We had a varied and very interesting meeting which ranged from coal mining in Woodland to some amazing plants and insects in the Carboniferous Period some 300 million years ago.
In the first half Mike Caldwell gave a fascinating account of his investigation into an area of SW Durham where his ancestors had lived during the early 19th Century. Woodland became a colliery village and the whole of SW Durham was heavily involved in mining at that time. We looked at the geology of the area with a cross section showing the numerous faults which limited the coal seams that were worth mining. Mike had managed to obtain the actual plans of the underground workings, and this provided an opportunity to explain some of the mining techniques. The deep mines closed in the mid - 20th Century but there was still open cast mining in the area. Finally, we were given a brief overview of the tectonic situation in the Carboniferous and this tied in nicely with David Saville’s talk after the break,
In the second half, David Saville continued with Part 2 of his excellent talk on ‘Life in Carboniferous’.
Great changes took place 350 million years ago over a period of 60 million years. The climate was driven by the Milankovitch Cycles which resulted in changes in sea levels. These in turn gave the repeating Yoredale cycles (cyclothems) of limestones, shales, sandstones and coal that we see in the North Pennines and Dales today.
The Carboniferous was also the period during which both terrestrial animal and plant life became well established. Plants evolved using the structural polymer lignin which could not be broken down by insects or fungi/ bacteria. The dead plant matter did not decompose and under pressure over time was converted to peat and then coal. Carbon dioxide levels dropped in the atmosphere and the oxygen levels increased at times to as much as 35%. Plants grew to enormous sizes (horsetails 20 metres high!) and insects were also very large (dragonflies for example with a two-foot wingspan!).
The next meeting is at The Witham on Monday morning June 22nd at 10 am. All are welcome. Please contact the convenor for details.
Bob Tuddenham