Geology Reference
In-Depth Information
Fig. 2
The Eocene-Quaternary
volcanism of Hoggar.
a
Panoramic view of Assekrem in
the Atakor massif.
b
Iharen
phonolitic plug with a phonolitic
plateau background;
c
Hadriane
trachytic plateau;
d
Trachytic
plug near Tamanrasset
Ajjer (2,500 km
2
), Atakor (2,150 km
2
), Tahalra
(1,800 km
2
), Manzaz (1,500 km
2
), Anahef (400 km
2
), Teria
(100 km
2
), Djanet (50 km
2
), and in Ezzane (800 km
2
).
According to Li
Adrar N
'
wood dating from the Oligocene and lower Miocene has been
reported in the Atakor massif (Rognon et al.
1983
); and
nally, from a cultural perspective, in Assekrem this massif
houses the hermitage of Charles de Foucault and his succes-
sors, built in 1910 and located at 2,780 m above sea level.
é
geois et al. (
2005
), the total extent of this
volcanic episode exceeds 1,650 km
3
. One of the most
beautiful geosites with basaltic cones and a phonolitic pla-
teau is the Atakor massif, which culminates at 3,003 m; it
includes the Assekrem (Fig.
2
a) where the hermitage of
“
2.2
Djanet and Tassili Massifs
Charles de Foucault and his successors is situated.
The volcanic activity of this district is Late Eocene-Early
Oligocene (35
fr
è
re
”
Tassili is an extensive sandstone massif, some 750 km in
length and 60
100 km wide covering 120,000 km
2
. Con-
sequently, it is considered to be the second-most important
national park in Algeria and one of the most important in
Africa because it extends beyond Algerian borders into
Libya and Niger. It was carved into varied relief by
t-Hamou et al.
2000
) and has
persisted to post-Neolithic times. Tuareg people tell stories
about eruptions that their ancestors have witnessed.
The Atakor massif is an exceptional site that presents
geological, cultural and educational interests. It includes the
highest peak in Algeria, Mount Tahat that reaches 3,003 m;
secondly, this massif constitutes an impressive natural
museum for a diversity of igneous rocks (Girod
1971
). Over
an area of 2,150 km
2
, there are a dozen varieties of igneous
rocks, some of which are rare in the geological record; the
most important igneous rocks are basalts, basanites, tephrites,
hawaiites, mugearites, benmoreites, phonolites, trachytes and
rhyolites (Girod
1971
)(Fig.
2
a
-
30 Ma), (A
ï
-
fl
uvial
erosion and wind action (Fig.
3
a
c).
The highest uplands, with an altitude of up to 2,000 m, are
dissected by canyons bordered with spectacular cliffs that reach
700 m in height. Occasionally, the rocks of the highlands,
initially sculptured exquisitely by wind are covered completely
by aeolian sands. The area hosts one of the most important
groupings of prehistoric rupestral engravings. Thousands of
drawings and engravings can be traced back to 10,000 BC
recording changes in the climate, fauna and
-
d). The area is also an
important site because of the morphological diversity of the
volcanic
-
ora in this part of
the Sahara (Fig.
3
e, f). These interesting national resources
have been listed among the World Heritage sites since 1982,
and have been classi
fl
landforms
(volcanic
dome,
strato-volcanoes,
strombolian cones, necks, dikes, sills, lava
ows with much
contrasted morphologies due to erosion). In addition silici
fl
ed
ed as a Biosphere Reserve in 1986.
