After two months of continuous drilling we have completed the borehole! The core cut through 501 metres of Early Carboniferous Ballagan Formation, at a site near Berwick-on-Tweed. The rock we drilled through spans approximately 15 million years of geological time, capturing the key interval in tetrapod evolution called Romer’s Gap.
The core will now be sent to the BGS Core Store in Keyworth for processing. It will be split in half and photographed, half will be stored, while the other half will be logged and sampled by myself and Tim Kearsey from the BGS. The core will allow us to produce a refined stratigraphy (dating scheme) of the Ballagan Formation and tie in the isolated field sites in which tetrapods are being found.
What did we find?
We drilled through many different types of rock: sandstone beds, grey and red siltstones, cementstones and gypsum units. We noticed many similarities with field sections, but also quite a few differences, such as the presence of many gypsum beds at the base of the core. Unfortunately we didn’t drill through to the underlying Kinnesswood Formation, but we did drill through many promising units in terms of fossils, and the high quality and large volume of core recovered should be enough to give us some robust dates.
The video 'Coring through 15 million years of the rock record at Berwick-on-Tweed' by Tim Kearsey gives a great two minute summary of the drilling operation.
You can also read an interview with Tim on the BGS GeoBlogyblog.
Until next timeCarys