The Eocene rocks in the Shabrawet area (north Eastern Desert, Egypt) have been subdivided into th... more The Eocene rocks in the Shabrawet area (north Eastern Desert, Egypt) have been subdivided into three formations that are from base to top: the Minia Formation (Late Ypresian), the Sannor Formation (Bartonian) and the Maadi Formation (Priabonian). These three formations are disconformable with each other. In addition, the whole Eocene succession is disconformably overlain by the Oligocene rocks and is underlain by the Cretaceous rocks with an angular unconformity surface. The Sannor Formation has been subdivided into three informal units: lower, middle and upper units. The overall sedimentary nature of the Eocene rocks in the study area is dominated by carbonate-siliciclastic rocks. Detailed microfacies analysis has enabled discrimination of 22 sedimentary microfacies types, which are grouped into six facies associations, equivalent to six depositional environments sited on an inner ramp setting. These depositional environments are floodplain-dominated fluvial, lacustrine/palustrine, tidal flat, restricted inner lagoon, shoal bar and outer lagoon with open circulation. A suitable depositional model of the Eocene rocks is given. In addition, four discrete benthonic foraminiferal biozones were reported in the Eocene succession, arranged from base to top: (1) Alveolina frumentiformis biozone (Late Ypresian), (2) Orthoplecta clavata biozone (Bartonian), (3) Dictyoconus aegyptiensis biozone (Bartonian) and (4) Discorbis vesicularis biozone (Priabonian). In terms of sequence stratigraphy, the studied Eocene succession exhibits three superimposed depositional sequences, each of which shows retrogradational (transgressive systems tract) and aggradational (highstand systems tract) to progradational (lowstand systems tract) packages of facies. The retrogradational package displays a predominance of outer lagoon and restricted inner lagoon facies. The aggradational package shows an increase of shoal bar and tidal flat facies, whereas the progradational package marks the occurrence of continental facies (floodplaindominated fluvial and lacustrine deposits). In this study, it is noticed that there are lateral and vertical changes in the depositional environments of the Eocene rocks, between shallow marine and continental environments. Also, many unconformities have been recorded in between and within these rock units. Such remarks indicate that the Eocene rocks were deposited within a highly tectonically active area that was consequently influenced by the transgression and regression of the Neo-Tethys. Such tectonic activity could be related to the Syrian Arc System that was renewed and enlarged several times during the Late Cretaceous up to the Neogene in the eastern and southeastern Mediterranean domain.
Lower Paleozoic rocks are exposed in various regions of Egypt (south central Sinai, north Eastern... more Lower Paleozoic rocks are exposed in various regions of Egypt (south central Sinai, north Eastern Desert and southwest Western Desert), in addition to occurring in the subsurface such as north Western Desert and the Gulf of Suez. The Lower Paleozoic rocks in Egypt include surface and subsurface rock units of formational status. The surface rock units are the Taba, Araba and Naqus formations. The subsurface rock units include the Shifa, Kohla and Basur formations. The Infracambrian Taba Formation has been discovered recently in the outcrops of the southeast central Sinai in the Taba-Ras El-Naqab area. It is missing and/or not recognized in the subsurface. The Taba Formation consists mainly of reddish brown, unfossiliferous gravelly fine-to medium-grained kaolinitic sandstones and subordinate horizons of paleosols. The Cambrian Araba Formation and its subsurface equivalent (the Shifa Formation) are essentially composed of reddish brown, fine-grained laminated sandstone and siltstone with abundant Skolithos and Cruziana sp. In contrast, the OrdovicianeSilurian Naqus Formation and its subsurface equivalents (the Kohla Formation and Basur Formation) are mainly composed of white, unfossiliferous, cross-bedded, medium-to coarse-grained sandstones with haphazardly distributed pebbles and cobbles. Sedimentological analysis indicates that the Araba Formation and its subsurface equivalent were deposited in a marginal-marine environment, whereas the Naqus Formation and its subsurface equivalents were laid down in a fluvio-glacial environment. Integrated stratigraphic and sedimentological studies of the Lower Paleozoic rocks permit reconstruction of the paleogeography of Egypt at that time. Egypt has been largely controlled since the Cambrian by the pre-existing structural framework of the pre-Phanerozoic basement rocks inherited from the Late Proterozoic Pan-African event. Additionally, sedimentation processes were controlled during Cambro-Ordovician times by tectonic movements, whereas glacio-eustatic control predominated during the Late OrdovicianeSilurian Period. These studies suggest that most areas of Egypt were exposed lands
The extensive spelean deposits in the Western Desert of Egypt at Crystal Mountain (Gebel Bellorat... more The extensive spelean deposits in the Western Desert of Egypt at Crystal Mountain (Gebel Bellorat) are considered to be 11-10 Ma, confirming the 'Vallesian' estimate made by Heissig (1982). Several new faunal elements have been discovered including anurans, snakes, soricids, bats, galagids, hystricids and glirids. This fauna indicates that the region was appreciably more humid 11-10 Ma than it is today, with at least 750 mm and possibly as much as 1,200 mm mean annual rainfall. The role of karst processes in the development of the oases of the Western Desert that may have been underestimated by previous researchers is emphasized.
This paper gives insight into continental sedimentary deposits that occur at the uppermost part o... more This paper gives insight into continental sedimentary deposits that occur at the uppermost part of the stratigraphic succession present in the northeastern sector of the Farafra Depression (Western Desert, Egypt). Using space imagery to complete the field work, the geology of the area has been mapped and the presence of a N-S oriented fault system is documented. The analysis of the morphotectonic features related to this fault system allows reconstructing the structural and sedimentological evolution of the area. The study indicates that the continental deposits were accumulated in alluvial systems that uncon-formably overlie shale and evaporitic rocks attributable to the Paleocene-Eocene Esna Formation. The deposits of the Esna Formation show soft-sediment deformation features, which include slump associated to dish and pillar sedimentary structures and provide evidence of syndepositional tectonic activity during the sedimentation of this unit. The outcrops are preserved in two areas on separated fault-bounded blocks. Proximal alluvial fan facies crop out in a dowthrown block close to the depression boundary. The proximal facies are made up mostly by polymictic conglomerates which occasionally contain boulders. The conglomerate clasts are mainly quartz, carbonate, anhydrite satin spar vein, mudrock, ironstone and nummulite fossils. The mid-fan facies consist of trough cross-bedded, rippled and cross-laminated quartzarenites with reworked glauconite grains and carbonate rock fragments, interpreted as deposited by distributary streams. The distal alluvial fan deposits consist of sandy marls that evolve toward the top of the sections into root-bioturbated lacustrine limestone beds that are locally silicified. The limestones are biomicrites containing characea, ostracods and gastropods with fenestral porosity.
The Upper Cretaceous/Lower Tertiary Maghra El-Bahari Formation at Gabal Ataqa and Gabal Shabrawet... more The Upper Cretaceous/Lower Tertiary Maghra El-Bahari Formation at Gabal Ataqa and Gabal Shabrawet in the northeastern portion of the Eastern Desert of Egypt is subdivided into two informal lithostratigraphic parts: lower and upper. The lower part has common features of alluvial floodplain-dominated deposits with occasional occurrences of crevasse splay deposits. The upper part has sediments typical of marginal lacustrine environments. Both the floodplain and marginal lacustrine deposits exhibit pedogenic features comprising various types of paleosols. Among other soil-forming processes, diversity in the paleosols studied is mainly attributed to paleoclimatic and paleohydrologic changes. The paleosol criteria suggest two climatic regimes, a subhumid-semiarid one succeeded by a semiarid-arid one. The continental depositional environments recognized (floodplain and lacustrine) with their associated paleosols helped in the recognition of a marine regression in the area studied. In a regional perspective, comparison of the data presented in this study with paleosol data spanning the same time period in other localities suggests that the proposed paleoclimatic changes may have been of regional extent.
This study aims to provide the depositional facies, sequence stratigraphic and paleoclimatic char... more This study aims to provide the depositional facies, sequence stratigraphic and paleoclimatic characteristics of the Mid-Eocene (Bartonian) continental succession exposed at Gebel El-Goza El-Hamra (Shabrawet area, NE Eastern Desert, Egypt). The studied succession consists of siliciclastic rocks followed upward by carbonate rocks. Detailed field observation and petrographic investigation indicate accumulation in floodplain-dominated alluvial and shallow lacustrine systems. The floodplain-dominated alluvial facies (45 m thick) is composed mainly of carbonate nodules-bearing, mottled mudrock with subordinate sandstone and conglomerate beds. The conglomerate and pebbly sandstone bodies interpreted as ephemeral braided channel deposits. The massive, laminated, planner cross-bedded, fine-to medium-grained sandstone bodies interlayered within mudstone reflect sheet flood deposits. The mudstones associated with paleosols represent distal floodplain deposits. The shallow lacustrine facies (15 m thick) is made up of an alternation of marlstone, dolostone and mudrock beds with charophytes and small gastropods. Pollen assemblages, stable δ 18 O and δ 13 C isotopes, and paleopedogenic features reflect prevalence of arid to semi-arid climatic conditions during the Bartonian. The sequence stratigraphic framework shows an overall fining-upward depositional sequence, consisting of Low-and High-accommodation Systems Tracts (LAST, HAST), and is bounded by two sequence boundaries (SB-1, SB-2). Conglomerate and pebbly sandstone deposits (braided channel and sheet flood deposits) of the lower part of the alluvial facies (FA-1) reflect a
This study aims to develop a better understanding of the stratigraphy of the southern side of the... more This study aims to develop a better understanding of the stratigraphy of the southern side of the Maritime Alps and of the Ligurian Sea during the Plio-Pleistocene. Five stratigraphic sections were measured and studied in the Segno River valley (Liguria, Italy). These sections are composed of Lower to Middle Pleistocene marine and continental deposits. Based on detailed mapping and sedimentological analysis, 12 marine and deltaic facies were identified. These facies were grouped into facies associations. Two allostratigraphic units were recognized, namely U1 and U2 from oldest to youngest. The lower unit (U1) represents the evolution of a coarse-grained delta developed in a valley or embayment. Within the deltaic sequence, transgressive and highstand systems tracts were recognized. The coarsening/shallowing upward trend observed within the sections suggests that the delta prograded rapidly in the landward portion of the canyon adjacent to the paleo-river outlet. The upper boundary of U1 is represented by a subaerial unconformity overlain by U2, which is composed of sediments deposited by several alluvial fan systems.
Geological Society, London, Special Publications, 2012
Upper Ordovician glaciogenic deposits are profoundly important as hydrocarbon reservoirs across N... more Upper Ordovician glaciogenic deposits are profoundly important as hydrocarbon reservoirs across North Africa, such as within the Illizi Basin of SE Algeria. In this study we present a new sedimentological and sequence stratigraphic model for Upper Ordovician glaciogenic deposits based on the analysis of core descriptions and wireline logs from 25 wells in the Tiguentourine Field. Within the glaciogenic succession, two ice advance–retreat cycles can be defined, consisting of glaciomarine ice-contact fan deposits and tillites. Deposits of the marine ice-contact fan systems generally show a retrogradational stacking pattern from ice-proximal to ice-distal deposits. This pattern is attributed to the deposition in front of a retreating ice sheet. The proximal marine ice-contact fan deposits consist of massive or low-angle cross-bedded pebbly sandstone. They are interpreted as the deposits of turbulent, high-energy plane-wall jets, emerging from subglacial meltwater conduits. These jet-ef...
This work addresses the characteristic sedimentary facies and stable isotopic (δ 13 C and δ 18 O)... more This work addresses the characteristic sedimentary facies and stable isotopic (δ 13 C and δ 18 O) signature of the tufa unit that occurs in the uppermost part of the stratigraphic succession at North and South Gunna hills in the Farafra Depression (Western Desert, Egypt). This has been done to reconstruct the depositional setting and genesis of the tufa unit. The tufa unit occurs as chaotic dark fallen blocks and pile-like carbonate mound covering the slope of a marine Paleocene-Eocene substrate. In outcrop and at close-up view, the tufa unit displays three main lithofacies: laminated, massive and granular tufa, which can be interpreted as deposited in a fluvial setting. The microfacies analysis reveals the dominance of a variety of micro-textures including: a) crystalline laminated texture showing different shapes (bacterial-shrubs, crystal shrubs, and recrystallized robust palisades of leaf-like crystals), b) clotted-peloidal texture and c) clotted-oncoidal texture, all of them reflecting an influence of biotic processes (likely cyanobacterial activity) during tufa deposition. The moderate covariance (r= 0.53) between δ 18 O and δ 13 C suggests some evaporation effect during the
This work deals with a high-resolution analysis of calcareous nannofossil in four exposed Paleoce... more This work deals with a high-resolution analysis of calcareous nannofossil in four exposed Paleocene-Lower Eocene successions in the Farafra Oasis, Western Desert, Egypt in order to detect the different types of stage boundaries and hiatuses. The studied four sections were collected from five localities (Gebel North Gunna, Gebel South Gunna, Ain Ramla, El-Quss Abu Said and Bir Karawin). In the study area, the Paleocene-Lower Eocene succession is made up of four formations, namely Dakhla (at base), Tarawan, Esna and Farafra (at top) that unconformably overlie the Maastrichtian Khoman Formation. The oldest Paleocene calcareous nannofossil Zone (NP 4) is recorded in the Dakhla Formation. It unconformably overlies the latest Maastrichtian Micula prinsii (CC 26b) subzone that is recognized in the uppermost part of the Khoman Formation at North Gunna section. Although Zone NP 4 is successively overlain by the
The petrography and geochemistry (major and trace elements) of the Jurassic sandstones from the K... more The petrography and geochemistry (major and trace elements) of the Jurassic sandstones from the Khashm El-Galala area (NW Gulf of Suez, Egypt) have been investigated to infer their provenance, tectonic setting, and degree of source rocks paleoweathering. The studied sedimentary succession is made up of two rock units, namely the Rieina Formation (Bajocian) and the Ras El-Abd Formation (Bathonian-Oxfordian). These formations consist mainly of sandstones, siltstones and claystones, with local interbeds of limestones. Petrographic, modal, and major elemental analyses demonstrate that the studied sandstones are texturally-matured quartz-arenites. The sediments were primarily derived from plutonic felsic igneous (granitic) rocks and recycled older quartzose sedimentary rocks, with a rare contribution from a metamorphic source. The detrital modes of sandstones suggest cratonic provenance. As indicated by Chemical Index of Alteration and Chemical Index of Weathering (averages values are 76.73 and 79.45, respectively), the source area of the studied sandstones was affected by a relatively high degree of chemical weathering and alteration under warm humid conditions. The trace element concentrations and their ratios (La/Th, Cr/Th, Th/Sc, Cr/V, and Y/Ni) suggest the predominant felsic character of source lithologies. Regarding the regional tectonic setting, discrimination diagrams based on major and trace elements indicate that the studied sandstones were deposited in a passive continental margin. In terms of palaeogeography, it can be suggested that the studied Jurassic sandstones were deposited on the margin of one of the rift basins existed in the northwestern part of the Arabo-Nubian Shield.
Fig. S2. Google Earth map with the studied sites. Landsat/Copernicus Data: SIO, NOAA, U.S. Navy, ... more Fig. S2. Google Earth map with the studied sites. Landsat/Copernicus Data: SIO, NOAA, U.S. Navy, NGA, GEPCO Mapa GISreal
The Eocene rocks in the Shabrawet area (north Eastern Desert, Egypt) have been subdivided into th... more The Eocene rocks in the Shabrawet area (north Eastern Desert, Egypt) have been subdivided into three formations that are from base to top: the Minia Formation (Late Ypresian), the Sannor Formation (Bartonian) and the Maadi Formation (Priabonian). These three formations are disconformable with each other. In addition, the whole Eocene succession is disconformably overlain by the Oligocene rocks and is underlain by the Cretaceous rocks with an angular unconformity surface. The Sannor Formation has been subdivided into three informal units: lower, middle and upper units. The overall sedimentary nature of the Eocene rocks in the study area is dominated by carbonate-siliciclastic rocks. Detailed microfacies analysis has enabled discrimination of 22 sedimentary microfacies types, which are grouped into six facies associations, equivalent to six depositional environments sited on an inner ramp setting. These depositional environments are floodplain-dominated fluvial, lacustrine/palustrine, tidal flat, restricted inner lagoon, shoal bar and outer lagoon with open circulation. A suitable depositional model of the Eocene rocks is given. In addition, four discrete benthonic foraminiferal biozones were reported in the Eocene succession, arranged from base to top: (1) Alveolina frumentiformis biozone (Late Ypresian), (2) Orthoplecta clavata biozone (Bartonian), (3) Dictyoconus aegyptiensis biozone (Bartonian) and (4) Discorbis vesicularis biozone (Priabonian). In terms of sequence stratigraphy, the studied Eocene succession exhibits three superimposed depositional sequences, each of which shows retrogradational (transgressive systems tract) and aggradational (highstand systems tract) to progradational (lowstand systems tract) packages of facies. The retrogradational package displays a predominance of outer lagoon and restricted inner lagoon facies. The aggradational package shows an increase of shoal bar and tidal flat facies, whereas the progradational package marks the occurrence of continental facies (floodplaindominated fluvial and lacustrine deposits). In this study, it is noticed that there are lateral and vertical changes in the depositional environments of the Eocene rocks, between shallow marine and continental environments. Also, many unconformities have been recorded in between and within these rock units. Such remarks indicate that the Eocene rocks were deposited within a highly tectonically active area that was consequently influenced by the transgression and regression of the Neo-Tethys. Such tectonic activity could be related to the Syrian Arc System that was renewed and enlarged several times during the Late Cretaceous up to the Neogene in the eastern and southeastern Mediterranean domain.
Lower Paleozoic rocks are exposed in various regions of Egypt (south central Sinai, north Eastern... more Lower Paleozoic rocks are exposed in various regions of Egypt (south central Sinai, north Eastern Desert and southwest Western Desert), in addition to occurring in the subsurface such as north Western Desert and the Gulf of Suez. The Lower Paleozoic rocks in Egypt include surface and subsurface rock units of formational status. The surface rock units are the Taba, Araba and Naqus formations. The subsurface rock units include the Shifa, Kohla and Basur formations. The Infracambrian Taba Formation has been discovered recently in the outcrops of the southeast central Sinai in the Taba-Ras El-Naqab area. It is missing and/or not recognized in the subsurface. The Taba Formation consists mainly of reddish brown, unfossiliferous gravelly fine-to medium-grained kaolinitic sandstones and subordinate horizons of paleosols. The Cambrian Araba Formation and its subsurface equivalent (the Shifa Formation) are essentially composed of reddish brown, fine-grained laminated sandstone and siltstone with abundant Skolithos and Cruziana sp. In contrast, the OrdovicianeSilurian Naqus Formation and its subsurface equivalents (the Kohla Formation and Basur Formation) are mainly composed of white, unfossiliferous, cross-bedded, medium-to coarse-grained sandstones with haphazardly distributed pebbles and cobbles. Sedimentological analysis indicates that the Araba Formation and its subsurface equivalent were deposited in a marginal-marine environment, whereas the Naqus Formation and its subsurface equivalents were laid down in a fluvio-glacial environment. Integrated stratigraphic and sedimentological studies of the Lower Paleozoic rocks permit reconstruction of the paleogeography of Egypt at that time. Egypt has been largely controlled since the Cambrian by the pre-existing structural framework of the pre-Phanerozoic basement rocks inherited from the Late Proterozoic Pan-African event. Additionally, sedimentation processes were controlled during Cambro-Ordovician times by tectonic movements, whereas glacio-eustatic control predominated during the Late OrdovicianeSilurian Period. These studies suggest that most areas of Egypt were exposed lands
The extensive spelean deposits in the Western Desert of Egypt at Crystal Mountain (Gebel Bellorat... more The extensive spelean deposits in the Western Desert of Egypt at Crystal Mountain (Gebel Bellorat) are considered to be 11-10 Ma, confirming the 'Vallesian' estimate made by Heissig (1982). Several new faunal elements have been discovered including anurans, snakes, soricids, bats, galagids, hystricids and glirids. This fauna indicates that the region was appreciably more humid 11-10 Ma than it is today, with at least 750 mm and possibly as much as 1,200 mm mean annual rainfall. The role of karst processes in the development of the oases of the Western Desert that may have been underestimated by previous researchers is emphasized.
This paper gives insight into continental sedimentary deposits that occur at the uppermost part o... more This paper gives insight into continental sedimentary deposits that occur at the uppermost part of the stratigraphic succession present in the northeastern sector of the Farafra Depression (Western Desert, Egypt). Using space imagery to complete the field work, the geology of the area has been mapped and the presence of a N-S oriented fault system is documented. The analysis of the morphotectonic features related to this fault system allows reconstructing the structural and sedimentological evolution of the area. The study indicates that the continental deposits were accumulated in alluvial systems that uncon-formably overlie shale and evaporitic rocks attributable to the Paleocene-Eocene Esna Formation. The deposits of the Esna Formation show soft-sediment deformation features, which include slump associated to dish and pillar sedimentary structures and provide evidence of syndepositional tectonic activity during the sedimentation of this unit. The outcrops are preserved in two areas on separated fault-bounded blocks. Proximal alluvial fan facies crop out in a dowthrown block close to the depression boundary. The proximal facies are made up mostly by polymictic conglomerates which occasionally contain boulders. The conglomerate clasts are mainly quartz, carbonate, anhydrite satin spar vein, mudrock, ironstone and nummulite fossils. The mid-fan facies consist of trough cross-bedded, rippled and cross-laminated quartzarenites with reworked glauconite grains and carbonate rock fragments, interpreted as deposited by distributary streams. The distal alluvial fan deposits consist of sandy marls that evolve toward the top of the sections into root-bioturbated lacustrine limestone beds that are locally silicified. The limestones are biomicrites containing characea, ostracods and gastropods with fenestral porosity.
The Upper Cretaceous/Lower Tertiary Maghra El-Bahari Formation at Gabal Ataqa and Gabal Shabrawet... more The Upper Cretaceous/Lower Tertiary Maghra El-Bahari Formation at Gabal Ataqa and Gabal Shabrawet in the northeastern portion of the Eastern Desert of Egypt is subdivided into two informal lithostratigraphic parts: lower and upper. The lower part has common features of alluvial floodplain-dominated deposits with occasional occurrences of crevasse splay deposits. The upper part has sediments typical of marginal lacustrine environments. Both the floodplain and marginal lacustrine deposits exhibit pedogenic features comprising various types of paleosols. Among other soil-forming processes, diversity in the paleosols studied is mainly attributed to paleoclimatic and paleohydrologic changes. The paleosol criteria suggest two climatic regimes, a subhumid-semiarid one succeeded by a semiarid-arid one. The continental depositional environments recognized (floodplain and lacustrine) with their associated paleosols helped in the recognition of a marine regression in the area studied. In a regional perspective, comparison of the data presented in this study with paleosol data spanning the same time period in other localities suggests that the proposed paleoclimatic changes may have been of regional extent.
This study aims to provide the depositional facies, sequence stratigraphic and paleoclimatic char... more This study aims to provide the depositional facies, sequence stratigraphic and paleoclimatic characteristics of the Mid-Eocene (Bartonian) continental succession exposed at Gebel El-Goza El-Hamra (Shabrawet area, NE Eastern Desert, Egypt). The studied succession consists of siliciclastic rocks followed upward by carbonate rocks. Detailed field observation and petrographic investigation indicate accumulation in floodplain-dominated alluvial and shallow lacustrine systems. The floodplain-dominated alluvial facies (45 m thick) is composed mainly of carbonate nodules-bearing, mottled mudrock with subordinate sandstone and conglomerate beds. The conglomerate and pebbly sandstone bodies interpreted as ephemeral braided channel deposits. The massive, laminated, planner cross-bedded, fine-to medium-grained sandstone bodies interlayered within mudstone reflect sheet flood deposits. The mudstones associated with paleosols represent distal floodplain deposits. The shallow lacustrine facies (15 m thick) is made up of an alternation of marlstone, dolostone and mudrock beds with charophytes and small gastropods. Pollen assemblages, stable δ 18 O and δ 13 C isotopes, and paleopedogenic features reflect prevalence of arid to semi-arid climatic conditions during the Bartonian. The sequence stratigraphic framework shows an overall fining-upward depositional sequence, consisting of Low-and High-accommodation Systems Tracts (LAST, HAST), and is bounded by two sequence boundaries (SB-1, SB-2). Conglomerate and pebbly sandstone deposits (braided channel and sheet flood deposits) of the lower part of the alluvial facies (FA-1) reflect a
This study aims to develop a better understanding of the stratigraphy of the southern side of the... more This study aims to develop a better understanding of the stratigraphy of the southern side of the Maritime Alps and of the Ligurian Sea during the Plio-Pleistocene. Five stratigraphic sections were measured and studied in the Segno River valley (Liguria, Italy). These sections are composed of Lower to Middle Pleistocene marine and continental deposits. Based on detailed mapping and sedimentological analysis, 12 marine and deltaic facies were identified. These facies were grouped into facies associations. Two allostratigraphic units were recognized, namely U1 and U2 from oldest to youngest. The lower unit (U1) represents the evolution of a coarse-grained delta developed in a valley or embayment. Within the deltaic sequence, transgressive and highstand systems tracts were recognized. The coarsening/shallowing upward trend observed within the sections suggests that the delta prograded rapidly in the landward portion of the canyon adjacent to the paleo-river outlet. The upper boundary of U1 is represented by a subaerial unconformity overlain by U2, which is composed of sediments deposited by several alluvial fan systems.
Geological Society, London, Special Publications, 2012
Upper Ordovician glaciogenic deposits are profoundly important as hydrocarbon reservoirs across N... more Upper Ordovician glaciogenic deposits are profoundly important as hydrocarbon reservoirs across North Africa, such as within the Illizi Basin of SE Algeria. In this study we present a new sedimentological and sequence stratigraphic model for Upper Ordovician glaciogenic deposits based on the analysis of core descriptions and wireline logs from 25 wells in the Tiguentourine Field. Within the glaciogenic succession, two ice advance–retreat cycles can be defined, consisting of glaciomarine ice-contact fan deposits and tillites. Deposits of the marine ice-contact fan systems generally show a retrogradational stacking pattern from ice-proximal to ice-distal deposits. This pattern is attributed to the deposition in front of a retreating ice sheet. The proximal marine ice-contact fan deposits consist of massive or low-angle cross-bedded pebbly sandstone. They are interpreted as the deposits of turbulent, high-energy plane-wall jets, emerging from subglacial meltwater conduits. These jet-ef...
This work addresses the characteristic sedimentary facies and stable isotopic (δ 13 C and δ 18 O)... more This work addresses the characteristic sedimentary facies and stable isotopic (δ 13 C and δ 18 O) signature of the tufa unit that occurs in the uppermost part of the stratigraphic succession at North and South Gunna hills in the Farafra Depression (Western Desert, Egypt). This has been done to reconstruct the depositional setting and genesis of the tufa unit. The tufa unit occurs as chaotic dark fallen blocks and pile-like carbonate mound covering the slope of a marine Paleocene-Eocene substrate. In outcrop and at close-up view, the tufa unit displays three main lithofacies: laminated, massive and granular tufa, which can be interpreted as deposited in a fluvial setting. The microfacies analysis reveals the dominance of a variety of micro-textures including: a) crystalline laminated texture showing different shapes (bacterial-shrubs, crystal shrubs, and recrystallized robust palisades of leaf-like crystals), b) clotted-peloidal texture and c) clotted-oncoidal texture, all of them reflecting an influence of biotic processes (likely cyanobacterial activity) during tufa deposition. The moderate covariance (r= 0.53) between δ 18 O and δ 13 C suggests some evaporation effect during the
This work deals with a high-resolution analysis of calcareous nannofossil in four exposed Paleoce... more This work deals with a high-resolution analysis of calcareous nannofossil in four exposed Paleocene-Lower Eocene successions in the Farafra Oasis, Western Desert, Egypt in order to detect the different types of stage boundaries and hiatuses. The studied four sections were collected from five localities (Gebel North Gunna, Gebel South Gunna, Ain Ramla, El-Quss Abu Said and Bir Karawin). In the study area, the Paleocene-Lower Eocene succession is made up of four formations, namely Dakhla (at base), Tarawan, Esna and Farafra (at top) that unconformably overlie the Maastrichtian Khoman Formation. The oldest Paleocene calcareous nannofossil Zone (NP 4) is recorded in the Dakhla Formation. It unconformably overlies the latest Maastrichtian Micula prinsii (CC 26b) subzone that is recognized in the uppermost part of the Khoman Formation at North Gunna section. Although Zone NP 4 is successively overlain by the
The petrography and geochemistry (major and trace elements) of the Jurassic sandstones from the K... more The petrography and geochemistry (major and trace elements) of the Jurassic sandstones from the Khashm El-Galala area (NW Gulf of Suez, Egypt) have been investigated to infer their provenance, tectonic setting, and degree of source rocks paleoweathering. The studied sedimentary succession is made up of two rock units, namely the Rieina Formation (Bajocian) and the Ras El-Abd Formation (Bathonian-Oxfordian). These formations consist mainly of sandstones, siltstones and claystones, with local interbeds of limestones. Petrographic, modal, and major elemental analyses demonstrate that the studied sandstones are texturally-matured quartz-arenites. The sediments were primarily derived from plutonic felsic igneous (granitic) rocks and recycled older quartzose sedimentary rocks, with a rare contribution from a metamorphic source. The detrital modes of sandstones suggest cratonic provenance. As indicated by Chemical Index of Alteration and Chemical Index of Weathering (averages values are 76.73 and 79.45, respectively), the source area of the studied sandstones was affected by a relatively high degree of chemical weathering and alteration under warm humid conditions. The trace element concentrations and their ratios (La/Th, Cr/Th, Th/Sc, Cr/V, and Y/Ni) suggest the predominant felsic character of source lithologies. Regarding the regional tectonic setting, discrimination diagrams based on major and trace elements indicate that the studied sandstones were deposited in a passive continental margin. In terms of palaeogeography, it can be suggested that the studied Jurassic sandstones were deposited on the margin of one of the rift basins existed in the northwestern part of the Arabo-Nubian Shield.
Fig. S2. Google Earth map with the studied sites. Landsat/Copernicus Data: SIO, NOAA, U.S. Navy, ... more Fig. S2. Google Earth map with the studied sites. Landsat/Copernicus Data: SIO, NOAA, U.S. Navy, NGA, GEPCO Mapa GISreal
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