unique science vessel. There are many ships that can perform any number of tasks for oceanographic and marine science. But, the JR is different because it’s a time machine. Only through deep coring into the seabed can we extract the record of past processes and environments.  The sound of “core on deck” is music to the ears of geoscientists on board excited to make new discoveries about how the Earth works.

More photos of Exp 374 here: