Geology of Kingsand/Cawsand

Geology of Kingsand/Cawsand
View from Cawsand looking north towards Sandway Cellar
A PDF copy of this booklet, as well as PDFs of
risk assessments, maps and other documents in
the box can be found in the virtual box,
accessible from the LABplus website (see signs
up around the lab to find out how to access the
website).
Further information can also be found at the
fieldtrip website (laptops are available from the
technician’s office)…
http://www2.plymouth.ac.uk/science/anderson/de
fault.htm

Introduction
Looking north­east from Kingsand (Grid
reference: 4347 5051) along the wave­cut
platform there is almost continuous exposure all
the way to Fort Picklecombe (see photo above).
This provides an excellent opportunity to study
these rocks in the field and learn/practice some
of the basic field techniques needed as a
Geoscientist during your degree and afterwards.
In particular the rocks at Sandway Cellar (Grid
reference: 4407 5102) are of great interest and
on the beach there is more to observe to build up
a picture of the relationships between different
rock types.
How to get there?
The twin villages of Kingsand and Cawsand are
situated across the River Tamar on the western
side of Plymouth Sound on what is known as the
Rame Peninsula. It takes about 8­10 miles by
road from Plymouth but only about 3.5 miles as
the crow flies.
Use the Ordnance survey map in the box to find
out where Kingsand/Cawsand are and think
about how you will get there. There are several
ways of getting to Kingsand/Cawsand:

1. by bus (81C) from Plymouth (takes about 1
hour). See bus timetable.
2. by the Cremyll Ferry, from Admiral’s Hard,
Stonehouse (8 minutes) and then either walking
along the coastal path (45 minutes) or catching a
bus (81C) to Kingsand (20 minutes). See
timetables for ferry and bus times.
3. by driving via the Torpoint Ferry and parking in
the village (about 1 hour). See the OS Explorer
map for the route. Come off the ferry in Torpoint
and drive straight on via the A374, turn left to
Antony and left again at Tregantle onto the
B3247 to Millbrook. Carry on up the hill past
Millbrook to Fourlanesend (school on the left)
and then turn right down the hill into Kingsand.
Parking is available at the side of the road by the
play park (free) or in one of the 2 car­parks in the
villages (pay & display).
Tides
Check the tide times as the exposures are tide
dependent. Look at the Tide tables in the box or
check online for the day you are planning to go
into the field. You should always be aware of
whether the tide is rising or falling while you are
working on a coastal section.

Website
You can also check the following website for all
this information:
http://www2.plymouth.ac.uk/science/anderson/de
fault.htm
What to bring?
You will need:
Suitable footwear which supports your ankles
Waterproof jacket and trousers
Compass clinometer & hand lens
Field notebook & pencil
Clipboard
Maps of the area at varying scales – available
online to print
Lunch/snacks & drinks
Handout with tasks to be completed/PDA
Ordnance survey maps can be borrowed from
the Cartographic Resources Unit, located in
LABplus. Copies of the detailed
Kingsand/Cawsand maps can be obtained as
PDFs from the virtual box.
Risk Assessment
You MUST read and sign the risk assessment,
leaving a copy with Meriel Fitzpatrick and taking
a copy with you into the field. Copies of the risk
assessment can be found in the virtual box.

What to expect
The information in this next section is intended
as an introduction to what you might see. The
PDAs will provide similar information when you
are in the field.
Once you arrive in the village use the maps or
PDA available to orientate yourself. Using the
larger scale map find your way to the Minnadhu,
also spelt Minnadew (a large grassy area to the
northeast of the village) Grid reference: 4350
5063.
The coastal path leading towards Minnadhu

Walk along from the gate which marks the
beginning of Mount Edgcumbe Country Park.
Walk along the path and then diagonally down
and along the grassy slope to the right, to the
very end where there is a gap/gateway in the
hedge straight ahead. Go down the narrow path
and metal steps onto the beach.
The gap in the hedge leading to the beach

View towards Sandway Cellar – pointed out by the red
arrow
Tasks to be completed:
Once you have reached Sandway Cellar
(marked with the red arrow) you should locate
yourself and visit the following sites, using the
PDA for assistance.

Site 1 – general view
Site 1
At this location you should be able to see the
sub­vertical layers (beds) of sedimentary rocks
which differ in their grainsize.

Site 1 – detailed view of sedimentary rocks
Tasks:
1. Examine the first rock type (Sample KC1) –
look at the rock with a hand­lens and note that it
is made up of grains (rather like the sand on a
beach). Use the grain­size chart to determine
the grainsize more accurately. Is it fine, medium
or coarse?

2. Examine the second rock type (Sample KC2)
– look at the rock with a hand­lens and note that
you cannot see individual grains. To determine
whether the rock is a siltstone or a claystone,
you can carry out the “chew” test. Take a small
piece and gently rub it against your teeth, or you
can rub it against your fingernail if you prefer. If
the material forms a paste it is dominated by clay
and it is a claystone. If it feels gritty it is a mix of
clay and silt and it is a siltstone.
3. Use your compass clinometer to measure the
dip and dip direction of the bedding at this
location (check on University Software – Earth
Science Courseware – Compass Clinometer if
you are not sure how to do this.
Don’t worry about the white material in these
rocks. These are veins and are a result of
fracturing. Note that they are only found in the
Sandstones and not the Mudstones, which are
softer.
Directions: From here walk northeast to site 2.

Site 2
Site 2 – general view of the orangey­red rock with the
sedimentary rocks in the foreground
You should see 3 rock types: two sedimentary
rocks like those you saw at Site 1 – Sandstones
(Sample KC1) & Mudstones (Sample KC2) and
an orangey­red rock (Sample KC3).

Tasks:
Find a good bedding surface and take a
measurement of the Dip/Dip Direction of the
sedimentary rocks – sandstones and mudstones.
Examine the very orangey/red rock (Sample
KC3) and describe it.
Can you see any bedding?
It is massive (i.e. has no bedding) and has
coarse crystals (up to 5 mm)
Close­up of crystals in the orangey­red rock

1. Look at the boundary between this rock and
the sedimentary rocks (Samples KC1 & 2).
2. What is the nature of this boundary?
3. What does this tell you about their relative
ages?
4. What is the orientation of this boundary? Use
your compass to take a measurement.
Directions: From here was south to Site 3.
Site 3
You are along strike from the sandstones and
mudstones that you measured at Site 1. You
should see one main rock type here (Sample KC
4). It is different to the others you have already
described.

Site 3 – general view of the site
This is very coarse sedimentary rock. It is a
conglomerate.
Tasks:
Examine the rocks exposed and describe the
range of blocks (clasts) found within them.
1. What is the largest sized clast in the
conglomerates (use your grainsize chart to
classify clasts of this size)?
2. What is the smallest sized clast (again use
your grainsize chart)?

3. How many different types of clast can you
identify?
4. Identify and describe any of the rock types
that form clasts in these conglomerates
(especially any that you may have seen earlier
today)?
5. Do the large clasts touch each other or do
they “float” in a matrix of finer material?
6. What is the Dip and Dip Direction of the
conglomerates?
7. Which are the younger rocks and why?
8. What is the nature of the boundary between
these two sets of rocks?
Directions: From here continue walking
southwest to Site 4.
Site 4
You can sometimes see two of the rock types
exposed here. But it depends how much sand is
covering the exposure. You may see the
sandstones like at Site 1 and the conglomerates
like at Site 3 lying directly above.

Site 4 – general view
Tasks:
Examine the first rock type (Sample KC1).
1. Can you see the grain size? Use your hand
lens and grain size chart to help you.
2. This is a sandstone, but is it Fine, Medium or
Coarse?
3. Can you see the bedding?
4. Take a measurement of the Dip/Dip Direction.
5. These rocks can also be seen at Sites 1 and
2.

Site 4 – showing the dip of the bedding in the first rock
type

Site 4 – showing the conglomerate filling in above the
sandstone
Examine the coarser rock type (Sample KC4).
1. This is a conglomerate similar to the one you
saw at Site 3.
2. Estimate the Dip/Dip Direction of the bedding.
Compare this with the measurement you took at
Site 3.
3. These rocks can be seen in much more detail
at Site 3.

4. What do you think the nature of the boundary
between Rock Types 1 & 2 is?
5. Are these conglomerates younger or older
than those Locality 3? Explain your reasoning.
Directions: From here walk south just beyond
the corner of the wall to Site 5.

Site 5
These rocks are the youngest you will see in the
succession here. They are completely different
to the other rock types you have already seen at
Sandways and originate from volcanic
extrusions.
Look for the obvious rocky platform which
extends from the corner of Sandway Cellar and
forms the southern edge to the beach.
This is a volcanic igneous rock.
Tasks:
1. Examine the rock (Sample KC5) and
describe the grain size. It is very fine but you
may be able to see individual crystals.
2. You should be able to observe some fine
wavy lineations in these rocks, which are flow
banding where the lava flowed (see photo
below).
3. You may also observe some very small holes
or vesicles. What do these tell you?
4. There is some very distinct jointing in these
rocks – take a measurement of the orientation of
these joints with your compass.

Flow banding
5. What is the relationship between these rocks
and the others you have been observing?
6. What geographical feature do these rocks
form?
Make some notes in your field notebook at each
site. Try to be methodical in the way in which
you make your notes.

Finally…
1. Think about the relationships between all the
rocks you have observed on this beach.
2. Try to put them in stratigraphic order with
reasons for your decisions.
You can also check the geological map online for
further information which may help you. This will
tell you the ages of the rocks which is something
you cannot ascertain in the field unless you find
evidence in the form of fossils.
Description of rock types in the
laboratory
Look in the box for samples of the rocks which
you will see in the field (labelled KC1­5). This is
an opportunity to look at the rock types in the
comfort of the laboratory. Make some notes and
compare these to the real outcrops when you
visit the location.