Monday, 28 January 2013

Viewing a Borehole: a hidden world revealed

Since the last blog I have continued on with sample processing… only 200 samples left to go! During that time there has been an exciting tetrapod paper published in Palaeontology by Jenny Clack, about a new species of tetrapod from the late Devonian of Greenland. You can read a blog about the paper here. Congratulations Jenny!

The day before we had the TW:eed team meeting in Leicester I spend a day viewing a borehole at the British Geological Survey in Keyworth, with colleagues Sarah Davies, Dave Millward and Janet Sherwin. This was an excellent ‘preview’ of the sort of thing we can expect from our 500 metre borehole that we plan to drill later this year.

The borehole cuts through the top part of the Ballagan Formation and the overlying Fell Sandstone Formation, from the early Carboniferous. It was drilled in the 1990s from the west of Northumberland, and although the core is although not 100% complete (samples have previously been extracted for study), the rock is in good condition.

The great thing about it is that we can use this borehole to compare with what we find in other areas, such as the Borders, and to build up a picture of the different sedimentary environments across a wide geographical area. In the photos below I illustrate part of the top of the Ballagan Formation where there is a lot of gypsum and anhydrite growth. This is really interesting as these minerals are salts that form due to the evaporation of water, telling us that the local environment was very arid at the time. We can investigate the relationship of these types of deposits with tetrapod fossils, to find out if tetrapods were living in lagoons or lakes that dried up, or if they avoided these seemingly inhospitable areas. As these minerals are rarely preserved in the field, we really are discovering a hidden world.

Top: Part of the borehole we viewed, with newspaper packed in the boxes. Each box is 1 metre in length. Bottom: A close up of some of the sediment containing gypsum and anhydrite.

Do you want to find out more about boreholes? Accessible on the web, the BGS GeoIndex is a record of all the boreholes ever drilled in the UK. You can see a map of onshore boreholes here. And while you are there, it is well worth checking out the other online resources from the BGS, such as the GeoBritain map.

Until next time

1 comment:

  1. Great blog!!! Where is your new borehole going to be drilled? What diameter will you be drilling?