The majestic contour of the Seven Sisters cliff sequence between
the River Cuckmere and Birling Gap in East Sussex is among the most
spectacular natural scenes in the British Isles. Sculpted by
melt-water and heavy rain during recent ice ages, and the erosive
power of the sea more recently, the present-day cliffs mark the end
of a series of natural inland gulleys.
Left: View from the
foreshore below Short Brow towards
Birling Gap in the distance.
Right: View from Birling Gap across the Seven
chalk cliffs and
foreshore at Seven Sisters reveals a diverse ecosystem dating from the
Cretaceous epoch, 87-84 million years ago. Fossils occur commonly
chalk, in particular
sponges, bivalves, and other benthic fauna that inhabited the
at the time.
Left: A flint pebble containing fragments of inoceramid
bivalve shell(s). Right: The internal
mould of an irregular echinoid Micraster integrated
with a flint nodule.
The most convenient place to access the cliffs and foreshore is at
Birling Gap - a cluster of residential properties and a large
cafe/pub (below-left). Plenty of free
parking is available throughout the year and a flight of steps
provide easy access to the beach (below-right). A local map of the
area can be accessed by clicking on the geology map at the top of
Left: Parking is
available alongside the beach access point at Birling Gap.
Right: Steps descending to the beach at Birling Gap.
The geology of Seven Sisters
The chalk at Seven Sisters belongs to the Upper Chalk, and
was deposited during the Coniacian and Santonian stages of the
Cretaceous epoch between 87-84 million years ago (mya). At this time
Seven Sisters and much of Great Britain, along with Europe, lay beneath a
relatively shallow sea around 40°N of the equator, on an equivalent latitude to the
Mediterranean Sea today.
In comparison with present-day conditions, global sea-levels during
the Late Cretaceous were over 200 meters higher. The higher sea levels
likely reflect a combination of extreme greenhouse conditions and
heightened plate tectonics. Elevated plate tectonic activity and the
associated volcanics delivered greenhouse gases to the atmosphere,
fuelling the greenhouse effect. Global high temperatures melted much
(perhaps all) of the ice at high latitudes, introducing significant
amounts of water to the world's oceans. Uplift of the ocean-floor in
regions of active plate tectonics displaced further water onto the
The evidence of higher sea levels is reflected in the white chalk
at Seven Sisters. The purity of the chalk indicates its formation
took place far from land, virtually free of terrestrial sands and silts
that would otherwise have coloured it. Chalk is
largely comprised of the the skeletal remains of planktonic algae
known as coccolithophores which accumulated to form a white ooze on the
seafloor. This soft sediment was later compacted and hardened
(lithified) to form chalk - a relatively soft rock itself. To
discover more about chalk
Today the chalk appears above sea level, the
result of lower present-day sea levels and widespread uplifting caused by the pressure of the European
and African continental plates colliding (generating the Alps), a process that took place at
its greatest extent 30-25 mya. More recently, following the end of the
last ice age and subsequent increase in sea levels (albeit to a less
extent than 84 million years ago), the coastline has moved inland,
exposing the elevated chalk to intensive erosion and sculpting it into a
Figure 1: Geology of the cliffs between
the River Cuckmere and Birling Gap, and onwards beneath the Belle Toute Lighthouse.
Photo taken from
One of the key markers visible in the cliff-face is the Seven Sisters Flint Band, a
conspicuous dark-coloured sheet flint visible within the Seaford Chalk
Formation. This particular sheet flint occurs near the cliff-base
towards the River Cuckmere and appears intermittently on the foreshore
towards Birling Gap.
Left: The Seven
Sisters Flint Band visible above the green algae towards the base of
the cliff beneath Short Brow. Right: Seven Sisters
Flint Band close-up.
Although flint is inorganic, the silica that formed it was originally
sourced from the remains of sea sponges and siliceous planktonic
micro-organisms (diatoms, radiolarians). Flints are concretions that
grew within the sediment after its deposition
by the precipitation of silica; filling burrows/cavities and
enveloping the remains of marine creatures, before dehydrating and
hardening into the microscopic quartz crystals which constitute
The photos below illustrate the unique flint-capped chalk pedestals
resulting where the Seven Sisters Flint Band occurs at beach level. To discover more about flint
Left: Where the
Seven Sisters Flint Band occurs at beach level it forms a hard
wearing upper surface on the foreshore.
Right: The SSFB opposite Birling Gap.
Travelling along the coast from Birling Gap a classic example of a
dissolution pipe can be observed at beach level. These structures
appear in cross-section as
the cliff retreats. Dissolution pipes form as rain water percolates
through the overlying
Quaternary sediments, becoming increasingly acidic in the process, and dissolving
the underlying chalk as gravity channels the water along natural
Left: A dissolution
pipe travels through the chalk and exits at beach
level. Right: A close-up reveals a high volume of ice-age
soil has passed along the pipe.
sediments were transported to the area during the most recent ice age,
115,000 - 10,000 years ago (Devensian stage of the Pleistocene
epoch), during which time much of Britain lay beneath a thick
ice-sheet. Although the limit of the ice-sheet extended only as far
south as Norfolk and the southern parts of Wales, the relative lack
of precipitation across the southern area created a mostly
inhospitable, wind swept, frozen desert landscape. The freezing
winds cut across the exposed land, carrying with them weathered
sands and soils. These sediments, known as loess, accumulated in the
chalk valleys of the Seven Sisters area (which had been shaped by earlier ice ages, as melt water eroded the landscape).
Since the return to more temperate conditions and subsequent
reduction of ice at higher latitudes, global sea-levels have risen
120m. The advancing sea, known as a marine transgression, has
submerged much of the former landmass, shifting the coastline inland and shaping
Seven Sisters as we know it.
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Where to look for fossils?
Fossils can be found on the foreshore and at the base of the cliffs
in either direction from Birling Gap, although for the purposes of this
page the focus is towards the northwest (right when looking out to sea). The most productive and safest place
to search for fossils is on the foreshore at low-tide. Chalk boulders
and flint nodules are scattered along the entire stretch, providing a
constant supply of fossils.
Left: Searching for fossils among and within the
flint pebbles on the foreshore. Right: Fossils can
be found in situ and within loose boulders.
Please note the beach platform and cliffs are assigned SSSI
status, which requires visitors avoid damaging (including hammering)
the area. From a fossil collecting 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
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?
Below are a selection of finds between Birling Gap and the River
Cuckmere. Where possible the specimens' genus has been indicated below
each photo, if a confident ID can't be achieved a question mark has
been added to indicate so. Among the common finds include echinoids,
brachiopods, bivalves and sponges; less common finds include
crustacean burrows lined with fish scales and starfish remains
Left: A large flint
pebble containing a partially exposed echinoid Micraster. Right: A beach-worn flint echinoid Micraster.
Left: A heavily worn internal flint mould of a
irregular echinoid Conulus. Right: The underside
of an irregular echinoid Conulus protruding from a flint
Left: A worn
irregular echinoid Echinocorys, the outer shell visible
in cross-section along its base.
Right: A bivalve Neithea(?) protruding from a flint
Left: A fragment of inoceramid bivalve shell
exposed in-situ on the foreshore opposite Birling Gap, Seaford Chalk
Right: A crustacean burrow lined with fish scales
Left: A flint pebble
containing fragments of inoceramid bivalve shell(s) and part of a small
sponge visible towards the top.
Right: Close-up of the sponge part.
Left: A small sponge
exposed on the surface of a foreshore boulder.
Right: A sponge on
the surface of a fallen boulder.
Tools & equipment
Left: Walking boots
are recommended for the rocky terrain. Right:
A hammer & chisel are ideal for extracting fossils.
It's a good idea to spend some time considering the tools and
equipment you're likely to require while fossil hunting at Seven
Sisters. 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
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
Chisel: A chisel is required in conjunction with a
hammer for removing fossils from the chalk. 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