Studying past and present

Reconstructing the climate and hydrology of the Amazon basin from 30,000 years ago to the present, finding out if vegetation in the Amazon changed as climate changed, and trying to determine how changes in Atlantic sea-surface temperature (SST) may have had a role in causing these changes are the main goals of the research associated with this cruise.

Because we're trying to understand the link between the ocean and the continent, we're examining many different types of samples and using a combination of methods (including inorganic and organic geochemical methods) to reach our study goals. This combination of sample types and methods will allow us to study not just the mud and sand transported into the ocean by the Amazon River, but also the plant and animal debris (the terrestrial biomass) that is transported in the Amazon outflow.

All of our study methods require both abundant material from gravity cores and the long cores (so that we can reconstruct the record of a long period of geologic time) and a good understanding of the modern environment in this region.

As a primary tenet of geology is often stated, "the present is the key to the past." In the context of research like this, this statement means that we study the characteristics and processes of the modern environment in order to understand both the processes that are likely to have operated in the past and the probable characteristics of the sediments that were produced by those processes.

An understanding of modern processes helps us make interpretations about past environments. This is one reason we need so much young, near-the-seafloor sediment -- so that we can learn more about the modern system and use that knowledge when we interpret the sediments that were deposited in the past.

The multicorer -- on the deck and ready to be deployed.

Enter the multicorer.

The multicorer can collect 8 short cores in a single deployment, making it an effective way to get lots of seafloor and shallow sub-bottom sediments in one deployment -- just what we need when trying to do so many different kinds of analyses.

It is a relatively simple tool to use and, with a little know-how, it is easy to extract multiple high-resolution samples from the individual cores. Andy Nunnery (one of the Duke PhD students on this cruise) has been doing just that.

Here's how he does it.

First, the individual cores are removed from the tripod and
hung on a wall-mounted rack.

The cores are measured and then removed from the rack and put into a core extrusion device. (The photo on the right shows the device without a core in place.)

The core is slowly pushed up through the its own core tube (by pushing up on the the white, plunger-like device) and samples are sliced off the top, typically in 1 or 2 cm slices (the photo on the left shows a core in the extraction device).

Because he is taking these samples for foram analysis, Andy treats each sample with formalin (which dyes the organic matter so it is easy to identify later) before placing it in a jar for storage and shipment back to the lab at Duke.

It's as easy as that.

Except, now all of the samples must be transported home and analyzed. The cruise, the cores, and all this sampling is only the beginning or this project!