Walther's law of correlation of facies states that facies that occur in vertical successions of strata also occur laterally adjacent to each other. It is based on the principle that only facies that can be observed beside each other presently can be superimposed in the rock record. Walther's law explains how lateral shifts in depositional environments over time result in vertically stacked facies that match the lateral sequence, creating time-transgressive sedimentary formations with the same vertical and horizontal facies relationships.

1. Walther’s law of correlation of facies
The principle that facies
that occur in conformable
vertical successions of
strata also occur in laterally
adjacent environments.
[A vertical progression of
facies can be found
corresponding lateral facies
changes]

2. Walther’s Principle
< vertical and horizontal facies match >
The various deposits of the same facies-area and
similarly the sum of the rocks of different facies-
areas are formed beside each other in space,
though in a cross section we see them lying on top
of each other.
As with biotypes, it is a basic statement of far
reaching significance that only those facies and
facies-areas can be superimposed primarily which
can be observed beside each other at the present
time.

3. Walther’s Law
• Sedimentary rock types record the environment
of their deposition.
• Depositional environments can shift laterally as
conditions change.
• When so, laterally related environments become
superimposed.
• Time-transgressive sedimentary formations, are
the result.
• The vertical succession and lateral sequence of
facies will be the same.

5. Walther’s Law
• Certain facies associations are common in the
rock record.
• For example, most clastic shoreline show a
series of depositional environments that are
progressively finer-grained in the offshore
direction.
• There are facies belts of coarses sands, and
silts and clays. If the relative sea level changes,
deposits of these facies belts accumulate.
• Three facies pattern are possible.

6. Walther’s Law
Facies belts could pile up vertically if the
relative rate of sea-level rise is exactly
balanced by the sedimentary output of the
land.

7. Walther’s Law
Facies show a transgressive pattern when the
sediment supply is overpower by a relative
rise in sea level, or when the land subsides
tectonically. Both cause the shoreline to move
landward

8. Walther’s Law
 Facies show a regression pattern when the
shoreline moves seaward due to an excess
sediment supply from land, when the land is
tectonically uplifted and the sea level retreats,
or when there is a relative lowering of sea
level.

9. Walther’s Law
Exceptions
• The law is invalid where the contact between
different lithologies is non-conformable (due to
lack of deposition), or during cases of rapid
environmental change when non-adjacent
environments may replace one another.