Climate records reconstructed from sediment cores require undisturbed layers of sediment that preserve chronology.  We prefer to find sites where a large amount of sediment deposited annually because high accumulation rates minimize the number of years spanned by a given sample.  For these reasons, scientists survey geographically applicable regions to choose coring sites which are both located in stable areas and have high sedimentation rates.

In addition to 3.5 kHz, we also use swath bathymetry, which provides a broader view of the surface sediment, to confirm that we are not coring near a canyon or slump feature.

Over time sediment accumulates on the ocean floor.  Typically this process is gradual and a cross section of the sediment below the seafloor reveals layer upon layer of deposits.  Our strategy is to take cores from different water depths along the continental margin, in this case along a feature called the Demerara Rise.  The different water masses intersect the Rise at different depths, and by taking cores from a depth transect through these water masses, we can eventually reconstruct deepwater geometry. For example, once we identify last glacial sediment in each of these cores, we can make chemical measurements on sediment samples to reconstruct the vertical distribution of water masses at this site.

We will make a variety of measurements on the water samples we collect. These measurements will be compared to measurements on benthic foraminifera, to evaluate how well our proxies record bottom water values.

Stratigraphy is the study of strata, sediment layers.  By looking at the magnetic susceptibility, gamma density, and biology throughout the core, even at sea, we can estimate the approximate age of the sediment and how quickly it is accumulating on the sea floor. As we gather more information about the age of the sediment, we can make decisions about whether to collect additional cores in the same area or to survey new areas.

Visit the Recoveries Page for recovery depth, location and data collected at sea!