Étude géomorphologique de la basse-vallée du Nahr el Kébir - article ; n°1 ; vol.9, pg 7-28

Paul Sanlaville

Description

Collection de la Maison de l'Orient méditerranéen. Série géographique et préhistorique - Année 1979 - Volume 9 - Numéro 1 - Pages 7-28
The geomorphology of the area of the Nahr el Kebir is of considerable interest since it is very rich in both Quaternary shorelines and fluviatile terraces, in which there are numerous flint artifacts.
1. General View
The Nahr el Kebir lies between two different geological areas : one is the Baer and Bassit mountainous area to the North, with greenstone rocks (ophiolites) which were formed here in the Maestrichtian ; the other is the Alaouite mountain range to the South, an anticline of Jurassic and Cretaceous carbonaceous rocks. Between these two mountain areas there was once an important Neogene gulf, in which sedimentation was mainly marly. Deposits of Pliocene age are very thick in the lower valley of the Nahr el Kebir (460 m of marls). According to Soviet geologists, the Nahr el Kebir lies exactly along an important accident, a geosuture, separating the Arabian Platform from the Tauric structure. This accident does not seem to have moved to any great extent during the Quaternary.
The lower part of the Nahr el Kebir valley has cut widely into Pliocene marls, and is sometimes 6 km wide. It is incised in a plateau, smoothly sloping towards the West, and forming a glacis ; in the South this is exclusively cut into the Pliocene, but also into rocks of different age and hardness in the North. The fluviatile terraces of the lower Nahr el Kebir valley occur down its length as buttes and hills, whereas on the plateau it is marine deposits which outcrop frequently, with the main shoreline at about 80 - 85 m above sea-level.
2. The marine deposits of the plateau
The topography of the plateau is very regular, except for some small breaks of slope. Fluvial deposits are the exception, while in contrast, marine deposits frequently occur, easily recognisable by their darker soils. They are formed, sometimes of sandstone or of conglomerates, up to 15 m thick, and sometimes of very rolled flint gravels or pebbles. The fauna, firmly cemented, is not rare, but it is banal.
The most important marine formation is connected by the 80 - 85 m shoreline, and can be seen between Fidio and Hennadi, as well as, in the North, between Qannjra and Kirsane. Marine deposits are very abundant down to 30 m along the Nahr Snoubar ;they rise gently and continuously from the present shoreline to the foot of the Cheikh Mohammed butte ; the same transgressive formation sometimes fossilised an erosional topography and we know of several shorelines with two unconformable marine series (el Haqime and Boustane). Along the Nahr el Kebir valley the faciès is fluvio-marine, with alternating marine (with fauna) and fluviatile series. This transgressive formation, which is continuous for about 60 km, from the Nahr el Arab in the North to Banyas in the South, certainly belongs to the penultimate interpluvial ; the Tyrrhenian with Strombus bubonius does not outcrop at the mouth of the Nahr el Kebir or in the Jebleh area, but it exists at Banyas, and near the Nahr el Arab it overlaps, with an unconformity, the Khellale- Hennadi Formation, which corresponds to the Jbailian of Lebanon.
The Baksa Formation is relatively well preserved on both sides of the Nahr el Kebir between 90 and 135 m. At Jabal Idriss, it has a fluvio-marine faciès. Probably it belongs to the antepenultimate interpluvial and corresponds to the Zaqrounian of Lebanon.
The Mchairfet Formation rises up to 190 m and is of great age (pre-Günz). Its altitude is approximately the same on both sides of the river, so that the Nahr el Kebir geosuture has not operated very much since the lower Quaternary.
3. Fluviatile terraces
Like the Orontes river, the Nahr el Kebir has a complete series of fluviatile terraces, the best in the entire Levantine coastal area. These terraces are generally stepped, owing to the wide incisions into the valley cut during the Quaternary. The fluviatile accumulations must be correlated with the glacial periods of temperate zones (regression periods) with a climatic control. The material is generally coarse, but it also includes thick, silty series. The buttes, benches and hills are generally structural surfaces. However, the two first Wurmian terraces were cut by two subsequent erosional surfaces ; the younger the terraces, the smoother the terrace profile becomes. The glacis slope is 1.3 % ; the Mindel terrace slope is 1 % ; the Riss, 0.55 % ; the Würmian, 0.33 %, probably because of an epeirogenic rise of this area during the Quaternary. Finally, these terraces decrease in age towards the East ; the axis of the valley has moved progressively eastward, because erosion is easier in Pliocene marls ; also there may have been a slight tilting of the basin of the river.
The altimetric situation, stratigraphy, faciès, surface alterations and artifacts allow us to propose a relative chronology of these terraces mainly due to the fact that South of Snoubar, the Jinndiriye Formation lies unconformably over the Hennadi-Kellale Formation :
The lower terrace (Qo) is quite important (3 or 4 m) and contains potsherds.
Three formations are Wurmian (QI). Two Ech-Chir Formations (QIa and QIb) contain Middle Paleolithic, but not Upper Paleolithic, artifacts, and are dated from the first half of the Würm. The first one is mainly silty ; both are 30 m thick. In the Ech-Chir-Khoura area the second one lies unconformably over the first. Near Jinndiriye, and Haqime, a colluvial-alluvial deposit with red, clayey matrix (Jraïmaqiye Formation) contains some Upper Paleolithic flints (QIc).
The Jinndinye Formation (QII, Rissian) has been very well preserved on the right bank, in the high cliff at Jinndiriye, Jabal Aamrouniye, Jabal Souayate, where the deposits are sometimes 30 m thick, coarse in the lower part, then silty (but not loessic, as stated by Wendt, 1971), then with a rarely-preserved pebble series at the top. The apparent base of this formation is at about 65 m above the talweg of the Nahr el Kebir.
The older formations are much rarer and only exceptionally form terraces. The Berzine Formation (QIII , Mindelian) is preserved only in three or four outcrops, but was clearly identified in Berzine, where it is at + 100 m, i. e. 90 m above the alluvial plain, and where
we found many artifacts. The Sitt Markho Formation (QIV, Günz) is know from only one outcrop, at 110 m above the river, and about 10 m below the plateau. The numerous decalcified flints, the altitude and the geoche- mical alteration of pebbles, show that this formation is very old.
22 pages
Source : Persée ; Ministère de la jeunesse, de l’éducation nationale et de la recherche, Direction de l’enseignement supérieur, Sous-direction des bibliothèques et de la documentation.

Informations

• Publié par: DIALOGUES_D-HISTOIRE_ANCIENNE
• Publié le: 01 janvier 1979
• Nombre de lectures: 52
• Langue: Français
• Poids de l'ouvrage: 2 Mo

Extrait

Paul Sanlaville
Étude géomorphologique de la basse-vallée du Nahr el Kébir
In: Quaternaire et préhistoire du Nahr el Kébir septentrional. Les débuts de l'occupation humaine dans la Syrie du
Nord et au Levant. Travaux de la RCP 438, sous la direction de Paul Sanlaville. Lyon : Maison de l'Orient et de la
Méditerranée Jean Pouilloux, 1979. pp. 7-28. (Collection de la Maison de l'Orient méditerranéen. Série
géographique et préhistorique)
Citer ce document / Cite this document :
Sanlaville Paul. Étude géomorphologique de la basse-vallée du Nahr el Kébir. In: Quaternaire et préhistoire du Nahr el Kébir
septentrional. Les débuts de l'occupation humaine dans la Syrie du Nord et au Levant. Travaux de la RCP 438, sous la direction
de Paul Sanlaville. Lyon : Maison de l'Orient et de la Méditerranée Jean Pouilloux, 1979. pp. 7-28. (Collection de la Maison de
l'Orient méditerranéen. Série géographique et préhistorique)
http://www.persee.fr/web/ouvrages/home/prescript/article/mom_0243-2439_1979_rpm_9_1_1506Abstract
The geomorphology of the area of the Nahr el Kebir is of considerable interest since it is very rich in
both Quaternary shorelines and fluviatile terraces, in which there are numerous flint artifacts.
1. General View
The Nahr el Kebir lies between two different geological areas : one is the Baer and Bassit mountainous
area to the North, with greenstone rocks (ophiolites) which were formed here in the Maestrichtian ; the
other is the Alaouite mountain range to the South, an anticline of Jurassic and Cretaceous
carbonaceous rocks. Between these two mountain areas there was once an important Neogene gulf, in
which sedimentation was mainly marly. Deposits of Pliocene age are very thick in the lower valley of the
Nahr el Kebir (460 m of marls). According to Soviet geologists, the Nahr el Kebir lies exactly along an
important accident, a geosuture, separating the Arabian Platform from the Tauric structure. This
accident does not seem to have moved to any great extent during the Quaternary.
The lower part of the Nahr el Kebir valley has cut widely into Pliocene marls, and is sometimes 6 km
wide. It is incised in a plateau, smoothly sloping towards the West, and forming a glacis ; in the South
this is exclusively cut into the Pliocene, but also into rocks of different age and hardness in the North.
The fluviatile terraces of the lower Nahr el Kebir valley occur down its length as buttes and hills,
whereas on the plateau it is marine deposits which outcrop frequently, with the main shoreline at about
80 - 85 m above sea-level.
2. The marine deposits of the plateau
The topography of the plateau is very regular, except for some small breaks of slope. Fluvial deposits
are the exception, while in contrast, marine deposits frequently occur, easily recognisable by their
darker soils. They are formed, sometimes of sandstone or of conglomerates, up to 15 m thick, and
sometimes of very rolled flint gravels or pebbles. The fauna, firmly cemented, is not rare, but it is banal.
The most important marine formation is connected by the 80 - 85 m shoreline, and can be seen
between Fidio and Hennadi, as well as, in the North, between Qannjra and Kirsane. Marine deposits are
very abundant down to 30 m along the Nahr Snoubar ;they rise gently and continuously from the
present shoreline to the foot of the Cheikh Mohammed butte ; the same transgressive formation
sometimes fossilised an erosional topography and we know of several shorelines with two
unconformable marine series (el Haqime and Boustane). Along the Nahr el Kebir valley the faciès is
fluvio-marine, with alternating marine (with fauna) and fluviatile series. This transgressive formation,
which is continuous for about 60 km, from the Nahr el Arab in the North to Banyas in the South, certainly
belongs to the penultimate interpluvial ; the Tyrrhenian with Strombus bubonius does not outcrop at the
mouth of the Nahr el Kebir or in the Jebleh area, but it exists at Banyas, and near the Nahr el Arab it
overlaps, with an unconformity, the Khellale- Hennadi Formation, which corresponds to the Jbailian of
Lebanon.
The Baksa Formation is relatively well preserved on both sides of the Nahr el Kebir between 90 and 135
m. At Jabal Idriss, it has a fluvio-marine faciès. Probably it belongs to the antepenultimate interpluvial
and corresponds to the Zaqrounian of Lebanon.
The Mchairfet Formation rises up to 190 m and is of great age (pre-Günz). Its altitude is approximately
the same on both sides of the river, so that the Nahr el Kebir geosuture has not operated very much
since the lower Quaternary.
3. Fluviatile terraces
Like the Orontes river, the Nahr el Kebir has a complete series of fluviatile terraces, the best in the
entire Levantine coastal area. These terraces are generally stepped, owing to the wide incisions into the
valley cut during the Quaternary. The fluviatile accumulations must be correlated with the glacial periods
of temperate zones (regression periods) with a climatic control. The material is generally coarse, but it
also includes thick, silty series. The buttes, benches and hills are generally structural surfaces.
However, the two first Wurmian terraces were cut by two subsequent erosional surfaces ; the younger
the terraces, the smoother the terrace profile becomes. The glacis slope is 1.3 % ; the Mindel terrace
slope is 1 % ; the Riss, 0.55 % ; the Würmian, 0.33 %, probably because of an epeirogenic rise of this
area during the Quaternary. Finally, these terraces decrease in age towards the East ; the axis of the
valley has moved progressively eastward, because erosion is easier in Pliocene marls ; also there may
have been a slight tilting of the basin of the river.The altimetric situation, stratigraphy, faciès, surface alterations and artifacts allow us to propose a
relative chronology of these terraces mainly due to the fact that South of Snoubar, the Jinndiriye
Formation lies unconformably over the Hennadi-Kellale Formation :
The lower terrace (Qo) is quite important (3 or 4 m) and contains potsherds.
Three formations are Wurmian (QI). Two Ech-Chir Formations (QIa and QIb) contain Middle Paleolithic,
but not Upper Paleolithic, artifacts, and are dated from the first half of the Würm. The first one is mainly
silty ; both are 30 m thick. In the Ech-Chir-Khoura area the second one lies unconformably over the first.
Near Jinndiriye, and Haqime, a colluvial-alluvial deposit with red, clayey matrix (Jraïmaqiye Formation)
contains some Upper Paleolithic flints (QIc).
The Jinndinye Formation (QII, Rissian) has been very well preserved on the right bank, in the high cliff
at Jinndiriye, Jabal Aamrouniye, Jabal Souayate, where the deposits are sometimes 30 m thick, coarse
in the lower part, then silty (but not loessic, as stated by Wendt, 1971), then with a rarely-preserved
pebble series at the top. The apparent base of this formation is at about 65 m above the talweg of the
Nahr el Kebir.
The older formations are much rarer and only exceptionally form terraces. The Berzine Formation (QIII ,
Mindelian) is preserved only in three or four outcrops, but was clearly identified in Berzine, where it is at
+ 100 m, i. e. 90 m above the alluvial plain, and where
we found many artifacts. The Sitt Markho Formation (QIV, Günz) is know from only one outcrop, at 110
m above the river, and about 10 m below the plateau. The numerous decalcified flints, the altitude and
the geoche- mical alteration of pebbles, show that this formation is very old.Ί-
PREMIERE PARTIE
ETUDE GEOMORPHOLOGIQUE
DE LA BASSE VALLÉE DU NAHR EL KÉBIR
Par Paul Sanlaville
En Syrie comme au Liban ou en Palestine, la côte vent délicate. La basse vallée du nahr el Kébir septen
orientale de la Méditerranée a conservé de nombreux trional se présente donc comme un cas tout à fait excep
témoins de plusieurs paléorivages quaternaires dont les tionnel, puisqu'à côté de trois lignes de rivage, au moins,
plus élevés dépassent 200 m d'altitude et qui correspon du Quaternaire ancien et moyen, on peut y observer un
dent à au moins quatre périodes de rang interglaciaire. remarquable étagement de terrasses fluviatiles, et que de
En revanche, les fleuves côtiers sont modestes et leurs nombreux artefacts sont associés aux différentes format
vallées, étroites, profondément enfoncées dans les ions (cartes hors-texte 1 et 2). Afin de tirer le meilleur
calcaires et au profil très tendu, n'ont pas été favorables parti de l'analyse de l'industrie, nous étudierons ici en
à la préservation de terrasses fluviatiles anciennes, dont détail la géomorphologie de cette région.
il ne reste que de rares lambeaux d'interprétation CHAPITRE I
PRESENTATION GENERALE
DE LA RÉGION DU NAHR EL KÉBIR
ques (Ponikarov, 1968) estiment que ces roches sont Trois grandes voies naturelles relient la Syrie inté
rieure à la côte méditerranéenne : au Nord, le bas-Oronte antérieures au Trias supérieur et qu'elles se sont dépla
et la dépression de l'Amouk ; au Sud, l'ensellement du cé