UKAFH were fortunate to gain access to this remarkable mile-wide working quarry on Saturday 13th October. A small group of us gathered on this unseasonably mild but breezy day for an excursion into the Middle Jurassic. We assembled in the site canteen for a briefing from UKAFH leader Sam Caethoven and the site management, taking time to enjoy the displays of some of the more exceptional finds to have been previously found at the quarry, before heading into the quarry itself.
Ketton Quarry is an enormous site which provides an extensive exposure of the middle Jurassic from rocks of Bathonian age (dating to around 165 million years ago) to Bajocian age (around 175 million years old). The mile-wide quarry has been worked for many decades and is now 115.6 hectares in size. With full access, this huge quarry provides opportunities to collect fossils from many different beds, however we were limited to an area of spoil where operations were not currently ongoing for safety and practical reasons. Despite this, fossils were still abundant.
The geology at Ketton is complex, with a range of Jurassic-aged rocks recorded. Mostly, three formations are visible in the quarries: the lowest is the oolitic Lincolnshire Limestone which was laid down in the middle Jurassic about 160 million years ago. This large, blocky, rock was formed from small grains of calcium carbonate which were deposited under a warm, shallow sub-tropical sea which was subject to reasonably strong currents. Above this is the Rutland Formation – bands of delta and shoreline muds and sands carried by rivers. Each band, with shelly remains at its base and tree roots at the top, was formed when sea-level rise topped the layer below. Many colours can be seen in fresh exposures of this formation. The exposures at the working quarry (Ketton Main Quarry) are the type formation for the Rutland Formation. Above the Rutland Formation is the Blisworth Limestone, laid down under quiet, shallow, warm conditions during a marine transgression. The Blisworth limestone is full of fossil corals and shells.
Ammonites can be found but bivalves, corals, brachiopods, gastropods, echinoids (such as Clypeus ploti), shark teeth and fish remains are more common. In the past, dinosaur footprints have been seen, along with fragments of their bones, but we were not that fortunate on this occasion.
Blocks of limestone are often full of bivalves, brachiopods, or corals but you need a good geological hammer and a chisel to extract them as they can be very solid, although some rocks will have weathered to the point that fossils can be easily picked out. There were also many loose fossils to collect. Throughout our time on site we were able to find many bivalves and echinoids as well as a few brachiopods and gastropods. Special mention goes to James who took the time to carefully search the fine matrial for quasi-microfossils and found numerous echinoid spines, fish teeth and an Acrodus sp. shark tooth.
At the end of our hunt we gathered in the canteen for refreshments and to enjoy seeing each thers’ finds. It’s quite unusual on a UKAFH hunt for us all to finish together and have somewhere to gather for show-and-tell afterwards and it is always a highly enjoyable part of the day. As well as seeing all the finds and learning more about the site, the quarry staff can also see what we have found, both to share in our enjoyment and to ensure that anything rare is reported and recorded.
UKAFH would like to thank Hanson Cement and the staff at Ketton quarry for allowing us to visit and taking care of us throughout the day, including briefing us, showing us the site and allowing us the use of their facilities.