The Multi Sensor Track (or MST) is able to measure the gamma attenuation and magnetic susceptibility of the gravity and long cores without damaging them in any way.  We can calculated the density throughout the core using the gamma attenuation data while the magnetic susceptibility data tell us about the composition of the mud - whether it has a lot of magnetic minerals.  We can estimate the age of our cores by comparing our MST records to records from previously studied and dated cores, all within a couple of days of recovery (and on a moving ship!).  Results of MST (updated!)

G. menardii are a species of foraminifera that are only present in the sediment during certain intervals. Due to the age of the sediment that we are likely to recover during this cruise we are most interested in the presence of G. menardii from present to ~20,000 years ago and then the reappearance between ~70,000 and ~120,000 years ago. We have been taking a small sample from the bottom of each section of core, washing away the dirt and looking in a microscope for the presence of G. menardii in the samples.

Multi Sensor Track (MST)

G. menardii stratigraphy

The red line is the magnetic susceptibility for long core CDH 11. The blue shaded regions with the Y (yes) are parts of the core where G. menardii was found, known as the “Z” and “X” zones, wheras in the white (No or “Y” zone) region, G. menardii were absent. G. menardii  data indicate that the youngest (shallowest) “yes” region is the Holocene (10,000 years ago to present), the “no” region is the last glacial period (ice age) and the earlier (deeper) “yes” sediment corresponds to the end of the last interglacial period (non ice age). The magnetic susceptibility data suggest that this core recorded abrupt climate events as seen in the blue oval. Because we know the ages of the transitions between times with and without G. menardii (between the “Yes” and “No” periods), we can estimate that on average, 30 cm of sediment accumulated every 1,000 years.   We can estimate the accumulation rates of our recovered cores by comparing them to this record because magnetic susceptibility records from a given region typically contain similar features and are easy to correlate with one another.