James Clark Ross — Week 3, 7-13 March 2008Census of Antarctic Marine Life diary 2008By Jan Strugnell8 March 2008Trip to Unnamed Island - it's all about the poo
This diary entry is from Dr James Smith, a geologist on board, who was one of a small party that were lucky enough to go on an excursion to a small island within Pine Island Bay for geological sampling. They were also lucky enough to see moulting Adélie penguins and elephant seals on the island!
The purpose of our visit to ‘Unnamed Island’ was to follow up to a trip made by one of our colleagues at BAS, Dr. Jo Johnson who visited the island in 2006.
Jo, then on the German research ship RV Polarstern, was busy collecting rock samples from around Pine Island Bay to date the thinning history of the West Antarctic Ice Sheet since its last glacial maximum (about 18,000 years ago). This work forms part of the GRADES-QWAD programme at BAS, which involves geologists, glaciologists and oceanographers.
The rock samples Jo collected from Unnamed Island have been used to date the emergence of the island from the sea or from beneath the expanded ice sheet several thousand years ago. Jo used a method called cosmogenic dating to date the rocks. This technique measures the amount cosmogenic radiation the rock has been subject to since it was first exposed to atmosphere (known as its exposure age).
The purpose of our visit was to look for other types of material to date in order to verify Jo's data. We knew from Jo's account of the island that it's covered, quite literally, in a layer of guano or penguin poo. Fortunately for us we can date penguin poo very accurately using radiocarbon dating so in theory, if we could find a thick enough sequence of poo, it could tell us when the island was first colonised by penguins and therefore provide us with a minimum age for when the island emerged from beneath the sea or the ice sheet.
After a quick look around the island we found a suitable mound of poo to sample. We first scraped away the surface poo with a spade and took a series of samples from the base up to the surface. For the record, penguin guano has a very distinctive and rather unpleasant smell that was, unfortunately for us, quickly transferred to our clothing, hands and equipment! We hope the new dates from Unnamed Island are worth it!
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