Field Guide to Dorset

A pictorial summary of some of the best coastal localities for geology along the Dorset coastline.

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This page is mainly a pictorial guide to the Geology of Dorset, the photographs having been taken during the Easter holidays, 2001, during the foot and mouth outbreak in the UK, and after one of the wettest winters ever. The consequences of these factors were that many of the coastal locations such as Kimmeridge Bay were not open to the public, that there were many new landslips and mudflows and that many of the clays and mudflows were still saturated and dangerous to walk on.

Location 1, Studland Bay

Looking southeast towards the Upper Chalk Cliffs of Foreland Point which form the southern boundary of

Studland Bay.

The basal Tertiary unconformity in the SW corner of the bay with Reading beds overying the Chalk, with karst features such as sink holes.

The Chalk/Tertiary boundary at the bottom left of the photograph, with the Reading Beds above.

Cliffs of theTertiary Reading beds in SW corner of the bay looking towards the Chalk boundary..

Location 2, Swanage

Looking north from the northern end of the Swanage Promenade to Foreland Point, with slipped wealden in the foreground and Chalk cliffs in the background.

Looking north from the northern end of the Swanage Promenade to the Chalk cliffs of Foreland Point, with slipped wealden in the foreground and the Wealden/Greensan/Chalk boundary in the midground.

Mudslides in the wealden beds at the northern end of the Swanage Promenade.

Looking north from the southern Swanage to the Chalk Cliffs of Foreland Point.

Location 3, Lulworh Cove

At Lulworth Cove the Chalk, Greensand, Wealden, Purbeck and Portland rock types of Upper Juarassic and Cretaceous age are visible. These have been folded and are now nearly vertical in many places, being one limb of the Purbeck Monocline. Lulwork Cove itself has formed from the sea eroding through the harder Portland and Purbeck beds at a slow rate and then eroding the much softer Wealden and Greensand beds at a much faster rate, the rate of erosion once again slowing at the rear wall of the cove which is formed of Chalk.

The Chalk/Greensand boundary in the NW corner of the cove.

The Chalk/Greensand boundary in the NW corner of the cove.

Bedding cyclicity in the Upper Greensand directly below the base of the Chalk with alternating Chert beds and Glauconitic sands and silts.

The steeply dipping Chalk/Upper Greensand contact.

Steeply dipping Chalk beds of the northern side of the cove.

The steeply dipping Purbeck and Portland beds of the eastern side of the cove.

The steeply dipping Greensand beds forming the widest part of the cove.

Highly eroded weak beds of sandstones, silts, lignite and ferruginous beds of the western side of the cove.

Location 4, Overcombe

The heavily eroded cliffs of Oxford clay looking eastward.

Fossil hunting in the Oxford Clay which has a rich bivalve fauna.

Location 5, Isle of Portland

The Isle of Portland looking from Weymouth Bay.

Portland Beds in an abandoned Portland Stone Quarry, NW Portland Island

The Portland Beds at Portland Bill

The Portland Beds at Portland Bill

The Portland Beds at Portland Bill

The Portland Beds overlying the Portland Sand and the Kimmeridge Clay looking SSW from Chesil.

Location 6, Chesil Beach

Chesil Beach viewed from the Isle of Portland

Location 7, Burton Bradstock (Burton Cliff East)

The Bride fault separates the Bridport Sands to the west from the Frome Clay to the east of the gap.

The cyclic Bridport Sands which span the Lower/Middle Jurassic boundary to the west of the car park.

The Frome Beds, the upper part of the Fuller's Earth of Middle Jurassic age to the west of the car park.

Location 8, Charmouth

Black Ven Marls of Lower Jurassic age at the base of Stonebarrow Hill to the east of Charmouth.

Cyclic Black Ven Marls of Lower Jurassic age at the base of Stonebarrow Hill to the east of Charmouth.

Location 9, Lyme Regis

The Cliffs looking east from Lyme Regis towards Charmouth.

Rhythmicity in the Blue Lias. Chippel Bay to the east of Lyme Regis. Typically thin kerogen rick shales grade into black shales with a sharp contact to an impure limestone.

Rhythmicity in the Blue Lias looking towards Charmouth.

Ammonite graveyard at Lyme Regis exposed on the wavecut platform.

Looking from the wavecut platform below Black Ven to the cliffs of Stonebarrow Hill (midground) and Golden Cap (background). Note the lighter coloured Upper Greensand cap of Golden cap. Below the Upper Greensand is the Gault Clay which sits unconformably on beds of Lower Jurassic age. major landslips and mudflows are present along these cliffs.