Kimmeridge is a small coastal village in Dorset, located 13 miles
of Weymouth, and has a resident population of approximately 110 people.
Despite its modest size the village commands international
recognition for the interval of geological time known as the Kimmeridgian Stage which takes its name from the Kimmeridge Clay
that was first described in the area.
The Kimmeridge Clay (Formation) is composed of fossil-rich
mudstones and oil shales which originally accumulated as soft
sediment at the bottom of the sea
approximately 156-148 million years ago. This interval of 8 million
years spans both the
Kimmeridgian Stage and part of the subsequent
Tithonian Stage of the Late Jurassic Epoch. Today much of the Kimmeridge Clay
is elevated above sea level and outcrops locally in the cliff-face
and on the foreshore between Brandy Bay in the west and Chapman's
Pool towards the southeast.
Fossils occur commonly throughout the Kimmeridge Clay, in
particular the shells of ammonites and bivalves. Less common finds include the
skeletal remains of marine reptiles and in extremely rare instances
the bones of dinosaurs and pterosaurs.
parking is available at Kimmeridge Bay.
Right: The view from the car park looking
southwest across Kimmeridge Bay towards Hobarrow Bay.
Access to Kimmeridge Bay is made along a narrow road which passes
through the village and continues
through Smedmore Estate (see map above). A toll to drive along the road is payable at a roadside
kiosk a short distance from the village. Plenty of parking is
available at the cliff-top, alternatively a small number of spaces
can usually be found at the southeast end of the bay alongside the
Although fossil hunting is permitted at Kimmeridge Bay, the use of
hammers is not. These restrictions apply to Kimmeridge Bay
specifically and normal fossil hunting can be undertaken outside the
bay in either direction. See 'Where to look for fossils?' further
down the page for more information.
The geology of the Kimmeridge area
Left: The Upper
Kimmeridge Clay Formation exposed in the cliffs southeast of
Kimmeridge Bay, towards Chapman's Pool (3 miles from Kimmeridge
Right: A conspicuous muddy dolomitic limestone within the Upper Kimmeridge Clay Formation
Brandy Bay, known locally as the Cattle Ledge Stone Band.
The rocks exposed in the cliffs and on the foreshore at
Kimmeridge Bay and towards Brandy Bay in the
west and Chapman's Pool in the southeast belong to the Kimmeridge
Clay Formation. The formation was first described in the area in
1816 and takes its name from the neighbouring village/bay.
The formation comprises rhythmic alternations (in places) of soft
mudstones, calcareous mudstones and kerogen-rich mudstones/shales, the
latter of which can yield oil and gas when heated. Layers of muddy
dolomitic limestone (as shown above-right) occur at a number of levels
and form prominent ledges on the beach. The formation is over 500 metres thick
locally, much of which occurs below beach level.
The mudstones were deposited at the
bottom of a warm relatively shallow sea that extended across much of
Great Britain and Europe during the Late Jurassic Epoch. In the
Kimmeridge area the water depth was likely between 50-100 metres and
the nearest significant landmass occurred c.40 miles to the south
and west. At this time the Kimmeridge area was located
closer to the equator, approximately 35°N, on an equivalent latitude to
the Mediterranean Sea today.
Despite the presence of fossilised benthic fauna (seafloor dwelling
seabed is understood to have been anoxic (stagnant) for much of the
time, with opportunist organisms (in particular bivalves) colonising the
area during brief periods of more oxygenated conditions. Among the theories raised to explain these
oxygenation events were violent storms. The abundance of fossil ammonites and other
organisms that spent their lives higher in the water column reflects
individuals that died and sank to the seabed, where the low oxygen levels
and corresponding reduced activity of scavengers and bacteria favoured the
preservation of their remains.
The Kimmeridge Clay Formation is divided into Lower and Upper parts,
which can be distinguished by the ammonite fauna in particular. The Lower
Kimmeridge Clay is characterised by species of Pictonia,
Rasenia and Aulacostephanus; whilst Pectinatites
and Pavlovia are present only in the Upper Kimmeridge Clay.
The Lower Kimmeridge Clay Formation corresponds with the Kimmeridgian Stage
of the Late Jurassic Epoch, an interval of approximately 5 million years
between 156 - 151 million years ago (mya). The Upper Kimmeridge Clay
Formation corresponds to the early part of the Tithonian Stage of the Late Jurassic
Epoch, an interval of approximately 3 million years between 151 - 148 mya.
In total the Kimmeridge Clay Formation spans approximately 8 million
years between 156 - 148 mya. See
geologic timescale for context.
In the Kimmeridge area geologic forces have uplifted the rock,
exposing the complete sequence of Upper Kimmeridge Clay and the uppermost beds of Lower Kimmeridge Clay (the lower beds
remain locally buried below the surface). See figures 1 and 2 below for a summary of the key
Figure 1: A summary of
the geological units in the cliffs and on the foreshore
at Brandy Bay and Hobarrow Bay, west of Kimmeridge Bay.
Figure 2: A summary of
the geological units southeast of
Kimmeridge Bay beneath Cavell Tower, Hen Cliff and towards Chapman's
At Kimmeridge Bay the underlying oil bearing rocks have been
commercially drilled using modern techniques since 1959, extracting
up to 80 barrels of oil daily. The oil reservoir (more akin to a
giant sponge-like rock than an underground lake) occurs locally 500m
beneath the surface. The British Petroleum oil well can be
viewed up close alongside the footpath above Kimmeridge Bay (shown below).
Left: The cliff-face
at Kimmeridge Bay with BP's oil well visible at the cliff-top.
Right: The oil well
produces up to 80 barrels per day.
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Where to look for fossils?
Fossils can be found at any point between Brandy Bay and Chapman's
Pool, including Kimmeridge Bay itself, although the latter tends to
be over collected due to the volume of tourists attracted to the
beach. As the use of hammers is not permitted at Kimmeridge Bay,
fossil hunting is confined to searching for fossil material visible
on the surface of beach pebbles, in particular ammonite shells.
Visitors wishing to avoid the over collected areas will likely find
more favourable conditions along the neighbouring coastal stretches,
in particular towards Chapman's Pool which is typically more
accessible than areas to the west. Frequent cliff falls ensure a
constant supply of fresh material on the beach, although care should
be taken to avoid the most dangerous areas. To read more about the
dangers of fossil hunting
Left: Fossils such
as this Subdichotomoceras websteri ammonite can be
found loose on the foreshore having fallen from the cliff.
Right: A close-up of the Subdichotomoceras websteri ammonite shown left,
found at Hen Cliff, Lower Kimmeridge Clay Formation.
Left: Fossils can be
observed in situ on the exposed bedrock at low-tide.
Lucinda explores for fossils along the coastline southeast of
Right: An Aulacostephanus
autissiodorensis ammonite observed in situ within the
Lower Kimmeridge Clay Formation at Brandy Bay.
Please note the beach platform and cliffs are assigned
SSSI status, which requires visitors avoid damaging (including
hammering) the area. From a fossil hunting perspective this means
it's not permitted to extract specimens that are in situ. Collecting
efforts should be directed towards the loose boulders and pebbles on the
foreshore. To read more about SSSI's
As with all coastal locations a fossil hunting trip is best timed to coincide
with a falling or low-tide. For a relatively low one-off cost we
recommend the use of Neptune Tides software, which provides
future tidal information around the UK. To download a free trial
Alternatively a free short range forecast covering the next 7 days
is available on the BBC website
What fossils might you find?
The fossils of the Kimmeridge Clay provide evidence of some of
the organisms living in the sea during the Late Jurassic. Among the evidence
of prehistoric life most frequently preserved
are the shells of ammonites and occasionally the 'closing hatch',
although rarely associated with the same specimen (see examples
below). Other finds include the shells of bivalves, some of which occur in great
numbers crushed within thin layers of sediment. Occasionally the
skeletal remains of marine reptiles e.g. ichthyosaurs and
plesiosaurs, and their fossilised faeces (coprolites) can also be found.
As well as the indigenous sealife, evidence of creatures that
inhabited the land and sky have also been
discovered by local collectors. These finds include the skeletal remains
of dinosaurs and pterosaurs, the bodies of which were presumably carried
by tidal currents into the area and subsequently sank to the seabed.
These fossils are among the rarest of the Kimmeridge Clay and are not
featured below, however their presence is noted for reference
Below are a selection of finds made over several visits to
Kimmeridge Bay and the neighbouring coastal stretches, which
illustrate some of the more commonly occurring fossils. Many thanks to
Robert Chandler and John Callomon for providing their expertise to
identify the ammonites featured.
Left: An Aulacostephanus autissiodorensis ammonite observed in situ
within the Lower Kimmeridge Clay Formation at Brandy Bay.
Right: A Subdichotomoceras websteri observed in
situ within the Lower Kimmeridge Clay Formation at Brandy Bay.
Pectinatites ammonite viewed through the zoom-lens in
the cliff-face at Hen Cliff, southeast of Kimmeridge Bay, Upper Kimmeridge Clay Formation.
Right: A second
Pectinatites ammonite, observed in situ on the foreshore
beneath Hen Cliff, Upper Kimmeridge Clay Formation.
Left: A large, heavily worn Aulacostephanus ammonite observed
in situ at Hobarrow Bay, Lower Kimmeridge Clay
Right: A Aulacostephanus eudoxus ammonite, found among loose
cliff debris at Brandy Bay, Lower Kimmeridge Clay Formation.
Left: A large oyster
Pectinatites ammonite found loose at the cliff-base, Upper
Kimmeridge Clay Formation.
Right: An ammonite mostly obscured by pyritised
oyster shells, Upper Kimmeridge Clay Formation, found loose on the
Left: A Pectinatites (Virgatosphinctoides)
ammonite among bivalves from the Upper
Kimmeridge Clay Formation at Brandy Bay.
Right: A close-up.
Left and right: Two
isolated anaptychus (one of a pair of plates that formed a 'closing
hatch') belonging to an Aspidoceras ammonite.
Isolated anaptychus such
as these are assigned their own
genus - in this instance Laevaptychus. Found at Brandy Bay (left)
and Hobarrow Bay (right),
Kimmeridge Clay Formation.
Left: A fragment of
rib belonging to a marine reptile (ichthyosaur?), found loose on the foreshore at
Right: An ichthyosaur(?) tooth (3cm) observed in
cross-section on the surface of a fallen boulder a short distance
from Kimmeridge Bay beneath Cavell Tower.
Left: A split piece
of mudstone from the Upper Kimmeridge Clay Formation at Brandy Bay,
containing a concentration of bivalve shells.
Right: A close-up.
Left: The internal mould of a
bivalve shell found at Hobarrow Bay, Lower Kimmeridge Clay
Myophorella bivalve, found loose at the cliff base at Brandy
Bay. Upper Kimmeridge Clay Formation(?).
Left: A large
bivalve shell in situ at Brandy Bay, the precise horizon is
Right: The internal moulds of a pair or brachiopod
valves, found on the surface of a fallen boulder beneath Hen Cliff, Upper
Kimmeridge Clay Formation.
Left: A coprolite
(fossilised faeces) of a marine reptile or large fish, exposed on
the surface of a sea weathered boulder at Brandy Bay.
Right: A fragment of carbonised drift wood on the surface
of a fallen boulder beneath Hen Cliff, presumably Upper Kimmeridge Clay Formation.
Tools & equipment
Left: Lucinda searching for fossils near Kimmeridge Bay.
Right: A selection of useful tools and equipment for fossil hunting in the Kimmeridge area.
It's a good idea to spend some time considering the tools and
equipment you're likely to require while fossil hunting in the
Kimmeridge area. Preparation in advance will help ensure your visit is
productive and safe. Below are some of the items you should consider
carrying with you. You can purchase a selection of geological tools
and equipment online from
Hammer: A strong hammer will be required to
split prospective rocks. The hammer should be as heavy as can be
easily managed without causing strain to the user. For individuals
with less physical strength and children (in particular) we
recommend a head weight no more than 500g. Please note that the use
of hammers within Kimmeridge Bay itself is not permitted.
Chisel: A chisel is required in conjunction with a
hammer for removing fossils from the rock. In most instances a
large chisel should be used for completing the bulk of the work,
while a smaller, more precise chisel should be used for finer work.
A chisel founded from cold steel is recommended as this metal is
especially engineered for hard materials.
Safety glasses: While
hammering rocks there's a risk of injury from rock splinters
unless the necessary eye protection is worn. Safety glasses ensure any splinters are deflected away from the eyes. Eye
protection should also be worn by spectators as splinters can
travel several metres from their origin.
Strong bag: When considering the type of bag to use it's worth setting aside
one that will only be used for fossil hunting, rocks are usually
dusty or muddy and will
make a mess of anything they come in contact with. The bag will also
need to carry a range of accessories which need to
be easily accessible. Among the features recommended include: brightly coloured,
a strong holder construction, back
support, strong straps, plenty of easily accessible pockets and a rain cover.
Walking boots: A good pair of walking boots will
protect you from ankle sprains, provide more grip on
slippery surfaces and keep you dry in wet conditions. During your
fossil hunt you're likely to encounter a variety of terrains so
footwear needs to be designed for a range of conditions.
For more information and examples of tools and equipment
recommended for fossil hunting
or shop online at
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Protecting your finds
It's important to spend some time considering the best way to
protect your finds onsite, in transit, on display and in storage.
Prior to your visit, consider the equipment and accessories you're
likely to need, as these will differ depending on the type of rock,
terrain and prevailing weather conditions.
wrapped in foam, ready for transport. Right:
A small compartment box containing cotton wool is ideal for
separating delicate specimens.
When you discover a fossil, examine the surrounding matrix (rock)
and consider how best to remove the specimen without breaking it;
patience and consideration are key. The aim of extraction is to
remove the specimen with some of the matrix attached, as this will
provide added protection during transit and future handling;
sometimes breaks are unavoidable, but with care you should be able
to extract most specimens intact. In the event of breakage,
carefully gather all the pieces together, as in most cases repairs
can be made at a later time.
For more information about collecting fossils please refer to the
following online guides:
Fossil Hunting and
Conserving Prehistoric Evidence.
Join us on a fossil hunt
Left: A birthday party with
a twist - fossil hunting at
Right: A family hold their prized ammonite at Beachy Head.
Discovering Fossils guided fossil hunts reveal evidence of life that
existed millions of years ago. Whether it's your first time fossil
hunting or you're looking to expand your subject knowledge, our fossil
hunts provide an enjoyable and educational experience for all. To find