On a scorching, sunny Sunday 5th August UKAFH members and guests headed to the south east corner of Kent to Betteshanger Country Park (near Deal) to hunt for Carboniferous plant fossils.
Betteshanger is a RIGS spoil heap at the old Betteshanger Colliery, which was the largest in Kent but was closed in 1989. Betteshanger Country Park was created by regeneration of the former Betteshanger colliery site and provides a large green parkland and recreation area ideal for walking, cycling and other outdoor activities. However as part of Geoconservation Kent (http://www.geoconservationkent.org.uk/), there is agreement to retain a fossil hunting area within the country park. The fossil collecting spoil heap, which is northeast of the original site, is set aside for the study of the fossils to be found in the coal measures formerly mined there and this was our destination for the day.
Our group of 25 assembled outside the visitor centre, which offers toilets, showers, information on the park and a small cafe alongside a childrens’ play area. From there it was quite a short walk to the fossil hunting area where Andy Temple of GeoConservation Kent awaited us as our special guest leader for the day. Andy regularly supports school and group trips and visits to Betteshanger and other Kent locations and is expert on the many, varied plant fossils to be found in the coal deposits. Sam Caethoven welcomed the group and introduced Andy who gave an overview on the site and what can be found.
Betteshanger is Upper Carboniferous (Silesian) in age, from the mid-Westphalian Stage (Asturian Substage of 323.2–315.2 Mya) to the Stephanian Stage (Stephanian B Substage of 315.2–307 Mya). The rocks are from between 316–311 Mya and mostly consist of the Kent 5 coal seam, with some Kent 7. Kent 5 is assigned to the Upper Coal Measures (Warwickshire Group) and Kent 7 to the (South Wales) Middle Coal Measures. Fossils show that there were areas of forest and river levees, with overbank deposition taking place.
Fossils at Betteshanger are found either lying on top of the spoil heap or by digging into the spoil. Remains of Arthropleura, a large arthropod, have been found at the site. However, unlike other coal measures sites in Europe, no insects have been found at Betteshanger.
When we arrived at the fossil area we were delighted to be informed by Andy that a digger had just been in to turn over the coal spoil and dig out fresh areas, removing the old spoil that had already been examined many times previously. As a result we were extremely fortunate to be able to find abundant, varied plant specimens!
Fossils were quickly being found, both in quantity and variety. Kath Kemsley found a smashing Neuropteris seed fern and Aiden Philpott found an exquisitely preserved Alethopteris seed fern. Jake Ashley found a very nice example of Lepidodendron (also known as a scale tree) which is an extinct lycopsid club moss. Kaitlin Asher found a fantastic selection of plant fossils and Nicky Parslow uncovered a beautifully detailed example of asterophyllites horsetail.
The swampy Carboniferous landscape was dominated by three types of plant: ferns (true ferns and seed ferns), lycopods and sphenopsids. Ferns were at their most abundant and diverse in the Carboniferous period but persist today. Giant lycopsids – clubmosses – such as Lepidodendron and Sigillaria grew to the height of trees and their fossilised bark is characterised by leaf scars. The fossils of the root systems of both these plants are called Stigmaria because they look so similar. These are examples of form taxa, where a collection of organisms is given a taxonomic name but is known to be a grouping based on similar morphological characteristics, rather than more extensive biological similarity. Finally the sphenopsids consist horsetails which were gigantic in the Palaeozoic but persist today in much smaller and less diverse forms. The leaves of horsetails, which form in whorls around the stem, are termed annularia but the root fossils are known as calamites.
Huge thanks to Andy Temple for bringing a fabulous display, expert advice, identification and preservation tips and plenty of very useful spare newspaper for wrapping finds!