الفهرس 
AcknowledgmentOnly 14 pages are availabe for public view
 |  | from | 126 |  |  |
| | | from | 126 | | |
Abstract
SUMMRY AND CONCLUSION
82
SUMMARY AND CONCLUSIONS
Previous studies on the calcareous rocks of the north-eastern desert
showed the need for further sedimentological studies of the Middle
Eocene rocks, especially after the growing interest by the state to search
for the necessary raw materials for cement industry.
The study area extends on shore of the Western side of Gulf of Suez
between Latitudes 29° 40’ and 30° 00 N, and Longitude 32° 00’ and 32°
30’ E, covering an area of about 800 sq km. forming a part of the great
Eocene plateau of the Northern Eastern Desert of Egypt.
It consists of a series of elongated and widely- spaced North-West and
East-West trending topographic highs and lows, which are mainly
structurally controlled. The topographic highs, are also structural highs
and mostly made up of hard Middle Eocene limestone beds, while the
topographic lows, are also of structural origin and are occupied by soft
rocks ranging in age from Late Eocene to Recent.
Both the pre-rift sediments (represented by the Tertiary rock units of
Middle and Late Eocene) and syn-rift sediments (represented by the
Oligocene and Miocene deposits) are occurred in the study area. The
current study is interested in the stratigraphy of the Middle Eocene rocks,
as well as the depositional environments that prevailed during their
deposition in the study area. Also, thin study throws light on the validity
of these raw materials for cement industry.
To achieve this purpose, two major stratigraphic columnar sections were
measured and sampled in detail to clarify the facies characteristics, cyclic
pattern of sedimentation and depositional changes of the studied
sequence. About 170 samples were collected in order to cover most of the
middle Eocene carbonate varieties encountered in the investigate area at
SUMMRY AND CONCLUSION
83
both Gabel Kahylia along the western bank of wadi Hagul Gabel
Okheider along Cairo-Sukhna road.
Lithostratigraphicaly; the Middle Eocene limestone (of Lutetian age)
exposures in the study area are subdivided into two rock units from base
to top are:
1- Minia Formation: It is recorded only in the southwestern part of the
studied area at Gabel Okheider (about 40m. thick), and unconformable
overlain by Mokattam Formation. It is composed of grayish white,
bedded to massive limestone and marly limestone, with thin intercalations
of dolomitic and sandy limestone intercalations. Planner cross bedded
limestone is also recorded in the middle parts of this formation. Very
dense bioturbation horizons are also present. In the investigated area, the
Minia Formation is of Middle Eocene (Lutetian) age.
2- Mokattam Formation: It is widely distributed in the study area at
both Gabel Okheider (reaches 65m.), and Gabel Kahylia (about 120m.
thick). In the study area, it is mainly composed of yellowish with, thinly
to thick bedded, hard limestone rich in fossils (mostly nummulitic). Thin
beds of dolomitic limestone, marly limestone and bioturbated horizons
are also present. In the investigated area, the Mokattam Formation is of
Middle Eocene (Late Lutetian) age.
Relationships between the studied rock units are noticed and the contact
between them is recognized.
For detailed sedimentological investigation, about 107 microscopic thin
sections representing the studied Middle Eocene sequence are described
and an adequate petrographic classifications is given using Dunham
classification (1962), which is modified by Embery and Klovan’s (1971).
SUMMRY AND CONCLUSION
84
Careful analyses of the studied microfacies lead to the delineation of six
main type of limestone depositional facies comprising 16 microfacies
types. They are: Packstone - to gainstone (30%), grainstone (28%),
packstone (22.4%), wackestone- to packstone (15%), wackestone (2.8%)
and lime -mud to wackestone (1.8%).
According to the diversity ratio of the allochems components existing in
each facies together with field studies, the studied Middle Eocene
carbonate sequence of the Minia Formation and the overlying Mokattam
Formation have been deposited on an isolated shallow marine platform
carbonate bank, with high carbonate productivity. This is evidenced by
the abundance and diversity of shallow marine fauna, frequent benthic
with total absence of palntics; extensive and diverse of carbonate facies
types; dominant of high -energy fabric and well developed large -scale
tangential cross-bedding.
Three main carbonate facies reflecting sedimentary environments have
been recognized: Nummulites bank facies, carbonate bar facies and
restricted lagoon facies are proposed.
1- Nummulites bank facies.
This facies constitutes the main part of the Mokattam Formation
succession at both the Kahylia and Okheider sections. In the northeastern
part of the studied area, at Kahylia section, it forms a pronounced
shallowing upward cycles with a noticeable variation in thickness (10-
27m thick) and alternated vertically with carbonate bar facies. It is of
minor importance in the Minia Formation succession at Okheider section,
where it collectively measures 7m thick.
SUMMRY AND CONCLUSION
85
It is composed of moderately hard bedded, massive nummulitic limestone
with benthic foraminiferal shells. Also it includes several microfacies
associations such as, nummulitic bioclastic wackestone to packstone,
mollusca bioclastic packstone, echinodermal bioclastic packstone,
benthonic foraminiferal grainstone and peloidal packstone to grainstone.
The effect of bioturbation must also be considered. This facies has been
developed in well-aerated shallow water, where swells represented
submerged paleohigh initiated on the Middle Eocene nummulites banks.
2- Carbonate bar facies.
This facies is common in the Mokattam Formation succession, which was
exposed in the northeastern part of the study area at Kahylia section and
alternated with the nummulites bank facies. It is represented by several
successive horizons, with marked variation in thickness (2 - 12m. thick).
It is also recorded in the Minia Formation sequence exposed in the
southwestern part of the area at Okheider section and is alternated with
lagoon facies and is represented by few horizons (8 - 12m thick). It is
composed of thick bedded limestone, generally of medium to coarse -
skeletal packstone and grainstone texture. It includes several microfacies
associations such as echinodermal bioclastic grainstone and foraminiferal
bioclastic packstone to grainstone. It is characterized by well rounded
allochems and crudely large-scale cross-bedding of tangential and trough
types. The cross-bedded packstone normally flanks and caps of the small
patch reefs. Occasionally it terminates with slightly dolomitize horizons
and rare bioturbation effect.
The densely fossiliferous tangential cross-bedded packstone to grainstone
designate large - scale tidal bars (tide - dominated carbonate bars) that
formed in the upper shallow subtidal regime.
SUMMRY AND CONCLUSION
86
3- Restricted lagoon facies.
The lagoon facies represent the main lithologic character of the Minia
Formation succession in the southwestern part of the area at Okheider
section, where it collectively measures 54m thick and is alternated
vertically with the carbonate bar facies. It is of minor importance in the
Mokattam Formation succession in each of the Okheider (about 20m
thick) and the Kahylia (about 4m thick) sections.
It is composed of dark grey to grayish white thick bedded, hard
fossiliferous limestone, mostly crowded with mollusca, miliolids,
echinodermal fragments, peloids and benthonic foraminifera and displays
slight to moderate bioturbation. It includes a wide variety of microfacies,
which is represented by, echinodermal bioclastic packstone, peloidal
bioclastic packstone – to grainstone, mollusca lime - mud to wackestone,
foraminiferal packstone microfacies. The lithologic and textural
characters of this facies suggest sedimentation on marine carbonate
platform with a slightly protected lagoon located behind the bank margin
in tropical, warm and shallow subtidal setting.
The depositional nature of the studied sedimentary facies of the both
Minia and Mokattam Formations developed during the Middle Eocene at
both the Kahylia and Okheider sections points to slight change in the
bathymetry of the sea due to sea – level oscillations during deposition
related to marine sea – level changes of the Tethyan Sea. Evidence of
these fluctuations is indicated by the cyclic nature of these facies and
their geographic migration at the northeastern (Kahylia) and southwestern
(Okheider), parts of the study area.
In the present work, an attempt is made to throw light on the common
diagenetic phenomena and their paragenesis. The diagenetic history of the
studied Middle Eocene carbonate sequence is discussed with special
SUMMRY AND CONCLUSION
87
reference to compaction, cementation, recrystalization, silicification,
ferrugination and dolomitization.
There is growing interest in searching for raw materials, which are
necessary for cement industry, especially after the construction of many
factories along Cairo -Suez and Cairo -Ain Sukhna roads. A Preliminary
study to determine the suitability of limestone as an industrial stone in the
study area has been carried out.
Samples were collected from the chosen exposures of the limestone
sequence representing the apparent variations covering the exposed
Middle Eocene limestone raw materials in the study area. It
approximately measures 109 meters thick at the eastern scarp of Gabal
Kahylia and reaches about 134 meters thick at Gabal Okheider along
Cairo -Sukhna road. These samples were subjected to complete chemical
analysis using X-ray fluorescence technique at Lafarge Cement
Company, Egypt. The chemical analysis results of all samples at both
Kahylia and Okheider sections have been discussed in some detail.
The average chemical analysis of the limestone raw materials was input
into the mix- design software program of Lafarge cement, Egypt,
company, using the results of previously analyses of clays by Lafarge
Cement Company to obtain the ideal cement quality parameters.
The average percentages of the most objectionable components such as
MgO are slightly higher (2.12%) in Okheider samples than Kahylia
samples (0.99%). Also, the average percentages of the undesirable
elements in cement industry such as SO3 and CL are slightly higher in
Okheider samples (SO3 is 0.11%) and (CL is 0.26%) than Kahylia
samples (SO3 is 0.01%), and (CL is 0.10). Also, petrographic studies
SUMMRY AND CONCLUSION
88
revealed that the Okheider limestone is highly dolomitized than the
Kahylia limestone.
Accordingly, the Kahylia limestone is more suitable for cement industry
than those of Okheider. Also it lies few kilometers north of the Lafarge
cement Egypt factory. Thus, the cost of transportation of the main raw
materials (limestone), will be lower (22.9 EP/Ton, obtained mix design
program), than those of Okheider limestone.