Pursuing the Pollen

Mairead, Dan and I went up to site on what felt like the last day of winter, but was in fact early June, to try to sample for preserved pollen. It is fair to say that looking for surviving pollen on site has not been the smoothest part of the project so far. We originally took lots of samples from features we dug, reasoning that any pollen would then be easy to date and link to the archaeology. The only problem with this plan was that when Mairead came to look at these samples then the pollen wasn’t well enough preserved to tell us anything reliable about the prehistoric environment.

Plan B, which we started to put into operation the other day, was to take an auger to the various boggy places around New Laund Hill in the hope of getting a sequence of bog close to the archaeology that dated back into prehistory. An auger, by the way, is a giant version of the thing gourmet judges use to test cheeses with. You poke it into the mud and it comes out full of sediment for you to examine. It has a T-shaped handle to aid the pushing and extra-sections, as on a chimney sweeps’ broom, if you want to go deeper.

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We poked away at many promisingly boggy locations around the hill but found that they were all dolines choked with limestone and clay, making a very hostile environment for pollen survival. At this point we had to move to plan C. This involved quizzing John as to where the nearest peat bog was and, when it turned out to be at the other end of Dinkling Green Farm, cadging a lift for us and all the kit in the Land-Rover.

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When we got there it turned out to be worth all the bouncing about. Mairead and Dan used the auger to find the deepest part of this bog. Once we were sure there was good preservation and more than a metre’s depth of peat they were able to move up to this device here, the Russian corer. The auger is good for looking at sediments but the advantage of the Russian corer is that it gives you a 50 mm diameter column of sediment served on a plate. It has a much wider head than an auger and has a closing stainless steel flap. Once it is in the ground you can, by turning the handle half a turn, shut the flap and trap a column of sediment inside. With the corer out of the ground you can carefully open the flap and ease the sediment into something like a plastic gutter and a whole section of the peat bog is nicely sealed up to be sampled at leisure in the warm and dry.

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The head of the Russian corer is only 0.5 m long so, like the auger, it comes with many additional sections to add depth (now you see why we were so keen on a lift in the Land-Rover). This is the lower of the two sections through our peat. The grey clay on the right hand side probably dates to the immediate post-glacial period, around 10 000 years ago. About 150 mm up the core you can see the transition where peat has started to form on the top of this clay. Dead plant material then continued to build up over the next 10 000 years to create the peat bog and, hopefully, trap lots of pollen to tell us about changes in the local environment.

With Mairead’s help, Dan will be working on this for his MSci dissertation over the next year, so I will be able to keep you posted with results as he gets them.

Rick

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