Prof. Osama E A Attia (original) (raw)
Uploads
Papers by Prof. Osama E A Attia
SEPM Journal of Sedimentary Research, 1995
Arabian Journal of Geosciences, 2015
Sedimentary Geology, 1997
At the top of Gebel Khoshera, the Middle Miocene gypsum is represented mainly by giant swallowtai... more At the top of Gebel Khoshera, the Middle Miocene gypsum is represented mainly by giant swallowtail twinned crystals, up to 2 meters in length, and Sabre-like crystals. Usually, the normal growth of these crystals forms thick flat lying crusts on the sediment floor. During submergence period, these crystals are usually aggregated on the bottom of the evaporite basin, in competition for free space, to form gypsum domes with variable size and dimensions. During emergence period of the subaqueous twinned gypsum, the crusts and domes are cracked into tepee polygonal structure indicating sabkhatization of the originally sub-aqueous gypsum crystals. Primary fluid inclusions data in selenite crystals are used to interpret depositional settings and parent water chemistry. The final melting temperature of ice in fluid inclusions falls between -6.2 °C and -8.6 °C. The existence of fluid inclusions with melting temperatures below -7.0%', indicate that the gypsum formed from simple evaporati...
The main constraints for sustainable agricultural development in Sinai are essentially the migrat... more The main constraints for sustainable agricultural development in Sinai are essentially the migration of sand dunes that occupy about 5000 Km2 of the coastal zone. This adversely affects the cultivated lands and the newlyreclaimed areas. The study area is located at the NW corner of Sinai Peninsula and it .is subjected to sand duneencroachment. Movement of sand dunes causes severe damage to the human settlements, roads, irrigation anddrainage constructions. Migration of aeolian sands results in the migration of longitudinal dunes at a rate of 2.25 m/y for those south of Bir El Abd and 13 m/y at Wadi El Gady. The rate of barchan dunes movement at Wadi El Massaged is 3.5 m/y. Also, a lateral movement of the segments of longitudinal dunes is recorded south of Bir El Abd and at Wadi El Gady. The morphodynamic model of the longitudinal dunes shows that deposition (percent) on the longitudinal dunes south of Bir El Abd is low relative to erosion. However, deposition on the longitudinal dun...
Environmental Monitoring and Assessment, 2013
Arabian Journal of Geosciences, 2013
Arabian Journal of Geosciences, 2012
The Upper Miocene (Messinian?) evaporite deposits in the Mediterranean coast of Egypt consist of ... more The Upper Miocene (Messinian?) evaporite deposits in the Mediterranean coast of Egypt consist of a reduced thickness of gypsum in comparison to other Mediterranean evaporites. The gypsum sequence consists of three layers; lower gypsified stromatolite, middle skeletal and grass-like gypsum and upper swallow-tail selenitic gypsum. Microscopic studies of primary fluid inclusions in the upper and lower layers are identified by their relation to growth surface of the crystals. Elongated primary fluid inclusions in gypsum occur along the (001) plane, where more equidimensional to elongate inclusions occur normal to the (í03) plane. Most fluid inclusions preserve a spike-like shape or negative crystal morphology. The tip of the spike points to the crystal growth direction. Primary fluid inclusions in the lower and upper layers are of a single phase (liquid) and two phases (liquid-solid) inclusions, arranged in arrays parallel to the growth zonation of the host crystals. The existence of su...
Continental sabkha is recorded in the extreme middle part of the southWestern Desert of Egypt rep... more Continental sabkha is recorded in the extreme middle
part of the southWestern Desert of Egypt representing one
of the most promising areas for sustainable development, especially
for agriculture. The geomorphologic units of the area
are formed under the influence of structural, lithological, and/
or climatic controls. These units include pediplain, depressions,
mass-wasted blocks, residual hills, drainage lines, and
aeolian landforms. The effective deflation process is reinforced
by the lack of protective vegetation cover and the susceptibility
of weakly consolidated rocks to wind removal. Different
rock units covering the area range in age from Early
Cretaceous to Quaternary. Quaternary deposits include playa/
sabkha deposits where the continental sabkha is divided into
four zones A, B, C, and D. Underground waters coming from
the north and east were progressively enriched in solute by
interaction with the surrounding sedimentary and igneous
rocks. Most of the evaporite minerals grow displacively as a
result of evaporative pumping. Mineralogically, the continental
sabkha salt complex includes gypsum, natroalunite,
tamarugite, bloedite, eugsterite, nitratine, halite, and D’ansite.
Some of the major and trace elements (SiO2, Al2O3, Fe2O3,
MgO, CaO, Na2O, K2O, as well as Rb, Ba, Zr, Sr, Y, V, and
Zn) were measured. The correlation and enrichment of these
major and trace elements indicate the origin of the salt complex
in the sabkha.
Middle Miocene gypsum on the eastern coast of the Gulf of Suez, west-central Sinai, Includes mass... more Middle Miocene gypsum on the eastern coast of the Gulf of Suez, west-central Sinai, Includes massive and bedded selenite. These selenites are interpreted as primary deposits because their textures and fabrics such as vertically oriented crystals
The Holocene evaporite sequence in the Ras Shukeir area conformably overlies marine shell banks a... more The Holocene evaporite sequence in the Ras Shukeir area conformably overlies marine shell banks and cross-bedded
to graded-bedded beach sands and gravels. The evaporite sequence is represented by gypsum-anhydrite layers that are
interbedded with mudstone layers. Field and petrographic investigations of the evaporite deposits revealed two facies types,
laminated evaporite facies (primary) and nodular to enterolithic anhydrite facies (diagenetic). The laminated evaporite
facies is subdivided, from the bottom to top, into regular laminated evaporite, chevron gypsum-algal micrite laminations
and wavy algal laminated evaporite. Based on their textures and fabrics, the regular and wavy laminated evaporite facies
are interpreted as primary deposits in a coastal lagoon and salina environment. The chevron gypsum-algal micrite facies
formed by the growth of chevron gypsum at the sediment-water interface within a shallow subtidal lagoonal environment
that was characterized by extensive benthic algal mats. The nodular to enterolithic anhydrite facies is secondary and formed
diagenetically within a siliciclastic supratidal sediment.
Some of the laminated evaporite facies have been diagenetically altered in a supratidal sabkha environment as evidenced
by the following: (1) the partial formation of nodular evaporite instead of laminated evaporite; (2) disruption of gypsum
laminations by plant roots and rootlets as well as by precipitation of lenticular gypsum on the root wall; and (3) partial
dissolution of halite laminae and the formation of wavy anhydrite laminae.
Consequently, the Holocene evaporites in the Ras Shukeir area were deposited in a shallow semi-closed to closed basin
that was separated from the Gulf of Suez trough. Changing sea level led to progradation of the evaporite facies from
subtidal to intertidal lagoon and salina to a supratidal sabkha.
SEPM Journal of Sedimentary Research, 1995
Arabian Journal of Geosciences, 2015
Sedimentary Geology, 1997
At the top of Gebel Khoshera, the Middle Miocene gypsum is represented mainly by giant swallowtai... more At the top of Gebel Khoshera, the Middle Miocene gypsum is represented mainly by giant swallowtail twinned crystals, up to 2 meters in length, and Sabre-like crystals. Usually, the normal growth of these crystals forms thick flat lying crusts on the sediment floor. During submergence period, these crystals are usually aggregated on the bottom of the evaporite basin, in competition for free space, to form gypsum domes with variable size and dimensions. During emergence period of the subaqueous twinned gypsum, the crusts and domes are cracked into tepee polygonal structure indicating sabkhatization of the originally sub-aqueous gypsum crystals. Primary fluid inclusions data in selenite crystals are used to interpret depositional settings and parent water chemistry. The final melting temperature of ice in fluid inclusions falls between -6.2 °C and -8.6 °C. The existence of fluid inclusions with melting temperatures below -7.0%', indicate that the gypsum formed from simple evaporati...
The main constraints for sustainable agricultural development in Sinai are essentially the migrat... more The main constraints for sustainable agricultural development in Sinai are essentially the migration of sand dunes that occupy about 5000 Km2 of the coastal zone. This adversely affects the cultivated lands and the newlyreclaimed areas. The study area is located at the NW corner of Sinai Peninsula and it .is subjected to sand duneencroachment. Movement of sand dunes causes severe damage to the human settlements, roads, irrigation anddrainage constructions. Migration of aeolian sands results in the migration of longitudinal dunes at a rate of 2.25 m/y for those south of Bir El Abd and 13 m/y at Wadi El Gady. The rate of barchan dunes movement at Wadi El Massaged is 3.5 m/y. Also, a lateral movement of the segments of longitudinal dunes is recorded south of Bir El Abd and at Wadi El Gady. The morphodynamic model of the longitudinal dunes shows that deposition (percent) on the longitudinal dunes south of Bir El Abd is low relative to erosion. However, deposition on the longitudinal dun...
Environmental Monitoring and Assessment, 2013
Arabian Journal of Geosciences, 2013
Arabian Journal of Geosciences, 2012
The Upper Miocene (Messinian?) evaporite deposits in the Mediterranean coast of Egypt consist of ... more The Upper Miocene (Messinian?) evaporite deposits in the Mediterranean coast of Egypt consist of a reduced thickness of gypsum in comparison to other Mediterranean evaporites. The gypsum sequence consists of three layers; lower gypsified stromatolite, middle skeletal and grass-like gypsum and upper swallow-tail selenitic gypsum. Microscopic studies of primary fluid inclusions in the upper and lower layers are identified by their relation to growth surface of the crystals. Elongated primary fluid inclusions in gypsum occur along the (001) plane, where more equidimensional to elongate inclusions occur normal to the (í03) plane. Most fluid inclusions preserve a spike-like shape or negative crystal morphology. The tip of the spike points to the crystal growth direction. Primary fluid inclusions in the lower and upper layers are of a single phase (liquid) and two phases (liquid-solid) inclusions, arranged in arrays parallel to the growth zonation of the host crystals. The existence of su...
Continental sabkha is recorded in the extreme middle part of the southWestern Desert of Egypt rep... more Continental sabkha is recorded in the extreme middle
part of the southWestern Desert of Egypt representing one
of the most promising areas for sustainable development, especially
for agriculture. The geomorphologic units of the area
are formed under the influence of structural, lithological, and/
or climatic controls. These units include pediplain, depressions,
mass-wasted blocks, residual hills, drainage lines, and
aeolian landforms. The effective deflation process is reinforced
by the lack of protective vegetation cover and the susceptibility
of weakly consolidated rocks to wind removal. Different
rock units covering the area range in age from Early
Cretaceous to Quaternary. Quaternary deposits include playa/
sabkha deposits where the continental sabkha is divided into
four zones A, B, C, and D. Underground waters coming from
the north and east were progressively enriched in solute by
interaction with the surrounding sedimentary and igneous
rocks. Most of the evaporite minerals grow displacively as a
result of evaporative pumping. Mineralogically, the continental
sabkha salt complex includes gypsum, natroalunite,
tamarugite, bloedite, eugsterite, nitratine, halite, and D’ansite.
Some of the major and trace elements (SiO2, Al2O3, Fe2O3,
MgO, CaO, Na2O, K2O, as well as Rb, Ba, Zr, Sr, Y, V, and
Zn) were measured. The correlation and enrichment of these
major and trace elements indicate the origin of the salt complex
in the sabkha.
Middle Miocene gypsum on the eastern coast of the Gulf of Suez, west-central Sinai, Includes mass... more Middle Miocene gypsum on the eastern coast of the Gulf of Suez, west-central Sinai, Includes massive and bedded selenite. These selenites are interpreted as primary deposits because their textures and fabrics such as vertically oriented crystals
The Holocene evaporite sequence in the Ras Shukeir area conformably overlies marine shell banks a... more The Holocene evaporite sequence in the Ras Shukeir area conformably overlies marine shell banks and cross-bedded
to graded-bedded beach sands and gravels. The evaporite sequence is represented by gypsum-anhydrite layers that are
interbedded with mudstone layers. Field and petrographic investigations of the evaporite deposits revealed two facies types,
laminated evaporite facies (primary) and nodular to enterolithic anhydrite facies (diagenetic). The laminated evaporite
facies is subdivided, from the bottom to top, into regular laminated evaporite, chevron gypsum-algal micrite laminations
and wavy algal laminated evaporite. Based on their textures and fabrics, the regular and wavy laminated evaporite facies
are interpreted as primary deposits in a coastal lagoon and salina environment. The chevron gypsum-algal micrite facies
formed by the growth of chevron gypsum at the sediment-water interface within a shallow subtidal lagoonal environment
that was characterized by extensive benthic algal mats. The nodular to enterolithic anhydrite facies is secondary and formed
diagenetically within a siliciclastic supratidal sediment.
Some of the laminated evaporite facies have been diagenetically altered in a supratidal sabkha environment as evidenced
by the following: (1) the partial formation of nodular evaporite instead of laminated evaporite; (2) disruption of gypsum
laminations by plant roots and rootlets as well as by precipitation of lenticular gypsum on the root wall; and (3) partial
dissolution of halite laminae and the formation of wavy anhydrite laminae.
Consequently, the Holocene evaporites in the Ras Shukeir area were deposited in a shallow semi-closed to closed basin
that was separated from the Gulf of Suez trough. Changing sea level led to progradation of the evaporite facies from
subtidal to intertidal lagoon and salina to a supratidal sabkha.