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Stratigraphic Lexicon
The Sedimentary Formations of The
Republic of Niger, Africa
Jacques LeBlanc
COLNES PUBLISHING
Tallin, Estonia
Author
Jacques LeBlanc
Geologist
Alberta, Canada
Reviewers
Gareth Dyke, University of Debrecen, Debrecen, Hungary
Ahmed Abd Elmola, Université de Poitiers, France
First published 2022
By ColNes Publishing OÜ
Sakala 7-2, 10141 Tallinn, Estonia
https://colnes.org
Copyright information
© 2022 The author. The author retains copyright over this book, which is licensed under a Creative
Commons license CC BY-NC 4.0.
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ISBN (PDF): 978-9916-9760-6-7
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DOI: 10.47909/978-9916-9760-6-7
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Table of Contents
Preface vi
Chapter 1 Introduction 1
Chapter 2 Understanding the Lexicon 5
Chapter 3 Terminology and Definitions 7
Chapter 4 A brief geological outline of Niger 13
Chapter 5 The Sedimentary Basins of Niger 18
Chapter 6 Paleontology 74
Chapter 7 Lexicon 84
References 376
Acknowledgments 426
Appendices 427
About the author 442
v
Preface
The current knowledge of the stratigraphy of Niger benefited greatly from the
mining, hydrocarbon, hydrogeological, and paleontological sciences. Exploration
by early explorers and studies of the aquifers initially sparked our understanding
of the surface and shallow formations. Then, the discoveries in 1957 of important
Uranium reserves and soon after in 1964 of the enormous Lower Cretaceous ver-
tebrate site of Gadoufaoua stressed the need to undertake detailed stratigraphical
investigations in the western Iullemmeden Basin. The geologist Hughes Faure
then published his important, and still relevant, 1966 thesis on the surface geol-
ogy of Eastern Niger. From that time onward, the Oil & Gas companies started
paying attention to the most prospective areas in the Eastern Niger Basin. During
the last decade, these same hydrocarbon companies finally allowed some geol-
ogists to share their knowledge of the sub-surface in relevant publications. It is
from all these studies that the present Lexicon draws its content. It provides the
historical background of all described geological units in Niger and summarizes
each unit's lithological and paleontological knowledge in an easy-to-search for-
mat.
vi
Chapter 1
Introduction
The author worked for three years in Niger during the late 1990s. In those days,
our knowledge of the surface sedimentary cover of the country had reached a de-
cent level of understanding; however, this was not the case for the sub-surface
formations related to the Oil & Gas exploration. Today, most of this information
has now been released in several publications that provide a much broader under-
standing of the stratigraphy in the country.
Literature on the geology and stratigraphy of the Republic of Niger dates to
the start of French colonization in the 1890s. This lexicon tries to broadly follow
the lithostratigraphy erected by the geologists during these past 130 years and has
identified 187 stratigraphic units (Appendix K). Although most names of Groups,
Subgroups, Formations, and Members in this Lexicon concern units that are con-
sidered legitimate, some obsolete (indicated with *) and little-known names are
also included. In some cases, a recommendation is made to abandon some geo-
logic names in favor of others or to disregard them completely.
This is the first-ever lexicon dedicated only to the country of Niger. Other
lexicons do exist, but they are old and with a much broader scope (Furon, 1935;
Faure et al., 1956; Haughton, 1963; Furon, 1966; Fabre et al., 1983). An updated
geological map does not accompany this new Lexicon; however, the historical
maps presented in the appendices still hold their usefulness and are frequently
referred to within the text. Also, in addition to the detailed description of each
unit, Tables given in the appendices summarize visually the stratigraphy of all the
Niger Basins and Sub-Basins.
For the uninitiated reader, using all the stratigraphic terms that were used
over time since the early days of exploration may be confusing. The early works
certainly still have their value from a scientific and historical point of view;
however, the science of stratigraphy has evolved drastically since the initial at-
tempts at documenting the geological units. Earlier, the geologists tended to use
1
long names that included the general lithology or paleontology of the unit being
described, i.e.: “siderolithic series of Ader Doutchi”, “Mosasaurus Shales”, “Cal-
caires à Libycoceras”, etc. Many of these names have persisted in the literature
since they were first published.
Also, according to the stratigraphic rules, formations are gathered today into
Groups and Subgroups. In Niger, and other North African countries, the for-
mations have historically been gathered into Groups and "Series", sometimes
interchangeably, without considering any nomenclature standard. The definition
of “Series” also does not comply with a "Subgroup" definition. According to
the “Glossary of Stratigraphic Terms” of the International Subcommission on
Stratigraphic Classification (ISSC) (see references), the modern definition of
“Series” (in French and English) is “A unit of the conventional hierarchy of
formal chronostratigraphic terms, ranking above a stage and below a system,
always a subdivision of a system”. Therefore, the lexicon takes this opportunity
to substitute the historical but erroneous meaning of “Series” for “Subgroup”
(“Sous-groupe” in French). The non-stratigraphic meaning of "series" will still be
referred to mean "a number of things or events coming one after another".
The internationally recognized “ICS International Chronostratigraphic
Chart” by Cohen et al. (v2021/10) is used in this lexicon to standardize the
Epochs and Stages of the geological time. Therefore, some terms of the Ge-
ological Time Scale used historically in Niger (and North Africa), such as
Westphalian, Namurian, and Siegenian, have been replaced by their modern
counterparts (see Appendix J). The importance of consistent stratigraphic nomen-
clature includes making sure publications are in conformance with the
International Stratigraphic Guide. It is essential to ensure stratigraphic consis-
tency between text, correlation charts, descriptions of stratigraphic units, figures,
and tables within papers and geologic maps. Therefore, it is highly recommended
that authors of new documents regarding the geology of Niger follow the stan-
dards established in this Lexicon, or the past errors will undoubtedly resurface.
Difficulties, Improvements, and Recommendations: Few difficulties that
were met while working on this document, some of the improvements to previous
lexicons, and pertinent recommendations are listed below:
1. Unfortunately, several authors continue placing the Madaouela and the Arlit
formations in the Upper Carboniferous. The palynological studies conducted
by Broutin et al. (1990) and Coquel et al. (1995) placed the age of the
Madaouela Formation in the Lower to Middle Permian Period instead of the
Upper Carboniferous. Therefore, the Madaouela Formation and the overly-
ing Arlit Formation are now located in the Permian. Since both formations
Stratigraphic Lexicon
2
belong to the Upper Tagora Group, the latter is also extended to the Middle
Permian.
2. The spelling of the name "Agadez" has been standardized for both the city
and the stratigraphic Group. The spelling "Agadès" no longer exists.
3. The Stratigraphic Guide of the International Commission on Stratigraphy
(Web-09) states, "If a unit is divided into two or more formal component
units, the geographic name of the original unit should not be employed for
any of the subdivisions". In other words, the "Irhazer Group" should not
have a unit below it called "Irhazer Formation". Similarly, the Teloua For-
mation should not be subdivided into sub-units named Teloua 1, Teloua 2,
and Teloua 3 Members. The same is true for the Tchirezrine Formation; it
should not be sub-divided with Tchirezrine 1 and Tchirezrine 2 Members
(Appendix E). Therefore, even though no attempt has been made here to re-
name these terms, it is highly recommended that the geological community
working in Niger proceed with renaming the Irhazer Fm and the Teloua 1, 2,
3, and Tchirezrine Mbrs (see point "10" below).
4. There is no longer the need to use the name “Aguelal Subgroup” since only
one unit now belongs to it; the Teloua 1 Member of the Teloua Formation
5. The authors writing about the DASA graben of the Tim Mersoï Sub-Basin
often place the Farrazekat Fm above the Teragh Fm without mentioning the
reasons; in all other occurrences, the Teragh Fm is above the Farrazekat Fm.
Even if faults are involved, it is not a reason to stratigraphically assign a
younger age to the Farrazekat Fm.
6. In the recent (post-2010) literature on the DASA graben, some authors show
the name “Tindirenen Formation” as a new stratigraphic level between the
Farrazekat and Teragh Formations without stating its origin and its formal
description. No information was found anywhere about its details and there-
fore it is not included in the stratigraphic sections given in the appendices.
7. The name “Felar-Felar Formation” (originating from Algeria) in the Upper
Ordovician of the Djado Basin is being discontinued and replaced by the
name of Chirfa Formation. The latter was formally described by Legrand
(1993) for the same interval in the Djado Basin of Niger.
8. Except for the Chirfa Formation, the terminology of the Djado Basin has
been borrowed from the Murzuq Basin of Libya; the Djado being an exten-
sion of the Murzuq.
9. Several units still lack basic information, such as the origin of the name, who
named it, etc. While this is true for several older formations, it is also true for
some newest names, such as Sokor, Madama, Yogou, Donga, and K1 forma-
tions.
10. It is highly recommended that the geological community creates and main-
tains a database of stratigraphic names (past, present & obsolete) and
requires authors intending to modify, remove or add a name to get approval
Chapter 1 Introduction
3
from the entity managing it.
It is hoped that the present work, the most up-to-date description of Niger's rock
units, will foster discussions within the geoscience community of the country and
provide a new and solid starting point to generate new research and allow discov-
eries in the field.
Stratigraphic Lexicon
4
Chapter 2
Understanding the Lexicon
Section 7 of this document is the Lexicon proper. The description of all units
(Groups, Subgroups, Formations, Members, etc.) has been included within a sim-
ilar format as the one shown below. If all the information exists regarding a Unit,
the format will look exactly like the template on this page; however, if some in-
formation is not known, the title line concerned will have been deleted.
Unit: NAME of the GROUP/SUBGROUP/FORMATION/MEMBER
stated in bold capitalized letters. When an asterisk (*) precedes it, the name is ob-
solete or recommended to be made obsolete.
Epoch/Age/Author: The Geological Epoch, and sometimes the Stage. The
author(s) who has defined the Age of the Unit is also mentioned when available.
This author may or may not be the same as the original author who named the
unit.
Original Author and/or Origin of the Name: This is the first author who
named and formally or informally described the unit in some way or another. The
origin of the name is mentioned when ever possible.
References: This is the list of the most pertinent references discussing the
stratigraphy and geology of the unit. Not necessarily an exhaustive list. It is pre-
sented chronologically.
Group/Subgroup: The geological Group and Subgroup to which the unit
belongs. When no Subgroups exist, only the Group will be mentioned (if avail-
able).
Synonymy: It is time-bound. Years or decades ago, the Unit, or part of the
unit, as it is known today, could have been known under other names for various
reasons. Sometimes it involves a misspelling that was wrongly carried over for
5
many years in the literature.
Equivalent(s): It is geographically bound. Correlation with units of the same
age in other areas within Niger or surrounding countries. It can imply facies
change or show similar fossils, lithology, geochronology, and structural style.
Basin/Sub-Basin/Apdx: The Sedimentary Basin and/or Sub-Basin (see
“Definition”) in which the unit belongs. This is also the place to mention all the
appendices of this Lexicon (if any) that discuss the unit. Note that “Sub-Basin”
may sometimes be replaced by “Area”, which stands for the geographic area
where the unit occurs.
Type/Reference/Stratotype Section: When known, it is the exact geo-
graphic locality of the geological section (see “Definitions”).
Lithology: Description of the type of sediments/rocks that compose the Unit.
Environment: The depositional environment of the unit as implied by its
sedimentology/lithology: i.e., marine, continental, lacustrine, deltaic, etc.
Thickness: The total thickness of the Unit.
Fossils: The main fossil types that define the unit.
Overlying Unit: Unless otherwise stated, it is the name of the Group/Sub-
group/Formation/Member stratigraphically above the unit being described. If the
information is available, and if the unit stratigraphically above it is not present
due to erosion or non-deposition, it can be much younger.
Underlying Unit: Unless otherwise stated, it is the name of the Group / Sub-
group / Formation / Member stratigraphically below the unit being described. If
the information is available, and if the unit stratigraphically below it is not pre-
sent due to erosion or non-deposition, it can be much older.
Remarks: Any pertinent comments.
Maps, Cross-Sections, Pictures: Any images that can help understand the
unit's written description.
Stratigraphic Lexicon
6
Chapter 3
Terminology and Definitions
• Bed: A layer of sediments or sedimentary rocks bounded above and below by
more or less well-defined bedding surfaces. A bed is the smallest formal unit
in the hierarchy of sedimentary lithostratigraphic units. It is commonly used
as a synonym for “stratum” and “layer”.
• CEA: The French Alternative Energies and Atomic Energy Commission, or
CEA, is a French public government-funded research organisation in the areas
of energy, defense and security, information technologies, and health tech-
nologies. It was founded in 1945.
• Complex: a) A lithostratigraphic unit comprising diverse types of any age or
any class or classes of rocks (sedimentary, igneous, metamorphic) and char-
acterized by irregularly mixed lithology or by highly complicated structural
relations to the extent that the original sequence of the component rocks may
be obscured, and the individual rocks or rock sequence cannot be readily
mapped. b) A lithodemic unit. An assemblage or mixture of rocks of two or
more genetic classes, i.e., igneous, sedimentary, or metamorphic, with or with-
out a highly complicated structure
• Craton: An old and stable part of the continental lithosphere
• Cuesta: A ridge with a gentle slope (dip) on one side and a steep slope (scarp)
on the other.
• Dallol: Paleochannel or fossil valley. It does not have the same meaning (hy-
drothermal vent) as in Ethiopia.
• Formation (abbreviated by "Fm"): A body of rocks of intermediate rank in
the hierarchy of lithostratigraphic units; it is defined and identified by its litho-
logic composition and stratigraphic position. The formation is the fundamental
unit in formal lithostratigraphic classification.
• Fulgurites: Commonly known as "fossilized lightning", are natural tubes,
clumps, or masses of sintered, vitrified, and/or fused soil, sand, rock, organic
debris, and other sediments that sometimes form when lightning discharges
into the ground.
• Graben: A piece of Earth's crust shifted downward (see also "Horst").
7
• Group: The formal lithostratigraphic unit next in rank above a formation. The
term is applied most to a sequence of two or more contiguous or associated
formations with significant and diagnostic lithologic features in common.
• Horst: A piece of Earth's crust shifted upward (see also "Graben").
• Kori (or “Oued”) [North African Arabic]: Local name to designate tempo-
rary stream beds and traditionally referring to a valley.
• Left and Right banks of a river: The riverbank on the left/right hand of a
person whose face is turned downstream.
• Lithostratigraphic unit: A body of rocks — sedimentary, igneous, or meta-
morphic — formally defined and recognized based on its observable and
distinctive lithologic properties or combination of lithologic properties and its
stratigraphic relations.
• Lycophytes: Vascular plant (tracheophyte) subgroup of the kingdom Plantae.
They are one of the oldest lineages of extant (living) vascular plants; the group
contains extinct plants that have been dated from the Silurian (ca. 425 million
years ago).
Figure 3-1. Lycophytes (Source: http://lifeofplant.blogspot.com/2011/
03/lycophytes.html).
• Member (abbreviated by "Mbr"): The formal lithostratigraphic unit next in
rank below a Formation; it is always a part of a Formation.
• Metacraton: Term used to describe a craton that has been remobilized during
an orogenic event but the characteristics of the original craton are still identi-
fiable.
• Nubian Sandstones: The term originated with Joseph Russegger in 1837
(Web-07) to describe a sandstone unit outcropping in Nubia, the region on
both sides of the Nile Valley on the border of Egypt and Sudan. It has since
Stratigraphic Lexicon
8
been assigned to almost any basal sandstone facies not only in Libya and Niger
(Djado Basin) but in many other areas throughout North Africa. This nearly
indiscriminate use of the term has created such confusion that for all practi-
cal purposes, the term “Nubian Sandstone” is useless or, at best misleading.
Pomeyrol (1968 & 1969) recommended the term to be dropped or at least se-
verely restricted in its use. The best and most accurate definition of the term
was given by Attia (1955). According to him, at Aswan in the Nile valley, the
Nubian Sandstone varies in thickness from 70 to 122 meters and is divisible
into three units. Unfortunately, the same Nubian Sandstone term has been ap-
plied to different formations in Egypt and other parts of North Africa. In the
Murzuq/Djado Basins, the term Nubian Sandstone Formation (or Nubian For-
mation) is applied to the Lower Cretaceous Msak Formation (See this term
under the Lexicon section). The Nubian terminology should cease to be used;
therefore, it will not be defined in the lexicon section.
• Pharuzian Belt (or the Trans-Sahara Orogen): The Pharusian Ocean
opened around 800 million years ago in the Neoproterozoic era after rifting
along the eastern margin of the West African craton during the breakup of Ro-
dinia. The ocean began to close around 730 million years ago with eastward
subduction of the Tilemsi arc, which was accreted against the Hoggar region
of the Saharan Metacraton. The western part of the Hoggar massif is made
of material from the Pharusian Ocean, including oceanic basalts, arc volcanic
and sedimentary rocks, and sediments shed into the Pharusian Ocean by the
West African craton and the eastern Hoggar. The closure was completed when
the West African and Saharan cratons collided around 635 million years ago
at the start of the Pan-African orogeny (www.wikipedia.org). The Pharuzian
Belt runs from north to south from Algeria to Benin, passing through eastern
Mali, the western half of Niger, and most of Nigeria (Fig. 3-2).
• Psammite: General term for sandstone. It is commonly used in various pub-
lications to describe a metamorphosed sedimentary rock with a sandstone
origin.
• Reference Section: The designated exposure of a named layered stratigraphic
unit or a stratigraphic boundary serves as the standard of reference. Surface
exposure of rock or a rock volume penetrated by a well in which lithologic
characteristics of a particular rock unit are well illustrated. The well in ques-
tion is called “Reference Well”.
• Reg: A large desert area covered with coarse gravel and small stones.
• Saharan Metacraton: Term used to describe a large area of continental crust
in the north-central part of Africa (Abdelsalam et al., 2002). It covers an area
of about 5,000,000 square kilometers (1,900,000 sq mi). It lies between the
Tuareg shield to the west, the Congo craton to the south, the Arabian-Nubian
Shield to the east, and the northern African continental margin. It lies under
southern Egypt, Libya, western Sudan, northern Kenya, Uganda, Congo, the
Chapter 3 Terminology and Definitions
9
Central African Republic, Cameroon, eastern Nigeria, eastern Niger, and Chad
(www.wikipedia.org). In Niger, it cuts more or less in half the Aïr Massif and
the crystalline rocks at the Damagaram Mounio & south Maradi. The western
portion of Niger (mainly the Iullemmeden basin) belongs to the Pharusian belt.
(Fig. 3-2 and inset in Fig. 5-39).
Figure 3-2. Location of the Saharan Metacraton (yellow), Pharusian
Belt (pale-green) and West African Craton (purple) together with their
relationship with Niger. The black circles represent the geochronologic
and isotopic data of the Saharan Metacraton, while the white circles
indicate localities mentioned in Abdelsalam’s article (Modified after
Abdelsalam et al., 2002).
• Sedimentary Basin: The term “Basin” has different meanings depending on
its location and containment. Groundwater Basin is for aquifers; drainage
Basin delineates a river system; oceanic Basin refers to the abyss, and sed-
imentary Basin is a depression in the earth’s crust filled with sediments.
Sedimentary Basins are on the scale of tens to hundreds of kilometres in
length-width and thousands of meters in depth. As such, they are usually tec-
tonic Basins formed by plate tectonic processes. Basins may also be described
in terms of depositional environment (fluvial, eolian, deltaic, lacustrine, con-
tinental, marine, reefal, abyssal) or sedimentary fill (clastic, carbonate,
evaporate, turbidite) or what economic resource they contain (petroleum,
natural gas, or coal). Only a tectonic classification explains the origin and evo-
lution of sedimentary Basins and their sediment fill. More details can be found
Stratigraphic Lexicon
10
in Sorkhabi (2019).
• Series (stratigraphic meaning with a capital “S”): A unit of the conven-
tional hierarchy of formal chronostratigraphic terms, ranking above a stage
and below a system, always a subdivision of a system.
• Series (non-stratigraphic meaning with small "s"): A few things or events
coming one after the other.
• Spirophyton: The former name of an ichnogenus or trace fossil of the Devon-
ian belonging to the Zoophycos.
• Stratotype: See “Type Locality”.
• Subgroup: A formally established subdivision of a group.
• Talach depression (or Talak depression): Same meaning as “Tin Séririne
syncline” (defined within the text). Only the term “Tin Séririne Syncline” will
be used in the lexicon.
• Talak-Tamesna Basin: Some older publications (from 1965 to at least 1980)
use the name “Talak Basin” or “Talak-Tamesna Basin” to define the exact area
covered today by the Tim Mersoï Sub-Basin of Niger. The origin of the name
comes most probably from the geographic names of “Ténéré du Tamesna” and
the sandy dune region of Talak in Western Niger which also extends into Al-
geria and Mali. This publication will not be using this term; instead, the name
“Tim Mersoï Basin” will be used as it has been used for many decades by most
authors. It is defined within the text.
• Ténéré: Large desert in part occupied by dunes. Few areas within Niger bear
this appellation (such as the “Ténéré du Tamesna” in the Tim Mersoï Sub-
Basin). However, the largest one (“Ténéré du Tafassasset”), is most often only
called “Ténéré”. The desert stretching between the Aïr and the line of rocky
outcrops borders the Djado basin. Its limit, in the north, is formed by the
Niger-Algeria border. In the south, by the great Erg Tibesti-Aïr, also called
"Erg du Ténéré". So defined, it is an area of about 100,000 square kilometres,
hyper-arid (Louis, 1970).
• Trough: A linear structural depression that extends laterally over a distance.
Although it is less steep than a trench, a trough can be a narrow basin or a ge-
ologic rift.
• Type Locality: Also called type area, or type section, is the locality where a
particular rock type, stratigraphic unit, fossil species, or mineral is first iden-
tified. If the stratigraphic unit in a locality is layered, it is called a stratotype,
whereas the standard of reference for unlayered rocks is the type locality.
• Unconformity: A surface of erosion between rock bodies, representing a sig-
nificant hiatus or gap in the stratigraphic succession. Unconformities result
from the subaerial or subaqueous exposure of rocks below the unconformity
and erosion with the loss of part of the older rocks. Several types of unconfor-
mities exist. Below are just a few of them which are used in the lexicon:
▪ Angular: An unconformity in which the bedding planes above and below
Chapter 3 Terminology and Definitions
11
are at an angle, denoting either tilting or folding before erosion and subse-
quent deposition or strong onlap.
▪ Nonconformity: An unconformity developed between sedimentary rocks
and older plutonic igneous or massive metamorphic rocks that have been
exposed to erosion before the overlying sediments covered them.
▪ Paraconformity: An obscure or uncertain unconformity in which no erosion
surface is discernible, or the contact is a simple bedding plane and in which
the beds above and below the break are parallel.
• West African Craton (WAC): One of the five cratons of the Precambrian
basement rock of Africa that make up the African Plate, the others being the
Kalahari craton, Congo craton, Saharan Metacraton, and Tanzania Craton. The
WAC extends across 14 countries in Western Africa (Morocco, Algeria, Mau-
ritania, Senegal, The Gambia, Guinea Bissau, Guinea, Mali, Burkina Faso,
Sierra Leone, Liberia, Ivory Coast, Ghana, Togo, and Benin) as well as a
tiny portion of eastern Niger (the Liptako-Gourma). It came together in the
late Precambrian and early Paleozoic eras to form the African continent. It
consists of two Archean centres juxtaposed against multiple Paleoproterozoic
domains made of greenstone belts, sedimentary basins, regional granitoid-
tonalite-trondhjemite-granodiorite (TTG) plutons, and large shear zones. The
craton is overlain by Neoproterozoic and younger sedimentary basins
(www.wikipedia.org) (Fig. 3-2).
Stratigraphic Lexicon
12
Chapter 4
A brief geological outline of Niger
The “République du Niger”1 is a landlocked country in West Africa named after
the Niger River. Libya borders it to the northeast, Chad to the east, Nigeria to the
south, Benin and Burkina Faso to the southwest, Mali to the west, and Algeria
to the northwest (Fig. 4-1). Niger covers almost 1,270,000 km2 (490,000 sq mi),
making it the largest country in West Africa. Over 80% of its land area lies in the
Sahara Desert. The country's predominantly Muslim population of about 22 mil-
lion (2019 data) lives mainly in clusters in the far south and west of the country.
Niger has 7 Regions or Departments (Fig. 4-2). The capital and largest city is Ni-
amey, located in Niger's southwest corner (www.wikipedia.org).
Figure 4.1. Localisation of the Republic of Niger within Africa (Source: http://
exploringafrica.matrix.msu.edu/country-overview/niger/).
1 In this document, the name of “République du Niger” will be abbreviated as “Niger”
only.
13
Figure 4-2. The seven departments of Niger: Niamey, Dosso, Tahoua,
Maradi, Zinder, Agadez and Diffa (Source: www.wikipedia.org).
Eastern Niger is included within the Saharan Metacraton, while the Western por-
tion is part of the Pharusian Belt. Only the Liptako-Gourma sector of Niger in
the west is included within the West African Craton (see Fig. 3-2). Precambrian
rocks outcrop all around the Republic (Fig. 4-3), while four major surface Pre-
cambrian basement areas are present within the country (Fig. 4-3, Fig. 4-6); these
are:
1. The crystalline rocks of the “Liptako Gourma” are known for their gold,
phosphate, manganese, copper, and molybdenum deposits.
2. The crystalline rocks of the “Aïr Massif” in the southeast of the Hoggar be-
long to the Tuareg shield (Ahmed et al., 2016).
3. The granitic rocks are exposed along the western margin of the Paleozoic
“Djado Basin” in the NE and in which gold was discovered in 2014 (shown
as “Djado Pb” in Fig. 4-6).
4. The crystalline rocks of the “Damagaram Mounio & south Maradi” near
Zinder. The Mounio is characterized by “young” microgranites, while “old”
granites indicate the Damagaram.
Except for the “Damagaram Mounio & south Maradi”, all the other areas have
commercial or artisanal gold mining exploitations (Fig. 4-4).
Stratigraphic Lexicon
14
Figure 4-3. Map showing the areas of West Africa where the
Precambrian basement outcrops, including those within Niger
(Source: Modified from Serrano-Martinez, 2015).
Figure 4-4. Gold mining localities of Niger (Source: Emmanuel
& Laurent, 2017).
The remaining portion of the country is covered by two main sedimentary basins
Chapter 4 A brief geological outline of Niger
15
(Fig. 4-6); themselves sub-divided into sub-basins:
1. The Iullemmeden Basin or Western Niger Basin (Fig. 4-6, Appendix A, Ap-
pendix B, Appendix E, Appendix H) (about 1000 km long and 900 km wide
and filled with Paleozoic to Cenozoic formations) is the vast expanse lo-
cated south of Hoggar. Its boundary to the north is defined by the basement
rocks of the "Adrar des Iforas", "Hoggar", and the "Aïr Mountains". It ex-
tends to the south until the basement rocks come back to the surface at the
latitude of the largest cities of Niger: Niamey, Maradi and Zinder. The north-
ern part of this vast structural basin is divided by the In Guezzam horst/
dome (Fig. 4-5), which extends north-south. To the west of the horst, in
the Tassili Oua N’Ahaggar region, the Tamesna Sub-Basin lies mainly in
Mali and Algeria (Mergl & Massa, 2004); in the east, the Tim Mersoï Sub-
Basin (Paleozoic-Mesozoic rocks known for their uranium, coal, and copper
deposits), located in the “Ténéré du Tamesna”, is almost entirely in Niger,
except for its northern portion included in the Tin Séririne syncline which
closes in Algeria (Valsardieu, 1971) [the former name of this syncline was
“In-Tedreft” (Furon, 1935)]. The largest tectonic structure impacting the Tim
Mersoï Sub-Basin (sometimes called “Talak-Tamesna Sub-Basin”) is the Ar-
lit-In-Azaoua (AIA) major fault which is affecting the whole continental
siliciclastic formations from Paleozoic to Mesozoic (Mamadou et al., 2016).
Finally, in the extreme SW of the Iullemmeden Basin, a small area of Upper
Ordovician rocks of the Kandi Sub-Basin of Benin outcrop near the town of
Gaya in Niger (see Kandi Fm in the lexicon).
Figure 4-5. The Iullemmeden Basin with its two Sub-Basins:
Tim Mersoï to the east of the In Guezzam Dome/Horst (Niger)
and Tamesna to the west of the horst (mainly in Mali & Alge-
ria) (Source: Alfidja et al., 2021).
Stratigraphic Lexicon
16
1. The Eastern Niger Basin (ENB) with its two distinct tectono-stratigraphic re-
gions:
A. The Eastern Niger Rift Basin (ENRB) (Mesozoic-Cenozoic), which is a
portion of the much larger Chad Basin (Fig. 4-6, Fig. 5-24) in Eastern
Niger, is the country’s oil prolific basin. It extends for 1000 km north-
south and 700 km west-east and includes seven grabens or sub-basins
(Fig. 5-25, Appendix A, Appendix H). It overlies a Precambrian crys-
talline basement and a Cambrian-Jurassic epimetamorphic basement.
B. The Djado Basin (Paleozoic-Mesozoic) in the extreme northeast of
Niger includes both the Djado Plateau and the Manguéni Plateau. (Fig.
4-6, Appendix A, Appendix C, Appendix G).
Figure 4-6. Geological map of Niger (and part of the surround-
ing countries) with the location of its four surface Precambrian
Basement areas, its three sedimentary basins, and a few sub-
basins (Modified from Persits et al., 2002). The orange outlines
represent the various sedimentary basins in and around Niger.
Chapter 4 A brief geological outline of Niger
17
Chapter 5
The Sedimentary Basins of Niger
The reader is also referred to the maps and stratigraphic columns in Appendices
A-J for a visual look at the geology of Niger.
5.1. THE IULLEMMEDEN BASIN (OR WESTERN
NIGER BASIN) (FIG. 5-1; FIG. 5-2; FIG. 5-3)
The Iullemmeden (spelt “Aouellimiden” in the older documents) are a federation
of Touareg people who occupy the central region of Niger (Dikouma, 1990). The
name was first given to the sedimentary basin by Radier (1953), who effectively
redefined the area previously described by Furon (1935) as the "Bassin de L'Oued
Azaouak" or “Azawagh” (Paris, 1995).
The Iullemmeden Basin, to the west of the Aïr Massif, is a vast structural de-
pression of about 360,000 km² covering virtually all of western Niger and with
extensions in Algeria, Mali, Benin, and Nigeria (a total of 800,000 km²). It is
filled with 1,500 to 2,000 meters of Cambrian to Pleistocene sediments of alter-
nating marine and continental origin.
18
Figure 5-1. Overview of the geology of the Iullemmeden Basin (Source: Modified
from Saley et al., 2019).
Figure 5-2. 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”
(Source: Modified after Kogbe, 1991).
Figure 5-3. Cross-section of the Tim Mersoï Sub-Basin. 1= Timesgar Fm; 2=
Graptolitic Shales; 3= Anou Izileg Fm and Oued Felaou Member; 4= Akara
Member; 5= Taberia & Farrazekat Fms; 6= Teragh Fm; 7= Talak Fm; 8= Gue-
zouman Fm; 9= Tchinezogue Fm; 10= Tarat Fm; 11= Madaouela & Arlit Fms;
12= Izégouandane Group; 13= Agadez & Irhazer Groups;
Chapter 5 The Sedimentary Basins of Niger
19
14= Tégama Group (Source:Modified after Kogbe, 1991).
The geological history of the Iullemmeden basin (and Tim Mersoï
SubBasin) begins in the Cambrian of the Tin Séririne syncline, southeast of
the Hoggar shield in Algeria and Niger (Joulia, 1959) (Fig. 5-4), which is the
northern extension to the Tim Mersoï Sub-Basin.
Figure 5-4. The Tim Mersoï Sub-Basin of the Iullemmeden Basin and its re-
lationship with the Tin Séririne syncline in Algeria. 1) Quaternary & Neogene
deposits; 2) Cenozoic volcanism; 3) Cretaceous; 4) Jurassic; 5) Triassic; 6)
Permian-Carboniferous; 7) Devonian; 8) Silurian; 9) Cambrian-Ordovician;
10) Anorogenic Volcanism of Aïr; 11) Faults; 12) Some uranium deposits or
showings (Source: Modified after Mammar, 2012).
The Tin Séririne structure is a simple asymmetrical syncline of north-south
axis having an almost flat bottom except close to the faults network on its western
border ("In Guezzam" promontory/horst), where high plunge (dip reaching 60°)
can be observed (Fig. 5-5). The eastern part of the structure is cut by an important
north-south Late Panafrican lineament, the 7°30" accident/fault, which passes just
slightly east of In Azaoua (Djellit et al., 2006).
Stratigraphic Lexicon
20
Figure 5-5. SW-NE section of the Tin Séririne structure parallel to the
Niger border (Source: Djellit et al., 2006).
The Tin Séririne Syncline/Tim Mersoï Sub-Basin is constituted by Paleozoic
rocks that overlay the Hoggar basement. At least near the In Guezzam area
(Fig. 4-5, Fig. 5-4), the lower part is composed of magmatic and sedimentary
complexes of Cambrian age but slightly metamorphized. The younger Paleozoic
sedimentary formations include rocks of Ordovician to Carboniferous age in Al-
geria (Fig. 5-6) and Cambrian-Ordovician to Permian age in Niger (Fig. 5-4)
(Djellit et al., 2006).
Chapter 5 The Sedimentary Basins of Niger
21
Figure 5-6. Simplified stratigraphy of the Tin Séririne syncline
(Source: Djellit et al., 2006). The Upper Devonian is present
more south and southwest of their study area.
These deposits are in straight bevels from North to South (Fig. 5-7); erosion
bevels for the Cambrian-Ordovician to Silurian and deposit bevels for the more
recent formations. These wedges, observable on the western edge of the Aïr, are
arranged in "downlap" in the deep parts of the basin; they testify to migration in
time of the axis of this basin towards the South.
Stratigraphic Lexicon
22
Figure 5-7. Schematic structural section of the Iullemmeden Basin west
of the Aïr Mountains. North-south section, on a 6° longitude line
(Source: Modified from Kogbe, 1991).
In Niger, the Paleozoic formations (margino-littoral and continental) outcrop in
the northern portion of the Tim Mersoï Sub-Basin near the Tamesna-Talak area,
along the western margin of the Aïr Massif (Fig. 5-8). The lower Paleozoic, Cam-
brian-Ordovician sediments (up to 500 m) are marginal marine. They comprise
basal conglomerates, and sandstones with Cruziana and Skolithos, uncon-
formably overlain by glacial deposits. They rest unconformably on the
Precambrian basement and are grouped into the Timesgar Fm, the Tindi Fm, and
the In Azaoua Fm. The Graptolitic Shales overlie them; the lateral equivalent
of the Silurian Tanzuft Shales of North Africa and Djado Basin. The overlying
Devonian sediments are predominantly sandstones with nonmarine deposits char-
acteristic of the Middle and Upper Devonian (Greigert & Pougnet, 1967) (Fig.
5-6). A marine transgressive episode is recorded during the Visean and Ser-
pukhovian/Lower Bashkirian, while a general regressive episode is recorded
during the Upper Bashkirian/Moscovian (Carboniferous). Uplift and folding oc-
curred during the Permian (Moody, 1997).
Chapter 5 The Sedimentary Basins of Niger
23
Figure 5-8. Geological map of the southern most portion of
the Tim Mersoï Sub-Basin (Source: modified from Young et al.,
2016). See Appendix E for the age of all formations.
Upper Carboniferous units host uranium occurrences, especially the Guezouman,
the Tarat and the Madaouela sandstones (Wagani et al., 2011). Carboniferous
units also host coal deposits in the Anou Araren area (NWT Uranium Corpora-
tion, 2011). Generally, Paleozoic strata thicken towards the Hoggar Mountains
and thin southwards, where they disappear (Schlüter, 2008).
In the area to the west of the Aïr, four stratigraphic groups can be dis-
tinguished from the Visean to Upper Jurassic: (1) the Terada Group, which
includes mudstones, sandstones, and siltstones; (2) the Tagora Group, containing
continental sandstones, marine sandstones, arkoses, and mudstones; (3) the Izé-
gouandane Group, composed of arkoses, mudstones, and analcimolite; and (4)
the Agadez Group, which is composed of sandstones, arkoses, and significant
amounts of volcanic material. The Permo-Triassic sediments alone have a max-
imum thickness of 300 m. These are massively bedded, locally cross-stratified,
with vertebrate remains and silicified wood found toward the top of the sequence.
Towards the north, the Permo-Triassic sediments rest unconformably on Upper
Bashkirian / Moscovian nonmarine deposits. To the south, they are overlain by
coarse-grained sandstones and conglomerates of the Teloua 2 Mbr of the Teloua
Fm (Moody, 1997).
The sediments cover of the Tim Mersoï Sub-Basin (total of 1300 m) has been
shaped by the reactivation of many tectonic structures, most of which were initi-
ated during the Panafrican orogenesis (600 Ma) and reactivated later during the
Visean (350-325 Ma) and Cretaceous (135-65 Ma). Thus, the Tim Mersoï Sub-
Stratigraphic Lexicon
24
Basin can be described as an N30-trending syncline that has been divided into
several blocks by N30-trending faults. However, the larger structure impacting
the Sub-Basin is the Arlit-In-Azaoua fault (AIA fault) (Fig. 5-9; Fig. 5-10): this
NS-trending structure seems to be the main metallotect of uraniferous mineral-
ization in the Tim Mersoï Sub-Basin (Extensive hydrothermal alterations related
to fluid circulations along the fault are described in several studies such as Ma-
madou et al. (2016), Billon and Patrier (2019) and Abd Elmola et al. (2020).
These alterations played a major role in the current lithology and in the Uranium
migration and mineralization). Uraniferous deposits in Niger have been discov-
ered in different sedimentary formations near this major regional fault; such as
the Arlit deposit (SOMAÏR) hosted in the Carboniferous Formation of Tarat,
the Akouta deposit (COMINAK) hosted in the Carboniferous Formation of Gue-
zouman and the Imouraren deposit (not yet exploited as of 2019) hosted in the
Jurassic Member of Tchirezrine 2 (Billon & Patrier, 2019).
Figure 5-9. General geological map of Niger showing the AIA fault
(Source: modified after Abd Elmola, 2020).
In recent years, the DASA graben (Fig. 5-11) was discovered about 120 km north
of Agadez city (Sani et al., 2020, 2021a, 2021b). Starting with the Carboniferous
resting on the Precambrian, this N70° trending graben includes the same sedi-
mentary column (850m) as those in the Tim Mersoï Sub-Basin up to the Lower
Cretaceous. Technically speaking, it is a sub-basin to the Tim Mersoï Sub-Basin.
Chapter 5 The Sedimentary Basins of Niger
25
Figure 5-10. Geological and structural map of part of the Tim Mersoï Sub-Basin
showing the location of Niger Uranium deposits of Arlit (Carboniferous Forma-
tion of Tarat), Akouta (Carboniferous Formation of Guezouman) and Imouraren
(Jurassic Member of Tchirezrine 2) in relation to two main faults (Source: Ma-
madou, 2016).
Stratigraphic Lexicon
26
Figure 5-11. DASA graben schematic geological section (Source: CSA
Global, 2017, 2019).
There seem to be ambiguities regarding the exact interval of the “Continental
Intercalaire” (Fig. 5-2 and Fig. 5-3) found in Algeria, Niger, Chad, Mali and Mau-
ritania. This issue is not recent. For instance, Furon (1935) writes that it is from
Permian to Albian but concedes that it could also include the Lower Cenomanian.
De Lapparent (1960) discusses at length the age of the sequence. He agrees on
the uppermost limit (Lower Cenomanian) but cannot pinpoint its base (Moscov-
ian, Permian, Triassic, or Jurassic?). According to Haughton (1963), the age of
the complex extends from some point in the Upper Jurassic through to the Lower
Cenomanian, the upper limit being fixed by the fact that in the Damergou, the
sequence is overlain by marine Upper Cenomanian beds carrying ammonites of
the type Neolobites. According to Furon (1964), when Kilian (1931) named the
sequence, he defined it as the interval between the continental Triassic, continen-
tal Jurassic, and the continental Lower Cretaceous up to the Lower Cenomanian.
Faure (1966) and Molinas (1965), on the other hand, state that Kilian (1931)
defined it as the interval between the Moscovian (Carboniferous / Pennsylvan-
ian) up to the Albian (for Molinas, 1965) and the Cenomanian (for Faure, 1966).
Greigert (1966) and Moody (1994) have a slightly different definition; they de-
fine the Continental Intercalaire as the post-Triassic to pre-Upper Cenomanian
deposits of the Iullemmeden Basin. Fabre et al. (1983) state: “As accepted by the
geologists of the C.E.Α. (eg Valsardieu, 1971) the Continental intercalaire begins
in Niger with the Arlit Unit [of Permian age] … up to the Lower Cenomanian”.
Subsequent authors, such as Coquel (1995), Gerbeaud (2006), Billon et al.
(2016), Mamadou (2016), and Billon et al. (2019) follow Fabre et al. (1983)’s
Chapter 5 The Sedimentary Basins of Niger
27
recommendation and continue using the interval between the Permian and the
Lower Cenomanian. The present document will adopt the same interpretation
as the one defined by Fabre et al. (1983). The Iullemmeden Basin will include
the Permian Arlit unit, the Izégouandane Group, the Agadez Group, the Irhazer
Group, the vast Lower Cretaceous group of Tégama, and finally, the Lower
Cenomanian Farak Formation. In eastern Niger, only the Téfidet Group and
the Lower Cenomanian Alanlara Formation (with equivalent Ezerza-Cheffadène
Fms) comprise the Continental Intercalaire. These disappear under the sands of
the erg of the "Ténéré du Tafassasset" between the 9° and 10° meridian, only
to reappear on the edges of the Bilma basin in Achegour, Fachi, and Dibella. In
Djado, three formations can be considered as Continental Intercalaire (Zarzaitine,
Taouratine and Msak). The term “Continental Hamadian” was also created by
Kilian (1931). Furon (1964) later recommended discarding it. However, the term
kept being used by most authors and is still relevant in the literature today (in the
present document, the term will still be used). (Fig. 5-1; Fig. 5-12).
As it will be discussed below, the Upper Cretaceous to Lower Eocene marine
transgressions (Fig. 5-16) repeatedly established a Transsaharan seaway from
the northern Tethys to the Gulf of Guinea (Fig. 5-14). Still, it did not reach
the south (along the Nigeria border) and northwest of the Iullemmeden Basin.
Thus, the Upper Cenomanian to Lower Eocene continental sediments (Appendix
H) (mostly unfossiliferous coarse sandstones more or less clayey corresponding
to fluvial, lacustrine, and deltaic environments) deposited in these basin margin
areas concurrent with the Late Cretaceous marine transgressions are known as
“Continental Hamadien” in Niger (in Benin they are known as Sendé Formation
of the Kandi Sub-Basin; in Nigeria, they correspond to the Illo Formation of the
southern Sokoto province and the Gundumi Formation of the northern Sokoto
province) (Greigert, 1963; Saley, 2018, Web-02).
The "Continental Intercalaire” and the “Continental Hamadian" trace an al-
most circular pattern in the Iullemmeden basin. They form a broad synclinal
structure truncated to the southwest by faults oriented NW-SE or N-S (Zaborski
et al., 1999). (Fig. 5-12 and Fig. 5-1).
Stratigraphic Lexicon
28
Figure 5-12. The Continental Intercalaire with the Continental
Hamadian (blue) tracing an almost circular pattern in the
Iullemmeden Basin (Source: modified from Greigert, 1966).
Mesozoic marine sedimentation in the Iullemmeden Basin began with the Ceno-
manian transgression. It is called the first transgression (out of six) (Fig. 5-16,
Fig. 5-17), which deposited the Iguéllala Mountains and White Limestone For-
mations (Greigert, 1966; Meister et al., 1992; Laouali-Idi et al., 2021). The
epicontinental sea bisected West Africa periodically from the Late Cretaceous to
the Early Eocene, in dramatic contrast to the current Sahara Desert that dominates
the same region today (Fig. 5-13; Fig. 5-14).
Chapter 5 The Sedimentary Basins of Niger
29
Figure 5-13. Transgressions/regressions in North/Central Africa during the
Cenomanian-Coniacian (top left), Santonian-Maastrichtian (top right), Pale-
ocene (bottom left), and Early-Middle Eocene (bottom right) (Guiraud et al.,
2005).
Known as the Trans-Saharan Seaway, this warm and shallow ocean was a man-
ifestation of globally elevated sea level associated with the rapid break-up of
the supercontinent Gondwana in the Late Mesozoic. Although it varied in size
through time, the Trans-Saharan Seaway is estimated to have covered as much as
3000 km2 of the African continent and was approximately 50 m deep (O’Leary et
al., 2019) (Fig. 5-14).
Stratigraphic Lexicon
30
Figure 5-14. Generalized reconstruction of the Trans-Saharan
Seaway during the Santonian-Maastrichtian (Modified after
O’Leary et al., 2019).
The marine sediments deposited by the Trans-Saharan Seaway are stratigraph-
ically found between the Continental Intercalaire group at the base and the
younger Continental Terminal group at the top (discussed below). Systematic
variation in sediments occurred in the Iullemmeden and Chad Basins (including
the Eastern Niger portion of the basin), with the emergence of limestone since
the Turonian and the prevalence of sandstone and subordinate mudstone and silt-
stone (Fig. 5-15). The Iullemmeden Basin provides an extreme example of such
change, with limestone dominating the basin from Turonian to Campanian. The
Iullemmeden and Chad Basins underwent a continental-marine-continental fa-
cies variation during the Cretaceous. The timing of the shift from continental
to marine facies changed from Cenomanian in the Chad Basin to the Turonian
in the Iullemmeden Basin. During the Cenomanian, a significant transgression
occurred, resulting in the marine facies sediments reaching the Chad Basins.
Transgression continued during the Turonian, with the Iullemmeden Basin cov-
ered by deposition of marine facies until the Campanian. The transgression was
synchronous with the global rise in sea level during this time, suggesting a direct
Chapter 5 The Sedimentary Basins of Niger
31
attribution of the transgression to the high sea-level event (An et al., 2017).
Figure 5-15. Stratigraphic data from the Iullemmeden and
Chad Basins (including the Eastern Niger Basin portion) dur-
ing the Cretaceous Period. The marine period is observed
between the Upper Cenomanian up to the base of the Maas-
trichtian in the Iullemmeden Basin (An et al., 2017).
The rocks created by the marine sediments are characterized by an alternating se-
quence of claystone/shales and limestones. Long periods of deposition of shales
with secondary gypsum formed due to sulfide evolution, separated by relatively
brief episodes of oxygenation (Ali et al., 2019). According to Greigert et al.
(1966), the sedimentary infilling of the Iullemmeden Basin during the period
ranging from Upper Cretaceous (Upper Cenomanian) to Paleocene-Ypresian
has revealed a succession of five transgressive episodes (Fig. 5-16). However,
Laouali-Idi et al. (2021)'s study has shown an additional one within the
Garadaoua Formation (Fig. 5-17). The vertical succession of facies identified for
this period includes from bottom to top:
• Calcareous sandstones and gypsum clays of the Upper Cenomanian-Lower
Stratigraphic Lexicon
32
Turonian age, deposited during the T1 & T2 transgressions (Iguéllala Moun-
tains Formation)
• Gypsiferous limestones and mudstones of Upper Turonian deposited during
the late T2 transgression (White Limestone Formation) and the sandy lime-
stones and marls of Campanian to Middle Maastrichtian age, related to T3
transgression (Alanbanya & Farin Doutchi Formations).
• Siltstones and argillites of Maastrichtian age, deposited during the T4 trans-
gression (In Wagar Formation with Libycoceras ismaeli and Laffiteina
bibensis and clay-limestones of Paleocene age, associated with transgression
T5 (Garadaoua Formation; Tamaské (G2) Member) with Ranikothalia
bermudez and Lochkartia hamei.
• The marls, sandstones, and conglomerates of the Keita (G4) Member (T6) of
the Garadaoua Formation.
Chapter 5 The Sedimentary Basins of Niger
33
Figure 5-16. The five Upper Cretaceous (Upper Cenomanian) to Paleocene-
Ypresian transgressions within the Iullemmeden Basin, according to Greigert et
al. (1966) (Source: Laouali-Idi et al., 2021).
Stratigraphic Lexicon
34
Figure 5-17. The six transgressions and related regressions as compiled from
Laouali-Idi et al. (2021).
During this period (Upper Cenomanian to Lower Eocene, with the most extensive
transgression during Turonian to Coniacian), marine life flourished in the Trans-
Saharan Seaway. Molluscs such as ammonites (Neolobites, Nigericeras [Fig.
5-18]), nautiloids, gastropods and oysters, fishes (Ceratodus, Enchodus, etc.),
crocodiles (Aegyptosuchus), and ostracod faunas are known to have migrated
through this seaway, based on their fossil remains found in the corresponding ma-
rine deposits in Niger (Douville, 1920; Schneegans, 1943; Arambourg & Joleaud,
1943; Lambert, 1943; Meister et al., 1992; O’Leary et al., 2019; etc.).
Chapter 5 The Sedimentary Basins of Niger
35
Figure 5-18. Ammonites from the marine Upper Cenomanian to Tur-
onian deposits of the Damergou region of Niger. 1-4) Neolobites
vibrayeanus; 5) Nigericeras gadeni (Source: Meister et al., 1992).
During the Maastrichtian, a considerable regression occurred when marine sed-
iments retreated from the Iullemmeden-Chad Basins. The term "Continental
Terminal" (Fig. 5-2) (abbreviated by “Ct”) was also created by Kilian (1931) and
Stratigraphic Lexicon
36
used for all deposits younger than the Middle Eocene, which cover the central
part of the Iullemmeden Basin. Over the Sahara region, it is not complete any-
where (Furon (1964)). At the edge of the Birrimian of the Liptako, the deposits
have only a few decimeters in depth, but they attain 450 m depth in the basin's
center.
Figure 5-19. Stratigraphic north-south transect along the Dallol Maouri (FAO,
1970; Heckmann, 2019). Ct1 = Ader Doutchi Fm; Ct2 & Ct3 = Birni N’Konni
Fm.
The base was assigned by Greigert and Pougnet (1967) to the Middle Eocene,
whereas Machens (1973) indicated an approximative Mio-Pliocene age for the
middle to upper strata. In the western part of Niger, the Ct3 formation, classically
called "Grès du Moyen Niger (Sandstone of the Middle Niger)" (Greigert, 1966),
represents the last filling deposits of the Iullemmeden Basin.
According to Bassot et al. (1981), the Continental Terminal of the Iullemme-
den basin east of the Adrar des Iforas in Mali and west of Agadez in Niger is
consistent with the marine layers of the Cretaceous-Paleocene and would reach
450 meters thick. It would be distinguished by a primary detrital sequence, with
lignites and ferruginous oolites surmounted by a sandy clay complex with levels
rich in pyrite and plant debris, and the clayey sandstones of Central Niger rich in
ferruginous concretions and oolites.
Boudouresque et al. (1982) restrict this term to post-Eocene and pre-Qua-
ternary and specify its content, genesis, and limits: this period (roughly
Mio-Pliocene) corresponds to a phase of erosion and sedimentation (oolithic lev-
els) and the uplift of the eastern edge of the basin, at the end of the Eocene (or
Chapter 5 The Sedimentary Basins of Niger
37
Oligocene), manifested by a discrepancy on the Ader Doutchi Formation, as well
as at the end of the Pliocene (or at the beginning of the Quaternary). In east-
ern Niger, the Continental Terminal overlays Eocene alterites, while in western
Niger, it overlays the marine Eocene (Faure, 1966). After further study, Lang et
al. (1986, 1990) proposed to return to Kilian’s definition (1931) and to reserve
the term "Continental Terminal" to the detrital quartzo-kaolinitic Formation with
Siderolitic facies, lying in stratigraphical unconformity on any substratum. There-
fore, its age can be situated between the Mid-Eocene and the Late Pliocene (Fig.
5-21).
As read above, the age of Ct1 (the “siderolithic series of Ader Doutchi”, or
Ader Doutchi Fm), Ct2 (“clayey-sandy series with lignites”), and Ct3 (“Sand-
stone of the Middle Niger”) [equivalent to the Birni N'Konni Fm] deposits have
long been approximated to be post-Middle Eocene and pre-Quaternary (Lang et
al., 1986 & 1990), however, more recent work by Beauvais et al. (2008) and
Heckmann (2019) now attributes the three deposits to the Oligocene (Fig. 5-20,
Fig. 5-19).
In the present document, the definition of “Continental Terminal” will follow
Lang et al. (1990)'s recommendation with the adjusted ages of Ct1, Ct2, and Ct3
to be of Oligocene age.
Figure 5-20. East-west structural cross-section of the Iullemmeden Basin (Zinder
to Niamey). (Modified from Ousmane et al., 2020).
Stratigraphic Lexicon
38
Figure 5-21. Composite section of Cenozoic strata in the Il-
lummeden Basin (Source: Modified from Swezey,2009).
The "Continental Terminal-complexe de base" is described as conglomeratic fa-
cies of the Continental Terminal but strongly resembles the descriptions of the
Continental Hamadien. Even Greigert himself hints the possibility of two dif-
ferent assemblages. Given a) their similar lithology, b) the lack of intermediate
marine sequences, and c) the lack of strong stratigraphic markers, differentiation
between the Continental Hamadien and the “Continental Terminal-complexe de
base” is not straightforward. Perhaps the “Complexe de base” is not a substratum
of the Continental Terminal but a margin facies of the Cretaceous Continental
Hamadian (Heckmann, 2019). A lithostratigraphic representation of the Con-
tinental Intercalaire, the Marine Transgressions/Regressions (Continental
Hamadien), and the Continental Terminal is shown in Fig. 5-22.
Chapter 5 The Sedimentary Basins of Niger
39
Figure 5-22. Lithostratigraphic correlation chart of Permian
to Recent sediments of the Iullemmeden (incl. Tim Mersoï)
Basin, the Termit Sub-Basin of the ENRB and the remaining
portion of the Chad Basin (Modified from Guiraud et al.,
2005). The Continental Intercalaire, the Marine Transgres-
sions/Regressions (Continental Hamadien) and Continental
Terminal are well represented. Lithologies: (1) volcanic; (2)
conglomerates; (3) sandstones; (4) clays, shales; (5) dolomitic
shales; (6) evaporites; (7) limestones; (8) clayey limestones;
(9) flints, cherts; (10) diatomites; (11) ferruginous oolites; (12)
laterites; (13) sand dunes.
Stratigraphic Lexicon
40
5.2 – EASTERN NIGER RIFT BASIN (ENRB)
The "Ténéré du Tafassasset" sector in eastern Niger is a region of collapsed struc-
tures about 1000 km long from the border with Algeria in the north down to Lake
Chad in the south (Fig. 5-23).
Figure 5-23. Location map of NE Niger (Baumhauer et al.,
2009, 2010).
It is known geologically as the "Eastern Niger Rift Basin” or “ENRB" (Fig. 5-25).
This Mesozoic-Cenozoic intra-continental rift basin trends NNW-SSE and is in-
cluded within the much larger Chad Basin Province (Brownfield, 2016) (Fig.
5-24). North of the Agadez lineament (at about the 17th parallel; Fig. 5-25), which
separates the ENRB into north and south sections, it comprises the Kafra, Grein,
Bilma, Ténéré and Téfidet grabens (or Sub-Basins), and south of the Agadez lin-
eament the Termit graben (or Sub-Basin) with an extension to the SW known
as the N’Guel Edji graben (sometimes spelled “N’Dgel Edgi”). The N’Guel
Edji graben is a relatively shallow graben about 100 km long and 40 km wide
(Fig. 5-25; Fig. 5-26; Fig. 5-29) filled with Lower Cretaceous clastic sediments
overlayed by Cenozoic lacustrine and fluvial formations. This small graben was
outlined during the 1970 seismic survey (Louis, 1970, page 240). Collectively,
the Ténéré and Termit grabens are sometimes called the Agadem Graben.
Chapter 5 The Sedimentary Basins of Niger
41
Figure 5-24. The Chad Basin Province (green outline) and the Cretaceous-Pa-
leogene/Neogene Rifts system (dotted red outline) within it (Source: Brownfield,
2016). Cross-section A-A’ is shown in Fig. 5-38.
Stratigraphic Lexicon
42
Figure 5-25. Simplified isopach of the Eastern Niger Rift Basin (comprising
the Kafra, Grein, Téfidet, Ténéré, Termit, and Bilma grabens/Sub-Basins) with
surrounding generalized surface geology (Source: Genik, 1992; modified after
Ahmed et al., 2020).
Chapter 5 The Sedimentary Basins of Niger
43
Figure 5-26. The simplified isopach of the Eastern Niger Rift
Basin in relation to the main towns in Niger (Source: Google
Earth and Genik, 1992; modified after Ahmed et al., 2020). Re-
fer also to Fig. 5-25.
The ENRB is the most important and the most extensive petroleum basin of the
West and Central African Rift System (WCARS), with over 100,000 km2 (Fig.
5-27). The rifts show tilted fault blocks and simple horsts & grabens (Fig. 5-28).
Figure 5-27. The West and Central African Rift System
(WCARS), with the Central African Shear Zone labeled CASZ
(Source: Gouvernement du Niger, Ministère du pétrole, 2020
and www.wikipedia.org).
Stratigraphic Lexicon
44
Figure 5-28. The horst & grabens of the Eastern Niger Basin (Source: modified
after Genik, 1992; Ahmed et al., 2020; also in Gouvernement du Niger, Ministère
du pétrole, 2020).
Figure 5-29. Cross-section through the Termit and N’Guel Edji grabens (Source:
Harouna et al., 2017).
The Eastern Niger Rift Basin is a superimposed rift basin with sedimentary struc-
tures emplaced during two rifts episodes. The Cretaceous episode is characterized
by large, tilted commonly faulted blocks trending NW-SE that were reactivated
in the Paleogene. In contrast, the Paleogene episode is characterized by normal
faulted blocks that trend NNW-SSE. The rifting resulted in different basin struc-
tures, with the north section dominated by asymmetric half-grabens while the
south section is dominated by full-grabens (Ahmed et al., 2020).
Chapter 5 The Sedimentary Basins of Niger
45
The Continental intercalaire outcrops in a very discontinuous manner be-
tween the Aïr massif and the Djado Plateau and the Téfidet Trough. Sandstone
formations (e.g., Téfidet Group, Dibella Formation, etc.) overlap Precambrian
rocks discordantly or, locally, Paleozoic sediments. These formations have been
attributed to the Lower Cretaceous following the discovery of some paleobotanic
remains and, above all, the fact that they are overlain by marine formations
(Alanlara Formation or its equivalent) dated Lower to Middle Cenomanian. The
thickness of the continental assemblages varies rapidly as one approaches the
faulted fringes which delimit the various troughs (Téfidet, Ténéré, Kafra), where
it may reach a thickness of 1000-2000 m. The infilling of these troughs began
only from the Upper Aptian (Lefranc et al., 1990).
In the Late Cretaceous, the global sea level rose, leading to marine sediments
transgression from the Tethys Sea and the South Atlantic on its rifted blocks. In
the Termit Sub-Basin (see below), over 5 km thick sediments were deposited into
a 150 km wide depression. In contrast, in the Ténéré Basin (see below), 4 to 6
km of marine, continental and lacustrine sediments were deposited (Ahmed et al.,
2020). The maximum thickness of the Mesozoic-Cenozoic strata is found in the
Termit Sub-Basin and is about 12,000 m (Fig. 5-30). The Mesozoic sequence is
composed of 300-2500 m of Lower Cretaceous clastics, and 800-4200 m of Up-
per Cretaceous shallow marine shales, sands, silts, and minor carbonates (Donga,
Yogou and Madama formations) (Liu et al., 2020) (Appendix H). The thickness
of the Cenozoic continental sands and shale sediments measures 350 to 2500 me-
ters. The Neogene and Quaternary sequences mainly consist of fluvial deposits
eroded mainly in the northern section of the ENRB (Ahmed et al., 2020).
The Continental Terminal in eastern Niger (Dollé and Homodji formations)
is comparable to western Niger: Siderolitic facies, with ferruginous oolites inter-
stratified levels near the base of the formations (Lang et al., 1990).
Stratigraphic Lexicon
46
Figure 5-30. Stratigraphic columns of selected rift sub-basins
within the Eastern Niger Basin (Source: Brownfield, 2016). Re-
fer to Fig. 5-25 for the position of the three sub-basins.
5.2.1 – Oil Exploration and Development History
The stratigraphic and structural knowledge of the ENRB (surface and sub-sur-
face) is largely due to the long history of petroleum exploration in the region. Oil
exploration in Niger began during the 1950s. For the first 20 years it consisted
mainly of reconnaissance surveys of the southern Hoggar, Djado, Talak and
Lake Chad areas and the south of Iullemmeden Basin. From 1970 to 1980, geo-
physical surveys were carried out in the Séguédine, Agadem and Termit areas
(Louis, 1970, for instance), in the southern and SW parts of the Iullemmeden
Basin and in the Djado Basin. Wells Séguédine-1 and Tiffa-1 were drilled in
1973-74 in the Kafra graben by Texaco Niger Inc. Well Madama-1 in the Ter-
mit graben, drilled in 1975, resulted in the first oil discovery in Niger. Four more
Chapter 5 The Sedimentary Basins of Niger
47
wells were drilled in the Termit Basin in 1977 by Esso Exploration & Produc-
tion Niger Inc. (Iaguil-1, Yogou-1, Moul-1 and Donga-1). Well Yogou-2 was
drilled by Esso in 1980, and eleven further wells were drilled in this area by Elf
Aquitaine in 1982-94 (Trakes-1, Sokor -1 to -5, Goumeri-1, Araga-1, Faringa-1,
Agadi-1 and Karam-1), leading to the discovery of more than one million tons
of oil in the Termit Basin. In 1997 and 1998, a further three wells were drilled
by Esso (Boujamah-1, Sountellane-1 and Soudana-1), followed by three wells by
Petronas/Texaco (Achigore-1, Jaouro-1 and Gani-1) in 2004 and early 2005. In
2006 Petronas/Texaco abandoned the Agadem permit in the Termit Sub-Basin,
deeming it uneconomical. Therefore, once again, the permit became the state's
property. These earlier investigations by Esso Exploration and Production Niger
Inc., Petronas/Texaco, Elf Aquitaine, etc., had acquired more than 15,000-line km
of seismic data together with some 30,000 km of aeromagnetic lines and drilled
more than 20 exploration wells.
In 2007, the Agadem block was re-allocated to China National Petroleum
Corporation (CNPC) through a public tender with a signed agreement between
the CNPC and the Niger government (2008) to construct a 20,000 barrels/day ca-
pacity refinery in Niger on a share capital arrangement of 60% China and 40%
Niger. Between 2008 and 2012, CNPC acquired the first-ever 3D seismic lines
(13,000 km2) over the Agadem permit and more than 18,000 km2 of 2D seis-
mic lines. 127 exploration wells were drilled, with 97 being discovery wells. In
2011, the first oil was produced from the Sokor and Goumeri fields. The refinery
was launched in the Zinder region, with well completions, construction of sur-
face facilities, and a 462.5 km-long pipeline from the oil fields to the refinery
realized. The exploration success of CNPC in the Agadem block raised the es-
timated reserve to 3.5 billion barrels of oil from the 328 million barrels earlier
recorded (over 1 billion barrels of recoverable oil at a 30% recovery rate esti-
mated) and about 17 billion m3 of gas from 10 billion (13 billion m3 recoverable).
Eleven wells in Sokor yield daily crude production of 12,000 stb/d, and ten wells
in Goumeridaily oil production of about 8000 stb/d. In 2013, 20% of the CNPC
Agadem license was sold to China Petroleum Corporation (CPC) Taiwan and
the same year, portions of the Agadem acreage (R1/R2) were mandatorily relin-
quished.
Between 2014 and 2018, Savannah Petroleum Plc. was awarded the CNPC
relinquished R1/R2 acreage. Another area, R3/R4, was also acquired in 2015,
putting the total acreage at 13,655 km2. Savannah Petroleum has acquired a
36,948 km Full Tensor Gravity (FTG) survey (2015) and an 806 km2 3D seismic
survey of a portion of R3 following its phase development plan. Three wells
drilled (Bushiya-1, Amidigh-1 and Kunama-1) so far in the R3 acreage indicated
light oil shows. Recently, a fourth well (Eridal-1) also in the R3 acreage has
Stratigraphic Lexicon
48
proven successful. The R1/R2 acreage covers 30.5% of the CNPC Agadem area
and contains an estimated net reserve of 812 MMBBL. (Harouna & Philp, 2012;
Harouna et al., 2017; Ahmed et al., 2020)
5.2.2 - The Ténéré Sub-Basin
The Ténéré Sub-Basin is a Mesozoic–Cenozoic intracontinental rift part of the
West and Central African Rift System (WCARS). It covers an area of approxi-
mately 2×104 km2 in the northwestern part of the Eastern Niger Basin (Fig. 5-25)
and extends for about 300 km north–south and 50 – 80 km west-east. The basin
is developed on a Precambrian basement and consists of a graben and two half-
grabens controlled by NW–SE-trending border faults (Fig. 5-31, Fig. 5-32). The
basin is divided into three structural units: the western depression, the eastern de-
pression I and the eastern depression II (Fig. 5-31).
Rifting in the Ténéré and nearby graben and half-graben in the Early–Late
Albian resulted in rapid subsidence and the deposition of fluviatile to lacustrine
sediments (Liu et al., 2017). Thus, in the Ténére Basin, Lower Cretaceous fluvial
and lacustrine mudstones and sandstones are up to 2000 m thick (Fig. 5-33).
Thick Upper Cretaceous sandstones and mudstones were deposited in shallow-
marine to paralic environments, which was suggested by both microfossil
distribution and geochemical characteristics of cutting samples in the Saha-1
Well (Liu et al., 2020). The Upper Cretaceous succession is divided into the
Donga (Cenomanian–Coniacian) and Yogou (Santonian and Campanian) for-
mations (Fig. 5-33). A regression during the Maastrichtian accompanied by
epeirogenic deformation led to an influx of detrital material with the deposition
of fluvial sandstones grading upwards into a sandy braided system (Zanguina et
al., 1998) known as the Madama Formation (Fig. 5-33).
A second phase of rifting from the Paleocene to the Middle Eocene occurred
in the graben and half-graben. It resulted in the deposition of the Pale-
ocene–Eocene Sokor 1 Formation sandstones. Early Oligocene synrift lacustrine
mudstones in the Ténére Basin are known as the Sokor 2 Formation. A regional
unconformity (c. 23.8 Ma) shows that widespread erosion of rift shoulders and
synrift strata took place soon after rifting, followed by thermal subsidence (in
the Miocene and Pliocene), which allowed deposition of coarse continental clas-
tics (Fig. 5-33) (Liu et al., 2017). Harouna et al. (2017) state that the
Eocene–Oligocene sediments are absent in part of this graben owing either to ero-
sion or non-deposition.
Chapter 5 The Sedimentary Basins of Niger
49
Figure 5-31. Generalized geological map showing the outline sedimentary basin
architecture schematic structures of the Ténéré Basin (Source: Liu et al., 2017)
(see Fig. 5-32 for the A-A’ cross-section).
Stratigraphic Lexicon
50
Figure 5-32. East-west structural cross-section across the Ténéré Basin shows
the rift architecture (see Fig. 5-31 for the location of the cross-section). (Source:
Liu et al., 2017).
Chapter 5 The Sedimentary Basins of Niger
51
Figure 5-33. Generalized stratigraphic column of the Ténére
Basin (Source: Liu et al., 2017).
5.2.3 - The Termit Sub-Basin
The Termit Sub-Basin is an extensional asymmetric Cretaceous-Cenozoic rift
Stratigraphic Lexicon
52
system, 575 km long and 150 - 300 km wide, located between parallels 14°15’
and 17° northern latitude and meridians 14° and 11°45’ western longitude (Alas-
sane et al., 2020). The general vertical profile of the Termit Basin starts with a
Precambrian basement consisting of igneous and metamorphic rock (Nasaruddin
et al., 2017). Mesozoic-Cenozoic strata overlie this from the Lower Cretaceous to
Quaternary deposited in fluvial, lacustrine, and marine environments and ranging
in thickness from about 3000 m to more than 12,000 m (Fig. 5-34) in the de-
pocenter of the Dinga Depression (Fig. 5-37). The Sub-Basin consists of Donga,
Yogou, and Madama Formations in the Upper Cretaceous, Sokor 1 in the Pale-
ocene-Eocene and Sokor 2 in the Oligocene (Fig. 5-35) (Amadou et al., 2021).
Chapter 5 The Sedimentary Basins of Niger
53
Figure 5-34. Lower Cretaceous to Neogene sedimentary rocks, de-
posited in fluvial, lacustrine, and marine environments within the Termit
Sub-Basin (Source: Gouvernement du Niger, Ministère du pétrole,
2020).
Stratigraphic Lexicon
54
Figure 5-35. Generalized stratigraphic column and structural and
stratigraphic sequence evolution of the Termit Sub-Basin. (Source: Lai
et al., 2019).
The structural evolution of the Termit Sub-Basin can be divided into three
stages, i.e. (1) pre-rifting Cambrian-Jurassic stable craton, (2) syn-rifting Early
Cretaceous fault subsidence, Late Cretaceous subsidence, and Paleogene fault
subsidence, and (3) post-rifting Neogene-Quaternary subsidence (Fig. 5-36).
Chapter 5 The Sedimentary Basins of Niger
55
Figure 5-36. Rift evolution of the Termit Sub-Basin (Source: Ahmed et
al., 2020).
The Termit Sub-Basin is divided into three tectonic units, which can also be fur-
Stratigraphic Lexicon
56
ther subdivided (Xiao et al., 2019; Zhou et al., 2017) (Fig. 5-37; Fig. 5-38):
• Dinga Depression in the north
▪ Dinga fault bench/zone
▪ Araga graben
▪ Dinga sag
• Moul Depression in the south
▪ Yogou slope
▪ Trakes slope
▪ Moul sag
• Fana & Soudana transfer zone/uplift in the middle
The central part of the Termit Sub-Basin (known as Agadem Block) has a
length of approximately 300 km and a width of ~60–110 km. The sub-basin is
divided into nine tectonic units: the Western platform, Iaguil platform, Dinga
step-fault zone, Dinga depression, Yogou slope, Fana uplift, Moul depression,
Araga graben and the Trakes slope (Lai et al., 2018 & 2020) (Fig. 5-37).
There are two kinds of fault in the Termit Sub-Basin (Xiao et al., 2019):
1. Prominent NW-SE trending normal faults and mainly distributed along the
edge of the basin.
2. NNW-SSE trending normal-faults, which is developed mainly in the center
of the Moul Depression.
These were generated (or re-activated) during one of the three episodes of tec-
tonic subsidence, which occurred during the Late Cretaceous, Maastrichtian to
Early Paleocene, and Oligocene (Harouna et al., 2017).
Chapter 5 The Sedimentary Basins of Niger
57
Figure 5-37. The schematic structure of the Agadem Block in
the Termit Sub-Basin and the representative geological profile
(section A-A') show the stratum and faults (Source: Lai et al.,
2020).
Figure 5-38. Sedimentary fill of the southern part of the Termit rift
Sub-Basin. Line of the section shown in Fig. 5-24 (Source: Brownfield,
2016).
Two petroleum systems have been discovered in the basin: one is the Sokor
1–Sokor 2 system, and the second is the Yogou–Sokor 1 system consisting of
shallow marine source rocks of the Upper Cretaceous Yogou Formation, main
sandstone reservoirs of the Paleocene–Eocene Sokor 1 Formation and regional
Stratigraphic Lexicon
58
seal rocks of the Oligocene Sokor 2 Formation. (Xiao et al., 2019). During the
Paleogene, up to 3 km of Cenozoic terrigenous sediments (e.g., delta, fluvial and
lacustrine sediments) were deposited in the Termit Sub-Basin (Sokor 1 and Sokor
2 formations). The Sub-Basin was significantly faulted and uplifted during the
Neogene to Quaternary and overlain by thick alluvial, fluvial, and lacustrine sed-
iments (Lai et al., 2018).
5.2.4 – The NW-SE Téfidet Trough
The NW-SE Téfidet Troughis in northern Niger and is the western branch of the
Ténéré rift mega system. Its name was assigned by Faure (1959). It is a 40 km
wide asymmetric graben oriented N140° on average. It extends in the Aïr Moun-
tains over about 120 km and is limited to the west by the Raghane shear zone,
which represents the western boundary of the Saharan metacraton (Fig. 3-2). To-
wards the southeast, the Téfidet trough is separated from the Termit Sub-Basin
by a strike-slip faults oriented ~N75°, called Agadez Line (Fig. 5-25, Fig. 5-39)
or the Guinean-Nubian Lineament (GNL) (Konaté et al., 2019).
The sector of the Téfidet is in the form of high cliffs enclosing the wadis, bor-
dering very indented plateaus with summits exceeding 1,200 meters in altitude.
Dips of several degrees are frequent, including sandstones raised vertically along
the edge of faults. Finally, volcanic events give rise to numerous basalt peaks
which pierce the sandstones (Louis, 1970). Pouclet et al. (1994) have determined
that the Cenozoic volcanism was initiated on the western side of the Téfidet Sub-
Basin during the Oligocene, which reached a maximum during the Miocene and
phased out in the Plio-Pleistocene. The sedimentary infilling of the Téfidet trough
(Fig. 5-39, Fig. 7-132) consists mainly of Lower Cretaceous coarse sandstones,
shales, and argillaceous fine-grained sandstones, and Upper Cretaceous lime-
stones and siltstones. It contains about 900 m of Cretaceous lacustrine and marine
sediments in its deepest southeastern part (Alanlara sector, Fig 5-40). From bot-
tom to top (Fig. 5-41), these sediments are followed by about 600 m of Lower
Cretaceous fluvio-lacustrine sediments, ~270 m of Upper Cretaceous marine, la-
custrine deposits, and ~30 m of Quaternary aeolian sands (Fig. 5-42). Towards
the northwest of the trough, the thickness of the various deposits decreases over-
all. Only the Lower Cretaceous sediments are present at some places, forming
thin shreds sealed by Cenozoic volcanic edifices (Konaté et al., 2019).
Chapter 5 The Sedimentary Basins of Niger
59
Figure 5-39. Geotectonic location of the Téfidet graben (TF) within the Tenerean
rift system. LA: Guinean-Nubian lineament; 1: basement; 2: pre-Quaternary sed-
iments; 3: Cenozoic volcanic; 4: Quaternary sediments (Source: Ahmed et al.,
2016).
Stratigraphic Lexicon
60
Figure 5-40. Structural map of the Téfidet trough
(Source: Konaté et al., 2019).
Figure 5-41. Synthetic lithostratigraphic column of the Téfidet
trough (Source: Modified from Konaté et al., 2019).
Chapter 5 The Sedimentary Basins of Niger
61
Figure 5-42. Geological map of the Téfidet Sub-Basin and surroundings
(Faure, 1966). The dark green stands for the Zoo Baba Fm; the pale
green for the Alanlara/Ezerza Fm. In the Téfidet Sub-Basin, the blue
color is a combination of the Tanguérat, Tagrezou and Angornakouer
formations (Téfidet Group). Outside of the sub-basin, it represents the
Eckhar, Elrhas and Tazolé formations (Tégama Group).
In the southwestern part of the trough, the infilling from bottom to top is the
continental Barremian?-Aptian-Albian Téfidet Group (composed of the Angor-
nakouer, Tagrezou, Tanguérat formations), the marine Lower Cenomanian
Alanlara Fm and the Cenomanian-Turonian Zoo Baba-Arentigué formations
(Fig. 5-41, Fig. 5-43) (see the definition of all Group/Formations within the Lex-
icon).
Stratigraphic Lexicon
62
Figure 5-43. Schematic section with
representative cross-sections
through the Téfidet Sub-Basin
(Source: modified from Faure,
1966, page 191). The Zoo Baba-Ar-
entigué Fms are represented by the
Cenomanian-Turonian.
5.2.5 – The Grein-Kafra Sub-Basin
The Grein-Kafra Sub-Basin, which extends for >600 km from the Algeria–Niger
border SE to Dibella, contains a 3000–4000 m thick Cretaceous–Paleogene/Neo-
gene succession (Harouna et al., 2017). The Kafra Graben is 250 km long and
Chapter 5 The Sedimentary Basins of Niger
63
40 to 50 km wide. The northern area is a half-graben tilted to the east, with a
ridge running parallel to the graben axis in the west along which Cretaceous strata
wedge out. The overlying Cenozoic formations may exceed a thickness of 3,000
m. A sharp reversal of dip characterizes the central area to the SW compared to
the northern region (transfer zone?). Intense faulting affects the eastern crest of
the block, where well Séguédine-1 is located. The southern area consists of a se-
ries of large, parallel tilted blocks associated with regional tilting to the east. Well
Tiffa-l is located on the crest of a fault block. Tilted fault blocks, rollover folds,
drape anticlines and reverse-faulted structures may provide structural traps in this
area (Zanguina et al., 1998). The Grein Graben extends south of the Kafra Graben
for about 180 km long. Structurally, it is a half-graben tilted to the east and com-
posed of a series of complex fault blocks. The sedimentary succession is over
4000 m thick, which is assumed to be like that of the Kafra and Ténéré-Termit
Grabens for the Cretaceous-Cenozoic sequence (Zanguina et al., 1998).
5.2.6 – The Bilma Sub-Basin
The Bilma Sub-Basin is located east of Ténéré. It is a region bounded by the line
of low relief of Achegour-Fachi to the west and Dibella to the south. Opposite the
Ténéré, there are some outcrops either in cliffs: Achegour, Fachi, Kafra, Chef-
fadène, Kaouar; or in regs. But most of the area is covered with flat sand and
dunes to the south. A high cliff facing west stretches from Séguédine to Bilma
(Louis, 1970; Baunhauer, 2010) (Fig. 5-23; Fig. 5-44). The graben was assumed
to be present during a 1970 seismic survey (Louis, 1970; page 239) and con-
firmed in a subsequent seismic survey in 1981-82. It occupies an area of 400 ×
300 km, with its longer axis delineated by the Bilma Escarpment (Fig. 5-44). The
upper sequence (Cretaceous-Cenozoic age) is about 800 to 1000 m thick and is
almost flat-lying except along faults where little folding is observed. The lower
sequence, which may be 3,000 or 4,000 m thick, includes two principal seis-
mic intervals: the upper interval, exhibiting a transparent seismic facies, covers
the underlying fault blocks; the lower one, which infills the fault blocks, shows
local fan-like patterns. The sequences' age is unknown and may be Early Cre-
taceous, Triassic or Permo-Triassic (Zanguina et al., 1998). The western half of
the basin, delimited by an outcropping basement to the North, South, and West,
has been filled by up to 1000 m of Cretaceous to Paleocene continental and ma-
rine sediments without any underlying Paleozoic strata (Faure, 1966). Hardly any
geological and geomorphological information has been published about the east-
ern parts of the Bilma Sub-Basin. To the west, the Bilma Sub-Basin is separated
from the Aïr Mountains by the grabens of Achegour and Adrar Madet, and to the
Southwest, by the Téfidet-Lake Chad graben system from the Termit Sub-Basin.
To the North, there is just a gradual transition to the Djado Basin (Baumhauer et
al., 2009) (Fig. 5-45).
Stratigraphic Lexicon
64
Figure 5-44. Generalized geological map of the Bilma Basin (Baumhauer, 2010).
Chapter 5 The Sedimentary Basins of Niger
65
Figure 5-45. Cross-section from the Aïr Mountains-Téfidet graben through the
Ténéré, Grein and Bilma grabens (B-B’) (Source: Ministère de l'énergie et du
pétrole, Gouvernement du Niger, 1995). See also Fig. 5-53 for a longer section.
5.3 – THE DJADO BASIN
The Djado basin of Niger (appellation coming from the Djado-Chirfa oasis in
northeastern Niger) is the southern extension of the Murzuq Basin of Libya (Fig.
5-46, Fig. 5-47); it is located in the extreme northeast of Niger (Fig. 5-48). In
some older literature, it was spelled “Jadu”. The first color geological map of the
whole region was drawn by Plauchut and Faure (1959) (Appendix C); this is an
age-based map pre-dating the naming of all the formations in the basin.
Stratigraphic Lexicon
66
Figure 5-46. Generalized geological map of the
Murzuq (Libya) and Djado (Niger) basins with the
political boundaries (Source: modified from Shalbak,
2015). The red line is the approximate location of the
cross-section seen in Fig. 5-47.
Figure 5-47. Geological cross-section of the Murzuq/Djado Basins
(Source: modified from Galeazzi, 2012). Refer to Fig. 5-46 for the loca-
tion of this cross-section.
Chapter 5 The Sedimentary Basins of Niger
67
Figure 5-48. Map of the Djado basin showing its general features
(Source: modified from Bernus et al., 1980).
The Murzuq-Djado Basins are bound by five main tectonic elements rooted in
the basement and reactivated during the Caledonian orogenic phase. These are Al
Qarqaf, Tihmbokah, Atshan, Tripoli-Tibesti, and the Mourizidi arches. Basement
rocks outcrop to the west of the Djado Basin (Eastern Hoggar) and the east (West
Tibesti) (Fig. 5-49, Fig. 5-50).
Stratigraphic Lexicon
68
Figure 5-49. Main tectonic elements of the Murzuq-Djado
Basin (Source: El-Hawat et al., 2008).
Figure 5-50. Paleozoic outcrops of North Africa in relation
to the Djado Basin of Niger (Source: modified from Shalbak,
2015).
The geological sequence of Paleozoic (Fig. 5-50) and Mesozoic rocks is basically
the same in surface and subsurface areas of the Djado Basin and stratigraphical
similarities exist between the Murzuq and Djado areas (Fig. 5-51).
Chapter 5 The Sedimentary Basins of Niger
69
Figure 5-51. Stratigraphic chart for the sedimentary infill and the main
tectonic events recorded in the southern Murzuq basin of Libya and
adapted for the Djado Basin of Niger (Source: modified from Shalbak,
2015).
An increasing continental influence can be noted in the southward direction. The
Paleozoic succession is more than 2,000 m thick in the area already explored by
drilling and increases in thickness northwards. The thickness of the Cambrian-
Ordovician varies from 400 to700 m.
The Murzuq-Djado Trough (Fig. 5-52) is an exclusively Paleozoic structural
element filled with strata of Cambrian to Carboniferous age, including several
hundred meters of Lower Silurian shale that locally provides an excellent to fair
source rock potential. The eastern edge of the Murzuq-Djado Trough forms the
western part of an early Paleozoic horst striking from Mourizidié NNW towards
the western part of the Gargaf Uplift (Tripoli-Tibesti Uplift) from about 14°30' E
and 24°N to about 12°45' E and 27°30' N (Fig. 5 in Klitzsch, 1970).
Stratigraphic Lexicon
70
Figure 5-52. Structural relief of NE Africa and Arabia
(Source: Shalbak, 2015, redrawn from Klitzsch,
2000).
Figure 5-53. Cross-section from the Aïr Mountains (A) through
part of the Eastern Niger Basin and the Djado Basin, ending in
Chad (A’) (Ministère de l'énergie et du pétrole, Gouvernement
du Niger, 1995). See also Fig. 5-45 for a shorter section.
Just south of the border with Libya, a collapsed NW–SE striking anticline, cor-
responding to a graben structure, can be identified. Along the graben floor with
strike direction to the SE, the Enneri Achelouma valley developed, separating the
“Plateau de Manguéni” in the NE from the “Plateau du Djado” in the SW (Fig.
5-48). The “Plateau du Djado” is composed of Paleozoic (Cambrian–Ordovi-
cian) sediments, whereas sediments building the “Plateau de Manguéni” belong
to the Cretaceous “Continental Intercalaire” and the Cenozoic “Continental Ter-
minal” (Fig. 5-53), which here both consists of mud and sandstones. Bedrock
outcroppings along the Achelouma valley are Upper Carboniferous limestones
Chapter 5 The Sedimentary Basins of Niger
71
and Lower Carboniferous sandstones. The “Plateau de Manguéni” surface dips
to the N–NE, whereas “Plateau du Djado” surface dips to the South (Fig. 5-54)
(Baumhauer et al., 2009).
The basin structure is controlled by north-south and NE-SW trending base-
ment faults, the latter being responsible for the significant folds (some cut by
faults) observed at the surface. This tectonic activity probably occurred during
Late Cretaceous and Paleogene/Neogene times. However it is superimposed on
previous tectonic trends (related to Caledonian deformation) with which facies
and thickness variations of Silurian and Early Devonian deposits are associated
(Zanguina et al., 1998).
The Paleozoic sequence of the Djado Basin lacks the thick Mesozoic cover
of the Murzuq basin to the north. Mesozoic formations, especially those from
the Triassic to the Lower Cretaceous, lack, for the most part, sufficient fossils to
determine any subdivisions. Consequently, these facies were summarized in the
past as Nubian sandstone (dark red and grey continental sandstones and conglom-
erates with occasional shale intervals). Upper Cretaceous petrified wood has been
reported from this sequence, which probably extends upward into the Cenozoic.
Also, according to Dalloni (1948, p. 31), some reptile bones were encountered at
Toummo, in the north of the Djado. However, subsequent investigations by geol-
ogists could not confirm this statement.
The Zarzaitine, Taouratine, and Msak formations (Continental Intercalaire)
of the Djado region were deposited on a Late Mesozoic, low relief land surface
with small, narrow, erosional valleys. The sandstone facies is found at the rim of
the Murzuq Basin, which builds up most of the “Plateau de Manguéni” and the
eastern parts of the “Plateau de Djado” (Fig. 5-48) and is present in the Bilma
and Emi Bao formations of the Bilma Sub-Basin. On the “Plateau du Manguéni”
three units can be observed (Fig. 5-55). These thin towards the south to 60-90 m,
possibly due to erosion and a depositional restriction (Late Cretaceous and Ceno-
zoic) to the northern and north-central areas.
Stratigraphic Lexicon
72
Figure 5-54. Three-dimensional illustration of the Achelouma valley
and the surrounding plateaus (Source: Baumhauer et al., 2009).
Figure 5-55. General Paleozoic to Cenozoic stratigraphy of the Djado
Region and Bilma Depression/Graben in Niger (Source: After Jacque-
mont et al., 1959).
Chapter 5 The Sedimentary Basins of Niger
73
Chapter 6
Paleontology
In 1964, while prospecting for uranium ore, geologists of the French Atomic
Energy Commission (CEA) found Early Cretaceous dinosaurian bones at Gado-
ufaoua in northeastern Niger 150 km south-east of Agadez (Fig. 6-1). Jean-Paul
Lehman, then director of the "Institut de Paléontologie" at the "Muséum National
d’Histoire Naturelle" in Paris, sent one of his students, Philippe Taquet, to follow
up on this discovery. Thus began the first purely palaeontological studies and ex-
peditions to Niger (Brett-Surmann, 2012).
During several expeditions between 1965 and 1975, a team under the sci-
entific direction of Taquet systematically surveyed this remarkably fossil-rich
region and collected some 25 tons of material (Fig. 6-2).
Figure 6-1. Some of Niger’s continental fossil localities: Gado-
ufaoua (green outline), Tiguidi cliff , and others.
74
Figure 6-2. The In Beceten team which participated in removing several tons of raw ma-
terial (Source: Buffetaut & Taquet, 1975).
These studies lead to the finding, excavation and often display of the crocodilian
skull Sarcosuchus Imperator, dinosaur footprints, the skeleton of the dinosaurian
iguanotontid Ouranosaurus Nigérensis Taqueti, silicified trunks, various articles,
and a doctoral thesis “Geology and Paleontology of the Gadoufaoua deposit”
supported by Philippe Taquet in 1973.
Starting in 1992, and for the three decades that followed, expeditions led
by Paul C. Sereno (University of Chicago) have repeatedly revisited the Gado-
ufaoua region and recovered numerous remarkable specimens of dinosaurs. This
same team also collected at In Abaka, in the In Gall area, bones belonging to
two new dinosaur species for Niger. They both lived 130,000,000 years ago. The
first was carnivorous, measuring 10 meters long and was named “Afrovenator
abakensis”. The second was an herbivorous Sauropod of the Brontosaurus fam-
ily (Jobaria tiguidensis) measuring 20 meters long with a very long neck and a
massive weight (Gado, 1996; Gado et al., 2001). New crocodile and turtle species
from Niger were also added to the ever-increasing collection of reptiles and ver-
tebrates from Niger.
The sediments of the Continental Intercalaire contain all the deposits of sili-
cified wood, crocodiles, fishes, turtles, and dinosaurs found in Niger. The text
and figures below summarize the main areas and stratigraphic intervals (see also
Fig. 6-12).
• Upper Permian (~255 Mya): See “Moradi Formation” in the Lexicon for all
Chapter 6 Paleontology
75
the details.
• Lower Triassic (~250 Mya): A primitive Chirotherium track was found in
the “Teloua 1 Member” at Aodelbi (Ginsburg et al., 1968). (Fig. 6-3).
Figure 6-3. Chiroterium track at Aodelbi, Niger. Foot = 11x6 cm
(Source: Taquet, 1976).
• Mid/Upper Jurassic (~160 Mya): Remains of crocodilians, fish and di-
nosaurians from the Irhazer Group (Fig. 6-5) (including Sauropod tracks (Fig.
6-4)) at “Mont Arli” and Tabidene, and the In Abaka specimens of the carniv-
orous dinosaurs “Afrovenator abakensis” and the herbivorous Sauropod of the
Brontosaurus family (Jobaria tiguidensis) and other specimens from In Gall
and Marandet.
Stratigraphic Lexicon
76
Figure 6-4. The trackway of a sauropod dinosaur, a huge herbivorous
quadruped, on the slopes of Mount Arli, near Agadez (Source: Taquet, 1998).
Chapter 6 Paleontology
77
Figure 6-5. Theropod teeth from the Tiouraren Fm (Irhazer Group)
(Source: Serrano-Martinez, 2015).
• Lower Cretaceous, Aptian (~115 Mya): Crocodilians and dinosaurians in
the Tégama Group in Tamaya Mellet (17°38'59.05"N & 5°23'0.13"E) (Gado
et al., 2001) (site discovered in 1977 by the German hydrologist engineer W.
Neumann) and especially in Gadoufaoua (Taquet, 1976). Gadoufaoua alone
includes at least one species of Coelacanthid, two species of Dipnoan fish, one
species of Amphibian, three species of Crocodilians including a giant one, two
species of Chelonians (Perez-Garcia, 2019) (Fig. 6-10), seven species of Di-
nosaurs and numerous accounts of silicified tree trunks (Fig. 6-6). The Aptian
vertebrate deposits are remarkable for the presence of a Carnosaur different
from Carcharodontosaurus saharicus; the presence of several Iguanodonti-
dae, of a giant Mesoeucrocodylia: Sarcosuchus imperator (Fig. 6-8, Fig. 6-9).
Ouranosaurus nigeriensis (Fig. 6-7) (Taquet, 1976; Bertozzo et al., 2017), a
slender, medium-sized Iguanodontid, lies anatomically and stratigraphically
between the extreme Lower Cretaceous Iguanodontids and the Upper Creta-
ceous Hadrosaurids. In the Aptian of Gadoufaoua, at least two Iguanodontids,
one of which, slender, is relatively close to Iguanodon mantelli and the other,
stocky, is closer to Iguanodon bernissartensis.
Stratigraphic Lexicon
78
Figure 6-6. Petrified/Silicified tree trunks at Gadoufaoua, sector of
“Niveau des Innocents” (Source: Taquet, 1976).
Figure 6-7. Top: Skeleton of the dinosaur Ouranosaurus nigeriensis in
Gadoufaoua. East of the Eméchédoui water well. Picture was taken in
1966 at the sector of “Niveau des Innocents”. Bottom: The same skele-
ton once assembled (Source: Taquet, 1976).
Chapter 6 Paleontology
79
Figure 6-8. Sarcosuchus imperator BROIN et
TAQUET 1966. Gadoufaoua, sector of “Niveau des
Innocents” exposed at "Galerie de paléontologie du
Muséum à Paris" (Source: Taquet, 2015) .
Figure 6-9. Skull of Sarcosuchus imperator BROIN
et TAQUET 1966 as found in Gadoufaoua, sector of
“Niveau des Innocents” (Source: Taquet, 1998).
Stratigraphic Lexicon
80
Figure 6-10. Shells of the pleurodiran turtle Francemys gado-
ufaouaensis of Gadoufaoua (Elrhaz Fm). A: shell in dorsal
view. B: carapace and lateral margins of the plastron, in ven-
tral view. C: shell in ventral view. D: plastron, in dorsal view.
E–H: shell in anterior (E): posterior (F): right lateral (G): and
left lateral (H): views (Source: Perez-Garcia, 2019).
• Lower Cretaceous, Albian (~110 Mya): The Albian vertebrate deposits
are characterized by the association of the Carnosaur Carcharodontosaurus
saharicus and the Pristid Onchopristis numidus and by the presence of a
Mesoeucrocodylia different from Sarcosuchus imperator, such as Elosuchus
felixi and Kaprosuchus saharicus from In Abangharit (de Lapparent, 1953; de
Lapparent de Broin, 2002).
• Upper Cretaceous, Lower Senonian (~86 Mya): Discovered by Greigert in
1966, the In Beceten (or Ibeceten) locality (Ibeceten Fm) represents the first
continental fauna of the Lower Senonian of Africa. Its flora/fauna includes
plants, oysters, fishes, amphibians, turtles, snakes, crocodilians (including
Libycosuchus sp, and Trematochampsa taqueti [Buffetaut, 1976]), and di-
nosaurs (Sauropod and Theropod) (Taquet, 1976 & 1977; de Lapparent de
Broin, 1974). In addition to the above, Bouju et al. (2020) state that small,
isolated pieces of reddish amber were collected in 2016 at Takalmaoua, De-
partment of Dakoro, in Maradi Region. The amber was found in a well, at a
depth of about 50 m, within rocks of Cenomanian/Senonian age (undefined
formation). These pieces contained no inclusion and were determined to orig-
inate from a conifer.
• Upper Cretaceous, Maastrichtian (~70 Mya): Crocodilian, dinosaurs
(Greigert et al., 1958; Greigert, 1966), mosasaurs (at least eight genera) (Ling-
ham-Soliar, 1991, 1998), turtles (de Lapparent de Broin & Chirio, 2020), and
fish remains (Capette, 1972) at Tillia, Tigarouba, Termert (or Termeurth),
Mount Igdaman, etc.
• Paleocene (~60 Mya): Paleocene marine deposits are found only on the west-
ern side of the country, in the Iullemmeden Basin as limestone or clay. At the
base are levels with sandy marl containing abundant remains of Crocodilians,
Chapter 6 Paleontology
81
Fishes (Capetta, 1972), and snake (Nigerophis mirus, Rage, 1975); Houssaye
et al., 2019). They were collected in Ader Doutchi and in Krebb de Sessao
in two bone-beds surrounding a level of gray schist material comprising Dy-
rosaurids Hyposaurus sp. (Crocodilians, Fig. 6-11), Tilemsisuchus lavocati
(marine crocodilian (Martin, 2013)) and Snakes, as well as fossil woods of the
following types studied by Koniguer et al. (1971).
▪ Paratrichilioxylon (?) Russelli KOENIGUER 1971 (Meliaceae),
▪ Euphorbioxylon nigerinum KOENIGUER 1971 (Euphorbiaceae),
▪ Sessaoxylon paleocenicum KOENIGUER 1971 (incertae sedis).
Above the sandy marls with vertebrate remains, marl and limestone were de-
posited, containing a reef fauna whose age would be Upper Paleocene (Ypresian)
(Taquet, 1976).
Figure 6-11. Geographical distribution of the Paleocene in the
Iullemmeden Basin with the localities where Crocodyliformes (Mesoeu-
crocodylia) were found in Mali (1= Tilemsi Valley), Niger (2= Krebb de
Sessao deposit at long. 4°12'-4°13'E, lat. 16°56'N; Fig. 6-1) and Nigeria
(3= Dange Formation, Wurno, Sokoto State). (Source: Jouve, 2007).
Stratigraphic Lexicon
82
Figure 6-12. Stratigraphic distribution of the main Niger fossil sites, with their
most important specimens.
Chapter 6 Paleontology
83
Chapter 7
Lexicon
• Obsolete names, or names recommended to be made obsolete, are marked with
an asterisk (*).
• Always refer to the maps and stratigraphic columns in Appendices A to J.
--------------------
Unit: ABINKY MEMBER (of the Tchirezrine Fm)
Epoch/Age/Author: Middle Jurassic
References: Joulia, 1951, 1960; Valsardieu, 1971; Fabre et al., 1983 ;
Moody, 1997 ; Abdoulaye et al., 2007 ; Billon & Patrier, 2019 ;
Group/Subgroup: Agadez / Wagadi
Synonymy: Analcimolites de l’Abinky ; Formation d’Abinky; Middle Mem-
ber of the “Grès de Tchirezrine”
Basin/Sub-Basin/Apdx: Iullemmeden / Tim Mersoï / Appendix E.
Type/Reference/Stratotype Section: Western side of the Aïr.
Lithology: The Abinky Mbr’s analcimolites (Fig. 7-2) and red sandstones
contain many fresh, unworn clastics and copper and uranium showings. Analci-
molites would come from the diagenetic recrystallization of volcanic ash. In the
lower passage zone, isogranular, feldspathic white sandstones contain analcime
spherulites and carbonates. Abdoulaye, Konaté et al. (2007) distinguish 6 facies
(top to bottom) (Fig. 7-1) :
• Facies 1: Massive yellow/ocre sandy analcimolite with brown stains
• Facies 2: Sandy analcimolite with yellow/ocre/greenish color lenses with
84
some recrystallisation.
• Facies 3: Coarse sandstones with white, ocre, greenish analcimolite lenses
• Facies 4: A 5 m thick level of brownish/reddish analcimolite
• Facies 5: Coarse sandstones with angular grains. Rare layers of analcimolite
lenses. Recrystallisation of silica is abundant in cavities.
• Facies 6: Massive sandstones with fine grains poorly cemented.
Environment: The sedimentary information shows a meandering channel and
underground flow (Fluvio-lacustrine sediments with red sandstones and analci-
molite beds).
Thickness: ~25 m
Fossils: Rootlet-bearing paleosols are common.
Overlying Unit: Tchirezrine 2 Mbr of the Tchirezrine Fm.
Underlying Unit: Tchirezrine 1 Mbr of the Tchirezrine Fm.
Maps, Cross-Sections, Pictures:
Chapter 7 Lexicon
85
Figure 7-1. Lithostratigraphic column of the Abinky Mbr (Source: Modified after
Abdoulaye et al., 2007).
Stratigraphic Lexicon
86
Figure 7-2. Massive analcimolite, Abinky Mbr (Source: CSA Global,
2017, 2019).
--------------------
Unit: ACHEGOUR FORMATION
Epoch/Age/Author: Lower Cretaceous (Albian?)
Original Author and/or Origin of the Name: Renault, 1953; From the
same name area.
References: Renault, 1953; Boureau, 1955 ; Faure et al., 1956; Furon, 1964 ;
Faure, 1966 ; Fabre et al., 1983; Meister et al., 1994;
Synonymy: Grès d’Achegour
Equivalents : Fachi Fm; Tiffa Fm; Dibella Fm. Analogous in some respects
to the sandstone cycles of the Tégama group.
Basin/Sub-Basin/Apdx: ENRB / Bilma / Appendix H
Chapter 7 Lexicon
87
Type/Reference/Stratotype Section: Fachi is an oasis surrounded by the
Ténéré desert and the dunes of the Erg of Bilma in eastern Niger.
Lithology: Monotonous sandstone formation which rests on the basement.
They were observed from the north of Ezerza to Fazeï, passing through Achegour
(all near Fachi). Sandstone of light colors, coarse or fine-grained, with oblique
and cross-bedded stratification in large banks; generally tender, these sandstones
are often strongly silicified near the faults which break up the outcrops. Traces of
plants are scarce. From top to bottom (Faure (1966)):
• 30m of fine sandstone with ferruginous intercalations.
• 150m of fine or medium sandstone with cross-bedded stratification compris-
ing a level with traces of Vegetation.
• 20m of coarse or conglomeratic heterogeneous sand, with cross-bedded strati-
fication.
• Rubefied unconformity surface with almost no rolled debris of quartz.
• Precambrian basement: slightly metamorphic arkoses and conglomerates.
Environment: Continental
Thickness: 0 to 700 m
Fossils: Traces of plants (Podocarpites saharianum Boureau and imprints
of leaves of Dicotyledonous Angiosperms (Laurophyllum and Cinnamomoides)).
Abundant fauna of vertebrae (dinosaurs and crocodiles).
Overlying Unit: Ezerza Fm.
Underlying Unit: Precambrian
Remarks: Represents the base of the surface formations in the Bilma basin.
It corresponds to the upper part of the "Continental Intercalaire" and makes up
the Tégama group in the region.
--------------------
Unit: ADER DOUTCHI FORMATION
Epoch/Age/Author: Oligocene (Beauvais et al., 2008)
Original Author and/or Origin of the Name:
References: Pougnet, 1949 ; Greigert, 1966; Dubois, 1979 ; Boudouresque
Stratigraphic Lexicon
88
et al., 1982; Fabre et al., 1983; Dubois et al., 1984 ; Bellion, 1987; Lang et al.,
1986, 1990; Hanon, 1990 ; Dikouma, 1990, 1994 ; Dikouma et al., 1993, 1994 ;
Tintant et al., 2001 ; Beauvais et al., 2008; Ali et al., 2019 ; Heckmann, 2019 ;
Ousmane et al., 2020; Laouali-Idi et al., 2019, 2021.
Group: Dallols
Synonymy: Série sidérolithique de l’Ader Doutchi (Greigert (1966)); Série
de l’Ader Doutchi (Fig. 7-38). Adar Doutchi (misspelling). In his "Kandi Fm"
(which is supposed to be Ordovician, as per its description in Benin), Pougnet
(1949) finds silicified wood near the town of Gaya. Since wood/plants did not yet
exist during the Ordovician, it can only be the Ader Doutchi Fm which contains
wood similar to the specimens encountered by Pougnet (Fig. 5-19, Fig. 7-64).
Equivalent(s): Continental Terminal 1 (or Ct1) at the base of the Continental
Terminal (Greigert (1966));
Basin/Apdx: Iullemmeden; Appendix H
Type/Reference/Stratotype Section: No ideal type section could be lo-
cated. Greigert et al. (1966) based their description on sections from wells.
Dubois (1979) described in detail several sections of which the most representa-
tive is located in Djibale (Fig. 7-21 & Fig. 7-4)
Lithology: It consists mainly of variegated argillites and argillaceous silt-
stones at the base. The Ader Doutchi Formation alternates irregular beds, made
up of kaolinitic clays, more or less lateritic, and ferruginous ooliths in its middle
part. The top of this formation consists of sandstone with ferruginous oolites (Fig.
7-3). Hannon (1990) describes it as follows (Fig. 7-4):
Set of ferruginous rocks; alternating decimetric to metric layers, of irregular
thickness, lenticular; rocks often hardened, of dark shades, black, brown, red, pur-
plish:
• Fine to coarse-grained quartz sand and sand, usually angular, ferruginous
cement, clayey and ferruginous or absent; ferruginous oolites in various pro-
portions; oblique stratifications.
• Conglomerates with angular quartz gravel generally less than 1 cm locally
containing schist pebbles; ferruginous, clayey, or siliceous matrix.
• Goethite oolites; diameter between 0.1 mm and 3mm; free, contiguous, or ce-
mented by silty, clayey, ferruginous matrices in various proportions.
• Gray clays and silts are often hard and rubefied and may contain ferruginous
Chapter 7 Lexicon
89
oolites.
Environment: Shallow and rough epicontinental sea, close to estuaries or deltas
responsible for the iron supply. This was proposed by Faure (1966), who at-
tributed the oolitic deposits to sedimentation of a "disappearing sea" within the
framework of an advanced phase of filling the Iullemmeden Basin.
Thickness: 430 m (Laouali-Idi, 2021). In the west of the Ader Doutchi
region, where it is overlayed by the Birni N'Konni Formation, the formation pre-
sents a gradually increasing thickness from south to north: from about 25 m in the
region of Malbaza-Tsernaoua to about 45 m in Tahoua. In the northwest (Keita,
Ibohamane), where the upper contact is eroded, it reaches a thickness of 55 m
(Hanon, 1990).
Fossils: Flora consisting of Echiperiporites icacinoides, Cicatricosisporites
dorogensis, Chenolophonidites costatus, Striatapollis bellus and Bombacacidites
sp., suggesting the proximity of savannah conditions.
Overlying Unit: Birni N’Konni Fm, when present
Underlying Unit: Rests in discordance either on the Garadaoua Fm, Precam-
brian basement or the continental Mesozoic
Remarks: That the formation belongs to the Continental terminal was con-
sidered by Faure (1966) with reservations. For Dubois and Lang (1984), this
ferruginous set constitutes the final phase of the marine sedimentary cycle; these
authors suggest the existence, at the top of the cycle thus defined, of a major cut
probably corresponding to a sedimentation gap and exclude it from the Continen-
tal terminal (Hanon (1990)).
Maps, Cross-Sections, Pictures:
Figure 7-3. Lithostratigraphy of the Ader Doutchi Fm
(Laouali-Idi et al., 2019).
Stratigraphic Lexicon
90
Figure 7-4. Lithostratigraphy of the Ader Doutchi Fm in
Djibale (Hanon, 1990).
--------------------
Unit: AGADEM FORMATION
Epoch/Age/Author: Upper Cretaceous (Coniacian-Campanian; Faure,
1966, pages 288 to 306)
Original Author and/or Origin of the Name: Seen by G. Rohlfs in 1868,
found in 1941 by Chief Warrant Officer Gobin, studied by R. Furon (1942) and
Ph. Renault in 1954. Furon (1942), emend. Faure (1954, 1966).
Chapter 7 Lexicon
91
References: Furon, 1942; Faure, 1954, 1966 ; Faure et al., 1956 ; Fabre et
al., 1983.
Synonymy: Série d’Agadem; Formation d’Agadem
Equivalent(s): Kafra Fm.
Basin/Sub-Basin/Apdx: ENRB / Termit / Appendix H
Type/Reference/Stratotype Section: Massif of Agadem
Lithology: At the top, gypsum clays and fine sandstone, sometimes with
glauconite; at the base, fine red or white sandstone, with cross-bedded stratifica-
tions with marine lamellibranchs
Environment: Marine
Thickness: 100 m
Fossils: Ammonites (Hoplitoides and Metengonoceras). Lamellibranchs
such as Fragum subperobliquum ν. Koenen, Parmicorbula incurvata, etc. (Fig.
7-5)
Overlying Unit: Galhama
Underlying Unit: Zoo Baba
Remarks: In the Dibella, Agadem, Bilma Regions
Maps, Cross-Sections, Pictures:
Stratigraphic Lexicon
92
Figure 7-5. General disposition of the sedimentary formations in the Agadem
Massif. Ŧ = Fossils. (Faure, 1966).
--------------------
Unit: AGADEZ GROUP
Epoch/Age/Author: Triassic to Middle Jurassic
Original Author and/or Origin of the Name: Chudeau, 1908; Appendix D)
References: Chudeau, 1908; Greigert et al., 1954; Faure et al., 1956 ;
Greigert & Pougnet, 1967, p. 108; Bigotte & Obelianne, 1968; Valsardieu, 1971;
Fabre et al., 1983; Moody & Sutcliffe, 1991; Kogbe, 1991; Wagani et al., 2011;
Billon et al., 2016.
Subgroups: Goufat, Wagadi, Lower Dabla. Note that the formerly included
Aguelal subgroup is no longer relevant (see "Aguelal" for more details)
Synonymy: Grès d’Agadès; Grès d’Agadez ;
Basin/Sub-Basin/Apdx: Iullemmeden / Tim Mersoï / Appendix D, Appen-
dix E
Type/Reference/Stratotype Section: From Mount Ibadaman on the 7°
meridian to the South-West horn of Aïr.
Chapter 7 Lexicon
93
Lithology: The Agadez Group (together with the Izégouandane Group of
the Permian Period) corresponds to red detrital deposits of the Tim Mersoï Sub-
Basin. It is derived from alteration products generated by a hot climate with
seasonal variations (wet and dry). Volcanic inflows have been recorded in this
group in the form of rhyolitic pebbles and ash. The subdivisions of this group
adopted in this lexicon are from top to bottom:
• Assaouas Formation (sandstone) at the top (a few meters to 30 m). Dinosauri-
ans and a level mineralized in copper and uranium are found in it.
• Tchirezrine Formation
• Tchirezrine 2 Mbr (70m)
• Abinky Mbr (~25m)
• Tchirezrine 1 Mbr (50m)
• Mousseden Formation (analcimolites) (0-30 m)
• Teloua Formation (sandstones and locally intercalated with conglomerates and
some clay beds) (Teloua 1, 2, 3 Mbrs) (80 m)
Note that the Alarcess conglomerate (Fig. 7-10) (0 to 10 m) containing pebbles
of eruptive rocks is now incorporated within the Teloua 2 Member of the Teloua
Fm (see the definition of this term).
Earlier, Bigotte and Obelianne (1968) had subdivided this continental group,
comprised between two discordances, into six cycles which were from top to bot-
tom: analcimolites of Abinky, sandstone of Tchirezrine 1 resting in discordance
on the analcimolites of Mousseden; finally, sandstones of Teloua 3, 2, 1. This
stratigraphy was supplemented and specified later (Valsardieu (1971)). See also
Subgroups of Dabla, Wagadi, Goufat and Aguelal.
Environment: Fluvial and lacustrine.
Thickness: ~270 m
Fossils: Dinosaurians (TAQUET 1976); Fossilized/silicified wood (Dadoxy-
lon) (Greigert et al. (1958)).
Overlying Unit: Irhazer Group / Irhazer Formation
Underlying Unit: Resting in discordance on the Izégouandane Group or the
crystalline basement.
Remarks: In the Agadez Group, the Anou Ararène and Anou Mellé con-
glomerates are part of the Teloua formation of Joulia (1959). In the present
publication, the Anou Ararène and the Anou Mellé conglomerates are now in-
Stratigraphic Lexicon
94
cluded within the Teloua 1 facies, while the Alarcess conglomerate is included
within the Teloua 2 facies (Fig. 7-10)
--------------------
Unit: *AGUELAL SUBGROUP
Epoch/Age/Author: Lower Triassic (Fabre et al., 1983)
Original Author and/or Origin of the Name: CEA in 1969
References: CEA, 1969; Valsardieu, 1971; Fabre et al., 1983.
Group: Agadez
Synonymy: Série d’Aguélal
Equivalent(s): See “Remarks” below
Basin/Sub-Basin/Apdx: Iullemmeden / Tim Mersoï / Appendix E
Type/Reference/Stratotype Section:
Lithology: Valsardieu (1971) distinguishes, from top to bottom: quartz sand-
stones (facies Teloua 1), the conglomerate of Anou Ararène (undefined) and the
conglomerate of Anou Mellé (Fig. 7-10). The sandstones, with recycled elements,
are characterized by the scarcity of feldspars and a scarce cement, clayey or anal-
cime. Towards the south, rolled pebbles of quartz and quartzites appear. The
stratifications are oblique or horizontal; the erosion surface indicates eastward or
NE flow.
Environment: The deposit agent would be partly fluvial and partly aeolian.
Thickness: 68 m
Fossils: Tracks of Cheirotherium and Batrachopus. These footprints have al-
lowed the Subgroup to be assigned a Triassic age.
Overlying Unit: Either by the Wagadi Subgroup north of Anou Makarene or
the Goufat Subgroup. The upper limit can be an erosional surface or an indurated
surface.
Chapter 7 Lexicon
95
Underlying Unit: In discordance on the Izégouandane Group. Locally, the
basal surface is underlined by a thin film (0 to 50 cm) of rolled pebbles, some of
which show facets of wind wear in a ferruginous and phosphated cement (used to
be called Anou Mellé), a witness of a former reg?
Remarks: In the Agadez Group, the Anou Ararène and Anou Mellé con-
glomerates are part of the Teloua formation of Joulia (1959). In the present
publication, the Anou Ararène and the Anou Mellé conglomerates are now in-
cluded within the Teloua 1 facies, while the Alarcess conglomerate is included
within the Teloua 2 facies (Fig. 7-10). Therefore, the names of these three con-
glomerates are now irrelevant. In addition, since the Teloua 1 Member of the
Teloua Formation is now the only unit included in the Aguelal Subgroup, it is
recommended that the term “Aguelal Subgroup” be made obsolete.
--------------------
Unit: *AïN TOUFAYEN SHALES
Epoch/Age/Author: Upper Cretaceous (Lower Cenomanian)
References: Molinas, 1965; Bigotte & Obelianne, 1968; Fabre et al., 1983;
Mateer et al., 1992.
Synonymy: Argiles d’Aïn Toufayen; *En Nassame Fm with the lower Mem-
ber of the Béréré Fm
Basin/Apdx: Iullemmeden / Appendix F
Lithology: See Farak Fm
Remarks: It is recommended to be made obsolete due to its minimal distrib-
ution and overlapping with other formations (Fig. 7-6). It is considered as a facies
overlapping with the Béréré and Farak formations.
Maps, Cross-Sections, Pictures:
Stratigraphic Lexicon
96
Figure 7-6. Distribution of the Cenomanian formations in the Central Iullemme-
den Basin as presented by Mateer et al. (1992).
--------------------
Unit: AKAKUS FORMATION
Epoch/Age/Author: Silurian (Wenlock-Ludlow) (Fig. 7-65)
Original Author and/or Origin of the Name: Desio, 1936a, 1936b. Origin
from Jabal Akakus in the Ghat area, southwest Libya, 100 km N of Takarkhouri
Pass. However, this description was incomplete, and a replacement type section
was established by Klitzsch (1969) from an area to the south of Ghat where a
complete section is present (Fig. 7-7).
References: Desio, 1936a, 1936b; Plauchut & Faure, 1959 ; Jacqué, 1963;
Freulon, 1964; Klitzsch, 1969 ; Massa & Jaeger, 1971 ; Berry et al., 1973 ;
Lababidi et al., 1985; Mergl et al., 2001 ; Shalbak, 2015; Hallett, 2002, 2016;
Synonymy: The former name of the formation was spelled “Acacus”. The
spelling was modified to its current form by Hallet (2002) after verifying the of-
ficial name records of localities in Libya
Equivalent(s): "Formation des Alternances Grèso-Argileuses" [Sandy-shale
Formation] in the Ghadames Basin of Libya. Lower part of "Grès Supérieurs de
Tassili".
Basin/Apdx: Djado / Appendix G
Chapter 7 Lexicon
97
Type/Reference/Stratotype Section: South of Ghat where a complete sec-
tion is present (Fig. 7-7) (Klitzsch, 1969).
Lithology: Mainly composed of fine-grained micaceous sandstones and silt-
stones, outcropping in both flanks of the Djado Basin. Freulon (1964) describes
it as "Generally quite fine sandstones, often with cross-bedded stratification and
ferruginous cement. Pelitic levels show numerous Harlania".
Environment: Shallow water. Massa and Jaeger (1971) suggested that the
fossils indicated a marine or lagoonal environment of deposition
Thickness: Freulon (1964, page 105) states a thickness of about 100 meters
in the Djado. The total thickness of the Silurian (Tanzuft & Akakus) varies, rang-
ing between 150 to 300 m in the western Djado Basin. Thickness is more reduced
along the eastern margin of the Djado Basin, with a maximum of 120 m, but Sil-
urian rocks may be also totally absent.
Fossils: Massa and Jaeger (1971) cited the following fossils, primarily ich-
nofossils, from the formation: Harlania (=Arthrophycus), Cubichnia, Risophycus
bilobatus, Palaeophycus, Pelecypodichnis, Cruziana furcifera, Cruziana irregu-
laris, Dimorphichnus, Acutiramus, several mollusks, and trilobite fragments.
Overlying Unit: Tadrat Formation, contact disconformable
Underlying Unit: Tanzuft Formation, contact conformable
Maps, Cross-Sections, Pictures:
Stratigraphic Lexicon
98
Figure 7-7. Stratigraphic column of the Akakus Formation at Klitzsch’s Type Lo-
cality in Libya (Source: Shalbak, 2015).
--------------------
Unit: AKARA MEMBER (of the Tin Séririne Fm)
Epoch/Age/Author: Middle Devonian
Original Author and/or Origin of the Name: Joulia, 1959; Claret & Tem-
père, 1968;
References: Joulia, 1959; Lessard, 1961; Claret & Tempère, 1968; Val-
sardieu, 1971; Fabre et al., 1983.
Chapter 7 Lexicon
99
Synonymy: “Akara Schist” ; “Schistes d’Akara” ; “Argiles à Stylioline”;
“Grès de Taberia”, “Grès d’Amesgueur”; Upper Member of the Tin Séririne for-
mation ; Akora Schist (misspelling) (Appendix I).
Basin/Sub-Basin/Apdx: Iullemmeden / Tim Mersoï / Appendix E, Appen-
dix I.
Lithology: Shales, siltstones, and multicolored psammites, thin calcareous
intercalations. The siltstones are well developed at the top, sometimes 7m in
thickness and containing lumachelle with Brachiopods.
Environment: Marine
Thickness: 32 to 264m, thinner in the west and south. The limestones with
brachiopods can be 50 to 80 m thick.
Fossils: Rich in Eopteropods (sea snails and sea slugs). Imprints of small
brachiopods (Productella subaculeata MURCH, cf. Spinocyrtia ostiolata
SCHLOTH ?, «Spirifer » sp., Chonetes coronatus CONRAD, cf. Leiorhynchus
mesacostale HALL). Locally these shales and siltstones are capped with a sand-
stone slab with Spinocyrtia sp. ex gr. ascendens SPRIESTERBACH and
Chonetes sp. ex gr. coronatus CONRAD
Overlying Unit: The Taberia Formation, which erodes the upper part of the
Akara Member locally.
Underlying Unit: Oued Felaou Member of the Tin Séririne Formation [This
Member was also known previously as “Grès de Touaret” as per Joulia (1959)’s
definition].
--------------------
Unit: AKOKAN MEMBER (of Talak Formation)
Epoch/Age/Author: Carboniferous (Mississippian – Upper Visean); Coquel
et al., 1995.
Original Author and/or Origin of the Name: Valsardieu, 1968, 1971;
References: Valsardieu, 1968, 1971; Fabre et al., 1983 ; Coquel et al., 1995 ;
Yahaya & Lang, 2000;
Stratigraphic Lexicon
100
Group: Terada
Synonymy: Unité d’Akokan
Equivalent(s): The Talak formation (which includes the Akokan Mbr) north
of Agadez is the equivalent of the Tim Mersoï Formation south of In Azaoua (Fig.
7-140; Fig. 7-10)
Basin/Sub-Basin/Apdx: Iullemmeden / Tim Mersoï / Appendix E, Appen-
dix I.
Lithology: Clay-siltstone, fine sandstone facies typical of tidal environ-
ments.
Environment: Tidal
Thickness: 40 m
Fossils: Rare lamellibranchs and Brachiopods (Coquel et al. (1995)).
Overlying Unit: Téléflak Mbr of the Guezouman Fm (Tagora Group) (when
present); otherwise, the Guezouman Fm. Erosional disconformity/Angular un-
conformity
Underlying Unit: Lower portion of the Talak Formation. Contact con-
formable
Maps, Cross-Sections, Pictures:
See Fig. 7-140
--------------------
Unit: ALANBANYA FORMATION
Epoch/Age/Author: Upper Cretaceous (Campanian to Lower Maastricht-
ian)
References: Jones, 1948; Greigert, 1966; Kogbe, 1973, 1979; Hanon, 1984,
1990; Dikouma, 1990 ; Rat et al., 1991; Zaborski & Morris, 1999; Ali et al.,
2019; Laouali-Idi et al., 2019, 2021.
Chapter 7 Lexicon
101
Group: Majias Group
Synonymy: Alambanya (misspelling); “Terme 1" of Greigert (1966); Lower
Sandstones and Mudstones.
Equivalent(s): Taloka Formation in the Sokoto sector of Nigeria. The
Taloka is also called the Lower Sandstones and Mudstones.
Basin/Apdx: Iullemmeden / Appendix H
Type/Reference/Stratotype Section: The formation occurs east of the 5°45'
meridian. It constitutes the ravine slopes of the Alanbanya valley east of Keita.
The two Members that can be distinguished in most of the Ader Doutchi are de-
fined in Ibohamane and around the town of Bouza (Fig. 7-21).
Lithology: In the Dakoro area of Niger, the Alanbanya Formation consists of
white, fine-grained friable sandstones and siltstones with thin intercalated mud-
stones and carbonaceous shales. The formation does not outcrop in the Kao
region, where it has, however, been recognized in the subsurface (Greigert,
1966). It is characterized by a fine grain size: clays and silts or sands with plant
debris and vertebrae remain, in particular crocodilians (Jones, 1948; Greigert,
1966; Kogbe, 1979). Hanon (1984, 1990) subdivides the formation of the Alan-
banya into two Members based on their grain size (Fig. 7-8; Fig. 7-9):
• "Sables d'Ibohamane" at the top (from 0 to 40 m): Fine to very fine clayey
sands and sands, white or of light colors, quartzose with rare white mica
platelets. Angular, unworn grain, generally between 50 and 200 microns. Beds
3 to 20 cm thick are separated by millimetric beds of hardened ferruginous
clays; the top of the beds truncated by the lower surface of the next bed, form-
ing large-scale, low-angular, cross-bedded stratifications. Parallel millimetric
laminations are underlined by color zoning. At the top of the member are 2 or
3 huge and regular metric banks (1 to 4 m) of homogeneous white silt or cen-
timetric bedding.
• "Silts de Bouza" at the base (from 100 to 130 m), silts and silts clayey
white, pink, homogeneous, compact or powdery; Metric beds with non-paral-
lel boundaries (erosion of the upper surfaces of the beds) separated by dark
gray or khaki clay beds. Isolated beds of fine sand.
Environment: It is of continental to littoral origin. At the base of these deposits
with an evident continental seal, some authors report the presence of lake or ma-
rine levels (Jones (1948); Greigert (1966)). Bivalves, gastropods and ostracods at
the Formation base, evidence a lacustrine environment. Start of the T3 transgres-
sion (Fig. 5-17).
Stratigraphic Lexicon
102
Thickness: 150 m
Fossils: Plant and crocodile remains, some calcareous beds containing bi-
valves, gastropods and ostracods at the base of the formation.
Overlying Unit: Farin Doutchi
Underlying Unit: Ibeceten or Doutchin-Zana formations
Maps, Cross-Sections, Pictures:
Figure 7-8. Lithostratigraphy of the Alanbanya Fm. (Laouali-Idi et al.,
2019).
Figure 7-9. Lithostratigraphy of the Alanbanya Fm at Ibohamane-Téléléguel and
the valley of Alanbanya (Hanon, 1990).
Chapter 7 Lexicon
103
--------------------
Unit: ALANLARA FORMATION
Epoch/Age/Author: Upper Cretaceous (Lower Cenomanian). Faure (1959)
includes it in the Cenomanian. Greigert and Pougnet (1967) include it in the
Lower Cenomanian. Fabre et al. (1983) place it in the Upper Cenomanian.
Konaté et al. (2019) put it back in the Lower Cenomanian.
Original Author and/or Origin of the Name: Faure (1959) for the name of
the nearby town of Alanlara.
References: Faure, 1959, 1966; Greigert, 1966 ; Greigert & Pougnet, 1967;
Fabre et al., 1983; Meister et al., 1994; Konaté et al., 2019.
Equivalent(s): Farak Formation; Ezerza-Cheffadène Formations.
Basin/Sub-Basin/Apdx: ENRB / Téfidet / Appendix F, Appendix H
Type/Reference/Stratotype Section: Accurate location not stated, however,
see Fig. 5-42, Fig. 5-43 for a general location.
Lithology: Faure (1959) selects the top of the formation just below the
limestone horizon with Neolobites. From top to bottom, it begins with black
limestones containing lamellibranch debris (marine), then beige to yellow, fine-
grained sandstones (continental), clay-limestone silts, and ends with
gastropod-rich sandy limestones (marine).
Environment: Mainly marine with occasional continental influences,
which allowed freshwater lungfish (Ceratodus) and land dinosaurs to thrive in
the area. The formation is the oldest witness to the first Cretaceous marine trans-
gression in this area.
Thickness: 200 m
Fossils: Faure (1959) observed a series of clays with rare oyster debris (no-
tably Ostrea deletrei - marine), conglomerates with bone debris of Ceratodus
(freshwater), fine sandstones with Exogyra (marine), and finally sandstones and
clays with vertebrate bones (Rebbachisaurus - continental). Rare molluscs, Di-
nosaurians.
Overlying Unit: Zoo Baba-Arentigué formation
Stratigraphic Lexicon
104
Underlying Unit: Tanguérat Formation (Téfidet Group)
Remarks: The whole is folded.
--------------------
Unit: *ALARCESS CONGLOMERATE
Epoch/Age/Author: Lower Triassic. Earlier documents state a “Jurassic(?)”
age. However, new correlations with the formations above and below and the in-
clusion of the Alarcess formation into the Goufat Subgroup and Agadez Group
strongly agree with a Lower Triassic age.
Original Author and/or Origin of the Name: Chudeau, 1907; Appendix D
References: Chudeau, 1907; Valsardieu, 1971; Fabre et al., 1983; Moody &
Sutcliffe, 1991.
Group/Subgroup: Agadez, Goufat
Synonymy: “Conglomerat d’Alarcess”; Alcarcesse (a misspelling in Moody
and Sutcliffe (1991)); “Grès bariolés conglomératiques”.
Equivalent(s): Now included within the Teloua 2 Mbr.
Basin/Sub-Basin/Apdx: Iullemmeden / Tim Mersoï / Appendix D, Appen-
dix E
Lithology: Conglomerate.
Environment: Pebbles of eruptive rocks emanating from volcanism linked
to the establishment of the Aïr intrusions
Thickness: 0-10 m
Overlying Unit: When present, it is overlain by the remaining portion of the
Teloua 2 Member of the Teloua Fm (Fig. 7-10).
Underlying Unit: When present, it is underlain by the Teloua 1 Member of
the Teloua Fm (Fig. 7-10).
Maps, Cross-Sections, Pictures:
Chapter 7 Lexicon
105
Figure 7-10. Historical regional stratigraphy of the Tim Mersoï Sub-Basin and
the former position of the Alarcess conglomerate, which has now been incorpo-
rated within the Teloua 2 Member of the Teloua Fm. (Valsardieu, 1971). Note 1:
Similar comments are true for the Anou-Ararène conglomerate, Anou-Mellé con-
glomerate and the Aokaré Member [see these terms]. Note 2: Joulia did not have
the Teragh Formation. It is seen correlating with the upper portion of Joulia’s
Farrazekat Formation; thus, only the Teragh Fm belongs to the Terada Group.
Note 3: Valsardieu splitted Joulia’s “Série de Talach” into the Akokan Member
within the Talak Formation.
--------------------
Unit: *AMESGUEUR (GRÈS D')
Epoch/Age/Author: Upper Devonian
References: Joulia, 1959; Lessard, 1961; Claret & Tempère, 1968; Val-
sardieu, 1971; Fabre et al., 1983.
Synonymy: “Grès de Taberia” or “lower Member of the Taberia formation”;
Taberia Formation
Basin/Sub-Basin/Apdx: Iullemmeden / Tim Mersoï / Appendix E, Appen-
dix I.
Stratigraphic Lexicon
106
Lithology: In the Tamesna, 150 m of an alternation of coarse ferruginous
sandstone and psammites, lagoonal, bivalves and Spirophytons. They are made
up of an alternation of fine sandstone, often ferruginous, with rare coarse inter-
vals, and Spirophyton shales and siltstones.
Environment: Marine
Thickness: 80 to 150 m
Fossils: Brachiopods, Retzia sp. and Mucrospirifer cf. mesacostalis HALL,
as well as a flora with Archeosigillaria vanuxemi GÖPPERT KlDSTON, Pro-
tolepidodrendropsis sp., Cyclostigma sp., Haplostigma sp. and Calamophytum
sp.
Overlying Unit: For the old nomenclature, see Appendix I. In this lexicon,
the overlying unit is the Farrazekat Fm.
Underlying Unit: For the old nomenclature, see Appendix I. The underlying
unit is the Akara Mbr of the Tin Séririne Fm in this lexicon.
Remarks: The name is now the “Taberia Fm”.
--------------------
Unit: *AMEZROU FORMATION
Epoch/Age/Author: Lower Cretaceous (Barremian? - Aptian)
References: Molinas, 1965; Bigotte & Obelianne, 1968 ; Baudet et al.,
1981 ; Fabre et al., 1983; Moody, 1997.
Synonymy: Grès d’Amezrou; Upper part of "GAD 1"; Amezrou sandstone;
Amezroun (misspelling)
Basin/Apdx: Iullemmeden / Appendix F
Equivalent(s): Old name for part of the Tazolé Formation
Lithology: The Amezrou (top of GAD 1), Anyeli and Tin Sakan (GAD 2),
Girmaga (GAD 3) and Mohra (GAD 4-5) formations are predominantly quartzitic
and arkosic arenites with intercalated variegated shales. The overall pattern of
sedimentation is a fining upward mega sequence. Each mega sequence argues for
Chapter 7 Lexicon
107
a change from braided to meandering river systems.
Thickness: The Amezrou is 50 m
Fossils: See “Tazolé Fm”
Overlying Unit: *Anyeli Fm.
Underlying Unit: *Terzikazan Fm.
Remarks: See “Tazolé Fm” and “Tégama Group”
--------------------
Unit: ANGORNAKOUER FORMATION
Epoch/Age/Author: Lower Cretaceous (Barremian? to Aptian).
References: Faure, 1959, 1966; Fabre et al., 1983 ; Konaté et al., 2019.
Group: Téfidet
Synonymy: Angornakeur (misspelling)
Equivalent(s): Tazolé formation
Basin/Sub-Basin/Apdx: ENRB / Téfidet / Appendix F
Lithology: Coarse sandstones, conglomeratic sandstones, feldspathic sand-
stones with oblique stratification. The sequence begins with beige to pink soft
coarse sandstones followed upward by fine-grained and variably argillaceous
sandstones. The beds may be conglomeratic or in some places, feldspathic with
cross stratifications (Konaté et al. (2019)).
Environment: Continental
Thickness: 250 m
Fossils: Abundant silicified wood (Dadoxylon) (Faure (1966)).
Overlying Unit: The finer and argillaceous layers of the Tagrezou formation
Stratigraphic Lexicon
108
Underlying Unit: Rests in angular unconformity on the Precambrian crys-
talline basement.
Remarks: Fig. 5-42, Fig. 5-43
--------------------
Unit: *ANOU ARARÈNE CONGLOMERATE
Basin/Sub-Basin/Apdx: Iullemmeden / Tim Mersoï / Appendix E
Remarks: See Aguelal Subgroup and Teloua 1 Mbr of the Teloua Fm. The
Anou Ararène conglomerate has been incorporated within the Teloua 1 Member
of the Teloua Fm (Fig. 7-10). (Valsardieu, 1971).
--------------------
Unit: ANOU IZILEG FORMATION
Epoch/Age/Author: Lower Devonian (Pragian-Emsian)
Original Author and/or Origin of the Name: Claret & Tempère, 1968 in
Algeria. Trompette [in Fabre et al., 1983] renamed the Idekel Sandstone as Anou
Izileg Formation in Niger
References: Joulia, 1959; Lessard, 1961; Claret & Tempère, 1968; Fabre et
al., 1983; Derycke & Goujet, 2011; Lobpries & Lapen, 2018; Lobpries, 2020.
Synonymy: *Grès d’Idekel [*Idekel Sandstone] *Idekel Formation
Basin/Sub-Basin/Apdx: Iullemmeden / Tim Mersoï / Appendix E, Appen-
dix I
Type/Reference/Stratotype Section:
Lithology: Begins with 20 m of conglomerates topped with predominantly
fine anisometric sandstone.
Environment: Fluvio-marine
Thickness: 0 to 155 m. On page 51 of Valsardieu (1971), it is stated a thick-
ness of 90 m in the area of Touaret.
Chapter 7 Lexicon
109
Fossils: West of In Guezzam, a Brachiopod fauna is found with Trigeria
gaudryi which has a Pragian character. This brachiopod fauna occurs in the finer
sands higher up in the sequence. Silicified woods. In Algeria, Derycke & Goujet
(2011) describe chondrichthyan and acanthodian faunas
Overlying Unit: Tin Séririne Formation, more specifically its Oued Felaou
Member.
Underlying Unit: It is transgressive towards the South, resting uncon-
formably sometimes on Silurian graptolitic shales, sometimes on the older
Proterozoic rocks.
Remarks: Lobpries & Lapen (2018) proposed that the circular feature (di-
ameter of approximately 10 km) observed at 21°21'14.56"N Latitude and
9°8'32.24"E Longitude in the Anou Izileg Formation of northern Niger formed
from either a meteorite impact (Fig. 7-11) after deposition of the host sedimentary
units or by some other, but less likely, geologic process. The same authors add
that forty meteorites of various types have been found in Niger to date (see
Jérémine et al., 1964 and Web-08 under "References"), but there are currently no
confirmed meteorite impact sites due mainly to the difficulty of access to conduct
groundwork.
Maps, Cross-Sections, Pictures:
Figura 7-11. The circular meteorite impact feature which is described by Lob-
pries & Lapen (2018) and Lobpries (2020) (Source: Image from Google Earth).
Stratigraphic Lexicon
110
--------------------
Unit: *ANOU MELLÉ CONGLOMERATES
Basin/Sub-Basin/Apdx: Iullemmeden / Tim Mersoï / Appendix E
Remarks: See Aguelal Subgroup and the Teloua 1 Member of the Teloua
Fm. The Anou Mellé conglomerate has been incorporated within the Teloua 1
Member of the Teloua Fm (Fig. 7-10) (Valsardieu, 1971).
--------------------
Unit: *ANYELI FORMATION
Epoch/Age/Author: Lower Cretaceous (Aptian)
References: Molinas, 1965; Bigotte & Obelianne, 1968 ; Baudet et al.,
1981 ; Fabre et al., 1983; Moody, 1997;
Synonymy: Grès d’Anyeli; Part of "GAD 2"; Anyeli sandstone.
Equivalent(s): Old name for part of the Tazolé Formation
Basin/Apdx: Iullemmeden / Appendix F
Lithology: See *Amezrou Formation
Environment: Continental
Thickness: 30 m
Fossils: See Tazolé Fm.
Overlying Unit: *Tin Sakan Fm.
Underlying Unit: *Amezrou Fm.
Remarks: See Tazolé Fm and Tégama Group
--------------------
Unit: AOKARÉ MEMBER (of the Moradi Fm)
Chapter 7 Lexicon
111
Epoch/Age/Author: Upper Permian
References: Valsardieu, 1971 ; Ministère des Mines et de l’Hydraulique, Di-
rection des Mines et de la Géologie, 1977; Fabre et al., 1983 ; Sidor et al., 2003;
CSA Global, 2017, 2019.
Group/Subgroup: Izégouandane (Upper)
Synonymy: Unité d’Aokaré
Basin/Sub-Basin/Apdx: Iullemmeden / Tim Mersoï / Appendix E
Lithology: As per Valsardieu (1971), these are the meandering “channels
of arkose” eroding the Moradi formation, following NNE flexures. These red,
coarse, heterogranular sandstones with analcime spherules and clay and lime-
stone cement may contain true analcimolites. The basal conglomerates of the
Aokaré unit, with large allochthonous (quartz, quartzite) or autochthonous (clay)
pebbles represent a last fluvial episode; phosphatic cement sandstones are as-
sociated with them. Aeolian red sandstones (?) overlay them. This unit would
correspond to a reactivation of the NNE fracture at Madaouela.
Environment: Continental (Fluvial meandering channels)
Overlying Unit: Teloua 1 Member of the Teloua Fm.
Underlying Unit: Lower portion of the Moradi Formation
Remarks: Upper Member of the Moradi Fm.
--------------------
Unit: AOULINGEN FORMATION
Epoch/Age/Author: Since it is equivalent to the Talak Fm, a Carboniferous
(Mississippian – Upper Visean) age is assigned; Coquel et al., 1995.
References: Valsardieu, 1971, Fig. 7-10; Fabre et al., 1983; Coquel et al.,
1995; CSA Global, 2007, 2019.
Group: Terada
Synonymy: “Silts à plantes d’Aoulingen”
Stratigraphic Lexicon
112
Equivalent(s): The siltstones and sandstones of the Aoulingen Formation
pass laterally to the north into the marine Talak Formation
Basin/Sub-Basin/Apdx: Iullemmeden / Tim Mersoï / Appendix E, Appen-
dix I
Lithology: Siltstones and sandstones
Environment: Marine
Thickness: 50 to 110 m
Overlying Unit: Guezouman Fm.
Underlying Unit: Teragh Fm
Maps, Cross-Sections, Pictures:
See Fig. 7-10.
--------------------
Unit: ARENTIGUÉ FORMATION
Epoch/Age/Author: Upper Cretaceous (Upper Cenomanian-Lower Turon-
ian)
Original Author and/or Origin of the Name: Faure, 1966.
References: Furon, 1964; Faure, 1966; Fabre et al., 1983 ; Meister et al.,
1994.
Synonymy: Zoo Baba-Arentigué formation
Equivalent(s): Zoo Baba Fm; Béréré Fm; Iguéllala Mountains Fm.
Basin/Sub-Basin/Apdx: ENRB / Bilma & Téfidet / Appendix F, Appendix
H
Lithology: Fine sandstones, clays, and ferruginous levels are comparable to
those of the Kafra formation. Grey, pink to black fossils-rich limestones. Includes
green gypsum-bearing shales.
Chapter 7 Lexicon
113
Environment: Marine
Thickness: 70 to 250 m in the Bilma Sub-Basin. In the Téfidet Sub-Basin,
the Zoo Baba – Arentigué Fms, defined as the “Série Cénomanienne-Turonienne”
by Faure (1959), is 60 m thick.
Fossils: Ammonites (Fig. 7-12, Fig. 7-13), Lamellibranchs, Gastropods, oys-
ters (Exogyra olisiponensis), and sea-urchins (Cidaris taouzensis). Even though
Furon (1964) does not mention the name of the Formation literally, he does say
for the same time interval in the area:
• Upper Cenomanian: clays and limestones with Neolobites.
• Lower Turonian: limestones with Nigericeras lamberti Schn., Veniella
byzancenica Perv., Plicatula fourneli Coq., then limestones with Pseudotisso-
tia (Bauchioceras) nigeriensis Wood, Granocardium productum Sow.
Overlying Unit: Séguédine Fm
Underlying Unit: Cheffadène Fm
Maps, Cross-Sections, Pictures:
Figure 7-12. Ammonites from the Arentigué-Zoo Baba Formations in the Chef-
fadène area. 1 & 2) Neolobites vibrayeanus brancai. 3 to 7) Thomelites (?)
tenerensis (Meister et al., 1994).
Stratigraphic Lexicon
114
Figure 7-13. Location of the marine Upper Cretaceous ammonite-bearing out-
crops of the Arentigué-Zoo Baba Formations within the Bilma and Téfidet
Sub-Basins (Source: Meister et al., 1994).
--------------------
Unit: ARGILLACEOUS SANDY FORMATION WITH TRACES
Epoch/Age/Author: Cambrian-Ordovician; Claret & Tempère, 1968.
Synonymy : Argilo-gréseux à Traces
Basin/Sub-Basin/Apdx: Iullemmeden / Tim Mersoï / Appendix E
Remarks: See "In-Azaoua Group". Present only in Algeria.
--------------------
Unit: *ARGILO-SABLEUSE À LIGNITES (SÉRIE)
Epoch/Age/Author: Oligocene (Beauvais et al., 2008).
References: Bellion, 1987; Lang et al., 1986, 1990; Beauvais et al., 2008;
Ousmane et al., 2020.
Group: Dallols
Synonymy: Continental Terminal 2 (or Ct2); Lower part of the Birni
N’Konni Fm.
Chapter 7 Lexicon
115
Basin/Apdx: Iullemmeden / Appendix H
Type/Reference/Stratotype Section:
Remarks: See Birni N’Konni Fm
--------------------
Unit: ARLIT FORMATION
Epoch/Age/Author: Middle Permian (most likely Wordian). It has long
been assumed to be of Upper Carboniferous (Pennsylvanian) age. However,
Broutin et al. (1990) have established an Early Permian age (equivalent to the
Kungurian of the Global Stages) to possibly(?) early Middle Permian (Roadian)
for the upper portion of the Tarat Formation (now the Madaouela Fm) based on
palynological data. (See Tarat Fm and Fig. 7-128). This has also been confirmed
by Coquel et al. (1995). The above directly affects the age of the Arlit Formation,
which is now also included in the Middle Permian, just above the Madaouela Fm.
Accordingly, Fabre (2005; page 333) displays a section with the upper portion of
the Tarat Fm (or Madaouela Fm) and the Arlit Fm included in the Permian (not
illustrated here but similar to what is seen in Fig. 7-128.)
References: Abdoul Aziz, 1968; Fabre et al., 1983; Broutin et al., 1990; Co-
quel et al., 1995; Fabre, 2005; Billon et al., 2016; Alfidja et al., 2021.
Group/Subgroup: Upper cycle of the Tagora Group (Upper Tagora) (Fig.
7-118).
Synonymy: Grès argileux d’Arlit
Basin/Sub-Basin/Apdx: Iullemmeden / Tim Mersoï / Appendix E
Lithology: This unit is represented by medium to fine clayey sandstone, with
brown or green argillite beds.
Environment: Fluvial, lacustrine, alluvial
Thickness: average of 5 to 10 m (0-32 m)
Fossils: Silicified wood at the top
Overlying Unit: Izégouande Fm (Izégouandane Group)
Stratigraphic Lexicon
116
Underlying Unit: Madaouela Fm or the Tarat Fm when the Madaouela is
absent (Alfidja et al., 2021)
--------------------
Unit: ASCHIA TINAMOU FORMATION
Epoch/Age/Author: Upper Cretaceous (Upper Turonian to Campanian)
(Faure (1966, page 168)
Original Author and/or Origin of the Name: Faure, 1966, page 167.
References: Faure, 1966; Fabre et al., 1983.
Equivalent(s): Yogou Fm & upper part of the Donga Fm in the Termit
Graben
Basin/Sub-Basin/Apdx: ENRB / Termit / Appendix H
Type/Reference/Stratotype Section: The Aschia Tinamou well SW of Ter-
mit Massif (Fig. 7-14; Fig. 7-136)
Lithology: Green or black clays, dark shales and gray or yellow limestones.
Gypsum, pyrite and fibrous calcite are abundant, as well as phosphate levels in
fish debris
Environment: Marine
Thickness: Faure (1966) states that the upper part of the Aschia Tinamou
Fm is 170 m. On page 50, he says the whole formation is 300m. The lower part
of the Aschia Tinamou Fm is, therefore, ~130m.
Fossils: The mollusc fauna is closely correlated with the Awgu Fm (Co-
niacian) in Nigeria. Fish, lamellibranchs, foraminifers, and ammonites (Tissotia
species limited to West Africa, such as Tissotia latelobata Solger).
Overlying Unit: Termit Fm
Underlying Unit: Béréré & Kandel Bouzou Fms
Remarks: There is no outcrop of the Formation. All were determined from
drill holes (Fig. 7-14).
Chapter 7 Lexicon
117
Maps, Cross-Sections, Pictures:
Figure 7-14. Hypothetic section showing the layers penetrated
by the well at Aschia Tinamou (Faure, 1966, page 169). Green
= Béréré/Kandel Bouzou Fms; Orange = Aschia Tinamou Fm;
Blue = Termit Fm.
--------------------
Unit: ASH SHABIYAT FORMATION
Epoch/Age/Author: Lower Ordovician (Tremadocian) (Havlicek et al.,
1973)
Original Author and/or Origin of the Name: Jabal Ash Shabiyat in the
eastern Murzuq Basin
References: Havlicek et al., 1973; Mergl et al., 2001; Shalbak, 2015; Hallet,
2016.
Group: Gargaf
Synonymy: Achebyat/Achabiyat Fm (both misspelling) (Mergl et al., 2001);
“Oblique supérieure” Fm; The spelling was modified to its current form by Hallet
(2002) after verifying the official name records of localities in Libya.
Basin/Apdx: Djado / Appendix G
Stratigraphic Lexicon
118
Type/Reference/Stratotype Section: Al Qarqaf Arch (Libya) (Fig. 5-49,
Fig. 7-15).
Lithology: Built-up of unfossiliferous (except for common trace fossils),
cross-bedded, mainly coarse-grained sandstones.
Environment: Fluvio-deltaic. It represents a maximum flooding interval
and is essentially a silty marine sandstone.
Thickness: ~ 70 m
Fossils: Common trace fossils (contains abundant Tigillites, Cruziana and
Harlania trace fossils.)
Overlying Unit: Hawaz Formation
Underlying Unit: Hasawnah Formation
Maps, Cross-Sections, Pictures:
Chapter 7 Lexicon
119
Figure 7-15. Stratigraphic column of the Ash Shabiyat
Formation at the Type Locality in Libya (Shalbak,
2015).
--------------------
Unit: ASSAOUAS FORMATION
Epoch/Age/Author: Middle Jurassic
Original Author and/or Origin of the Name: Joulia, 1951-1957.
References: Joulia, 1951-1957; Valsardieu, 1971 ; Fabre et al., 1983.
Group/Subgroup: Agadez, Dabla
Synonymy: Grès d’Assaouas (not to confuse with the Cambrian-Ordovician
Stratigraphic Lexicon
120
In-Azaoua Fm)
Basin/Sub-Basin/Apdx: Iullemmeden / Tim Mersoï / Appendix E
Lithology: Intercalations of argillites in silty sediments. Valsardieu (1971,
page 221) describes the formation between the Irhazer and the Tchirezrine for-
mations as
Brown argillites dotted with medium to fine sandstone, isogranular, felds-
pathic, micaceous, clayey, with abundant calcareous cement, brown. The
existence of oblique microstratifications is reminiscent of the existence at the
time of deposition of an oriented sedimentation not so intense. The sandstones
occupy stratiform lenses isolated in the argillites, or sporadic layers overlaid on
the Tchirezrine 2 sandstones. The sandstones are beige to greenish, coarse, het-
erogranular, feldspathic, film-cemented, phyllite(p. 221).
Environment: Lacustrine
Thickness: 0-30 m
Fossils: Invertebrates, vertebrate tracks, abundant plant imprints in sand-
stones, fish, dinosaurs. Estheries (Euestheria lamberti, E. margínata, DEFRETIN
et al., 1956), lamellibranchs (Cuneopsis, Unio, Cyrena, MONGIN, 1963), ver-
tebrate remains (Sauropods, Theropods, Crocodiles, fish) and pentadactyles et
tridactyles tracks (de Lapparent et al., 1966) have been found in the unit of As-
saouas and the Irhazer Formation.
Overlying Unit: Irhazer Formation
Underlying Unit: Tchirezrine 2 Mbr of the Tchirezrine Fm
Remarks: The Assaouas Fm is not always present between the Irhazer and
Tchirezrine formations. Sometimes it is reduced to small lenses of channel sand-
stones.
--------------------
Unit: ASSEDJEFAR FORMATION
Epoch/Age/Author: Lower Carboniferous (Upper Mississippian, Ser-
pukhovian)
Chapter 7 Lexicon
121
Original Author and/or Origin of the Name: It was defined by Lelubre
(1952b) as a sequence of deltaic and shallow marine rocks conformably overlying
the Marar Formation in the Hamadat Tanghirt area of west Libya
References: Lelubre, 1952b; Plauchut & Faure, 1959; Collomb, 1962 ;
Jacqué, 1963; De Rouvre, 1984 ; Lababidi et al., 1985; Mergl et al., 2001; Fabre,
2005; Tawadros, 2011; Shalbak, 2015; Hallett, 2002, 2016.
Basin/Apdx: Djado / Appendix G
Type/Reference/Stratotype Section: The type locality was designated by
Collomb (1962) 80 km west of Awaynat Wanin in the Adrar Uan Assedjefar Hill
(28°30′N, 11°30′E)
Lithology: Made up of green shales, often with gypsum beds alternating
with calcareous levels.
Environment: It represents a low-energy lagoonal to shallow shelf envi-
ronment where dolomitic limestones, siltstones and ferruginous and gypsiferous
sandstones were deposited. These facies indicate a retreat of the sea.
Thickness: 140 m at the Type Locality (Fig. 7-16; Fig. 7-97; Fig. 7-98). 160
m in the Djado (Fabre (2005)), thinning southward to 60 m.
Fossils: The restricted marine to lacustrine environment is indicated by algal
stromatolites and concretionary limestones ("Collenia" horizons and Caliche lay-
ers). The sequence contains a rich marine fauna of brachiopods (characterized
by the large syringothyrid Syringothyris jourdyi and the terebratulid Beecheria,
as well as Streptorhynchus, the productids Antiquatonia, Flexaria, Ovatia,
Rhipidomella, Composita, Syringothyris, Anthracospirifer and small rhynchonel-
lids), pelecypods, corals and foraminifera plus abundant silicified wood.
Overlying Unit: Dimbabah Formation
Underlying Unit: Conformably with the Marar Formation
Maps, Cross-Sections, Pictures:
Stratigraphic Lexicon
122
Figure 7-16. Stratigraphic column of the Assedjefar Formation at the Type Lo-
cality in Libya (Source: Shalbak, 2015).
--------------------
Unit: AWAYNAT WANIN FORMATION
Epoch/Age/Author: Middle-Upper Devonian (Eifelian to Famennian at the
Type Locality, and Eifelian to Frasnian in the Djado basin). Mergl et al., 2001.
Original Author and/or Origin of the Name: Lelubre, 1946 & 1948.
References: Lelubre, 1946 & 1948; Plauchut & Faure, 1959 ; Massa & Col-
lomb, 1960 ; Jacqué, 1963; Freulon, 1964; Lejal-Nicol, 1972; Klitzsch et al.,
1973; Fabre et al., 1983 ; Lababidi et al., 1985; Mergl & Massa, 1992; Mergl et
al., 2001; Shalbak, 2015; Hallett, 2002, 2016.
Synonymy: Aouinet-Ouenine Fm; Awaynat Wanin Group; Awainat Wanin
Fm (misspelling); Aouinet-Ouenine Group & Tahara Formation combined (Fig.
Chapter 7 Lexicon
123
7-19). The spelling was modified to its current form by Hallet (2002) after veri-
fying the official name records of localities in Libya.
Equivalent(s): From Fabre et al. (1983), the Awaynat Wanin could be the
equivalent to their combined “*Ohebran (top) and *Dadafuy (bottom) series” in
the Djado.
Basin/Apdx: Djado (Fig. 7-17) / Appendix G
Type/Reference/Stratotype Section: Northwest flank of the Al Qarqaf
Arch, Libya.
Lithology: The type section shows six repeated 'cyclothems' (Fig. 7-18; Fig.
7-19) of claystone, sometimes ferruginous or gypsiferous, siltstones and sand-
stones. The sandstones are frequently cross-bedded. In the Djado Basin, Mergl et
al. (2001) do not subdivide the Awaynat Wanin into cyclothems since it was dif-
ficult to differentiate them.
Without naming the formation, Fabre et al. (1983) mention the Middle and
Upper Devonian in the Djado Basin:
With the Middle-Upper Devonian, monotonous clay-sandstone sedimenta-
tion appears. The Devonian is only characterized in the region of Chirfa by
about ten meters of shales with (PLAUCHUT and FAURE, 1959) Spirifer sp.
eg. ascendens POECKELMAN, Leiorhynchus sp. eg. mecacostale CONRAD,
Tropidoleptus sp. eg. carinatus CONRAD, lamellibranchs and styliolines which
indicate either the Upper Givetian or the Givetian-Frasnian passage. The Upper
Devonian, a few tens of meters thick to nearly 200 m, is formed by alternating
shales and fine ferruginous sandstone, sometimes calcareous, with Spirophytons
(Fig. 7-114), a flora composed of Archaeosigillaria sp. and Protolepidendropsis
sp. and Pholadomya, Posydonomya, Mytilus, Tentaculites, encrines and rhyn-
chonella associated with marine incursions (p. 124).
Environment: The sequence represents a deltaic environment ranging from
delta front to fluvial-distributary channels, all reworked by tides and storm waves.
Thickness: Each cycle is averaging 15-30m in thickness, with a total thick-
ness of 162m at the Type Locality.
Fossils: At Type locality: Mainly brachiopods, sometimes concentrated into
coquinas; Desmochitina sp., Ancyrochitina cf. comigera Cell. and Sc., Eisena-
chitina castor Jans., Vrechitina sp. A Jard and Yapan., Ancyrochitina pilosa
Stratigraphic Lexicon
124
var. corta Taug., Ancyrochitina sp. Legault, Fungochitina pilosa Cell. and Scott,
Sphaerochitina fenestrata Taug. and Jekh., Lagenochitina macrostoma Taug. and
Jekh. In the Djado Basin: Continental influences are increasing with frequent
fragments of lycophytes and lignite. In contrast, marine horizons are rare, with
few bivalves and crinoids. The trace fossil Spirophyton, generally well preserved
and covering sandstones bedding planes, is a more frequent fossil. This ich-
nofacies is spread over the whole area. Also, abundant but poorly preserved
ferruginous wood debris is encountered.
Overlying Unit: Marar Fm.
Underlying Unit: Wan Kasa Fm. Conformable contact.
Maps, Cross-Sections, Pictures:
Figure 7-17. Outcrop and subsurface extents of the Awainat Wanin Formation in
Libya and into the Djado basin of Niger (Source: Modified from Shalbak, 2015).
Chapter 7 Lexicon
125
Figure 7-18. Stratigraphic Column of the Awaynat Wanin Formation at
the Type Locality in Libya, displaying the six cyclothems (Source: Shal-
Stratigraphic Lexicon
126
bak, 2015).
Figure 7-19. Successive Nomenclature of the Awaynat
Wanin Formation (Source: Hallet, 2002).
--------------------
Unit: AWBARI MEMBER (of the Msak Fm)
Basin/Apdx: Djado / Appendix G
Remarks: See “Msak Fm”
--------------------
Unit: BÉRÉRÉ FORMATION
Epoch/Age/Author: Upper Cretaceous (Upper Cenomanian – Lower Tur-
onian). Furon (1964) mentions the “formation inférieur de Béréré” (Upper
Cenomanian) and the “formation supérieur de Béréré” Lower Turonian).
Original Author and/or Origin of the Name: Joulia, 1953.
References: Furon, 1933, 1934, 1935, 1964 ; Cottreau, 1934; Joulia, 1953;
Faure, 1966, page 159; Fabre et al., 1983; Moody et al., 1991 ; Rat et al., 1991 ;
Mathey et al., 1991; Mateer et al., 1992 ; Meister, 1992; Mathey et al., 1995 ;
Moody, 1997.
Group: Damergou
Synonymy: Part of the old Talrass and Aïn Toufayen Formations (Fig. 7-6).
Chapter 7 Lexicon
127
Equivalent(s): Iguéllala Mountains Fm; Zoo Baba Fm (Fig. 7-70); Aren-
tigué Fm; It is the "Lumachelle à Neolobites" (Greigert, 1966) which only exists
in the extreme north of the Damergou.
Basin/Apdx: Iullemmeden / Appendix H
Type/Reference/Stratotype Section: East of Tanout, in the extreme north
of the Damergou
Lithology: The upper part is marine with limestones and sandy yellow
dolomitic limestones. Overall, the bulk of the formation displays laminated clays
separating fine sandstones and clays; lumachellic limestone beds. Clays, lime-
stones are containing fine quartz grains, medium-grained feldspathic and
micaceous sandstones, which are bioclastic, slightly glauconitic and cemented by
sparite (Fig. 7-20).
Environment: Marine
Thickness: ~66 m
Fossils: The macrofauna, varied and well-preserved, comprises echino-
derms, bivalves (particularly Exogyra), gastropods, nautiloids, and ammonites
(Neolobites vibrayeani), Plicatula Fourneli Coq, Micropedina olisiponensis
Forbes, Cardium productum Sow., Pholadomya pedernalis Roemer, Hoplitoides
nigeriensis Woods, Metengonoceras dumbli Cragin, Metengonoceras nigeriensis
Furon, Nigericeras Gadeni Chudeau, Nigericeras jacqueti Schn., Nigericeras
lamberti Schn., Nigericeras gignouxi Schn., Vascoceras crassus Furon, Paravas-
coceras Chevalieri Furon, Paravascoceras Chudeaui Furon, Paravascoceras
nigeriensis Woods.
Overlying Unit: Gangara Fm
Underlying Unit: Farak Fm
Remarks: This is the beginning of the first of several marine transgressions
across West Africa.
Maps, Cross-Sections, Pictures:
Stratigraphic Lexicon
128
Figure 7-20. SW-NE cross-section within the Damergou area from Up-
per Cenomanian to Upper Turonian (Béréré and Gangara formations).
Created from data in Meister et al., 1992.
--------------------
Unit: BILMA FORMATION
Epoch/Age/Author: Upper Cretaceous (Maastrichtian - Paleocene).
Original Author and/or Origin of the Name: Plauchut et al., 1959.
References: Plauchut et al., 1959; Faure, 1966; Fabre et al., 1983 ; Meister
et al., 1994.
Equivalent(s): Galhama Fm, Emi-Bao Fm, Termit Fm.
Basin/Sub-Basin/Apdx: ENRB / Bilma / Appendix H
Type/Reference/Stratotype Section: The Bilma cliff (or cuesta) (Fig.
5-44).
Lithology: Brown sandstones, sometimes coarse with cross-bedded stratifi-
cations with intercalations of white kaolinitic clays.
Environment: Continental
Thickness: 250-300 m
Chapter 7 Lexicon
129
Fossils: The ferruginous levels show plant debris; Dadoxylon (Araucarioxy-
lon) sp.
Overlying Unit: None
Underlying Unit: Kafra Fm
--------------------
Unit: BIRNI N’KONNI FORMATION
Epoch/Age/Author: Oligocene (Beauvais et al., 2008)
Original Author and/or Origin of the Name: This name was proposed by
Dikouma (1990) after studying the stratigraphy of Ader Doutchi North and by
analogy with the Sokoto Group of Nigeria.
References: Pougnet, 1949; Hanon, 1990; Dikouma, 1990; Moody, 1997;
Beauvais et al., 2008; Heckmann, 2019; Ousmane et al., 2020.
Group: Dallols
Synonymy: "Grès argileux du Moyen Niger (Ct3)" (Fig. 7-23) [Middle
Niger clay rich sandstone] together with "Série argilo-sableuse à lignites (Ct2)"
[lignitic clay rich sandstones] (Fig. 7-38). Also, the “Gaya Formation” of Pougnet
(1949).
Basin/Apdx: Iullemmeden / Appendix H
Type/Reference/Stratotype Section: The most complete sections are ob-
served about 5 km east of the town of Birni N'Konni on the flanks of the hills of
Tyerasa Mango and Tyerasa Goune (Fig. 7-21)
Lithology: Sandy-argillaceous set, presenting facies varying between practi-
cally pure clays and conglomeratic sandstones. Four Members are present, from
top to bottom (Fig. 7-22):
• K4: 58m in Tyerasa; decametric alternations of the following two facies:
▪ fine-grained clayey sandstone of white or beige quartz; abundant,
white clay matrix; branched tubulations with a pink silty clay fill-
ing, plentiful in some banks (bioturbations).
▪ Soft pink sand and sandstone; medium to a very coarse grain of
Stratigraphic Lexicon
130
angular quartz; ferruginous clay binder not very abundant; oblique
stratifications, decreasing in grain size, rare bioturbations.
In the region of Birni N'Konni, the upper 8 meters of the Member are made up of
a slab of a dark ferruginous conglomeratic sandstone with oblique stratifications.
• K3: from 0 to 4 m; fine ironstone silt; locally abundant ferruginous oolites;
this thick and hard horizon is evident in the topography.
• K2: from 20 to 25 m; fine, medium, coarse, pinkish brown, brick red sand-
stone; fine grain at the base, becoming coarser towards the median zone of
the member or appearing conglomeratic facies (with elements up to 1 cm) of
rolled quartz and rare clay pebbles, then gradual passage to finer and finer
sandstone and, at the top of the Member, has sandy clays; Oblique strat-
ifications, sorting of grains. In the north of the Birni N'Konni region, the
conglomerates are more abundant and have more angular elements; locally,
they constitute the entire Member.
• K1: from 30 to 60 m?; compact white kaolin clays; often poorly marked strati-
fication; locally very fine alternations (millimeters or infra-mm) of white clays
and very fine white sands, parallel laminations. North of parallel 14° 30', the
thickness of layers between the top of Member K1 and the top of the underly-
ing Ader Doutchi Formation reaches 60 m. The lower part of this interval does
not show any outcrop for about 30 m.
Environment: Continental. The sedimentological characteristics of the different
facies encountered in the formation suggest shallow water conditions with fluc-
tuating energy levels and corresponding to the coastal, lake, and fluvial
environments.
Thickness: 480m. In the Birni N'Konni region, the thickness of the forma-
tion is about 120 m.
Fossils: Fossils of gastropods and lamellibranchs epigenized in goethite and
hematite are quite frequent at Member K3. Pila wernei (Philippi), Unio sp., Cor-
bicula aff. africana (Krauss) and Corbicula sp. could be determined in Toudou
and Tyerasa Goune; these fossils have no precise stratigraphic significance.
Tubular perforations in the clayey sand of the K4 Member can be attributed to
old burrows or root ducts.
Overlying Unit: Quaternary
Underlying Unit: Ader Doutchi Fm.
Remarks: Top formation of the Continental Terminal
Chapter 7 Lexicon
131
Maps, Cross-Sections, Pictures:
Figure 7-21. Map of the Birni N’Konni and Tahoua regions. The Tyerasa type lo-
cality of the Birni N’Konni Fm is shown in the bottom left corner (Source: Hanon,
1990).
Stratigraphic Lexicon
132
Figure 7-22. Stratigraphic section of the Birni N’Konni Fm at Tyerasa
(Source: Hanon, 1990).
Chapter 7 Lexicon
133
Figure 7-23. Ct3’s lithologic column around the capital Ni-
amey (Source: Ousmane et al., 2020).
--------------------
Stratigraphic Lexicon
134
Unit: *BORAK FORMATION
Epoch/Age/Author: Lower Cretaceous (Albian; top may be Lower Ceno-
manian); Bigotte & Obelianne, 1968.
References: Molinas, 1965; Bigotte & Obelianne, 1968; Baudet et al., 1981;
Fabre et al., 1983; Moody (1997).
Group: Tégama
Synonymy: Grès de Borak; Part of "GAD 8"; Borak sandstone; Aïn To-
ufayen Grès de Borak. Old name for part of the Echkar Fm.
Basin/Apdx: Iullemmeden / Appendix F
Type/Reference/Stratotype Section: Gadoufaoua paleontological site (Fig.
6-1).
Lithology: Shales with channel sandstones are characteristic of the Borak
Formation (GAD 8), although the more significant presence of clastic sediments
infers a likely braided river influence.
Environment: Continental, Fluvial
Thickness: 80 m
Fossils: See Echkar Fm.
Overlying Unit: *Aïn Toufayen Fm of the old terminology. Farak Fm of the
new terminology
Underlying Unit: *Ekisman Fm of the old terminology. The lower portion
of the Echkar Fm.
Remarks: See “Tégama Group”
--------------------
Unit: BOULAKOURA FORMATION
Epoch/Age/Author: Cenozoic (Oligocene)
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135
Original Author and/or Origin of the Name: Faure, 1966 (pages 349-350
& Fig.4 on page 27).
References: Faure, 1966; Gavaud, 1975 ; Fabre et al., 1983.
Synonymy: "Bella Kora" Fm
Equivalent(s): The oolite pebbles caught in a quaternary ferruginous cuirass
of the Zaouzaoua (Damergou) and BoulaKoura (Koutous) formations are rem-
nants of the erosion of the Ader Doutchi formation (Ct1);
Basin/Area/Apdx: Iullemmeden / South Damergou and Koutous / Appen-
dix H
Type/Reference/Stratotype Section: Upper portion of the Koutous Plateau,
Damergou (Fig. 7-24).
Lithology: Pebbles and blocks of continental origin cemented by iron oxide.
The blocks contain ferruginous oolites identical to the Dollé and Homodji for-
mations. This leads Faure (1966) to think that the ferruginous oolitic formation
extended above the Koutous before being dismantled and rearranged in the ter-
races of the Early Quaternary.
Environment: Continental
Thickness: 2 to 4 m
Fossils: none
Overlying Unit: Quaternary
Underlying Unit: Koutous Group
Maps, Cross-Sections, Pictures:
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136
Figure 7-24.The Boulakoura Formation on the upper portion of the
Koutous Plateau, Damergou (Faure, 1966, page 350).
--------------------
Unit: *BOUTOUTOU FORMATION
Epoch/Age/Author: Oligocene/Miocene?
Original Author and/or Origin of the Name: Boutoutou (Ader Doutchi),
Lapparent, 1904.
References: Lapparent, 1904; Garde, 1911; Lambert, 1937; Faure et al.,
1956.
Basin/Area: Iullemmeden / Ader Doutchi
Remarks: A. de Lapparent (1904) published an Eocene fauna from Niger
to which are added doubtful marine molluscs, coming from Boutoutou (Ader
Doutchi) (at about 14°N & 4°E), and considered as Oligocene or even Miocene.
Garde (1911), and then R. Lambert (1937) rejected this dubious indication which
never received confirmation.
--------------------
Unit: CHAD FORMATION
Epoch/Age/Author: Quaternary (Pleistocene; Carter, 1963) age for the sur-
face sediments in Niger and Nigeria. Ola-Buraimo et al. (2017) have determined
a Late Miocene to Quaternary (Pleistocene) age for the formation in the Bornu
Basin of northeastern Nigeria in drill holes. It is most likely the same in Niger.
Essentially, the Chad Formation represents all the deposits in Niger dated from
the Miocene to the Pleistocene eastward from Southeast Aïr and Damergou.
Chapter 7 Lexicon
137
Original Author and/or Origin of the Name: Raeburn et al., 1934.
References: Furon, 1935, 1956 ; Carter, 1963; Furon, 1964; Faure, 1966;
Greigert, 1966; Louis, 1970; Petters, 1981; Wright, 1986, pages 94-95; Ola-Bu-
raimo et al., 2017.
Synonymy: “Chad Series” according to Furon (1956). Greigert (1966) calls
it "Formations du Tchad". In his 1966 map of the Geology of Niger (appendix
A), he includes all the consolidated quaternary alluvium and deposits of Eastern
Niger (undifferentiated) in the Chad Formation (Fig. 7-25).
Basin/Sub-Basin/Apdx: ENRB / see note under "Remarks"/Appendix H.
Type/Reference/Stratotype Section: Bornu Basin of northeastern Nigeria
in drill holes. The best section in Niger would be close to Lake Chad.
Lithology: Furon (1956) states that in Nigeria, it is “Green and grey clays
and sands with basal feldspathic grits. The formation becomes sandier upwards.
Diatomaceous earth occasionally present”. According to Wright (1986), the
formation in Niger is composed of Quaternary sands and alluvium (clays and di-
atomite) that obscure older sediments over all the area occupied by the Eastern
Niger Rift basin. According to Adegoke et al. (2014), the formation in Nigeria,
just to the south, is made-up of a Quaternary sedimentary sequence of fine to
coarse-grained sand and clay. The sand is uncemented with angular and subangu-
lar quartz grains of variable colour from yellow, brown, and white to grey. At the
same time, the clay is massive and locally gritty in texture due to the presence of
angular to subangular quartz grains.
Environment: Fluvial, lacustrine.
Thickness: 600 m in Nigeria. If Louis (1970) is correct, it will reach a thick-
ness of 300 meters in the Ténéré (Niger). This same author provides a seismic
profile (Fig. 7-29) showing a thickness of 400 m for the assumed Chad Formation
east, north, and west of Lake Chad (Termit and N’Guel Edji grabens).
Fossils: Pleistocene mammals (Hippopotamus imaguncula Hopwood) found
at Gubio in Bornu (Nigeria) suggested a Pleistocene age for the surface beds
(Furon, 1956).
Overlying Unit: Either none or the Korama and/or Manga Formations.
Underlying Unit: Zaouzaoua Fm, Homodji Fm (Fig. 7-28), Dollé Fm, Sokor
Stratigraphic Lexicon
138
2 Fm.
Remarks: The sediments of the Chad formation were deposited over the
area of the former Lake Mega-Chad (Wright, 1986) (Fig. 7-26 and Fig. 7-27). The
extension of this large lake is confirmed by deposits of laminated diatomites, sev-
eral meters thick, which are found superimposed on the red sands of the old erg,
in the Ténéré, at Fachi, Bilma, Dibella, Agadem, Termit, etc. These diatomites,
dated to C14, range between -20,000 and -5,000 years old. They are, therefore, rel-
atively very recent. Petters (1981) extends the formation area to the Téfidet and
Tégama/Damergou areas, always within the watershed limits of the ENRB. Louis
(1970) also confirms the presence of the formation in the Ténéré region based on
seismic as well as in drill holes west of Lake Chad in Niger (Fig. 7-28 and Fig.
7-29).
Maps, Cross-Sections, Pictures:
Figure 7-25. Greigert's (1966) definition of the Chad Forma-
tion (see Appendix A-2).
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139
Figure 7-26. The Quaternary Lake Mega-Chad as drawn by Faure (1966) in
Furon (1964). The numbers written along its contour are dated from archeologi-
cal sites (-4,900 = 4,900 years ago).
Stratigraphic Lexicon
140
Figure 7-27. The Quaternary Lake Mega-Chad (in
pale blue), encompassing areas within Niger, Chad,
Cameroon, and Nigeria (Chad Basin), compared to
today’s Lake Chad (dark blue) (Source: Bouchette,
2010).
Figure 7-28. Section showing part of the deposits of
the Chad Formation in Niger and Nigeria (Source:
Petters, 1981).
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141
Figure 7-29. Seismic line and profile showing the assumed Chad Formation east,
north, and west of Lake Chad (Louis, 1970).
--------------------
Unit: CHEFFADÈNE FORMATION
Epoch/Age/Author: Upper Cretaceous (Lower Cenomanian)
Original Author and/or Origin of the Name: Faure, 1966; Takes its name
from the small village of Cheffadène
References: Furon, 1964; Faure, 1966; Fabre et al., 1983; Meister et al.,
1994; Konaté et al., 2019.
Synonymy: Grès de Cheffadène
Equivalent(s): Alanlara Formation ; Ezerza Formation; Ezerza-Cheffadène
Formation
Basin/Sub-Basin/Apdx: ENRB / Bilma / Appendix H
Type/Reference/Stratotype Section: A cliff (18 m) at 63 km S.-S.-E. of
Tiffa
Lithology: Ferruginous sandstone, beige, coarse levels with cross-bedded
stratifications, white clay. According to Furon (1964), the upper part contains
some marine levels. Compared to the Ezerza Fm, the Cheffadène Formation dis-
plays thick sandstone beds; the clays are above all kaolinitic, and the limestones
have practically disappeared (Fig. 7-30).
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142
Environment: Continental except for the very top layers, which contain
marine levels
Thickness: 200 m
Fossils: South-East of Cheffadène, limestone slabs superimposed and con-
taining fossils from the Lower Turonian.
Overlying Unit: Arentigué Fm
Underlying Unit: Tiffa Fm
Remarks: Top formation of the Continental Intercalaire in this area.
Maps, Cross-Sections, Pictures:
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143
Figure 7-30. The Cheffadène Fm. Section “A” is taken on the cliff, 5 km south
of Cheffadène. Section “B” was measured up to 22.5 km south of Cheffadène
(Faure, 1966, pages 244-245). Note that up to 30m of the formation is missing
above section “B”.
--------------------
Unit: CHIRFA FORMATION
Stratigraphic Lexicon
144
Epoch/Age/Author: Upper Ordovician (Hirnantian in the Djado Basin; Fig.
7-35). Cautleyan to Hirnantian in Algeria/Libya (Legrand, 2003b), Fig. 7-33.
Original Author and/or Origin of the Name: Legrand (1993); From the
Chirfa oasis, northern Niger.
References: Jacquemont et al., 1959; Jacqué, 1963; Croisile et al., 1963a,
1963b ; Beuf et al., 1971 ; Fabre et al., 1983; Mergl et al., 2000, 2001; Legrand,
1993, 2003, 2011; Denis et al., 2006; Denis et al., 2005, 2007a, 2007b, 2009,
2010; Buoncristiani et al., 2008; Hinsbergen et al., 2011; Shalbak, 2015; Hallet,
2002, 2016; Gutierrez-Marco et al., 2017.
Synonymy: *Felar-Felar Fm of Niger (Denis et al., 2006; Denis et al., 2005,
2007a, 2007b, 2009, 2010). Called «Felar-Felar complex» in older Nigerien pub-
lications. Legrand (1993) named the “Formation Argilo-Gréseuse de Felar-Felar”
of Algeria as “Formation Argilo-Gréseuse de Chirfa” in the Djado of Niger (Fig.
7-32).
Equivalent(s): Felar-Felar Fm of Algeria.
• As mentioned in Fabre et al. (1983) and Legrand (1993), the facies would be
the same as Beuf et al. (1971)'s Tamadjert formation in Algeria, which is the
same as Legrand et al. (1959)'s “Formation Argilo-Gréseuse de Felar-Felar”
of Algeria.
• Upper Member of the Mamuniyat Formation of Libya (compare Fig. 7-34 with
Fig. 7-35).
Basin/Apdx: Djado / Appendix G
Type/Reference/Stratotype Section: Its equivalent name of “Felar-Felar”
came from a location far from Niger on the western flank of the Amguid Spur
Ridge in Algeria. In Niger, it is located east of the Chirfa oasis.
Lithology: Ocre to green shales, often sandy intercalated with lenses of
sandstone beds, sometimes coarse with a cement, often carbonaceous (Legrand,
1993). The Chirfa Fm of Niger comprises lower and upper glacially related
complexes (Stadial 1 and 2), separated by non-glacial offshore sediments (Inter-
stadial). Each glacially related complex includes two to three distinct subglacial
shear zones (SSZ) (Fig. 7-35). The formation base is bounded by subglacial shear
zone 1 (SSZ 1), while the top is bounded by subglacial shear zone 5 (SSZ 5). The
formation is made up of muddy, laminated diamicton with abundant quartz grains
and sparse cobbles deforming underlying laminae (dropstones). These facies cor-
respond to glaciomarine conditions, during which clay suspended in seawater was
Chapter 7 Lexicon
145
deposited and clasts trapped in calved icebergs, or the base of an ice shelf was
released as dropstones. Subglacial shear zones (SSZ 2; Fig. 7-36) lie within the
infill of the lower paleovalley, at least a few meters above its base. A thin muddy
diamicton separates SSZ 2 from subglacial shear zone 3 (SSZ 3) in the lower
paleovalley infill. SSZ 3 is overlain by muddy diamicton and green-yellow silty
to fine-sandy clays and argillaceous sandstones with hummocky cross-stratifica-
tions, indicating an open marine storm-influenced, upper offshore depositional
environment. The thickest part of the Chirfa Formation consists of these facies
of a storm-influenced paleoenvironment, which filled the paleovalley. It indicates
a distal environment that rapidly developed in the Djado Basin in conjunction
with the major recession (interstadial) separating the two significant ice-sheet
advances. The Chirfa Fm indicates that the ice front retreated southwards by
1,000 km. The terminal part of the formation is a thin and muddy diamicton re-
lated to the deglaciation and is superimposed by post-glacial shale-dominated
distal marine offshore Silurian deposits. The transition from subglacial to off-
shore environments was thus very rapid and without the development of any
transitional sedimentary episode (i.e., fluvial, tidal or wave reworking). Struc-
tures corresponding to sandstone ridges are found within the Chirfa Fm (Fig.
7-37). Sandstone ridges are several meters high, about 10 m wide and hundreds
of meters long. Sandstone ridge sedimentological characteristics indicate that
sandstone ridges result from the scouring of the Chirfa Fm by sub-glacial, turbu-
lent, and pressurized meltwater; then, subglacial cavities were infilled with sand
derived from glacial abrasion. Sandstone ridge networks are comparable with
tunnel channels and document unusual drainage structures of the inner part of the
palaeo-ice sheet.
Environment: Glacial, periglacial, Glacio-marine, fluvial channel infill
(Fig. 7-31)
Thickness: ~80 m (Fig. 7-35).
Fossils: Graptolites (Glyptograptus (Glyptograptus ?) ojsuensis Koren &
Mikhailova; Normalograptus ojsuensis; Metabolograptus ojsuensis –