Santa Cruz Core Scanning Laboratory

Cores collected from coastal, fluvial, estuarine, lacustrine, and marine environments are brought to the Core Scanning Lab for detailed analysis. The lab features a Geotek rotating x-ray computed tomography (RXCT) system and a Geotek multi-sensor core logger. 

RXCT

The Geotek RXCT creates ultra high-resolution density imagery of sediment and coral cores. The system resides at the USGS Pacific Coastal and Marine Science Center in Santa Cruz, California. It requires the operator to participate in specialized training and hold X-ray radiation and safety certifications.

In medicine, radiologists use computed tomography (CT) scans to collect highly detailed images of your body. Similarly, the RXCT creates a complete 3-D image rendering of a sediment core by combining a series of X-ray images taken from different angles around it (thus, the "rotating" part of the name). The system then uses computer processing to create cross-sectional images (slices) of the core. Thus, a CT scan provides more detailed information than a simple 2-D X-ray image.

The images created by the RXCT allow scientists to look into a core at any area and at any angle, without having to carve into it. Looking at the structure and composition of cores in this fashion helps scientists determine the history of the location where the core was collected, such as the seafloor, a lakebed, or a marshy area. For example, if they find a sandy layer in an otherwise calm environment, like a coastal marsh which is normally just peat and mud, this may be evidence of a big wave event that carried sand from the beach and nearshore back into the marsh area. Further inspection of the CT image may reveal subtle sedimentary characteristics of the sandy deposit such as changes in grainsize, heavy mineral layers, and rip-up clasts that may help researchers determine whether deposition occurred during a tsunami or a storm. 

MSCL 

The first stop for many of these cores is the Geotek multi-sensor core logger (MSCL). The MSCL measures P-wave velocity, magnetic susceptibility, electrical resistivity, and gamma density at intervals from 1 millimeter to 1 centimeter along cores up to 1.5 meters long. The device can also line-scan photograph split cores at a resolution of 10 microns