Coring is a very useful technique in the archaeologists toolkit. It involves driving a steel rod, with a hollow chamber, into the ground, rotating it to take a sample, and lifting it back out, hopefully with the core sample still in the chamber! The sediment core recovered this way provides evidence of the buried layers beneath the ground surface, but without too much disturbance of the ground. Repeating this process sampling deeper and deeper allows us to build up a model of the layers deep in the ground, provided the cores that are taken overlap. Just as with archaeological stratigraphy the basic rule is that the layer below the one above is the earlier of the two, and each layer downwards takes you slightly further back in time. We have been coring for sediment, particularly peat layers, in order to understand how the former lakes at the Kaims site in filled over thousands of years. And what these layers can tell us about the past environment.
The work we have done with Dr Richard Tipping and Dr Danny Paterson has been particularly fascinating, in fact just listening to Richard talk about the cores of sediment is a real education. An education continued when we visited the laboratory at Stirling University to see how the cores are investigated.
We have investigated quite a number of transects across the wetland, in order to reconstruct the profile of the former lake. We have also processed one of the cores for pollen in order to reconstruct the past environment. The core was 5m long and taken from the area of the bog to the south of the east-west section of the Winlaw Burn, at the bottom of Hoppenwood Bank. The sediment layers were dated by comparing them with a pollen stratigraphy analysed in, the nearby, Embleton’s Bog by Bartley (in 1966). Sediments dated between c. 4,500 cal BC until c. 3,650 cal BC, across the Mesolithic-Neolithic transition, were analysed in detail. This is a particularly important period in our history and also was intended to help us understand what the area was like at the time when some of the earliest archaeological features we have identified were in use.
We know that on dry soils the late Mesolithic woodland (prior to c. 4000 calibrated BC) was probably dominated by oak and hazel with ash, Rowan and aspen, with rare traces elm and lime. This woodland was disturbed in the late Mesolithic, as we find herbs associated with open ground herbs within the core, but there are no pollen types to prove this was deliberate and caused by human activity that might suggest the arrival of the earliest farming communities. Indeed the elm decline (between 4,300 BC and 3,300 BC) is a single modest event and pollen, that probably represents wheat, is first recorded after the elm decline. Though even then crop-growing appears to be modest.