Imagine you are about to read the newest best selling book, but when you open it there is nothing but chapter titles – no text. From the chapter titles alone you might have an idea of the plot or even the main characters, but you miss the details. You miss the nuances that make up the story. Previous E-O Boundary cores were made up of just the chapter titles of climate history. Here, at one of the last sites on Expedition 342, we’ve brought up a core that has the full story of the Eocene-Oligocene transition. It’s amazing!
Part of the E-O Boundary Core.
In a previous post I talked about the E-O Boundary as a time when the Earth was transitioning from a greenhouse world to an icehouse world, about 33 million years ago. Most records we have of the E-O boundary come from the southern hemisphere or the equatorial oceans. These southern records provide excellent insight into the formation of the icecap on Antarctica – a major change for the global climate system. However, glaciation of the northern hemisphere remained mysterious. We only had the “chapter titles” of the arctic story.
The newest E-O Boundary cores that we brought on deck yesterday are expanded. That means that the transition from greenhouse to icehouse is spread through multiple cores. It is a super high-resolution look at what happened in the northern hemisphere, especially Greenland, as the world transitioned into the icehouse state. We now have the text that goes with each chapter title.
Initial finds are pretty spectacular. Based on our shipboard measurements, evidence of dropstones, and other ice rafted debris, we think that icebergs were calving off of the glaciers in Greenland before Antarctica was fully glaciated. Amazing!
Sampling the expanded E-O Boundary Core.
Just one of the many transitions seen within the record.