Quaternary Sedimentary Rocks of Ethiopia
Quaternary Sedimentary Rocks of Ethiopia
Quaternary Sedimentary Rocks of Ethiopia
Palaeoclimate
Quaternary Geology
• Distribution in the country
• Mode of Occurrence
• Stratigraphy of the quaternary
• Palaeo-environment of the quaternary
• Important mineral deposits
• Concluding remarks a (discussion)
The Quaternary of Ethiopia
In this chapter we will be able to:
• understand Geological formations and processes
that controlled the geology during the past 2
million years:
• learn Palaeo-climatic conditions as recorded by
geological formation
and
• visualize The significance of Quaternary in
Human evolution and civilization
Quaternary period: introduction to geological time
scale
Quaternary Geology in the context of Geological
development of Ethiopia
( a summary)
Quaternary Geology of Ethiopia
Distribution and main components
Quaternary period is the most
active period where geology is
in the making.
Sedimentary rocks:
comprise of
consolidated volcaniclstic sediments interbeded with
volcanic rocks in the rift to
sediments deposited as evaporates in lacks, currently
filling the lowlands and
the top soil (unconsolidated to semi consolidated ones).
Quaternary geology of Ethiopia
distribution……
• Quaternary sediments of
different genetic types
fluvial,
lacustrine,
marine,
Aeolian,
eluvia
are wide spread all over
Ethiopia.
•
Quaternary sediments…..
• In the Rift valley, the
Sediments are mostly
of lacustrine origin and
interbedded with
Quaternary volcanics at
the lakes district.
• The lacustrine beds are
mostly re-deposited
volcanic sands, tuff
with calcareous
material and diatomite.
Among well studies Quaternary
sediments in Ethiopia…
1. Hadar Formation
• The Hadar Fomration was defined along the
tributaries of Awash River (Central Afar).
The sediments are characterized by clays,
siltstones, sandstones and conglomerates of
lacustrine, deltiac and fluviatile facies. Several
tuff horizons and one fissural basalt flow are
interbedded in the formation.
Well studied Quaternary sediments….
2. Omo River Basin Sediments
• These sediments are Palio-pleistocene
continental deposits which cover most parts of
the Kibish, Omo and Usno Branches of the
Turkana Rift.
• four formations: Mursi, Nkalabong, Usno and
Shungura are described.
• They form the Omo Group sediments. The
sediments of the Mursi Formation lie
unconformably on a tilted pre-rift rhyolite
Among Well studied sediments….
Afar, Dallol and surrounding areas
• Pleistocene-Holocene parts of Afar is represented
by terraces of salts, sand, gravel, gypsiferous and
fossiliferous limestone of lacustrine origin which
are found in the Lakes Aferera and Assali area.
• Pleistocene Marine existed only in the northern
part of the Afar Depression and the Red Sea
Coast.
• In the Northern Afar salt formations of Dallol also
belong to the Quaternary.
Details of Dallol stratigraphy
Quaternary sediments, their linkage with tectonics in
Rift valley…..
• at the beginning of the
Quaternary an ancestral
lake was almost certainly
continuous with Abaya-
Chamo Lakes to the south
and the Awash basin to
the north
• it was separated by late
Pleistocene tectonic
movements ( including
• Rift parallel, axial faulting
• Across rift, transverse
faults
Quaternary Fluvial deposits
• Along the Sudan
border large area is
covered by
undifferentiated fluvial
outwash
• Varied thickness,
• Comprised of detrital
sediments
(conglomerate, silt-
sand mud dominant).
Palaeo-environment of the quaternary
Introduction:
• Geological formations are powerful signature of
Palaeo-environment.
• The Quaternary of Ethiopia is less disturbed, non
metamorphosed sequence of volcanic and
sedimentary rocks.
• They bear some remains/ fossil/ of human which
can be dated either directly or indirectly and
indicative of some plaeo-environment as well
• Variation in sediment types (lacustrine deposits,
evaporates, salt and detrital sediments) together
with volcanic succession are excellent record
holders and dictators of the palaeo-environment.
Quaternary Palaeo-environment (lithology
record )…..
• The Geological record of Quaternary shows fast
fluctuating Palaeo-environmental conditions
including: wet, humid, dray, and arid conditions:
• For example:
• Diatomite deposit: Wet, Fresh water lake
environment suitable for tropical vegetation
cover and habitats of mankind
• Evaporates: indicative of aridity, desert condition,
saline water, not suitable for vegetation and
hostile for habitat (extinction, migration)
Quaternary Palaeo-environment…
Lithology indication and control
Examples :
Volcanism: (Lava flows, ash fall, pyroclasti falls etc in the
Quaternary):
=> Environmental degradation, climatic pollution through
ejection of toxic gases, such as sulfur, volcanic brine
(acid) and ash.
• Recipe for catastrophe, extinction of fauna and flora.
Quaternary Palaeo-environment… cont
(Tectonic impact)
Tectonic induced Palaeo-environmatal changes:
Uplift and subsidence of the blocks (Rifting
related)
Formation and destruction of water body,
change in depth of water body, change in
salinity of water body and etc.
=> local and regional palaeo-enviornment
Quaternary climates and Human origin
• East African palaeo-environments are highly
variable in that:- they are,
• marked by extreme fluctuations in moisture
availability,
-> has far-reaching implications for the origin,
evolution and dispersal of Homo sapiens in
and beyond the region.
Quaternary Climate and Human………
• The first members of the
Australopithecus genus, attributed
to Australopithecus anamensis
(bipedalist), appeared around four
million years ago from Omo Vlley
(Leakey et al., 1995).
• They are followed by
Australopithecus Afarensis, which
is very well known from the fossil
record and includes the
remarkably complete ‘Lucy’
specimen (3.2. my, From Hadar
formation of Afar).
Quaternary Climate and Human………
• The first fossil evidence of Homo comes from
1.8 to 1.9 million year old EARS deposits.
• Homo habilis was then followed by the
appearance of Homo erectus, which is
associated with sweeping changes in brain
size, life history, and body size and shape.
• Post-cranially, Homo erectus is very similar to
anatomically modern humans.
Quaternary Climate and Human………
the most important episode in hominin evolution
occurred in East Africa around 1.8-1.9 Ma.
• It is the time when hominin diversity reached its
highest level with the appearance of the robust
Paranthropus species, as well as the first
specimens attributed to genus Homo.
• it was also the period when episodic migration of
hominins out of the Rift Valley and into Eurasia.
Quaternary Climate and Human………
• Point of discussion
Discuss How?
Locally ( in Ethiopia)
Discuss globally
Economic Minerals associated with
Quaternary sedimentary rocks
Concluding comments:
• How important do you think the Quaternary
and why?
• Descussion