Poxwell Quarries are two old, very overgrown quarries, but a small outcrop in the second quarry can still reveal the productive Purbeck beds that contain well-documented insect remains. Most of the quarry is in Portland Stone of white or cream appearance. This contains moulds of typical Portland molluscs. Although uncommon, you can also find fish, ostracods and small shells. However, you will probably need a microscope for viewing your finds.
♦ From the A352, take the A353 to Poxwell. You will pass through the hamlet and on a sharp bend in the road, (just before the turning to Ringstead Bay) you will see an old quarry on the left hand side. It’s a busy stretch of road but parking just might be possible on a grassy area. However, there is a farm entrance near the quarry and more than one or two cars would be at risk of blocking access to the farm. The entrance is in constant use and must not be be blocked.
This is not a very suitable place, either in terms of parking or of size of exposure, for coach parties. A former road cutting is now overgrown and is a dangerous place in terms of fast passing road traffic.
Poxwell is shown on 1:25,000 scale maps, and is referred to as Poxwell Manor in 1:50,000 scale maps. Poxwell is a small hamlet situated about 7 km northeast of Weymouth. The map reference of the quarry itself is SY 743835. The disused quarry has a mobile phone mast and warning sign.
♦ Once parked on the grassy area, walk to the quarry, where you can examine the Purbeck beds, although they are not as productive as tin the past.
♦ The second quarry is a very short walk away. You will see a signpost with ‘Public footpath’, which heads through a gate, then the farm and uphill. Take this footpath.
♦ Walk up the hill. Be careful, as you can easily miss the old quarry as it is very overgrown. On the left hand side, you will notice the ground dips suddenly all the way up the hill. This is the relevant quarry. The Dorset RIGS have done some sterling work in managing this site and the strata is often cleared of vegetation, meaning the most productive bed is still accessible.
♦ Ref: 50.65070°N, 2.37004°W
FIND FREQUENCY: ♦♦ – Providing you collect samples from the right beds, this location is can be productive and full of microfossils.
CHILDREN: ♦ – Locations for microfossils are generally not recommend for children who want to find fossils, as the finds will be made back at home or in the lab once you process your samples. This activity is not particularly exciting for young children!
ACCESS: ♦ – Poxwell Quarries can be difficult to find. However, if you have a 1:25,000 scale map, the quarries are marked.
TYPE: – The productive beds are in an old, disused and very overgrown quarry.
At Poxwell there is a small but good quarry section showing the Portland – Purbeck junction very clearly.This is a SSSI of Portland Limestone and Lower Purbeck beds of the Lulworth Formation. Some 15 metres are exposed with creamy chalky micrites of the Chert Member and grey chalky pelmicrites of the Portland Freestone Member. Midway through the Freestones lies a chert band. The basal Purbeck shows two well-defined dirt beds. Fossil trees, bivalves, gastropods, ostracods, ammonites and sponge spicules may be found.
Do not over collect. Take only a few samples from the scree. Microfossils are found within the white chalky layer of micrites and some within the harder layer directly above this layer. You will know when you have the correct layer, as it feels like soft chalk and will rub off easily on your hands. It is in the middle beds of the small outcrop, about 140 cm above the ground.
The best way to process your samples is to break them down with dilute acetic acid (for example, white vinegar). This will separate the fossils. If this is not possible, then the material is quite soft and small pieces can easily be crumbled in your hands. This method may cause some fossils to become damaged.
Larger lumps can be broken down into smaller pieces using a small hammer. Once you have broken up the sample, use water to wash the sediments and remove any sand, ideally by using a sieve. Then wet sieve the samples at 500, 200, and 150 microns. Sieves and microscopes can be purchased from UKGE Ltd.
Microfossils from Poxwell Quarries are abundant. This location is well known for its insect and fish remains, including small fragments of beetles. Ostracods and small shells are also very common here.
In the quarry facing the road is a short face at right angles to a 15m long exposure of the Portland Stone Formation, with the lowest Purbeck strata above. The upper Chert Beds form the lower slopes of the long face, though this is mostly obscured by talus. The Freestone Beds are of a chalky, micritic texture, the first being topped by a thin chert bed in which sponge spicules can be seen. Above lies a chalky biomicrite abundant in large bivalves, such as Laevitrigonia gibbosa, Protocardia and Pleuromya, some of which may be bored. Occasional moulds of gastropods and micrite intraclasts can be found. Two Dirt Beds, the Basal and Lower Dirt Beds, can be seen in the overlying Purbeck strata, with algal limestones between.
The sequence at Poxwell Quarry is as follows:
- Grey limestone with coarser texture (possibly ooliths) at the top
- Creamy yellow laminated marl
- Light brown or buff coloured clay, sandy at the top
- Fine grained marl
- Clay, slight orange colour at base
- Thick bed of sandy material, possibly limestone or calcite cement
- Creamy clay or marl
- Fine grained micrite
- Bed of fine sand with some lignite
- Grey orange clay
- Hard laminated grey micrite
- Grey cream laminated clay
- Buff coloured micritic limestone
- Orange brown clay
- White grey limestone with some ostracods
- Creamy laminated limestone with some ostracods
- Laminated buff coloured clay
- Creamy coloured limestone
- Base (often not visible) of creamy coloured limestone with abundant ostracods.
Common sense when collecting at all locations should be taken. There are no real dangers at this location apart from care should be made at the first quarry, as the cliff face overhangs a lot. However the fossils are found at the second quarry, and this is so overgrown that cliff falls are not possible.
Fossils from Poxwell Quarries are microfossils, so you will need to take samples back home to process and then view under a microscope. A sieve is also recommended for processing samples on site.
This site is an SSSI. This means you can visit the site, but hammering the bedrock is not permitted. For full information about the reasons for the status of the site and restrictions please download the PDF from Natural England – SSSI Information – Poxwell Quarries