Geological Guide to Swanage

At New Swanage, the cliffs begin with Wealden Shales. These include the Unio Bed. The Wealden is from the Barremian stage, and the Wealden/Perbeck boundary is present at Swanage although currently obscured. The Wealden Shales show evidence of very salty conditions and is why fossils are not plentiful. Blocks of thin Wealden limestone can also be seen on the beach. There is around 750m of Wealden at Swanage.

Further North and you will come to the Lower Greensand. This is very similar to that from the Isle of Wight with the Atherfield Clay and Ferruginous Sands exposed. Exposures are poor due to a lack of recent cliff falls, but some exposures remain. There is 61m of Lower Greensand here covering the following beds.

Following this, you will come to the Gault, the junction can be seen by a basal bed of quartz. Further north, The Upper Greensand marks the start of the more fossiliferous beds. Here, a hard blue-grey stone band is full of ammonites seen 8.5m below the top.

Finally, the Lower Chalk and Chalk Basement Beds mark the most northern end of this excursion, with the Plenus Marls being the most exposed part of the chalk. Some exposures of the the Middle chalk follow this.

Wealden and Lower Greensand


Wealden Shale


Upper Greensand and Lower Chalk.