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Slide 1

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Sedimentary structures
`Interpretation of maps, photographs
and graphic logs showing the following
features: bedding, cross-bedding,
graded bedding, desiccation features,
sole structures'
(WJEC syllabus)
L.Blair 2005…read more

Slide 2

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Sedimentary structures can be used to interpret
the depositional environment of sedimentary rocks.
They can also be used to infer the energy
conditions of the environment and whether a
sequence of rock has been overturned (`way up
Table 5.26 page 92 Geoscience has very good
information regarding sedimentary structures.
Make your own notes about the ones that are
mentioned in the syllabus (slide 1).
(You can print this powerpoint as a `handout' and
make notes next to the pictures.)
Useful website:
L.Blair 2005…read more

Slide 3

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One of the most obvious features of sedimentary
rocks and sediment is the layered structure which
they exhibit. The layers are evident because of
differences in mineralogy, clast size, degree of
sorting, or colour of the different layers. In rocks,
these differences may be made more prominent by
the differences in resistance to weathering or
colour changes brought out by weathering.
L.Blair 2005…read more

Slide 4

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Sedimentary beds (or
strata) are deposited
horizontally. Often
these remain
undeformed and we see
horizontal beds in the
field. Within these beds
there may be further
sedimentary features we
can use to determine the
environment of
L.Blair 2005…read more

Slide 5

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Bedding is picked out by Coloured beds
different colours of rock
(indicating different
cements or constituent
minerals in the rock),
different grain sizes
(indicating a change in
energy), different fossils (a
change in environment or a
break in deposition) or
different degree of
weathering (causing some
layers to weather
preferentially and others to
stand out).
L.Blair 2005…read more

Slide 6

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Sedimentary rocks are
usually laid down in
layers over long
periods of time.
Sometimes the layers
of rock are the same
above and below. In
this case we cannot
see the distinction
between individual
layers of sediment.
The rock is massive -
it lacks visible layers.
L.Blair 2005…read more

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