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Journal entry from Hamilton's Antarctica 2001 research expedition:

Seymour Island is presenting some interesting problems. A reconnaissance this morning showed the area where the researchers planned to set up their camp was completely inaccessible due to a large amount of pack ice that had been blown into the bay by the constant north winds we have had for the past day or two. Traveling around to the opposite side of the island revealed a couple of potential campsites. Unfortunately if one of these is used a large portion of each day will be spent walking to and from the sample locations, not to mention that all the collected samples will have to be carried back to the camp. In an effort to maximize the field time for the party we are going to wait a day to see if the ice jam near the preferred site clears. If not, the field party will be put ashore at the less desirable site. Meanwhile we have put back to sea and will be running seabeam data collection for the next 20 hours mapping the sea floor topography within the Erebus & Terror Gulf. This will put us back off Seymour Island around 8 a.m. tomorrow. Hopefully conditions will improve for the field team.

Seymour Island is a small kidney bean-shaped island oriented roughly N-S, composed of Cretaceous thru Eocene sedimentary rocks with the Cretaceous rocks on the south end of the island and Eocene on the northern end. The Eocene (57 to 34 million years ago) was a period in earth history that saw dramatic climate cooling. Early Eocene climates were warm globally, with no ice in the Antarctic, palm trees growing in the Rocky Mountains and crocodiles living above the Arctic Circle. This all changed quickly and by 33 million years ago Antarctica was covered with multiple small ice caps. The rock layers exposed at Seymour Island were deposited in a shallow sea during this time and hopefully changes in the diversity and ecology of the invertebrate fauna preserved in these rocks will reflect this dramatic climate change. Richard Aronson of Dauphin Island Sea Lab, Daniel Blake of the University of Illinois and their team will be collecting fossil shells from the various layers of rocks exposed and comparing how the diversity and morphology of these animals change with time. Their hypothesis is that with the cooling climate shell crushing predators that abound in warmer waters will decline and so, with time, the shell morphology developed to protect against crushing will also disappear.

Obviously, if the hypothesis is based on a cooling climate, evidence of cooling must also be present along with these changes. Here is where the second part of the project comes in. Linda Ivany of Syracuse University, will use samples collected from the same horizons as Aronson and Blake to generate a temperature curve for the Eocene section of Seymour Island. Using isotopes of oxygen incorporated into the calcium carbonate of the shells it is possible to generate a ratio of these isotopes. Production of calcium carbonate in colder water increases the concentration of O18 within the calcium carbonate, so shells found to have a ratio with higher O18 values were produced in colder waters than those with lower O18 values.

Combining the two studies, a trend with time of increasing numbers of thinner, less ornamented shells whose calcium carbonate produces an increased concentration of O18 would be just the kind of evidence needed to support the hypothesis.

Hopefully the shore party will get on shore tomorrow and sample collecting to test this can begin. Sincere thanks to Linda Ivany for her assistance explaining this research to me.

Cheers from the sunny south.

Dave Tewksbury

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