Polish Archaeology in the Mediterranean (11.1999(2000))

DEIR EL-BAHARI

EGYPT

Esna Shale is made up of two main parts:
green shales at the base, and interbedded
green shales, and relatively harder yellow
marly limestones at the top. The marly
bands lie closer to each other and become
enriched in lime upward, making the tran-
sition into the Thebes Formation. The
Thebes Formation commences with fine-
grained limestone and chalky limestone
rich in bands and nodules of cherts, proba-
bly deposited at bathyal depths, and ends
with repetitive skeletal limestone and oys-
ter banks formed in a shallow-water set-
ting.
The vertical cliff rising some 200 m in
back of the temple is structurally unstable
because of the following:
1. The thick limestone succession of the
Thebes Formation resting over the Esna
Shale. The latter consists essentially of clay
minerals, which are structurally unstable,
particularly during heavy rainfall.

2. The lowermost part of the Thebes
Formation is jointed with relatively
close spacing of the joints. This struc-
turally unstable part overlies directly
the Esna Shale and stands with its ver-
tical face just behind the retaining wall
of the temple.
3. Since the Esna Shale represents the toe
of the Thebes Formation vertical cliff,
this stratigraphic situation is struc-
turally unstable.
4. The uppermost part of the vertical cliff
of the Thebes Formation over the tem-
ple consists essentially of closely joint-
ed, flaggy limestone with typical "pile-
of-brick" structure. This limestone con-
stitutes the edge of the cliff, and is
structurally unstable due to its litho-
logical profile, and to the occurrence of
tension joints with very wide openings
in different, inconsistent directions and
the angle of dip.

FACTORS THREATENING ROCK COLLAPSE

Rock failures are usually of complex ori-
gin, with several factors contributing to
them simultaneously. The risk factors
include:
A. Heavy rainfall from individual storms
(as exemplified by the one of Nov. 4,
1994) causing numerous shallow slides,
where high water pressure can rapidly
reach the slip surfaces of the Esna
Shales. The topmost part of the Thebes
Formation at the cliff edge character-
ized by wide opening of tension joints
represents the head zone which captures
runoff over the cliff and increases infil-
tration through the very deep joints of
the Thebes Formation.
B. The Esna shale toe of the vertical cliff of
the Thebes Formation. If removed
either naturally by erosion or by an arti-

ficial process, it will reduce the resist-
ance to movement of the column-like
blocks of the Thebes Formation.
C. Advanced erosion of the top parts of the
column-like rocks of the Thebes
Formation. Temperature fluctuations
and rainwater runoff are working con-
tinuously on eroding the "caps" of these
rocks. The removal of this material
reposing on the natural lines of sliding
of rock would diminish its driving force
and increase the stability of the large
blocks.
D. Vibrations caused by earthquakes,
a number of which have occurred in the
Fuxor area in recorded history.
E. Other vibration-causing potentially
dangerous phenomena of modern civi-
lization, such as heavy road traffic

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