Download Stratigraphy and tectonic history of the Iullemmeden Basin in West

S.AfrJ.Geol.,1991,94(1),19-32
19
Stratigraphy and tectonic history of the Iullemmeden Basin in West Africa
C.A. Kogbe
Rock View International, Geoscience Consulting Associates,TourOnyx, 10 Rue Vandrezanne, 75013 Paris, France
Accepted 21 January 1991
The Iullemmeden Basin with a tectono-epeirogenic origin is one of the three important sub-Saharan inland basins. It
extends for about 1 000 km from north to south and 800 km from east to west. The basin consists of a broad syncline
with a maximum depth of about 1000 m, except within two major depressions which are structurally controlled. Three
principal fault-trends predominate. These are NNE-SSW, NW-SE and WSW-ENE. The most important is the
NNE-SSW-trend which is responsible for the existence of the two depressions within the basin. The NW-SE trending
faults mark the western limit of the basin and display a downthrow of about 500 m. The WSW-ENE faults are
concentrated in the north-eastern part of the basin on the western margins of the Air mountains. The epeirogenic
movements within the basin are evident from the beginning of the Palaeozoic and continued until the late Cretaceous
when the opening of the Goa trench took place. These movements were responsible for the south-western progradation
of sediments within the basin. Sedimentation resumed during the Palaeozoic and continued throughout the Mesozoic
and Cainozoic with occasional breaks. The Cambro-Ordovician formations rest directly on the basement in the northeastern portion of the basin along the margins of the Air mountains where basement outcrops have been intensively
peneplained. Further towards the centre of the basin, Devonian and Carboniferous formations outcrop and are
punctuated by inliers of basement rocks. Permian and Lower Cretaceous deposits outcrop progressively further south
and the sedimentary sequence becomes increasingly younger south-westwards. Upper Cretaceous and Tertiary deposits
outcrop around the centre of the basin forming an undulating plain with occasional hills with an elevation of about
100 m above the plains. The geological history of the basin displays a close relationship between tectonics and
sedimen tation.
Die Iullemmeden Kom met 'n tektono-epirogeniese oorsprong is een van die drie belangrike sub-Sahariese
binnelandse komme. Oit strek ongeveer 1 000 km van noord na suid en 800 km van oos na wes. Die kom bestaan uit
'n brec sinklien met 'n maksimum diepte van ongeveer 1 000 m, behalwe in twee hoofdepressies wat struktureel
beheer is. Orie hoofverskuiwings oorheers. Oit is NNO-SSW, NW-SO, en WSW-ONO. Die belangrikste is die
NNO-SSW-neiging wat verantwoordclik is vir die bestaan van die twee depressies binne die kom. Die verskuiwings
mel 'n NW-SO-neiging vorm die weslelike limiet van die kom en loon 'n val van ongeveer 500 m. Die WSW-ONOverskuiwings is gekonsentreer in die noordoostelike deel van die kom aan die westelike grense van die Alr-berge. Die
epirogeniese bewegings binne die kom blyk vanaf die begin van die PaleosoYkum en het voortgeduur tot die Laat-Kryt
loe die oopmaak van die Goa-lrog plaasgevind het. Hierdie bewegings was verantwoordelik vir die suidwestelike
progradasie van sedimente binne die kom. Sedimentasie is hervat gedurende die PaleosoYkum en het deur die
Mesosoi"kum en SenosoYkum voortgeduur met enkele onderbrekings. Oie Kambro-Ordovisie formasies rus direk op die
vloer in die noordoostelike gedeelte van die kom langs die grense van die AIr-berge waar vloerdagsome intensief tot
skiervlaktes gecrodeer is. Devoniese en Karboniese formasies dagsoom verder na die middel van die kom en word
onderbreek deur vensters van vloergesteentes. Permiese- en Onder-Krytafsettings dagsoom progressief verder suid en
die sedimentcre opeenvolging word toenemend jonger suidweswaarts. Bo-Kryt- en Tersiereafsettings dagsoom rondom
die middelpunt van die kom en vorm 'n golwende vlakte met enkele heuwels, met 'n elevasie van ongeveer 100 m bo
die vlaktes. Oie geologiese geskiedenis van die kom toon 'n noue verband tussen tektoniek en sedimentasie.
Introduction
Stratigraphy and tectonics
The Iullemmeden Basin with its pentagonal shape extends
through five countries: Niger, Nigeria, Mali, Algeria, and
Benin. It covers an area of about 800 000 km 2 and is
bounded by: the Adrar des Iforas, the Hoggar, and the Air
mountains in the north; the Gourma and Liptako massives
and the crystalline rocks at the northern boundary of the
Benin Republic to the west; and the Nigerian basement
rocks to the south and southeast (Figure 1).
The basin is underlain by crystalline basement consisting
of igneous and metamorphic rocks. It is connected to the
Taoudeni Basin in the west by the Goa trench also known as
the 'Detroit Soudanais' which is situated between the Adrar
des Iforas and the Gourma highlands. The Damergou
passage provides a connection with the Chad Basin to the
east (Greigert, 1966; Dubois, 1979). The basement complex
is directly overlain by Cambrian rocks in the north around
the Tassilli, Air, and Hoggar mountains. The sedimentary
formations become progressively younger from the northeast to the south-west indicating the direction of the
successive marine Cretaceous transgressions.
The general stratigraphic sequence of the basin is now fairly
well established thanks to the efforts of many pioneer
French geologists including Joulia (1959, 1963, and 1989),
Radier (1959), Greigert (1966), and Faure (1966).
Geologists of the French Atomic Energy Agency including
Bigotte, Obellianne, and Valsardieu worked extensively in
Niger. Jones (1948) and Kogbe (1979) published
monographs on the Nigerian sector of the basin and Alidou
(1983) also published a monograph on the sector of the
basin in northern Benin. Table 1 summarises the
stratigraphic sequence within the Iullemmeden Basin.
Palaeozoic
The Palaeozoic formations outcrop in the north-eastern
portion of the basin, locally known as the Tamesna Basin.
They form a band around the southern portion of the Tassilli
highlands within the Central Sahara. Alidou (1983)
described Palaeozoic trace-fossils from the south-western
portion of the basin in northern Benin Republic thus
S .-AfT .Tydskr .Geol., 1991 ,94(1)
20
o
M.d.,.
.
.
~
C.n.rl ..
WESTERN
DESERT
D.ker
•
+
+
+
4-
+
+
+
+
4• V.ound.
+
+
+
o
Figure 1 Geological map showing the location of the Iullemmeden Basin and other Saharan basins of Africa. 1
= Palaeozoic rocks; 3 = Mesozoic and Cainozoic rocks; 4 = Cainozoic volcanic rocks; 5 = faults/thrusts.
confirming the presence of Palaeozoic outcrops in the area.
The basement horst of 'In Guezzain' divides the Tamesna
basin into two sections; the Tin Seririne or Tim Mersoi
section to the east and the Tassilli Oua N' Ahaggar section to
the west. The Tin Seririne section is folded into a large
syncline oriented roughly north-south while the Tassilli Oua
N' Ahaggar trends east-west but is folded into several small
synclines with north-south orientation. The lithostratigraphy
of the Palaeozoic sequence in the lullemmeden Basin is
shown in Table 2.
The Palaeozoic sediments in the northern portion of the
lullemmeden Basin are subdivided into two sections by a
major fault (see Figure 2). The lower section is
unconformable on the basement complex and consists of
Cambrian and Ordovician sandstones and shales overlain by
Silurian calcareous-silty clays and sandstones with
graptolites. One erosional unconformity exists at the base of
the Cambrian and a more important one occurs at the top of
the In-Azaoua sandstones of Middle Ordovician age.
The upper section is unconformable on the lower one
described above, and comprises lowennost conglomerates
succeeded by Lower Devonian sandstones (Grcs d'ldekel).
The Middle Devonian consists of sandstones with
ferruginous oolites, and calcareous shales with a rich
=
Precambrian rocks; 2
brachiopod fauna. The Upper Devonian is represented by
alternating coarse-grained ferruginous sandstones and
fossiliferous gypsiferous shales. The Carboniferous consists
of three sedimentary sequences: the Terada Series; the
Lower and Upper Tagora Series (Table 2).
The Terada Series consists of basal conglomerates and
f1uvio-glacial sandstones described by Valsardieu (1971).
The Lower and Upper Tagora Series consist of fluviodeltaic sandstones. Each of the series is overlain by marine
shales or an alternation of marine shales and continental
sandstones. After the deposition of the marine Carboniferous
deposits, there was a long period of erosion and continental
sedimentation which ended with the Upper Cretaceous
transgression over the basin.
The Palaeozoic sequences thin towards the centre of the
basin, each overlapping the previous one from north to south
(see Figure 2). Sedimentation is obviously structurally
controlled.
The Palaeozoic geological history of the Iullemmeden
Basin is characterised by the presence of erosional
unconformities separating the mega-sedimentary sequences.
Two minor structural unconformities exist at the end of the
Silurian and the middle of the Carboniferous. They may be
traces of Caledonian and Hercynian orogenic events.
S.Afr.1 .Geol.,1991 ,94(1)
Table 1
21
Post-Precambrian formations of the lullemmeden Basin (after Taquet, 1976)
CAINOZOIC
Quaternary
Alluvial deposits, Eolian, glacis, terrases, ferruginous crust
Mio-Pliocene
or 'Continental
tenninal'
Clayey sands of Middle Niger (Gt3)
Red sandstones and red clays
Clayey sands with lignite (Ct2)
(Continental)
Middle to Eocene
Paleocene
Siderolitic sands of Adrer Dutchi (Ctl)
Attupulgite clays
Limestone with Ranilwthalia bermudezi and Lokhartia haimei
Clays and limestone with Elphidiella, sables
(Continental)
(Confined marine)
(Neritic deep sea)
(Coastal marine)
MESOZOIC
Maastrichtian
tenninaI
Limestone with Libycoceras and Laffitteina
Continental
Hamadian
Neritic (deep sea)
Maastrichtian
to
Campanian
Upper sandstones and mudstones
Mosasaurus Shales (Libycoceras)
Coastal marine
Sandstones and mudstones
Coastal lagoon
Lower Senonian
Clays and limestones
Upper Turonian
White calcareous series
Lower Turonian
Limestones with N igericeras
Upper Cenomanian
Limestones with N eolobites vibrayeanus
Marine
Lower Cenomanian
Farak Fonnation
(Continental)
Albian
to
Neocomian
Tegama series
Berriasien
to
Jurassic
Dabla series
Mid-Jurassic
to
Triassic
Agadcs
Echkar Formation
Elrhaz Fonnation
Tazole Fonnation
haszer clays
Assouas sandstones
Tchirezrine 2 sandstones
Wagadi
Abinky Analcimolites
Tchirezrine I sandstones
Goufat
Analcimolites of Moussede
sandstones
Izcguandane series
Penn ian
Moradi clayey sandstones
Tamamait Sandstones
Tarat Sandstones
Carboniferous
(Uppcr Visean)
Lower Tagora series
Tchinezogue clays and fine-grained
sandstones
Guezouman Sandstones
------- -------
Lower
Carhoni rerous
(Lower Visean)
Devonian
(Continental)
(Continental)
Tejia Argilites
Izeguande Arkoses
Upper Tagora series
--
Intercalaire
Teloua 1 Sandstones
Lower
---
(Continental)
Teloua 2 Sandstones
Aguclal
PALEOZOIC
(Continental)
Continental
~---.-----
--
---.--~-.--
-.---
Terada series
Talach clays with gypsum
Arkoses, conglomerate
of Reragh = Farazekat
(marine)
(Continental)
Upper
Amesguer sandstone with gypsum
(marine)
Middle
Akara Schist
(marine)
Lower
Fine sandstones, oolitic
Sandstones
Silurian
Upper Ordovician
Shales with graptolites
Fine sands and clays, limestones
CambroOrdovician
In Azawa sandstones
Sandstones and clays
Sandstones
(Continental)
(marine)
PRECAMBRIAN BASEMENT
S .-Afr .Tydskr .Geol., 1991 ,94(1)
22
The
The
The
The
Table 2 Idealized lithostratigraphic section of the
N-E sector of the IIlummenden Basin (after Valsardieu,
1971 )
CHRONOSTRATIGRAPHY
The Izegouandane Formation
STRUCTURAL GEOLOGY
This formation outcrops between Tim Mersoi in the northwest and north of Agades above the 1r 30' N latitude. It
consists of arkoses, shales, sandstones and sandy shales of
detritic fluvio-Iacustrine origin deposited under a semi-arid
climate. The thickness decreases southwards from a
maximum of about 300 m. Fossil wood fragments of
Dadoxylon rolli have been collected from the basal arkosic
sediments.
They are common in the German Permo-Triassic and thus
confirm the Permian age of the formation. Fossil vertebrates
including the reptile Moradisaurus grandis Taquet (1967,
1969) were collected from the top of the formation. This
reptile, with close affinity to species described from Texas
and Russia, dates the top of the formation as Upper Permian
(Taquet, 1972, 1976). The Izcgouandane Formation is
undoubtedly Permian in age.
According to Valsardieu (1971) and Cazoulat (1985) the
Izegouandane Formation was deposited during a tectonically
active period. At the flank of the basin around Air, acid
volcanic intrusions were emplaced, probably during the
early stages of sedimentation. The intrusions became
prominent towards the end of the Permian when the
volcano-sedimentary series of Moradi were deposited.
8ca1.r------,-----.....-:::--;----r-------.----.,
I~
I
ABINJ<Y
Acid YOlcanlcs
TCHIREZRONE 1
I Acid YOlcanlcs
MOUSSEDEN
Tegama Group at the top
Dabla Series / Irhazer Group
Agades Sandstone
Izegouandane Formation at the base
Agades Sandstone Group
The Continental Intercalaire (Permian to Lower
Cenomanian)
This group outcrops at the western flank of the Air massif
(Figure 3). It is separated from the underlying Izegouandane
Formation by an unconformity. The Agades Sandstone
Group is made up of several mappable units including at its
base, the Teloua sandstones which may be sub-divided into
two members of fine- to coarse-grained sandstones with
cross-stratification. 'Pieces of magmatic rocks' within the
basal conglomerates might have originated from ring
complexes at Damagaram and N!ounio which were
emplaced around 300 2: 20 M.a. (Karche & Vachette,
Killian (1931) defined the Continental Intercalaire as
continental sediments above the marine Carboniferous and
below the Upper Cenomanian transgression. They therefore
range from Permian to Lower Cenomanian in age. In the
Iullemmeden Basin, the Continental Intercalaire has been
subdivided by 10ulia (1963) into several distinct major units
separated by mappable unconformities. They consist of the
following units (see Figure 2):
I
I
N
1000
21°
DEVONIAN
20°
CARBONIFEROUS
1
1000
I
til:
:
p.. 1
I
,$ 0
~ II~'
1
UPPER JURASSIC
• BERRIASIAN
/7°
I LOWER CRE1J\CEOUS
I,TO LOWER CENOMANIAN
1
/2 I
I
o
~ II
1::S 1
1
22°!
1
SILUIUAN
•
I
1
1
1
~~~~".I~~~~O
'---_.....
o
~Okm
+
+
+
SOC L t
I~I
+
1000
PHECI\MIlHII\N
CNUlONACEOUS
I
I
Cu\YS
~
~
Sl\NDSTONE
Figure 2 Cross-section of the Tin Seririne Basin. 1 = Timesugar sandstone; 2 = Graptolite •Schales'; 3 = Idekel and Touaret sandstones; 4 = Akara 'Schales'; 5 = Amesguer sandstone; 6 = Farazgkat sandstones (or Teragh arkose); 7 = Talach clays; 8 = Guezouman
sandstones; 9 = Tchinezogue clays; 10 = Tarat sandstones; 11
Tegama sandstones.
= Madaougla clays; 12 = Izggouandane Series; 13 = Irhazer clays; 14 =
S.AfrJ .Geol., 1991 ,94(1)
23
1978). They may also have originated from the volcanic
activity of Carboniferous or Permian age discussed earlier.
This conglomerate thins out and later disappears northwards.
The Teloua sandstones are overlain by conglomerates,
coarse-grained
sandstones
of
Tehirezrine-l
and
analcimolites of Abinky or Karafou.
The Agades sandstone diminishes in thickness from
north-west (250 m) to the south-west. It consists of detrital,
poorly-sorted sediments. Only the base of the Teloua
sandstones is dated, by reptilian trace fossils of
Chirotherioum, a primitive form described from the Lower
Triassic (Taquet, 1976). The stratigraphic position of the
Agades Sandstone Group between the Permian
Izegouandanne Formation and the Irhazer shales of Late
Jurassic age suggests a Triassic to a Lower-Middle Jurassic
age for the Agades Sandstone. More detailed dating of the
different formations within the Agades Sandstone Group has
not been possible to date due to scarcity of fossils.
LEGEND
lrhazer group
The Dabla Series or Irhazer Group
Agades sandstone
This series consists of two formations; the Tchirezrine-2
sandstones and the Irhazer shales. They outcrop in the northeastern portion of the Iullemmeden Basin where they attain
a maximum thickness of 600 m (Valsardieu, 1971).
The Tchirezrine-2 sandstones overlie the Tchirezrine-l
sandstones of the Agades Group unconformably. They are
probably Late Jurassic in age. The Irhazer Formation
consists of sandy clays or carbonates deposited under
fluviatile or lacustrine conditions. The depositional
environment was calm and sub-tropical. The very large
thickness of this formation as well as the lithologic
characteristics suggest a slow but continuous depression of
the basin and the absence of any major tectonic movement.
IzegouandanlZ ArkoslZ
Talden Clays
Farrazekat Sandstone
Pre Cambrian Basement
Figure 3 Schematic structural section of the Iullemmeden Basin
west of the Air Mountains. North-south section, on 6° longitude
line.
Table 3
Lithostratigraphy of the Nigerian Sector of the lullemmeden Basin
Age
Fonnation
Quaternary
Sandy drifts, lateites
Group
Environment
Continental
Continental
Unconfonnity
Miocene
to
Gwandu Fonnation
Tenninal
Upper Eocene(?)
Unconfonnity
Middle Eocene
Primary oolitic ironstone
-------------------------------------------------------------------------------------------------------------------------------------to
Gamba Fonnation
Paleocene Late
Dange Fonnation
Maastrichtian
Wumo Fonnation
Sokoto Group
Kalambaina Fonnation
marine
Unconfonnity
Brackish water
Rima Group
to
Dukamaje Fonnation
Campanian
Taloka Fonnation
Earliest Cretaceous
Illo and Gundumi Fonnations
with brief marine
intercalation
Unconfonnity
Continental
intercalaire
to
Late Jurassic
Major unconfonnity
Precambrian
Basement complex
Continental
S.-Afr.Tydskr.Geol.,1991,94(1)
24
00550
SOKOTO
GUSAU
!
!
!
EOCENE
).(A EST RI CHTIAN
?
CENOf.(ANIAH
ES3
EARLY
CRETACEOUS
•
LATE
JURASSIC
1:-":'
-.-::-1 sat
~
I: =I
Mdrl
Clay
~ Fine S_nd
ro:l Coars<
~ S.1nd
Figure 4(a) Schematic lithostratigraphic section through the south-eastern part of the Iullemmeden Basin. W
Oukamaje; T = Talika; G-I = Gundumi and Illo.
The Tegama Group (Le Groupe du Tegama)
This group includes all continental sediments outcropping
along a vast plateau between the Iullemmeden and the Chad
Basins. The group extends through the north and the centre
of the basin as far south as the 15° N latitude where it has
been penetrated by a borehole. The Tegama Group lies
directly on the Irhazer clays, unconformably. It is
characterised by sediments that are dominantly sandy with
clayey or calcareous intercalations (Bellion, 1989). These
fluviatile and lacustrine deposits occurred within broad
valleys and marshland under humid tropical and semi-arid
conditions. Previous workers (Faure 1966, Greigert 1966,
Joulia, 1959a), have sub-divided the Tegama Group into two
series. These consist of the Tegama Series, overlain by the
Farak Series. The Tegama Series was subdivided into 3
formations (Tazole or Tiguedi at the base, overlain by the
Eirhaz and Echkar, respectively, see Table 2).
The Tegama Series consists of sandstones, siltstones and
clays deposited during two major sedimentary cycles. The
basal Tazole Formation and the Echkar Formation at the top
consist of coarse feldspathic sandstones, with crossstratification. The intermediate Eirhaz Formation is more
argillaceous or sandy-calcareous. It is rich in fossil bones of
dinosaurs and crocodiles. South of AYr the Eirhaz Formation
thins out and the Tegama Group consists predominantly of
sandstones (Faure, 1966).
The Farak Series is a transitional series between the lower
continental deposits of Lower Cretaceous age and the upper
marine deposits of Middle and Late Cretaceous age. The
thickness is around 200 m. The series is characterised by
finely bedded variegated massive clays and fine sandstones
and siltstones, locally micaceous. At the top the Farak Series
contains several layers of lacustrine limestones with fish,
crocodile and dinosaurian remains (Greigert et ai., 1954;
Taquet, 1976).
The Continental Intercalaire in the Iullemmeden basin
terminates with fine sediments marking the end of a major
detritic stage. According to Faure (1966), the Farak Series is
Wurno; Ou
a lateral equivalent of the Alanlara Formation of marine
origin in eastern Niger. This formation is dated as Early to
Late Cenomanian. This therefore implies that the top of the
Continental Intercalaire is diachronous. It is older than Late
Cenomanian in the Damergou and slightly younger in
Tefidet. The maximum thickness of the Tegama Group is
about 800 m north of Demergou. It attains its minimum
thickness of about 200 m at In-Ababgarit further south. To
the west at Tamesna the thickness varies between 500 and
600 m (Lapparent, 1953). Facies variation is frequent.
The Gundumi and 1110 Formations of north-western
Nigeria
In north-west Nigeria, the Gundumi and 1110 Formations
along the south-eastern flank of the Iullemmeden Basin are
EPOCH
£OC£NE
N. W. NIG£RIA
GMNOU
s.
W. NIGER
CONTINENTAL
TERN/NAL
GAHlJA
·KALAI-fBAINA
PAL.£O-
CElIE
LME
CRETACEOUS
c .... ~
~
ADAR DOUTOII
WURNO
UPPER
SANDSTONES
.~
TAl.OKA
C-<f4CCtIVS
GUNDUMI
.f.
,~ rc
+
""'.11<
lLLO
SHAl.ES
l.OWER
SANDSTONES
CONTlN£NTAL
INT£RCALAIR£
Figure 4(b) Lithostratigraphy of the Iullemeden Basin in northwest Nigeria.
25
S.Afr.J .Oeo!., 1991 ,94(1)
lateral equivalents of the Tegama Group (Figures 4a & b,
Table 3) (Kogbe, 1981). The Gundumi Formation lies
unconformably on the basement and consists of basal
conglomerates and gravels with sand and variegated clays
increasing upwards. The maximum thickness is about
350 m. The 1110 Formation includes interbedded clays and
grits with an intermediate pisolitic and nodular clay member
which attains over 240 m in thickness.
The Upper Cenomanian and Lower Turonian
The Later Cretaceous resumed with a major marine
transgression during which the Tethys Ocean extended
inland as far south as the Iullemmeden Basin, where it was
probably in contact with a south Atlantic marine
transgression through the Benue Trough (Kogbe, 1979,
1981; Figure 5). The Cenomanian transgression extended
into the Lower Turonian, putting an end to the development
of the Continental Intercalaire. The Cenomanian - Turonian
deposits consist predominantly of calcareous sandstones,
fine sandstones, shales with gypsum, glauconite and fossils.
They show rapid changes in facies and typify a detritic
continental platform style of sedimentation, following a
general transgression interrupted by a brief regressive
episode. In the Iguellala mountains north-east of Fennert
(Figure 6), Greigert (1966) described a section with 25 m of
slightly calcareous sandstones, sometimes glauconitic and
phosphatic, with slightly sandy shales with gypsum. The
sediments are richly fossiliferous and contain lamellibranchs, gastropods, brachiopods and ammonites including
Neolobites vibrayeanus, a typical Upper Cenomanian
ammonite which was found at the base of the section.
Vascoceras, Paravascoceras, Acanthoceras and Nigericeras
were found at the top, thus confinning a Lower Turonian
age for the top of the section. North-westwards, the
sequence continues undisturbed as far as Mount TazerzaH
Kebir after which it thins and becomes more sandy and
fossiliferous. West of the 3° 40' meridian in the republic of
Figure 5 Palaeogeographic map of West Africa during the
Cenomanian and Early Turonian. Hatched area denotes marine
inundation and arrows direction of transgressions.
Mali, the deposits become more continental with prominent
cross-bedded sandstones separating the upper level with
Nigericeras from the lower level with Neolobites.
The maximum thickness of the Cenomanian-Turonian
deposits occurs between the Iquellala mountains and the
TazerzaYt Kebir mountains which suggests that the Upper
Cenomanian and Lower Turonian transgression of the
Tethys Ocean invaded the Iullemmeden Basin from the
north-east. This view is supported by the enhanced marine
nature of the sediments in the same region. It is therefore
unlikely that the transgression was from the west of the
Adrar des Iforas as suggested by some authors (petters,
1978).
The Upper Turonian and Lower Senonian
The Lower Turonian calcareous limestones with Nigericeras
are directly overlain by an alterating sequence of limestones
and shales or clays. These sediments can be sub-divided into
two portions. The lower portion is poorly fossiliferous while
the upper portion is more calcareous and fossiliferous. It is
referred to as the 'Serie des calcaires blancs' by French
workers.
This whitish limestone outcrops along the 3° Meridian
north of Tenekert in Mali as far as north-east of Adar
Doutchi at Tan Haidara in Niger (Figure 6). The limestone
contains
remains
of gastropods,
echinoids,
and
lamellibranchs which are difficult to identify with any
precision. They are overlain by shales and limestones of
Lower Senonian age.
The rather considerable thickness of the 'Serie des
calcaires blancs' attaining 250 - 300 m around Tama"ia,
suggests slight subsidence of the basin during the upper
Turonian.
The Upper Senonian (Maastrichtian)
The Maastrichtian is characterised by alternating fine
sandstones, siltstones and clays rich in lignite and fossil
vertebrates. This paralic sequence is intercalated with
marine shales with limestone, deposited during a brief
episode of marine incursion (Kogbe, 1972, 1976, 1979,
1981). The Maastrichtian deposits of the Iullemmeden Basin
in north-western Nigeria constitute the Rima Group of
sediments, comprising the Taloka, the Dukamaje and the
Wurno Fonnations (Table 3). These sediments outcrop
extensively along the south-eastern flank of the basin
particularly in the sector commonly referred to as the
Sokoto Basin. Their type sections have been described by
Kogbe (1981). The Rima Group lies unconformably on the
pre-Maastrichtian beds. This erosional unconformity is well
exposed in Wurno.
The Taloka Fonnation, with a maximum thickness of
about 100m, consists essentially of white, friable fine
sandstones and carbonaceous mudstones and shales.
The Dukamaje Formation consists predominantly of
shales with some limestones and mudstones. The formation
varies from about 12 m at the type locality to less than
0,5 m, 50 km further south. The fauna includes the Upper
Maastrichtian ammonite Lybicoceras sp., found at
Dukamaje and Gilbedi. The presence of two horizons in
Gilbedi is significant and supports the view that the bone
S .-Afr.Tydskr .Geol., 1991,94(1)
26
~
.
....·t ... ( •
•
W
to·
IA
...
?•
\
,
\
...
...
...
I:
Limit ·of the sea before the Neolobftes
transgression
Limit of the "Neotobftes" transgression
_____ -_
2
Limit of the "Nlgerlceras" transgression - - - - - - - - )
The first "Lfbycoceras" transgression
Figure 6 The Cenomanian-Turonian and Lower Maastrichtian transgressions in the Iullemmeden Basin. AD
Monts Tazersait Kebir; I-M = Monts Iguellala and Monts Maya. Modified after Greigert (1966).
bed is due to the action of winnowing forces along the
strand-line of a transgressive sea during the Maastrichtian
(Kogbe, 1974).
The Wurno Formation is quite similar to the Taloka
Formation. The sediments consist of pale, friable fine
sandstones, siltstones and intercalated mudstones (see
Figure 7a). In boreholes, the sediments are dark-coloured
due to the presence of carbonaceous material and finely
disseminated iron sulphides. Small-scale 10ad-casL~,
bioturbation structures and flaser bedding are common in
the Wurno, as is the case with the TaJoka Formation.
The base of the Wurno Formation is only observed
around Wurno; south of Rabat, the intermediate Dukamaje
------"
= Adar Doutchi; TK =
Formation thins out and the Wurno and Taloka Formations
can no longer be differentiated. They thin south-westwards
and outcrop very rarely. The Wurno Formation is over 50 m
thick. According to Bellion (1989), the top of the Wurno
Formation grades into very fossiliferous limestones towards
the west of the basin. The fossils confirm an Upper
Maastrichtian age.
The major discontinuity underlying the Rima group
(Kogbe, 1981) is both erosional and tectonic in origin. The
important tectonic episode which occurred in the Benue
valley during the late Santonian (Wright, 1976) must have
affected parts of the lullemmeden Basin before the
deposition of the Rima Group of sediments.
S.AfrJ.Geol., 1991 ,94(1)
27
QUATERNAIRE
r-- ----
-
10
\.U
\.U
Z
z
<.:>
Lo.J
......
<:>~
-
....J
a..
Gwandu
<.:>
<:>
-I:
••••
coo ;~~~~~:t--Pr!CTWY C:lIiUc Ironstone
c. Gamba
a. :;,
c
~
Cl)
6-
UJ
~.q
z
UJ
8Lo.J
z
0
<-
C)
8
...
....J
~
UJ
\.U
<:
a..
Katambafn
-=--
0
0
0
9
8
Dange
(/)
Wumo
z
C.
Lo.J
....::x:-
Z
\.U
<.:>
-
....a::
.q
<I)
<:
<:
I:
:;,
0
-z
C)
I:
<:
ro
C
<:
a..
<.:>
<-
-
OUkamaJe
a.
L
PisoliUc :::.d Hodul..
~
L
oS
;::
UJ
a::
(.)
--- "
Taloka
UJ
-<C
If? <f'
1110
~
(.)
5
0:
;:,
~
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//
:::>
~t
~
Gundumf
C1
~
.~
:::>
"?
2
0 ..
['00
lamellibranchs and gastropods. Figure 7a is a section at the
cement quarry near Sokoto showing the Kalambaina and
Gamba Formations and the ferruginous oolite horizon.
The Gamba Formation overlies the Kalambaina and
consists of grey laminated shale with 'false folding' due to
the removal by solution of parts of the underlying limestone
of the Kalambaina Formation and subsequent slumping of
the overlying beds. The Gamba Formation is characterised
by a distinct horizon with abundant phosphatic pellets and
coproliths.
The Oolitic Ironstone overlies the Gamba Formation. The
oolites are primary. According to Du bois & Lang (1981),
the Gamba Formation and the Oolitic Ironstone are of
Ypresian (Middle Eocene) age. It is, however, more
probable that the Oolitic Ironstones are of Lower Eocene
age, since the Gamba Formation has been precisely dated as
Upper Palaeocene by diagnostic microfauna (Kogbe et ai.,
1972).
The Cretaceous - Tertiary boundary is marked in the
south-eastern sector of the Iullemmeden Basin by an
unconformity which is both structural and erosional.
The Continental Terminal
The Continental Terminal is made up of all the continental
deposits overlying the marine Eocene and underlying the
Quaternary sediments. The term was introduced by Killian
(1931) for Tertiary non-marine sediments in Sub-Saharan
Africa. The lower and upper boundaries of the Continental
Terminal are of geodynamic significance. In the
~'O-1
PAlEOZOIOVE et PRECN18RI EN
PRE-
PALAEOZOIC
CAldBRIAN
Figure 7(a) Idealized section through the Mesozoic-Cenozoic
sequence of the southern flank of the Iullemmeden Basin (northwest Nigeria). 1 = conglomeratic fluviatile pebbles; 2 = fossil
wood; 3 = siltstone; 4 = lignite; 5 = fossil bone; 6
bioturbation structures; 7 = gypsum; 8 = laminated shale; 9 =
ferruginous oolites; 10
=
lateritic crust.
MESOZOIC
NUBIAN
-
L ->K-r ~
"7
IIl11tIlItttttttttttlttl tttttlttttlUIlIl ItttltltttttttItttttt
\
t
I
r
wdI dellncd upper
I
I
I
and \ower \Imlts
I'
\
~
I
Palaeocene
The Palaeocene has been subdivided into three formations
(Monod, 1939; Cornet, 1943, 1948; Radier, 1959; Kogbe,
1979, 1981, 1986). In north-west Nigeria, the Palaeocene
sediments constitute the Sokoto Group, consisting of the
D:mge, Kabmbaina and Gamba Formations. Kogbe (1981)
introduced a fourth subdivision which is made up
exclusively of ferruginous oolites (Figure 7a).
The oldest Palaeocene unit is the Dange Formation which
consists of slightly indurated bluish-grey shale, interbedded
with thin layers of yellowish-brown limestone. In outcrops,
the maximum thickness of the formation is about 22 m near
Sokoto, but in subsurface weBs, it attains a thickness of over
45 m. The Dange Formation is overlain by the Kalambaina
Formation which consists of a marine white, clayey
limestone and shale. The thickness varies between 5 m in
the north to over 18 m further south. The formation is rich
in invertebrate fossils, mainly echinoids, corals, nautiloids,
kllin
I
I
and lower limits
\
1
I
·lJ
I
!{AROO
I
1
I
I
I
.p
I
I
I
hlllll
I
I
I
I
lowerllm1ts
I
I
I
I
i
upper and
I
t
I
I
I
i
major geodynamic
I
J...,
I
I
I
CONTINENTAL
TERMINAL
j
I
I
t
till IUIII it
t
I
(unconformitiesl
I
~
I
well dellncd upper
I
,
,
I
I
CONTINENTAL
INTERCALAIRE
I
I
\
I
I
Lower Tertiary
gUATERNARY
TERTIARY
1
t
I
I
i
j
I
I
1
I
\tt~1 11111111
well defined upper
and Iowcrllm1ts
(unconformitiesl
I
OTIIERS
.. J
I
I
ConUnenthl Sequences
West
Intercalated Within marine
Sequertces.
(Bcnue. coa~laI basins etc.)
Canadlan
Tasilll
Kwanga
Figure 7(b)
I
I!"",m"
DrI!t
(K.a\aharI.
Congo. Sahara.
etc.)
Possible correlation of some major continental
sequences in Africa. U
=
Upper; L
=
Lower; M
=
Middle.
28
S.-Afr.Tydskr.Geol.,1991,94(1)
Iullemmeden Basin, the Continental Terminal was subdivided into three major units defined by Greigert (1966) as
the 'Serie Siderolithique de L'Adrar Doutchi' (Ct 1) at the
base, 'la serie argilo-sableuse A lignites' (Ct 2) in the
middle and 'Les gres argileux du Moyen Niger' (Ct 3) at the
top. According to Lang et al. (1986) Ct 1 is of Lower to
Middle Eocene age and marks the end of the marine
sedimentary cycle in the Iullemmeden basin. Kogbe &
Sowunmi (1975) dated the Continental Terminal in northwest Nigeria (Gwandu Formation of the Sokoto basin) as
Miocene - Pliocene with a noticeable absence of the
Oligocene which probably represents a period of nondeposition. Figure 7b attempts to correlate the Continental
sequences in the Iullemmeden Basin with those of other
basins in Africa.
Quaternary
The end of the Cenozoic in the Iullemmeden Basin is
marked by uplift movements and erosion, resulting in the
formation of terraces capped by ferruginous crusts or
laterites.
ALGERIA
o
2~---r-:~~~~~~~~:g~~~~~~~~~~!Jr-~~~----'fO
LEGEND
1
[[]J Crywtanmc bucmcu rocb-
1
E::3 PalaeozoOc: Carmatiom
J'Rc.mbria
Figure 8
Structural map of the post-Palaeozoic Iullemmeden Basin.
S.Afr.1 .Geol.,1991 ,94(1)
29
.'::-'~'\'
~o~-o~,'t'
HE
C.V,~~
sw
d·h
C OUR ... A
LOW E R • MI DOL E E 0 C ENE
Mi.=·· pliocene
I
4
PALEOCENE
:
I
I
I
I Nt,.,
..
1000
.
..
.
+
PRECAMDIUAN
~1
~
2000
Carbonates
3000
.
Clays
Sandstones and
Conglomerates
PALEOZOIC?
Figure 9 Schematic geological section through the Iullemmeden Basin. 1 = sandstones, conglomerates; 2 = clays; 3 = carbonate
rocks; 4 = 'Neolobites' marker horizon; 5 = 1st level 'Libycorceras'; 6 = 2nd level 'Libycorceras'; Ce-Tu = Cenomanian-Turonian.
Modified after Greigert (1966).
Tectonics
There has been no detailed structural analysis of the
Iullemmeden Basin. Several workers, including loulia
(1957), Greigert (1966), Greigert & Pougnet (1967) and
Kogbe (1979), have discussed or described structural
elements from different sections of the basin. Bellion (1989)
attempted a chronologic description of the tectonic history
of the basin but a comprehensive, detailed analysis of the
structural characteristics will only be possible when
additional geophysical and borehole data permit.
Caledonian and Hercynian movements affected the
Palaeozoic rocks outcropping towards the north-east margin
of the basin. The Mesozoic and Cainozoic deposits are
truncated by reactivated basement faults and folds. They
constitute a very broad syncline with an axis oriented
approximately north-south.
The Iullemmeden Basin is a broad syncline with gently
dipping flanks. The axis trends roughly N-S between the 3°
and 4° E meridians. The total depth of the basin is about
1 000 m except in a few basement depressions associated
with faults within the basin and also inside the Goa trough,
where the thickness of the sediments is over 3 000 m
(Guiraud et al., 1985).
The Mesozoic and Tertiary formations are sub-horizontal
except in very rare localities where they are gently folded or
tilted. The south-western limit of the basin is bounded by a
major NW-SE trending fault which limits the basement
complex of the Liptako and Gourma massif towards the
west (Figures 8 and 9).
Two other major fault trends are
prominent in the Iullemmeden Basin. The most important
has a NNE-SSW direction and is responsible for the
existence of the two principal depressions within the basin
(Talach depression, Azaouak depression), as well as the InGuezzam horst. The other fault direction is WSW-ENE.
The WSW-ENE faults are concentrated in the north-east
part of the basin, west of the Air mountains.
According to Bertrand-Sarfati et ai. (1977), the
Iullemmeden Basin is a cratonic basin created by tectonic
epeirogenic movement. These movements are evident from
the beginning of the Palaeozoic and continued until the Late
Cretaceous when the opening of the Goa trench took place.
The movements were responsible for the south-west
progradation of sediments deposited within the basin which
became progressively younger from north-east to
south-west (Figure 10).
Tectonic movements within the basin affect the thickness
of the sedimentary sequence and also influence variation of
the facies (Greigert, 1966; Greigert & Pougnet, 1967). The
search for uranium in the north-east comer of the basin
around the Ai"r massive revealed the close relationship
between tectonics and sedimentation in that region. PostCarboniferous unconformities in the area are associated with
tectonism and Permian to 1urassic fine detritic sedimentation
is contemporaneous with acid volcanic activity related to
tectonic movements. Folded beds are scarce in the
Iullemmeden Basin and are mostly localised in the northeast, where they are evident in Cenomanian and Turonian
sediments with a dip of less than 5°. On the geological map
of Niger (Greigert & Pougnet, 1967) anticlinal axes of
folded beds around the Maya, Iguellala, TazerzaH Kebir and
Tamai"a mountains between the 4° and 6°E Meridians are
shown. The axes trend N-S to NE-SW in general. These
folded beds are younger than the Upper Cretaceous, but it is
quite probable that some folding already existed before the
Upper Cretaceous.
The Goa Trench
This graben links up the Iullemmeden and the Taoudenni
Basins. It is bounded by NW-SE trending faults except
towards the southern sector where the faults are roughly
E-W. The Goa trough is superimposed on the Pan-African
suture (Fabre et al., 1982) resulting from the collision of the
Touareg shield and the West Africa Craton. The Cretaceous
sediments within the basin attain a maximum thickness of
about 3 500 to 4 000 m (Guiraud et al., 1985). As
mentioned earlier, the trough was formed during the Lower
Cretaceous and the rhythmic nature of the sedimentation
suggests that the deepening of the graben was more or less
continuous. The E-W faults bounding the southern part of
the trough fall within the 'Guineo-Nubian' regional
S .-Afr .Tydskr .Geol.,1991 ,94(1)
30
M.
c:::l
..
12
~ 11
E5.:3
E:3
rs;:s:ss
~
rrmm
E;;:J
e:z.zJ
10
9
8
7
6
5
I ~~ ... ~ ..J
"3
~
2
([IJ]
o. oue OIS
Figure 10 Schematic geological map of the Iullemmeden Basin. 1 = Precambrian; 2 = Cambrian to
Carboniferous; 3 = Permian; 4 = Triassic and Jurassic; 5 = Jurassic-Berriasian; 6 = Lower Cretaceous to
Lower Cenomanian; 7 = Upper Cenomanian to Santonian; 8 = Campanian (?) and Maastrichtian; 9 =
Continental Intercalaire and/or Continental hamadian; 10 = Maastrichtian terminal to Middle Eocene; 11
= Continental Terminal; 12 = Quaternary; M = Mali; N = Nigeria, C-I = Cote d'Ivoire; B = Benin; T =
Togo; G
= Guinea; S = Sierra Leone; B-F = Burkina Faso.
Iullemment trend (Figure lla,b) along which basic volcanic
activities were recorded in the Chad Republic during the
Lower Cretaceous (Guiraud et al., op. cit). The southern end
of this lineament trend in the Republic of Guinea has
experienced important seismic activity recently ( Kogbe &
Delbos, 1983; Bellion et al. 1984).
At the end of the Cretaceous, the Iullemmeden Basin
experienced regional activity resulting in faulting and uplift
as well as the closure of the N-E marine passage with the
Tethys Ocean. The opening of a new 'sea-way' further west
along the 'Detroit Soudanais' took place (Figure 12). This
explains the change in direction of the Upper Maastrichtian
S.Afr.1 .Geol.,1991,94(1)
31
- Palaeogene transgression with regard to the Turonian and
Cenomanian transgressions.
During the mid-Eocene, tectonic movements in the
Iullemmeden Basin resulted in very gentle tilting of the
Lower Eocene and older beds as well as uplift and final
regression of the sea from the basin. An important erosional
episode followed and the Continental Terminal was later
deposited unconformably on the older marine beds.
References
Alidou, S. (1983). Etude geologique du bassin paleo-mesozofque
de Kandi (Nord-Est du Benin, Afrique de l'Ouest). These
Doct. es Sci., Dijon et Cotonou, 328 pp.
...
".
Figure 12 Palaeogeographic map of West Africa during the
Upper Maastrichtian and Palaeocene. Hatched area denotes marine
inundation and arrows direction of transgressions.
•
•..
Figure l1(a) Distribution of fault trends in the western and
southern flanks of the AiI Mountains.
Bellion, Y. (1989). Histoire geodynamique post-paleozoIque de
l'Afrique de l'Ouest d'apres l'etude de quelques bassins
sedimentaires (Senegal, Taoudenni; Iullemmeden, Tchad) .
Publ. Occasionnelle CIFEG, Paris, 17, 302 pp.
----, Hebrard, L. & Robineau, B. (1984). Sismicite historique de
l'Afrique de l'Ouest. Essai D'inventaire. Remarques et
commentaires. Bull. Assoc. Seneg. Etudes Quat. Ouest Afri.,
73,57-72.
Bertrand-Sarfati, J., Moussine-Pouchkine, A. & Fabre, J. (1977).
Geodynamique des aires sedimentaires cratoniques. Quelques
exemples sahariens. Bull. Cent. Rech et Expl. Elf-Aquitaine, 1,
217-231.
Cazoulat, M. (1985). Geologic environment of the Uranium
deposits in the Carboniferous and Jurassic sandstones of the
Western margin of the AIr mountains in the Republic of
Niger. In: Geological environment of sandstone type Uranium
deposits. Tecdoc, 328, IAEA, Vienna, 247-263.
'b'SI"
~20'
~
•
+
t
. +
Bot/t.ou
£(di
Figure neb) Schematic map of the Guineo-Nubian lineaments. 1 = limit of the Precambrian basement; 2 = unconformity; 3 =
tectonic lineament; 4 = liassic dolerites; 5 = intrusive rocks; 6 = Neogene-Quaternary volcanic rocks; 7 = Guinean Earthquake epicentre
(22/12/1983); A = Asswan; G = Gourma; L = Los; Le = Seraleon; N = Nara; Tf = Tefidet. Modified after Guiraud et al. (1985b).
S.-Afr.Tydskr.Geol.,1991,94(1)
32
Cornet, A. (1948). Sur la realite des mouvements post-Cretaces
au Sahara. Trav. Inst. Rech. Sahara, 65, 33-46.
Dubois, D. (1979). Etude geologique des Formations oolithiques
ferrugineuses du bassin des Iullemmeden (Republique du
Niger). These 3eme Cycle, Orleans et Niamey, 123 pp.
Fabre, J., Ba, H., Black, R., Caby, R., Lablanc, M., Lesquer, A.,
Ball, E., Bertrand, H., Bertrand, J.M., Boulier, A. A,
Davison, I., Lyg S., Moussine-Pouchkine, A & Wright, L.
(1982). Carte geologique et gravim.etrique de I'Adrar des
Iforas 1:500 000 et notice explicative: La Chafne
panafricaine, son avant pays et la zone de suture au Mali.
Publ. Dir. Nat. Geol. et Mines, Bamako, 85 pp.
Faure, H. (1966). Reconnaissance geologique des Formations
sedimentaires post-paLeozofques du Niger Oriental. These
Doct. es Sci., Paris, 1962, Pub. N° 1, BRGM, 630 pp.
Greigert, J., Joulia, F. & Lapparent, A.F. (de) (1954). Repartition
stratigraphique des gisements de vertebres dans Ie Cretace du
Niger. CR. Acad. Sci. Paris, 239, p. 433.
---- (1966). Description des Formations Cretaces et Tertiaires du
bassin des Iullemmeden. Dir. des Mines et de la Geol.,
Niasmey, Niger, Pub. 2, BRGM, 234 pp.
---- & Pougnet, R. (1967). Carte geologique de la republique du
Niger 1:200000, BRGM, Paris.
Guiraud, R., Issawi, B. & Bellion, Y. (1985a). Les lineaments
guineo-nubiens: un trait structural majeur a l'echelle de la
plaque africaine. CR. Acad. Sci. Paris, 300 Ser. 11, p. 17.
----, Bellion, Y., Benkhelil, J. & Moreau, C. (1985b). Posthercynian tectonics in North Africa and West Africa. In:
Bowden, P. & Kinnaird, J.A. (Eds.), African Geology Reviews
Saint Andrews 1985. John Wiley, New York.
Jones, B. (1948). Sedimentary rocks of the Sokoto Province.
Bull. Geol. Surv. Nigeria Kaduna, 18, 79 pp.
Joulia, F. (1957). Sur l'existence d'un important systeme de
fractures interessant Ie Continental Intercalaire a l' ouest de
l'Air (Niger, A.O.F.). Bull. Soc. Geol. Fr., 137-143.
---- (1959a). Les series primaires au nord et au nord-ouest de
l'AiI (Sahara Central). Discordances observees. Bull. Soc.
Geol. Fr., p. 186.
---- (1959b). Precisions sur la discordance Cambro-Ordovicienne
d'In Azoua Niger. CR. Somm. Soc. Geol. Fr., p. 177.
---- (1963). Carte geoLogique de reconnaissance de La bordure
sedimentaire de fAir a 1 :500000. Ed. BRGM Orleans,
France.
Karche, J.P. & Vachette, M. (1978). Age et migration de
l'activite magmatique dans les complexes paleozoiques du
Niger: Consequences. Bull. Soc. Geol. Fr., 6, 941-953.
Killian, C. (1931). Les principaux complexes continentaux du
Sahara CR. Somm. Soc. Geol. Fr., p. 109.
Kogbe, C.A. (1970). Geology of the South Eastern (Sokoto)
Sector of the Iullemmeden Basin. Bull. Dep. GeoL. A.B.U.
Zaria, Nigeria, 2,420 pp.
---- (1972). Geology of the Upper Cretaceous and Lower Tertiary
sediments of the Nigerian Sector of the Iullemmeden Basin
(West Africa). Geologische Rundschau, 62, 197-211.
---- (1974). Paleo-ecologic significance of vertebrate fossils in the
Dukamaje and Dange Formations (Maastrichtian and
Paleocene) of north-western Nigeria. J. Mining and Geology
(Nigeria), 8, 49-55.
---- (1981). Cretaceous and Tertiary of the Iullemmeden Basin in
Nigeria (West Afri.). Cretaceous Research, 2, 129-186.
---- & Sowunmi, O. (1975). The age of the Continental Terminal
as suggested by Sporopollinitic analysis. 'SAVANA' Ahm.
Bell. Univ. Nigeria, 4, 47-55.
---- & Delbos, L. (1984). The Recent Guinean earthquake:
probable origin and geographic implications. PANGEA,
CIFEG Paris, 2, 4-9.
Lang, J., Kogbe, C.A., Alidou, S., Alzouma, K., Dubois, D.,
Houessou, A. & Trihet, J. (1986). La serie sederolitique du
Tertiaire ouest-africain et Ie concepts de Continental Terminal.
Bull. Soc. Geol. France, 4, 605-622.
----, Kogbe, C.A., Alidou, S., Alzouma, K.A., Bellion, G.,
Dubois, D., Durand, A., Guiraud, R., Houessou, A., De Klasz,
I., Romann, E., Salard-Chelsoldaeff, M. & Trichet, J. (1990).
The Continental Terminal in West Africa. J. Afr. Earth Sci.,
10,79-99.
Lapparent, A.F. (1953). Sur la Stratigraphie du Tamesna (Sahara
meridioal). C.R. Acad. Sci. Paris, 2238, p. 2255.
Monod, Th. (1939). Notes geologiques sur les confins Sahariens
du Soudan francais. Rev. Gifogr. Phys. GeoL. Dyn., XII,
461-478.
Petters, S.W. (1978). Maastrichtian-Paleocene foraminifera from
NW Nigeria and their Paleogeography. Acra Paleon. Polonia,
23, 131-152.
Radier, H. (1953). Contribution a letude stratigraphique et
structurale du detroit soudanais. Bull. Soc. Geol. Fr., 3-10.
Taquet, Ph. (1967). Decouvertes paLeontologiques recentes dans
Ie Nord du Niger. In: Problemes actuels de PaLeontologie.
C.N.R.S. Fr., 415-418.
---- (1969). Premiere decouverte en Afrique d'un reptile
Captorhinomorphe (Cotilosaurien). CR. Aca. Sc. Paris, Ser.
D, 268, p. 779.
---- (1972). Un exemple de datation et de correlatio
stratigraphique base sur les Captorhinomorphes (Reptiles
Cotylosauriens). Mem. BRGM, 77,407-409.
---- (1976). Geologie et Paleontologie du gisement de
Gadoufaoua (Aptien du Niger). Calliers de PaLeontologie
CNR.S., 192 pp.
Valsardieu, C. (1971). Etude geologique et paleogeographique du
bassin du Tim Mersoi. These es Sci., Nice, 518 pp.
Wright, J.B. (1976). Origins of the Benue trough - a Critical
review. In: Geology of Nigeria (C.A Kogbe, Ed). Elizabethan
Publishing Co., Lagos., 309-317.