Following a fruitless trip to search for adders yesterday, three of us decided to visit a particularly interesting quarry at S Elmsall. The quarry is a Site of Special Scientific Interest because of some shapes that can be seen in the wall of the quarry. These shapes are the remains of ancient structures called stromatolites. Stromatolites are of interest because they provide the earliest signs of life on Earth, with some of the traces in the fossil record being 3.5 billion years old.My knowlege of geology is superficial but what follows is my understanding of what can be seen in the quarry.
Stromatolites develop very slowly in shallow and highly saline water and they look like boulders. They are created by mats of single-celled organisms, such as cyanobacteria or algae. Mineral particles trapped by the organisms gradually build up in layers to form the stromatolite. Follow this link if you would like to see modern stromatolites.
The following photograph shows a small piece of fossilised stromatolite and it has been polished to reveal the layers.
In the wall of the quarry, there is a clear horizontal boundary. Below this line, there is a layer of grainstones. Above the line, there are the fossilised remains of a reef and within that zone.
You can see domed shapes that are the fossilised remains of stromatolites. The remains date from the late Permian period, making them more than 250 million years old.