الفهرس 
GEOLOGY Of Kharga And Dakhla Oasps
nubia formationOnly 14 pages are availabe for public view
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Abstract
The presc;nt thesis dt-s.ls with thEi study of th.:: laktt
deposits (Pleistocene-Recent) in the New Valley area, from
their geological, ~ineralogical and geochemical points of
view, Eight locations were chosen for this study. These
area Mahariqo, Genah, Bolaqll,· Baris, El-Max, (Khe.rga
Oasis), Kh~rga-Dakhla road, El-Zayat and Mawhoob (Dakhla
Oasis).
The distribution of lake deposits bot4 vertically and
horizontally, was studied in the field by measur~g 5eVeral
sections. Their characteristic sedimentological and morphological
features were studied and described. The lake
deposits ~re generally situated in the low-lying areas and
show a well-marked stratification, Different sedimentnry
structures are observed within these deposits (e.g. graded
bedding, c.rcss bedding, color banding, small scale faulting
and unconfc~~ty), These deposits lack fossils ~xcept for
some plant reooins which are collliUon in them.
Lake deposita exhibit two main morphological forme:
The first one, which is the most common is their extensive
foriL, which is called ”flat plaina”· The second, is in
the forxu of small l<Ollgitudill.a.l ridgQa o~urring in groups
oriented in a NNVi-SSE direction. These forme are called
”hU.lL.Il.ocks”,GrR.in size R.nalysi_s o:f:’ lake deposits rev•’il>.ls that
these deposits range in size be+;Vleen medium .sc nd. and me.J 1 ”’”” s • It
They are well to moderately sorted, nearly sy~etrical
skewed and range f’rom platykurtic to lepto:kurtic characters.
The relation~hips between grain size parameters
indicate that these deposits were deposited in an aeolianbeach
environment (marginal). Discriminant functions of
Sahu show that they were deposited in a shallow marginal
environments of deposition (e.g. J.alres, J?onds, lagoons •••
etc.) with a significant role of t:uro:i.dit~- cnr~”•m+,<;, At
soms stages of deposition, aeolian J?rocesses prevailed
and the sediments were carried and deposited in these
shall. ow environments giving rise to a small scale, deltaic-;-·
like deposits. The aeolian processes prevailed in dry
seasons. The ”CAll” pattern of Pa.ssega indicates that the
finer materials were deposited from uniform suBoenslon and
with a clear effect of turbidity currents •
.Peti’ological studies indicate that these d~pos5.t9
consist mainly of different varieties of sands and si\~s
(e.g. sand, mvi sand, si l:t~ sand, sandy sli-t ... etc.).
Tho. sands :Lncreai!!IB and concentrate at the centre of o.epression,
while 5 j It increase northward and westward. The
carbonate content increases in the same ~nner as the S!lt
content. The different varieties of heavy and light m:l_neral
assembla-ge t;D.Count.red .in the lake deposi te. ar2 ’-’”” r,yforiLation :ad th~; iD.d.ividual W . .n~;rals haV~; the lia!Le characteristics.
Based on their petrological. characters th” lake
deposits are thought to have been tru.usported and deposited
in a fresh-water tmviron.ment (as indicated :fron. plant
ren.ains) and originated from the nearby formations. These
deposits became more sandy near the Nubian sandstone fornation
(at the centre) alld more si t”t~ and calcareous near
the calcareous and the s i It”~ formations (northwa.rd 8ll.d
westwa.rd) •
Study of the morphological features of the clay minerals,
using the electron microscope showed that kaolinite
is found as moderately well-crystallized pseudobexagonal
flake-shaged particles, six-sided, stick-like and aggregates
with different shades. Montmorillonite is represented
by irregular, n:.ore or less ”quidimensional thin flakes as
well as by irregular flake-shaped aggregates. Illite is
represente~ by swall poorly defined, platy particles, occasionalJ.
y w’c +:h angular borders and colll.tr.only grouped .’.n irregular
aggregates without any distinct outli.nes. Some
Llontoorillonite-illite JLixod layer clay is re:;>resented in
the electron micrograph by spherulitic clusters and thin
platy particles of undefined habits.
X-ray diffraction analysis of bulk samples and oriented
samples (untreated, glycolated and heated samples) of lake quartz, calcite, dolomite and gypsum.
Infrared analysis showed that the lake d~positF consist
essentially of the main chemical groups! OH, Si-O~·b..i.,
Si-0, and c-o whic-h represent kaolinite, illite, quartz
and carbonate minerals.
Chemical analysis of the lake deposits shows that they
consist essentially of Ri02 , A.l2o7 , calcareous and organic
materials. The silica is present f’B qua-.:-tz and e .. « c. ~:1.-0
group within clttr structures (as d.eteeted. .from X-ra’Y e-c1
infrared l!.nalysee). A.lwnina occurs essentially in the
form of clay minerals (kaolinite, illite, ruontmorillonite).
The calcareous materials (CaO, MgO) occur in the form of
caleite and dolomite. The organic matter is mainly due to
plant remains present in the lake deposits. The san8.:7 lake
deposits are generally poor in calcareous mate~ials ?nd the
opposite is true in the case of the si IT~ d<erns;_+;s. S<”’ID<?
salty materials ware detected in theBe d91}0s5r:o an rbf’0F!Bd
from halite (NaCl) occurrence.
The geochemical relatiouships (in the light of the
results of Degens, 1965), indicate that the lake deposits
are more enriched with the average shale, which con+-ai.ns
more illite than kaolinite and montmorillonite.