Tuesday, 7 June 2016

Ancient landscapes of the early Carboniferous

What was the landscape like that the tetrapods were living on?

This week Tim Kearsey and TW:eed Team colleagues Carys Bennett, David Millward, Sarah Davies, Mel Leng and John Marshall have had a paper published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology. You can see a copy of the paper online here. For this part of the project the team studied fossilised soils (palaeosols) from the outcrops that the tetrapods were found in, from two field sites and in the borehole. By studying palaeosols we can try to find out what the environment and climate was like out of the water. Was there anything special about the landscape that caused the tetrapods to evolve to become terrestrially adapted?  

One of the figures from Tim’s paper that documents the different types of roots and rooting depths present

We discovered that the landscape was covered with lots of different habitats, including marsh wetlands, small stands of trees and areas of low vegetation. The overall landscape would have looked similar to the Florida Everglades of the USA. Fossilised root traces suggest that there was a wide range of different types of vegetation from trees to small ferns. 
Tim pointing out a large tree root that was in situ at one of the field sites
From the geochemistry of the palaeosols we found that the area mean annual rainfall was 1000 –1500 mm per year in the Carboniferous. However, this rainfall was strongly seasonal as there is evidence of deep cracks in the soils which suggest a pronounced dry season. This confirms what others have found that at the time the tetrapods were living, that Southern Scotland was in a monsoonal tropical climate. When it rained large areas got flooded and may have presented new habitats for the tetrapods. However, many of these would have dried out in the dry season meaning the ability to live both on land and in the water would be an advantage.

Congratulations to Tim and the team!

Until next time