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Article

Planktonic Foraminifera of the Middle and Upper Eocene Successions at the Northwestern and Northeastern Sides of the Nile Valley, Egypt: Stratigraphic and Paleoenvironmental Implications

by
Safaa Abu Bakr
1,
Ibrahim M. Abd El-Gaied
2,
Sayed M. Abd El-Aziz
3,
Mostafa M. Sayed
4,5,6,* and
Abdelaziz Mahmoud
1
1
Department of Geology, Faculty of Science, Helwan University, Cairo 11795, Egypt
2
Faculty of Earth Science, Beni-Suef University, Beni-Suef 62511, Egypt
3
Department of Geology, Faculty of Science, Fayoum University, Fayoum 63511, Egypt
4
Geology Department, Faculty of Science, Beni-Suef University, Beni-Suef 62511, Egypt
5
Department of Geology, Faculty of Earth Sciences, Geography and Astronomy, University of Vienna, 1090 Vienna, Austria
6
Department of Palaeontology, Faculty of Earth Sciences, Geography and Astronomy, University of Vienna, 1090 Vienna, Austria
*
Author to whom correspondence should be addressed.
Diversity 2025, 17(2), 116; https://doi.org/10.3390/d17020116
Submission received: 2 January 2025 / Revised: 28 January 2025 / Accepted: 29 January 2025 / Published: 5 February 2025
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Versions Notes

Abstract

:
This study deals with the biostratigraphic determination and paleoenvironmental reconstruction of the middle–upper Eocene sediments along the northwestern and northeastern banks of the Nile Valley, Egypt. The studied successions are classified into four rock units as follow: The Qarara (Lutetian–Bartonian), the El Fashn (Bartonian), the Gehannam, and the Beni Suef (Bartonian–Priabonian) formations. A total of eighty planktonic foraminifera species belonging to twenty-two genera and eight families are identified, and their vertical distribution enabled us to recognize four planktonic biozones, namely the Morozovelloides lehneri Zone (late Lutetian–early Bartonian), Orbulinoides beckmanni Zone (early Bartonian), Morozovelloides crassatus Zone (late Bartonian), and Globigerinatheka semiinvoluta Zone (late Bartonian–early Priabonian). The faunal assemblages characterizing these zones showed a great similarity with those recorded in the lower latitudes (tropical and sub-tropical) regions and correlated with the planktonic zones in the northern and southern Tethyan provinces. The appearance of Orbulinoides beckmanni distinguishes the early Bartonian period, its lowest occurrence defines the upper boundary of the Morozovelloides lehneri Zone, and its highest occurrence marks the lower boundary of the Morozovelloides crassatus Zone. The disappearance of the spinose forms of morozovellids and the large acarininids, besides the highest occurrence of Morozovelloides crassatus, defines the lower boundary of the Globigerinatheka semiinvoluta Zone. The middle/upper Eocene boundary is traced based on the last and first appearance of the marker planktonic species and located herein within the Globigerinatheka semiinvoluta Zone. The paleontological data, including the planktonic to benthic foraminiferal ratio (P/B), statistical analyses of different foraminiferal groups, and ternary plot diagrams in conjunction with the sedimentological features, indicate changes in the depositional settings, fluctuating between the inner to middle and outer neritic environment and the uppermost bathyal environment at some levels.

1. Introduction

The Eocene rocks in Egypt are exposed over large areas and cover about 21% of the total surface area; therefore, extensive studies have been performed on these rocks. The stratigraphy and paleontology of the Eocene successions exposed along the western and eastern sides of the Nile Valley have drawn the attention of many authors since the work of Bishay [1,2] to the more recent studies of Abdallah et al. [3], El Dawy and Dakrory [4], Aly et al. [5], Hegab et al. [6], Saber and Salama [7], Abd El-Gaied et al., [8,9], Salama et al. [10], and Sayed et al. [11,12].
Some studies subdivided the Eocene outcrops between the Assuit and Beni Suef area on both sides of the Nile Valley from base to top into the following formations: Manfalut, Tall El-Amarna, Minia, Samalut (lower Eocene), Maghagha, Qarara, El Fashn (middle Eocene), Beni Suef (middle–upper Eocene), and Maadi formations (upper Eocene) [5,7,9,10,11,12,13,14]. Others classified the Eocene sequence along the sides of the River Nile between Aswan and Cairo into the following formations: the Thebes, Drunka, Manfalut, Ibrahimi, Minia, Samalut (lower Eocene), Maghagha, Qarara, Mokattam (middle Eocene), Beni Suef, and Maadi formations (middle to upper Eocene) [15]. The stratigraphy of the Eocene sediments exposed in the southwest Beni Suef area was previously studied by Omara et al. [16]. They subdivided the succession into three rock units belonging to the late Lutetian age, named as the Qarara, El Fashn, and Beni Suef formations. They also identified three foraminiferal biozones, which are Nummulites gizehensis (Qarara Formation), Nummulites beaumonti (El Fashn Formation), and Truncorotaloides rohri, which coincide with the Beni Suef Formation. Mansour et al. [17] studied the middle and upper Eocene rocks in the east and northeast of the Beni Suef area and subdivided the succession into the Mokattam Formation (late Lutetian), the Beni Suef Formation (early late Eocene), which further subdivided into the Qurn Member at the base and the Tarbul ember at the top, and the Maadi ormation (late Eocene). They also subdivided the studied sections based on the foraminiferal content into nine bio-zones. Recently, Saber and Salama [7] focused on the facies analysis and the sequence stratigraphy for the Eocene exposures in Gabal Diya, Gabal Abyiad (southeast El Fashn City), and Gebel Homret Shaiboun (northeast Beni Suef area). They identified four third-order depositional sequences that deposited in a shallow homoclinal ramp and subdivided the succession into four rock units, named the Qarara (upper Lutetian), El Fashn (Bartonian), Beni Suef, and Maadi (Priabonian) formations. On the other hand, Beadnell [18] studied the Eocene succession in the Fayoum area and subdivided it into four series arranged from the base as the Wadi Rayan series, Ravine beds series of the middle Eocene age, Birket Qarun series, and Qasr El-Sagha series of the late Eocene age. These series are followed upward by the Gebel El Qattrani bed fluvio-marine series, whereas Abdallah et al. [3] classified the middle and upper Eocene succession exposed in the eastern Fayoum depression into two formations: the Gehannam Formation (middle/upper Eocene) and the Birket Qarun Formation (upper Eocene). They interpreted the prevailing environmental conditions depending on the identified benthic foraminifera and ostracoda. Abd El-Aziz and Abd El-Gaied [19] constructed two planktonic foraminiferal biozones from the these rock units, which are the Truncorotaloides rohri Zone (late middle Eocene) and the Turborotalia pseudoampliapertura Zone (late Eocene). Meanwhile, Abd El-Gaied and Abd El-Aziz [13] studied the biostratigraphy of a composite section collected from the Wadi Bayad El Arab and Gebel Homret Shaibun area based on the planktonic foraminifera and proposed a different result than those in the present study. They identified two planktonic foraminiferal biozones, which are the Truncorotaloides rohri Zone (late middle Eocene) and Turborotalia pseudoampliapertura Zone (late Eocene).
More recently, Salama et al. [10] identified seventy planktonic foraminiferal species from the middle and upper Eocene succession in the north of the Eastern Desert, Egypt, and recorded three planktonic zones, which are the E13. Morozovelloides crassatus Zone (Bartonian), E14. Globigerinatheka semiinvoluta Zone (late Bartonian–early Priabonian), and E15. Globigerinatheka index Zone (Priabonian). They located the middle/upper Eocene boundary within the Globigerinatheka semiinvoluta Zone and defined the upper boundary of the Morozovelloides crassatus Zone at the complete extinction of the spinose planktonic assemblages related to the morozovellids and the large acarininids. Moreover, Ramadan et al. [20] recorded thirty-six planktonic foraminifera species from the upper Eocene succession exposed at the northeastern part of the Nile Valley of Egypt and recognized two planktonic zones, named as the E14. Globigerinatheka semiinvoluta Zone, and E15. Globigerinatheka index Zone. Sayed et al. [11] used the ostracod assemblages to recognize paleoenvironmental conditions that prevailed during the deposition of the middle and upper Eocene sediments in the Beni Suef area. They recorded three ostracod zones from this time interval, correlating with the planktonic zones, namely the Morozovelloides crassatus, Globigerinatheka semiinvoluta, Globigerinatheka index zones.
The Eocene rocks exposed in the study area, especially at the Gabal Abyiad and El Garabaa sections at the eastern and western banks of Nile Valley, respectively, have received relatively little attention, where no detailed micro-paleontological and bio-stratigraphical study by means of the planktonic foraminifera has been performed until now.
Despite the previous biostratigraphic results that have been carried out in nearby areas, they were poorly discussed, and the studied sections are well suited to provide a better understanding of the biostratigraphic zonations of the middle–upper Eocene successions along both sides of the Nile Valley. The present work aims to present a detailed study of the stratigraphy and micropaleontology of the middle and upper Eocene rocks exposed along the northwestern and northeastern banks of the Nile Valley by means of the planktonic foraminifera in order to establish the middle and upper Eocene biostratigraphic framework, to correlate the recorded planktonic zones with those in the southern Tethyan province and the nearby areas, and to deepen knowledge about the environmental evolution of this region. For these purposes, three stratigraphic surface sections are selected, measured, and described in detail. The first section is located near Beni Suef-El Fayoum new asphaltic road at El Garabaa Village, about 20 km west Beni Suef City, between a latitude of 29°15′ N and a longitude of 30°58′ E. The second section is situated at Wadi Bayad El Arab, about 12 km east of Beni Suef City, between a latitude of 29°02′ N and a longitude of 31°17′ E. The third section is represented by the Gabal Abyiad section, east El Fashn City, between a latitude of 28°45′ N and a longitude of 31°14′ E (Figure 1).

2. Litho-Stratigraphy

In the present work, the middle and upper successions are classified into four litho-stratigraphic units: The Qarara, the El Fashn, the Gehannam, and the Beni Suef formations. Field photos for these rock units are included in Figure 2, Figure 3 and Figure 4. These rock units are described in detail as follows:

2.1. Qarara Formation (Lutetian–Bartonian)

The present rock unit was firstly named and described by Bishay [2] in Gabal Qarara, east Maghagha City, and was represented by limestone succession reaching 170 m thick. According to Said [22], this succession is unconformably underlain by the Maghagha Formation, which is related to the middle Eocene and consists mainly of limestone and marl with thin layers of reddish clay and is characterized by the occurrence of Nummulitic banks at the basal part. In the present study, the Qarara Formation is only exposed at Gabal Abyiad, occupying the upper part of the section, and measures about 48 m thick. The lower part of this rock unit attains a thickness of about 18 m and is composed mainly of intercalations of egg yellow, gypsiferous marls rich in planktonic and benthic foraminifera, and yellowish to grayish white limestone with yellowish green, gypsiferous shale. The middle part (8 m thick) comprises yellowish gray argillaceous limestone with a thin marl bed (50 cm thick) flooded with both planktonic and benthic foraminifera. The topmost part of the Qarara Formation measures 12 m thick and is composed of grayish to snow white chalky limestone (with rare to common foraminiferal assemblages) and hard ledges of limestone with thin bands and nodules of flint (Figure 5).
The occurrence of the marker planktonic foraminifera species, such as Morozovelloides lehneri, M. bandyi, M. coronatus, M. crassatus, Acarinina bullbrooki, A. matthewsae, A. pentacamerata, A. praetopilensis, A. rohri, A. spinuloinflata, A. topilensis, Orbulinoides beckmanni, and Chiloguembelitria oveyi, besides both small and large benthic (Nummulites gizehensis) foraminifera, assigned a late Lutetian–Bartonian age to this rock unit [2,7,12,14,15,23].

2.2. El Fashn Formation (Bartonian)

The term of this rock unit was firstly introduced by Bishay [2], discussing a sedimentary succession 88 m thick overlying the Qarara Formation and underlying the Beni Suef Formation, exposed at wadi El Sheikh, southeast El Fashn City. In the present study, this formation is exposed in the Gabal Abyiad and Wadi Bayad El Arab sections. In Gabal Abyiad, this formation measures 86 m thick and overlies the Qarara Formation (Figure 5). The lower part of this rock unit has a thickness of about 26 m, consisting of greenish gray gypsiferous shale with thin intercalations of egg yellow marls and yellowish to grayish white limestone. The middle part measures 27 m thick, comprising intercalations of yellowish gray to white marls, snow white chalky limestone, and grayish white bedded limestone. The upper part of the El Fashn Formation at the Gabal Abyiad section measures 33 m thick and consists mainly of scarp former light gray to snow white bedded limestone with yellowish gray marl at its middle part. In the Wadi byad El Arab section, this formation is 22 m thick and is overlaid by the Beni Suef Formation. It consists of yellowish gray shale with gypsum veins and light gray marl at the base, followed upward by yellowish gray to white, scarp former argillaceous, and marly limestone with cherty bands at the top. This rock unit is also flooded with well-preserved and highly diversified planktonic and benthic foraminifera. The presence of the marker planktonic foraminifera species, such as Orbulinoides beckmanni, Subbotina senni, Morozovelloides crassatus, Chiloguembelitria oveyi, Turborotalia frontosa, Igorina broedermani, Acarinina collectea, A. bullbrooki, A. libyaensis, A. matthewsae, A. mayoensis, A. pentacamerata, A. rohri, A. spinuloinflata, A. topilensis, Globigerinatheka mexicana, G. tropicalis, and Streptochilus martini, besides the small and large benthic foraminifera, assign the Bartonian age to this rock unit [10,12,13,23].

2.3. Gehannam Formation (Bartonian–Priabonian)

The term Gehannam Formation was firstly named by Said [24] at Qaret Gehannam, Fayoum area, where it measures 70 m thick and conformably overlies the Wadi El Rayan Formation and underlies the Birket Quran Formation. This rock unit was previously known as “Ravine beds” by Beadnell [18], who described it as a middle Eocene sedimentary sequence underlying the alluvium deposits at ravines in the Fayoum province. In the present study, the Gehannam Formation is exposed in the El Garabaa section and measures 48 m thick. Its lower part consists of repeated beds of light gray marl capped by grayish white argillaceous to dolomitic limestone (23 m thick), while the upper part comprises grayish white argillaceous limestone, yellowish white marly limestone, and yellowish gray limestone with thin beds of marl at the top part, measuring a thickness of about 25 m (Figure 5). The foraminiferal assemblages within this rock unit are represented by rare to common occurrences of the planktonic species, which are restricted to the lower part of the section. Meanwhile, the benthic foraminifera shows high abundance, diversity, and distribution throughout the whole succession. The occurrence of the marker planktonic foraminifera species (Morozovelloides crassatus, Acarinina bullbrooki, A. rohri, A. spinuloinflata, and A. medizzai) in the lower part of this formation, besides the sudden disappearance of the planktonic spinose forms, and the continuous appearance of the benthic foraminifera in the upper part suggests a Bartonian–Priabonian age for that part of the Gehannam Formation [25,26,27,28,29].

2.4. Beni Suef Formation (Bartonian–Priabonian)

Bishay [2] introduced this term to describe the succession at Gebel Homret Shaibon, northeast Beni Suef. It measures 100 m thick at its type locality and conformably overlies the El Fashn Formation and underlies the Maadi Formation. Mansour et al. [17] subdivided this formation at Gabal Tarbul, northeast Beni Suef, into two members: the Qurn Member at the base and the Tarbul Member at the top. In the present study, the Beni Suef Formation is exposed in the Gabal Abyiad section, at 26 m thick (the Qurn Member only), and at the Bayad El Arab section, at 77 m thick (the Qurn and the Tarbul members) (Figure 5).

2.4.1. Qurn Member (Bartonian–Priabonian)

In Gabal Abyiad, the Qurn Member of the Beni Suef Formation is only exposed, measuring 26 m thick. It is composed of yellowish gray, gypsiferous, slop former marl, and shale topped by light gray hard limestone. Abundant, well-preserved planktonic (about 49 species), and benthic foraminiferal fauna are distributed through the exposed part of the member. At Wadi Bayad El Arab, the Qurn Member is completely exposed, overlies the El Fashn Formation, and underlies the Tarbul Member of the Beni Suef Formation. It attains a thickness of about 37, consisting of repeated beds of light to yellowish gray, gypsiferous, slop-former shale capped by grayish white argillaceous, and marly fossiliferous limestone. The basal shale part of this member (about 8 m, samples 10, 11, and 12) is represented by common occurrences of the spinose and smoothed planktonic (18 species) and benthic foraminifera, while the remaining part of the member is only represented by benthic foraminifera. The marker planktonic foraminifera species in the Qurn Member at the Gabal Abyiad and Wadi Bayad El Arab sections, where the Globigerinatheka semiinvoluta Zone is recorded in the upper part of the member above the Morozovilloides crassatus Zone, besides common occurrences of planktonic species in the basal part of the same member in the Wadi Bayad El Arab section, suggest a Bartonian–Priabonian age [10].

2.4.2. Tarbul Member (Priabonian)

In the present work, this member is exposed in the Wadi Bayad El Arab section and measures 40 m thick, composed of repeated beds of egg yellow, Nummulitic marl capped by yellowish gray argillaceous to marly limestone. The lower part of this member displays rare to common occurrences of the smooth planktonic foraminiferal assemblages, while both the large and small benthic foraminifera, besides ostracodes, are recorded in the lower and upper parts. Based on the associated faunal content, the Tarbul Member is assigned a Partonian age [10,13].

3. Materials and Methods

Three surface sections representing the middle and upper Eocene were selected carefully from the northwestern and northeastern parts of the Nile Valley province and described. In total, 125 rock samples were collected from the measured sections, with sampling interval ranges from 1 to 2 m (50 cm at some levels). The majority of samples were collected from the Gabal Abyiad section (approximately 82 rock samples) during the summer of 2022, representing the Qarara, El Fashn, and the lower part of the Beni Suef formations. Additionally, 30 rock samples were obtained from the Wadi Bayad El Arab section in November 2022, representing the upper part of the El Fashn and Beni Suef formations, and 13 samples were collected from the El Garabaa section during the summer of 2023, comprising the Gehannam Formation. About 250 g were taken from each sample to examine their foraminiferal contents. The samples were soaked in water for three days, washed under running water, and sieved using a 63 μm sieve. The residue was dried in an oven at 80 °C, and then the foraminiferal assemblages were picked, described, and identified to species-level using the stereo-binocular microscope (OPTIKA, Via Rigla, 30, Bergamo, Italy). The identified species were photographed using the Scanning Electron Microscope (SEM), JSM 5400 LD (JEOL, Tokyo, Japan) at Beni Suef University, and the type species were stored in the Geology Department, Faculty of Science, Helwan University. The schemes of Loeblich and Tappan [30], Pearson et al. [31], and Pearson and Wade [32] are followed in the systematic classification of the identified species. In each washed sample, about 20 g from the dried residue (usually of a size greater than 63 μm) is used in counting the total numbers of specimens. The planktonic percentage (P%) in the total foraminiferal specimens, besides the arenacous (A%) and calcareous (C%) percentages, and the epifaunal (Ep%) and infaunal (In%) benthic ratios are calculated. Furthermore, the ternary plot diagram of Murray [33] has been applied for interpreting the depositional settings of the studied successions, based on the percentages of the following suborders: Miliolina (M%), Textulariina (T%), and Rotaliina (R%).

4. Results

4.1. Planktonic Foraminifera Associations

The examination of 125 rock samples resulted in the identification of eighty planktonic foraminiferal species belonging to twenty-two genera, eight families, and two superfamilies. Most of the identified species are photographed and illustrated in three figures (Figure 6, Figure 7 and Figure 8). These planktonic assemblages are summarized in Table 1 and related to two main groups. The first group belongs to the superfamily Globigerinoidea of the calcitic, trochospiral tests with a smooth, micro- to macro-perforate and muricate to pustulose wall, simple arched, and an umbilical to extra-umbilical primary aperture with a narrow lip or rimless. Supplementary apertures are also present, sometimes with bullae or thick lips. The assemblages of this group are represented by four families which are as follows: 1—Globigerinidae, which is represented by abundant to common specimens related to the genera Catapsydrax, Globorotaloides, Paragloporotalia, Parasubbotina, Pseudoglobigerinella, Globigerina, Globoturbototalita, Subbotina, Turborotalita, and the sub-globular to globular forms of Globigerinatheka and Orbulinoides. 2—Truncorotaloididae, which is represented by abundant acarininid forms, with robust tests and supplementary apertures in most individuals and included in the genus Acarinina, and frequent associations of the keeled lineage of morozovellids, which disappeared near the middle/upper Eocene boundary and are represented by the genus Morozovelloides, in addition to some specimens related to the igorinid lineage and represented by the genus Igorina. 3—Globoquadrinidae, with assemblages related to the genus Dentoglobigerina. 4—Hedbergellidae, with abundant planispirally forms related to the genus Pseudohastigerina and a common association of the long-ranging turborotaliids forms that belong to the genus Turborotalia. The second group belongs to the superfamily Heterohelicoidea, which is characterized by a calcitic, smooth to muricate wall, biserial and triserial tests, and which is mainly planispiral in the early stage and uniserial in the adult stage. The aperture generally is a low to high arch at the base of the final chamber. This group in the present study is included in four families, which are 1—Guembelitriidae, with triserial tests throughout, and represented in the genus Chiloguembelitria; 2—Chiloguembelinidae, with a biserial test throughout and included in the genera Chiloguembelina and Streptochilus; 3—Heterohelicidea, represented by species related to the genus Bifarina with an initial biserial test, becoming uniserial with a terminal to areal aperture; and 4—Globigerinitidae, which is represented here by species characterized by postulate, low trochospiral tests with intra-umbilical apertures and related to the genus Tenuitella.

4.2. Biostratigraphy

The vertical distribution of the identified planktonic species in the studied successions led to the recognition of four bio-zones, covering a time interval from the late Lutetian to the early Priabonian. The stratigraphic range charts of the reported species, besides the proposed planktonic zones, are presented in Figure 9, Figure 10 and Figure 11. The correlation of these zones with those previously recorded in Egypt and the surrounding areas is given in Figure 12. The works of Berggren and Pearson [34] and Wade et al. [35] are followed in this study.

4.2.1. E 11. Morozovelloides lehneri Zone

  • Category: Partial-Range Zone
  • Age: middle Eocene (late Lutetian–early Bartonian)
  • Definition: This zone was defined by Wade et al. [35] as the biostratigraphic interval distinguished by the partial range of Morozovelloides lehneri between the highest occurrence HO of Guembelitroides nuttali and the lowest occurrence LO of Orbulinoides beckmanni. This zone remains the same as in Berggren and Pearson [34], especially for the nomenclature and definition.
  • Remarks: In the present study, the recorded zone represents the lower and middle parts of the Qarara Formation in the Gabal Abyiad section, measuring about 25 m thick. It is conformably underlying the Orbulinoides beckmanni Total-Range Zone. The lower boundary is not recorded because the Gumbelitroides nuttali species does not appear, while its upper boundary is located at the first appearance of Orbulinoides beckmanni and some associated species, such as Acarinina collectea, A. primitiva, Subbotica senni, Globigerinatheka barri, Turborotalia praecentralis, and Paragloborotalia nana. In the tropical and subtropical regions, Morozovelloides lehneri and Orbulinoides beckmanni are well represented, but in temperate areas, they are often missing. So, this zone is recognized through the coexistence of Turborotalia frontosa and T. possagnoensis with the first appearance of T. pomeroli [36]. In Egypt (west central Sinai), Haggag and Luterbacher [37] suggested that the Morozovella (Morozovelloides herein) lehneri Zone represents the stratigraphic interval including both the Morozovella lehneri Zone, the Orbulinoides beckmanni Zone, and the upper boundary of the suggested zone located at the first appearance of the Globigerina (=Dentoglobigerina) tripartite [38].
  • Assemblages: Thirty-seven species are recorded in this zone (Figure 10), and the more characteristic species are Acarinina bullbrooki, Acarinina libyaensis, Acarinina mayoensis, Acarinina pentacamerata, Acarinina praetopilensis, Acarinina rohri, Acarinina spinuloinflata, Acarinina topilensis, Catapsydrax africanus, Globigerinatheka mexicana, Igorina broedermani, Morozovelloides bandyi, Morozovelloides coronatus, Morozovelloides lehneri, Parasubbotina griffinae, Parasubbotina inaequispira, Pseudoglobigerinella cf. bolivariana, Pseudohastigerina micra, Turborotalia boweri, Turborotalia centralis, Turborotalia pseudomayeri, and Turborotalia possagnoensis.
  • Correlation: As shown in Figure 12, the present zone is globally equivalent with the middle Eocene P12 Morozovella lenheri Zone of Bolli [39], Blow [40], Toumarkine and Luterbacher [36], Berggren and Miller [41], Berggren et al. [42], Mukhopadhyay [43]. Also, it is equivalent with the E11 Morozovelloides lenheri Zone of Berggren and Pearson [34] and Wade et al. [35]. In Iran, Babazadeh and Cluzel [44] recorded this zone from the same time interval. In Egypt, Abdallah et al. [3], Haggag and Luterbacher [37,45], Shahin [46], and Bassiouni et al. [47] suggested that the middle Eocene Morozovella lehneri Zone is extended to include the interval of both the Morozovella lehneri Zone and the Orbulinoides beckmanni Zone. Meanwhile, Anan [48], Selima [49], and Abd El-Shafy et al. [38] recorded the present zone from the middle Eocene of the Western Desert, Nile Valley, and west central Sinai areas, respectively.

4.2.2. E 12. Orbulinoides beckmanni Zone

  • Category: Total-Range Zone
  • Age: middle Eocene (Bartonian)
  • Definition: This zone was defined by Bolli [39] as the Porticulasphaera mexicana Zone and was renamed by Cordey [50] and Blow and Saito [51] as the Orbulinoides beckmanni Zone for taxonomic reasons. It represents the biostratigraphic interval of the total range of the nominate taxon between its lowest occurrence LO and highest occurrence HO.
  • Remarks: In this work, the present zone is recorded in the Gabal Abyiad section and has a thickness of about 39 m. It includes the upper 17 m of the Qarara Formation and the lower 22 m of the El Fashn Formation. The lower and upper boundary is marked by the first and last appearance of the nominate species. It is conformably overlying the Morozovelloides lehneri Zone and underlies the Morozovelloides crassatus Zone. The present zone is well represented in the Mediterranean area (lower latitudes), while in the temperate regions, it is generally missing, and the recognition of this time interval is through the occurrence of Turborotalia pomeroli, which considers the only representative of Turborotalia cerroazulensis lineage [36], while in the southern Atlantic, Turborotalia cerroazulensis appeared within this zone, as mentioned by Toumarkine [52].
  • Assemblages: Forty-eight species are recorded in this zone (Figure 10), and the more characteristic assemblages besides the zonal marker are Acarinina bullbrooki, Acarinina collectea, Acarinina matthewsae, Acarinina primativa, Acarinina praetopilensis, Acarinina rohri, Acarinina spinuloinflata, Acarinina topilensis, Bifarina sclseseyensis, Catapsydrax howei, Chiloguembelitria oveyi, Globigirinatheka barri, Globigirinatheka mexicana, Globigerinatheka tropicalis, Morozovelloides crassatus, Paragloborotalia nana, Parasubbotina griffinae, Pseudoglobigerinella cf. bolivariana, Subbotina senni, Turborotalia boweri, Turborotalita carcoselleensis, T.cerroazulensis, T. frontosa, T. praecentralis, and T. pseudomayeri.
  • Correlation: Globally, the present zone is equivalent with the middle Eocene P13 Orbulinoides beckmanni Zone of Toumarkine and Luterbacher [36], Berggren and Miller [41], Berggren et al. [42], and Mukhopadhyay [43] and the E12 Orbulinoides beckmanni Zone of Berggren and Pearson [34] and Wade et al. [35] in the tropical–subtropical regions. It also corresponded to the Globigerapsis beckmanni Zone of Blow [40] and matched with the Orbulinoides beckmanni Zone recorded from the middle Eocene of the Caribbean area [53] and Syria [54]. In Egypt, Abd El-Shafy et al. [38] recorded this zone from the middle Eocene of west central Sinai. Additionally, Anan [48] and Selima [49] recorded the Orbulinoides beckmanni Zone from the same time interval in the Western Desert and Nile Valley.

4.2.3. E 13. Morozovelloides crassatus Zone

  • Category: Highest Occurrence Zone
  • Age: middle Eocene (Bartonian)
  • Definition: The present zone was defined as a highest occurrence zone by Wade et al. [35] and includes the biostratigraphic interval between the HO of Orbulinoides beckmanni to the HO of Morozovelloides crassatus. The nomenclature and definition of this zone remains the same as in Berggren and Pearson [34].
  • Remarks: The present zone is recorded in the Gebal Abyiad section, measuring 85 m thick and represented by fifty-seven planktonic species, includes the upper part of the El Fashn Formation and the lower part of the Qurn Member of the Beni Suef Formation, and is also recorded in the Bayad El Arab section, measuring 29 m thick, includes forty-five species, and represents the exposed part of the El Fashn Formation and the basal part of the Qurn Member of the Beni Suef Formation. This zone also occupies the lower part of the Gehanam Formation in the Garabaa section and measures 23 m thick, represented by seventeen planktonic species. The lower boundary of this zone in the present study is located at the last occurrence of Orbulinoides beckmanni, while its upper boundary is distinguished by the disappearance of Morozovelloides crassatus and the associated spinose morozovellids and the large acarininids assemblages. Many authors considered the extinction of nearly all spinose planktonic assemblages (morozovellids and acarininids) in the tropical and sub-tropical regions of open marine conditions, which marks the upper boundary of the P14 Truncorotaloides rohri Zone, and traced the contact between the middle and the late Eocene [36,37,40,55]. The extinction of these forams occurs abruptly, while in the cooler regions, it is less distinct and the middle/upper Eocene boundary is often difficult to determine [36]. Moreover, some authors considered the middle /late Eocene boundary to be located within the Globigerinatheka semiinvoluta Zone [10,34,35,38,42,43,56]. Berggren et al. [42] considered that Globigerinatheka semiinvoluta is slightly older than the last occurrence of Acarinina rohri and the associated spinose forams. In this work, the present zone coincides with the E13 Morozovelloides crassatus Zone of Berggren and Pearson [34] and Wade et al. [35], where they considered Morozovelloides crassatus to be the senior synonym of Morozovelloides spinulosa and the HO of this species, with most of the spinose forms being synchronous.
  • Assemblages: Sixty-four planktonic species are identified from this zone (Figure 9, Figure 10 and Figure 11). The more characteristic species besides the zonal marker are Acarinina bullbrooki, A.libyaensis, A. matthewsae, A. medizzai, A. pentacamerata, A. rohri, A. spinuloinflata, A. topilensis, Catapsydrax dissimilis, Ca. africanus, Chiloguembelina cubensis, C. ototara, Dentoglobigerina galavisi, D. pseudovenzuelana, D. tripartite, Globigerinatheka barri, G. index, G. mexicana, G. rubriformis, G. tropicalis, Globorotaloides suteri, Globoturborotalia euapertura, G. martini, G. ouachitensis, G. praebulloides, Morozovelloides bandyi, M. coronatus, Pseudohastigerina danvilensis, P. micra, and Turborotalia cerroazulensis, T. cocoaensis, T. increbescens, T. pomeroli, Subbotina angiporoides, S. eocaena, S. hagni, S. minima, Streptochilus martini, and S. yeguaensis.
  • Correlation: The present zone is completely equivalent with the E13 Morozovelloides crassatus Zone, which was recorded from the late middle Eocene of the tropical–subtropical regions [34,35], Tunisia [56], and Egypt [10]. Worldwide, this is matched with the P14 Truncorotaloides rohri Zone, defined from the same time interval by Bolli, [39], Toumarkine and Bolli [57], Blow [40], Toumarkine and Luterbacher [36], Berggren and Miller [41], and Imam [58] and is also equated with the Truncorotaloides rohri/Morozovella spinulosa Zone of Berggren et al. [42]. It is also matched with the Morozovelloides crassatus/Globigerinatheka kugleri Zone, which was recorded from the late middle Eocene of Iran by Babazadeh and Cluzel [44]. In Egypt, the present zone is equivalent with the Truncorotaloides rohri Zone, defined by many authors from late middle Eocene in different localities [13,28,29,37,47,55,59].
Diversity 17 00116 g012
Figure 12. Correlation of the recorded planktonic biozones [3,10,28,29,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,55,56,58] in the studied sections with those planktonic zones in Egypt and other regions.
Figure 12. Correlation of the recorded planktonic biozones [3,10,28,29,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,55,56,58] in the studied sections with those planktonic zones in Egypt and other regions.
Diversity 17 00116 g012

4.2.4. E 14. Globigerinatheka semiinvoluta Zone

  • Category: Highest Occurrence Zone
  • Age: late middle Eocene–early late Eocene (Bartonian–Priabonian)
  • Definition: This zone was previously defined by Bolli [39] and was then modified by Wade et al. [35] as a highest occurrence zone, defined by the interval between the HO of Morozovelloides crassatus to the HO of Globigerinatheka semiinvoluta.
  • Remarks: The present zone is recorded in the Gabal Abyiad section, measuring 11 m thick and represented by eighteen planktonic species, includes the upper exposed part of the Qurn Member of the Beni Suef Formation. It is also recorded in the Bayad El Arab section at 48 m thick, represented by twenty-one planktonic species and including the upper part (27 m thick) of the Qurn Member and the lower part (21 m thick) of the Tarbul Member of the Beni Suef Formation. It unconformably overlies the late middle Eocene Morozovelloides crassatus Zone. Its lower boundary is taken at the last appearance of Morozovelloides crassatus and the associated spinose assemblages of morozovellids and large acarininids, whereas its upper boundary is not defined because of the absence of the nominate taxon. The present zone is characterized by the occurrence of Turborotalia cerroazulensis and T. cocoaensis, which represent the advanced forms of Turborotalia cerroazulensis lineage, besides specimens of Turborotalia ampliapertura and T. centralis, in addition to common assemblages of Subbotina eocaena, S. angiporoides, Dentoglobigerina venezuelana, and D. tripartita which characterize the assemblages of this zone in the tropical and sub-tropical regions, as mentioned by Toumarkine and Luterbacher [36]. In the temperate regions or higher latitudes, the marker species to this zone is absent, abundant assemblages of Globigerinatheka subconglobata luterbacheri, and Gk. index occur, and most of the spinose planktonic species disappear at the contact between the late middle and late Eocene; only the very small spinose acarininids and globigerinids continue into the late Eocene [36,57,60].
  • Assemblages: Twenty-nine planktonic species are identified from this zone (Figure 10 and Figure 11). The more characteristic assemblages are Acarinina medizzai, Catapsydrax dissimilis, Chiloguembelina cubensis, Dentoglobigerina tripartite, D. venezuelana, Globigerinatheka index, GK. subconglobata, Globoturborotalita gnauki, G. martini, G. occlusa, Globorotaloides suteri, Parasubbotina inaequispira, Paragloborotalia nana, Pseudohastegerina micra, P. naguawichiensis, Tenuitella angustiumbilicata, Turborotalia ampliapertura, T. centralis, T. cerroazulensis, T. cocoaensis, Subbotina angiporoides, S. corpulenta, S. eocaena, S. linaperta, and S. yaguaensis.
  • Correlation: Globally, the present zone is equivalent to the late Eocene Globigerinatheka semiinvoluta Zone [36,39,40,41,47,48,58]. Meanwhile, the more recent studies assigned a late middle–early late Eocene age to this zone [10,28,29,34,35,42,56]. Also, this zone could be correlated with the Turborotalia pseudoampliapertura and Globigerinatheka semiinvoluta zones recorded from the late Eocene in different areas of Egypt [3,37,46,55]. It is also matched with the Globigerapsis semiinvoluta Zone, defined by Bolli and Cita [61] from Italy and is also correlated with the same zone defined by Al-Helou [54] from Syria.

5. Discussion

5.1. Paleoenvironment

Foraminifera show extreme sensitivity to paleoenvironmental changes, which make them crucial tools for paleoecological estimation. Knowing the ecological preferences of the identified species offers a better understanding of the environmental evaluation. The depositional settings of the studied sections are reconstructed based on detailed lithological observations, coupled with the occurrence of macrofauna (gastropods and bivalves), trace fossils, and the recorded benthic foraminiferal assemblages. The statistical analysis of the obtained data, which are mainly focused on the total foraminiferal numbers in each samples, were counted, and we calculated the planktonic to benthic ratios (P%) and calcareous to arenaceous ratios (C%), the epifaunal and infaunal ratios. Also, some statistical analyses on the calcareous benthic foraminifera, including Miliolina %, Lagenina %, and Rotalia %, were calculated.
These ecologic parameters are summarized in Figure 13 and Figure 14. Additionally, the ternary plot diagram (after Murray [33]) was used in this study (Figure 15).

5.1.1. Qarara Formation

This rock unit is exposed in the Gabal Abyiad section and is composed mainly of limestone and thin marl beds throughout, with shale bed at the base. The marl beds are rich in both planktonic and benthic foraminifera, while the limestone and shale beds contain rare to common faunal assemblages. As shown in Figure 14A, the planktonic ratios fluctuate between 0% and 53.8% in some beds. In addition, the calcareous ratios represented by high percentages reach 100% in some intervals and the benthic epifaunal ratios are higher than the infaunal values, reaching 92.5% at some levels, suggesting an inner to middle shelf environment with high oxygen levels and a deeper outer neritic environment under low oxygen levels at some intervals. This opinion is mainly based on the occurrence of epifaunal species such as Eponides spp., Cibicides spp., Pararotalia spp., and Cancris spp., which prefer oxic settings and inner shelf environments [9,12,62].
These environmental conditions are greatly similar with those prevailing in the deposition of the Lutetian–early Bartonian Observatory Formation in the Cairo–Helwan area, north Eastern Desert, Egypt [8]. Furthermore, the inner to middle neritic environments are also characterized by low values of the planktonic foraminifera and the dominance of benthic ratio, as mentioned by Phleger [63], Hewaidy and Strougo [64], Saber and Salama [7], and Ramadan et al. [19]. According to the work of Bassiouni and Luger [65], the inner neritic environment is characterized by a planktonic ratio between 1 and 10%, the middle neritic is between 25 and 41%, and the outer neritic is more than 61%.

5.1.2. El Fashn Formation

The present rock unit is completely exposed in the Gabal Abyiad section and represented by its upper part in the Bayad El Arab section. It is composed mainly of shales at the lower part, followed upward by limestone with thin marl at the middle part and topped by limestone at its upper part. Both of the planktonic and benthic foraminifera are represented by common to abundant assemblages through this rock unit. The planktonic specimens highly occurred in the shale and marl beds and are greatly represented by assemblages related to the acarininids, morozovellids, and, only somewhat, the sub-globular and globular species. Furthermore, the calcareous benthic foraminifera are represented by the high numbers of specimens related to the Rotaliina throughout. The planktonic ratios fluctuate between 0 and 40% and, at some levels, exceed 50% (bed no. 67), whereas the benthic Lagenina ratios are between 0 and 50% and the Rotaliina ratios are between 70 and 90%, reaching 100% at some levels. The ratios of epifaunal assemblages are between 30 and 90%, as shown in Figure 14A–C. The plots of the benthic foraminiferal fauna for this formation on the Ternary diagram are distributed in the Rotaliina corner and close to the Rotaliina-Miliolina line, near the Rotaliina corner (Figure 15B,C). The study of Boersma [62] indicated that the planktonic/benthic ratio for the middle neritic environment is between 15 and 30%, while for the outer neritic environment, it reaches 50%. He also mentioned that for the upper continental slope, the planktonic ratio reaches 50–85%. The occurrence of spinose planktonic foraminiferal genera related to the acarininids and morozovillids indicated that these fauna were prominent surface dwellers characterizing the tropical and subtropical regions, and the rapid global extinction of these assemblages through the end of the middle Eocene (late Bartonian) was abrupt (Pearson et al. [63], Wade [64], Abd El-Gaied and Abd El-Aziz [13], and Cotton et al. [65]). Luger [66] mentioned that the planktonic/benthic ratios for the middle neritic environment are approximately 30%, whereas values above 50% characterize the slope environment. Moreover, Hewaidy [67], Abd El-Gaied et al. [8], and Ramadan et al. [20] mentioned that the planktonic ratios between 11 and 15% suggest an open shallower middle neritic environment. Saint Marc [68] stated that the low values of the arenaceous foraminifera characterize the environments with normal salinity, high contents of calcium carbonate, and well-oxygenated waters.
The above mentioned data, besides the previous studies, and the lithological characteristics indicate that the El Fashn Formation in the present study was deposited in a middle to outer neritic marine environment with moderate to low oxygen levels and warm water conditions. The environmental conditions that influenced the deposition of this rock unit are remarkably similar to those responsible for the deposition of the Bartonian El Fashn Formation in the northeastern Desert [10,11,12].

5.1.3. Gehannam Formation

The present rock unit is exposed in the Garabaa section and mainly composed of marls rich in benthic and planktonic foraminifera in the lower part, while limestones in the upper part are only marked by the occurrence of the benthic foraminifera. The abundance of the planktonic foraminifera in this rock unit is lower than those in the El Fashn and the Qarara formations. In addition, the abundance of the benthic Buliminids and Uvigerinids associations is much greater in the lower part of the formation than those in the upper part. The assemblages related to the Lenticulina group are represented by well-preserved, large-sized, and frequent associations throughout the formation. Moreover, assemblages which belong to the genus Bolivina also occurred, but with smaller sized tests and sparser numbers. As summarized in Figure 14D, the planktonic ratios are low, between 0 and 8.5%, became higher at the basal part and decrease upwards, and display complete absence through the upper part of the section. Conversely, the benthic ratios are much greater, exceeding 90% and reaching 100% at the upper parts. Additionally, the arenaceous specimens are represented, with values ranging between 0 and 14.5% and reaching 21.7%. at some levels (bed no. 6). On the other hand, the percentage of the infaunal benthos is recorded by high values, reaching 74.8% at the base and decreasing upwards, reaching 32% at the upper bed. The foraminiferal plots of this formation on the Ternary diagram are concentrated at the Rotaliina corner and slightly scattered through the Rotaliina-Miliolina field (Figure 15A). The occurrence of assemblages related to the genera Uvigerina reflect deep outer neritic and the uppermost bathyal environments, dysoxic to low oxic settings, and moderate eutrophic conditions [8,33,69,70,71]. The assemblages of the Bulimina and Uvigerina genera are also distinguishing the oxygen-minimum and the organic rich sediments, as mentioned by Miller and Lohmann [72]. Moreover, the occurrence of the Lenticulina group indicates mesotrophic conditions [73]. Meanwhile, the low values of the arenaceous/calcareous ratio characterize deposition in environments with well-oxygenated conditions, high temperature, normal salinity, and high calcium carbonate above the Carbonate Compensation Depth (CCCD), as mentioned by Saint Marc [68]. Also, El Ashwah and El Deep [74] stated that the deep middle neritic environment has an arenaceous/calcareous ratio equal to 4.17%, while the outer neritic is between 11.1% and 14.9%, the high ratio of the arenaceous/calcareous characterizes the cold water conditions, and the very low percentage (2.04%) distinguishes the warm waters.
The above mentioned analysis, besides the lithological characteristics, and the previous studies attest that the Gehannam Formation in the present study was deposited in an outer neritic environment under low oxygen water levels and high organic flux to the depositional basin for the lower part, a neritic marine environment with moderate oxygenated levels for the middle part, and warm water conditions for the upper part. These environmental conditions closely resemble those that controlled the deposition of the Bartonian–Priabonian Gehannam Formation in the Fayoum area [3,27].

5.1.4. Beni Suef Formation

This rock unit is classified into two members: the lower Qurn Member, which is mainly composed of shales capped by limestone, and the upper Tarbul Member, consisting of repeated beds of marls followed by limestones. The shales of the Qurn Member and the marls of the lower part of the Tarbul Member are rich in both the planktonic and benthic species, while the marls of the upper part of the Tarbul Member are rich in the small and large benthic foraminifera. The analysis of the foraminiferal numbers in this rock unit revealed a higher planktonic ratio, reaching about 79.7% at some levels for the Qurn Member in the Bayad El Arab section, whereas this ratio decreased and reached 26% in the lower part of the Tarbul Member. The arenaceous/calcareous ratio fluctuated between 0 and 32%, and the infaunal ratio was greatly higher in the Qurn Member compared with those in the Tarbul Member, where it reaches about 80%, as shown in Figure 14. The rotaliina is represented by abundant assemblages related to the genera Bulimina, Uvigerina, Anomalinoides, Lenticulina, and Cibicidoides, showing higher values compared with those of the lagenina and miliolina, reaching 100% in some samples. Moreover, abundant specimens related to the large benthic foraminifera (Nummulites) are distributed through the Tarbul Member. The plots of the benthic foraminiferal contents for the Beni Suef Formation on the Ternary diagram are distributed in the Rotaliina field and along the Rotaliina-Textulariina line near the Rotaliina corner (Figure 15B,C). The occurrence of the costate buliminid, hispido-costate to costate uvigerinid, and Bolivinid fauna characterize the outer neritic and the uppermost bathyal environment, where these fauna can live in depleted oxygen conditions [8,33,69,75]. Additionally, Murray [33] mentioned that the species related to the genera Uvigerina and Lenticulina reflect normal marine outer neritic to bathyal environments; also, the occurrence of assemblages related to the families Anomalinidae, Buliminidae, Nonionidae, and Bagginidae are indicative of the outer shelf and bathyal environments [75]. The occurrence of abundant nummulitid assemblages marks the inner to middle neritic environments and indicates water depths of less than 100 m, according to the works of Berggren [76] and Barr and Berggren [69]. The high ratios of the planktonic foraminifera (50%) with abundant specimens related to the genera Bulimina, Uvigerina, and Bolivina indicate a deposition in outer neritic environments with low oxygen conditions and high organic flux content at the bottom sediments [77,78,79,80]. The above mentioned discussion suggests that the Qurn Member of the Beni Suef Formation was deposited in an outer neritic to the uppermost bathyal environment with low oxygen levels, while the lower part of the Tarbul Member was deposited in a middle neritic marine environment under moderate oxygenated and warm water settings and the upper Tarbul Member was deposited in a shallower inner neritic environment with well-oxygenated and warm water conditions. This Bartonian/Priabonian shallowing corresponds to the sequence boundary (SB3), which has previously been identified in different localities in Egypt [7,81,82,83,84,85] and other neighboring areas including southern Israel and the Sirt basin [86]. Globally, this boundary was recognized by Haq et al. [87] and Hardenbol et al. [88], coinciding with the eustatic sea-level fall, marking the end of the middle Eocene [89]. This regional lowering of the sea level is related to the collision between the African, Arabian, and Eurasian plates [86,90,91].

6. Conclusions

The investigation of 125 rock samples collected from the exposed sections in the northwestern and northeastern parts of the Nile Valley, Egypt, resulted in the identifications of eighty planktonic foraminiferal species. These assemblages are related to two main groups, the first belongs to the superfamily Globigerinoidea, while the second one belongs to the superfamily Heterohelicoidea. The studied successions are classified into four litho-stratigraphic units, which are, in descending order, the Qarara, the El Fashn, the Gehannam (middle Eocene), and Beni Suef formations (middle–late Eocene). The stratigraphic distribution of the identified planktonic species enabled us to construct four planktonic biozones, named the Morozovelloides lehneri Zone (late Lutetian–Bartonian), Orbulinoides beckmanni Zone (early Bartonian), Morozovelloides crassatus Zone (Bartonian), and Globigerinatheka semiinvoluta Zone (late Bartonian–early Priabonian). These zones are described and correlated with those in Egypt and in the northern and southern Tethyan province. The environmental parameters suggest that the Qarara formation was deposited in an inner to middle neritic marine environment and at some levels in an outer neritic environment, whereas the El Fashn Formation was deposited in a middle to outer neritic marine environment. Moreover, the lower part of the Gehannam Formation was deposited in an outer neritic environment, while its upper part was deposited in a middle neritic marine environment. The Qurn Member of the Beni Suef Formation was deposited in an outer neritic to uppermost bathyal environment, while the lower part of the Tarbul Member accumulated in a middle neritic marine environment and its upper part was deposited in a shallower inner neritic environment. The environmental conditions that controlled the deposition of the middle and upper Eocene in the studied sections reflect a great similarity with those in the tropical and sub-tropical regions.

Author Contributions

Conceptualization, A.M. and I.M.A.E.-G.; methodology, S.A.B., I.M.A.E.-G., S.M.A.E.-A. and M.M.S.; validation, A.M., S.M.A.E.-A., M.M.S. and I.M.A.E.-G.; formal analysis, S.A.B. and I.M.A.E.-G.; investigation, S.A.B., S.M.A.E.-A., A.M. and I.M.A.E.-G.; data curation, S.A.B. and I.M.A.E.-G.; writing—original draft preparation, S.A.B. and I.M.A.E.-G.; writing—review and editing, A.M., S.A.B., M.M.S. and I.M.A.E.-G.; visualization, A.M. and I.M.A.E.-G.; supervision, A.M. and I.M.A.E.-G. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no funding.

Institutional Review Board Statement

Not Applicable.

Data Availability Statement

All data are available in the manuscript.

Acknowledgments

We are thankful to the IOAP of Open Access Funding by the University of Vienna.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. (A) Location map of Egypt; (B) Geologic map showing the studied sections (modified after Conoco [21]).
Figure 1. (A) Location map of Egypt; (B) Geologic map showing the studied sections (modified after Conoco [21]).
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Figure 2. (A,B) El Garabaa section, the marl at the base of the section near the cultivated land; (C,D) intercalations of marls with thin limestone beds at the lower part of the section; (E,F) limestone with thin marls at the upper part of the section.
Figure 2. (A,B) El Garabaa section, the marl at the base of the section near the cultivated land; (C,D) intercalations of marls with thin limestone beds at the lower part of the section; (E,F) limestone with thin marls at the upper part of the section.
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Figure 3. (A) General view of Gabal Abyiad section; (B) the El Fashn Formation; (C) the upper part of the Qarara Formation; (D) the exposed part of the Beni Suef Formation at the upper part of the Gabal Abied section; (E) close view of Thalassenoid limestone in the upper part of the Qarara Formation.
Figure 3. (A) General view of Gabal Abyiad section; (B) the El Fashn Formation; (C) the upper part of the Qarara Formation; (D) the exposed part of the Beni Suef Formation at the upper part of the Gabal Abied section; (E) close view of Thalassenoid limestone in the upper part of the Qarara Formation.
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Figure 4. (A) General view of Wadi Bayad El Arab section; (B) the upper part of the El Fashn Formation flowed by the Qurn and the Tarbul members of the Beni Suef Formation; (C) slop former of the shale capped by limestone at the lower part of the Qurn Member; (D) ferruginous thin layer topped the shale of the lower part of the Qurn Member; (E) the marls at the upper part of the Tarbul Member.
Figure 4. (A) General view of Wadi Bayad El Arab section; (B) the upper part of the El Fashn Formation flowed by the Qurn and the Tarbul members of the Beni Suef Formation; (C) slop former of the shale capped by limestone at the lower part of the Qurn Member; (D) ferruginous thin layer topped the shale of the lower part of the Qurn Member; (E) the marls at the upper part of the Tarbul Member.
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Figure 5. Litho- and biostratigraphic units of the middle and upper Eocene succession in the three studied sections.
Figure 5. Litho- and biostratigraphic units of the middle and upper Eocene succession in the three studied sections.
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Figure 6. SEM photos of some planktonic species recorded in the studied sections. (1) Catapsydrax dissimilis (Cushman and Bermudez), ventral view, sample no. 2, the El Fashn Fm, W. Bayad El Arab section; (2) Catapsydrax unicavus (Bolli), Loeblich and Tappan, ventral view, sample no. 73, the Qurn Member, the Beni Suef Fm, G. Abyiad section; (3) Catapsydrax africanus (Blow and Banner), ventral view, sample no. 9, the Qarara Fm, G. Abyiad section; (4) Paragloborotalia nana (Bolli), ventral view, sample no. b, the Gehannam Fm, Garabaa section; (5) Parasubbotina inaequispira (Subbotina), ventral view, sample no. 1, the Gehannam Fm, Garabaa section; (6, 7) Parasubbotina griffinae (Blow), peripheral and ventral views sample no. 19,the Qarara Fm, G. Abyiad section; (8, 9) Pseudoglobigerinella cf. bolivariana (Bolli), ventral and peripheral views, sample no. 9, the Qarara Fm, G. Abyiad section; (10) Globoturborotalita martini (Blow and Banner), ventral view, sample no. 43, the El Fashn Fm, G. Abyiad section; (11) Globoturborotalita gnauki (Blow and Banner), ventral view, sample no. 22, the Tarbul Member, the Beni Suef Fm, W. Bayad El Arab section; (12) Globoturborotalita praebulloides (Blow), ventral view, sample no. 3, the Qurn Member, the Beni Suef Fm, W. Bayad El Arab section; (13) Globoturborotalita euapertura (Jenkins), ventral view, sample no. 72, the Qurn Member, the Beni Suef Fm, G. Abyiad section; (14) Subbotina angiporoides (Hornibrook), ventral view, sample no. 43, the El Fashn Fm, G. Abyiad section; (15) Subbotina minima (Jenkins), ventral view, sample no. 68, the El Fashn Fm, G. Abyiad section; (16) Subbotina hagni (Gohrbandt), ventral view, sample no.b, the Gehannam Fm, Garabaa section; (17) Subbotina praeturritilina (Blow and Banner), ventral view, sample no. 1, the Gehannam Fm, Garabaa section; (18) Subbotina yeguaensis (Weinzierl and Applin), ventral view, sample no. 5, the Qurn Member, the Beni Suef Fm, W. Bayad El Arab section; (19) Subbotina corpulenta (Subbotina), ventral view, sample no. 22, the Tarbul Member, the Beni Suef Fm, W. Bayad El Arab section; (20) Turborotalita carcoselleensis (Toumarkine and Bolli), ventral view, sample no. 19, the Qarara Fm, G. Abyiad section. Bar scale 100 µm.
Figure 6. SEM photos of some planktonic species recorded in the studied sections. (1) Catapsydrax dissimilis (Cushman and Bermudez), ventral view, sample no. 2, the El Fashn Fm, W. Bayad El Arab section; (2) Catapsydrax unicavus (Bolli), Loeblich and Tappan, ventral view, sample no. 73, the Qurn Member, the Beni Suef Fm, G. Abyiad section; (3) Catapsydrax africanus (Blow and Banner), ventral view, sample no. 9, the Qarara Fm, G. Abyiad section; (4) Paragloborotalia nana (Bolli), ventral view, sample no. b, the Gehannam Fm, Garabaa section; (5) Parasubbotina inaequispira (Subbotina), ventral view, sample no. 1, the Gehannam Fm, Garabaa section; (6, 7) Parasubbotina griffinae (Blow), peripheral and ventral views sample no. 19,the Qarara Fm, G. Abyiad section; (8, 9) Pseudoglobigerinella cf. bolivariana (Bolli), ventral and peripheral views, sample no. 9, the Qarara Fm, G. Abyiad section; (10) Globoturborotalita martini (Blow and Banner), ventral view, sample no. 43, the El Fashn Fm, G. Abyiad section; (11) Globoturborotalita gnauki (Blow and Banner), ventral view, sample no. 22, the Tarbul Member, the Beni Suef Fm, W. Bayad El Arab section; (12) Globoturborotalita praebulloides (Blow), ventral view, sample no. 3, the Qurn Member, the Beni Suef Fm, W. Bayad El Arab section; (13) Globoturborotalita euapertura (Jenkins), ventral view, sample no. 72, the Qurn Member, the Beni Suef Fm, G. Abyiad section; (14) Subbotina angiporoides (Hornibrook), ventral view, sample no. 43, the El Fashn Fm, G. Abyiad section; (15) Subbotina minima (Jenkins), ventral view, sample no. 68, the El Fashn Fm, G. Abyiad section; (16) Subbotina hagni (Gohrbandt), ventral view, sample no.b, the Gehannam Fm, Garabaa section; (17) Subbotina praeturritilina (Blow and Banner), ventral view, sample no. 1, the Gehannam Fm, Garabaa section; (18) Subbotina yeguaensis (Weinzierl and Applin), ventral view, sample no. 5, the Qurn Member, the Beni Suef Fm, W. Bayad El Arab section; (19) Subbotina corpulenta (Subbotina), ventral view, sample no. 22, the Tarbul Member, the Beni Suef Fm, W. Bayad El Arab section; (20) Turborotalita carcoselleensis (Toumarkine and Bolli), ventral view, sample no. 19, the Qarara Fm, G. Abyiad section. Bar scale 100 µm.
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Figure 7. SEM photos for some planktonic species recorded in the studied sections (1) Globigerinatheka barri Bronnimann, ventral view, sample no. 76, the Qurn Member, the Beni Suef Fm, G. Abyiad section; (2, 3) Globigerinatheka index (Finlay), ventral view, sample no. 5, the Qurn Member, the Beni Suef Fm, W. Bayad El Arab section; (4) Globigerinatheka mexicana (Cushman), ventral view, sample no. 9, the Qarara Fm, G. Abyiad section; (5, 6) Globigerinatheka rubriformis (Subbotina), ventral views, sample no. 43, the El Fashn Fm, G. Abyiad section; (7) Globigerinatheka tropicalis (Blow and Banner), ventral view, sample no. 73, the Qurn Member, the Beni Suef Fm, G. Abyiad section; (8) Globigerinatheka subconglobata (Shutskaya), ventral view, sample no. 10, the Qurn Member, the Beni Suef Fm, W. Bayad El Arab section; (9) Orbulinoides beckmanni (Saito), sample no. 19, the Qarara Fm, G. Abyiad section; (10) Acarinina bullbrooki (Bolli), ventral view, sample no. 5, the Gehannam Fm, Garabaa section; (11) Acarinina collectea (Finlay), ventral view, sample no. 37, the El Fashn Fm, G. Abyiad section; (12) Acarinina hayensi (Samanta), ventral view, sample no. 19, the Qarara Fm, G. Abyiad section; (13) Acarinina libyaensis (El Khoudary), ventral view, sample no. 43, the El Fashn Fm, G. Abyiad section; (14) Acarinina mayoensis (Brönnimann and Bermudez), ventral view, sample no. 30, the El Fashn Fm, G. Abyiad section; (15) Acarinina medizzai (Toumarkine and Bolli), ventral view, sample no. 76, the Qurn Member, the Beni Suef Fm, G. Abyiad section; (16) Acarinina pentacamerata (Subbotina), ventral view, sample no. 55, the El Fashn Fm, G. Abyiad section; (17) Acarinina piparoensis (Brönnimann and Bermudez), ventral view, sample no. 19, the Qarara Fm, G. Abyiad section; (18) Acarinina praetopilensis (Blow), ventral view, sample no. 30, the El Fashn Fm, G. Abyiad section; (19) Acarinina rohri (Brönnimann and Bermudez), ventral view, sample no. 1, the Gehannam Fm, Garabaa section; (20) Acarinina spinuloinflata (Bandy), ventral view, sample no. 47, the El Fashn Fm, G. Abyiad section. Bar scale 100 µm.
Figure 7. SEM photos for some planktonic species recorded in the studied sections (1) Globigerinatheka barri Bronnimann, ventral view, sample no. 76, the Qurn Member, the Beni Suef Fm, G. Abyiad section; (2, 3) Globigerinatheka index (Finlay), ventral view, sample no. 5, the Qurn Member, the Beni Suef Fm, W. Bayad El Arab section; (4) Globigerinatheka mexicana (Cushman), ventral view, sample no. 9, the Qarara Fm, G. Abyiad section; (5, 6) Globigerinatheka rubriformis (Subbotina), ventral views, sample no. 43, the El Fashn Fm, G. Abyiad section; (7) Globigerinatheka tropicalis (Blow and Banner), ventral view, sample no. 73, the Qurn Member, the Beni Suef Fm, G. Abyiad section; (8) Globigerinatheka subconglobata (Shutskaya), ventral view, sample no. 10, the Qurn Member, the Beni Suef Fm, W. Bayad El Arab section; (9) Orbulinoides beckmanni (Saito), sample no. 19, the Qarara Fm, G. Abyiad section; (10) Acarinina bullbrooki (Bolli), ventral view, sample no. 5, the Gehannam Fm, Garabaa section; (11) Acarinina collectea (Finlay), ventral view, sample no. 37, the El Fashn Fm, G. Abyiad section; (12) Acarinina hayensi (Samanta), ventral view, sample no. 19, the Qarara Fm, G. Abyiad section; (13) Acarinina libyaensis (El Khoudary), ventral view, sample no. 43, the El Fashn Fm, G. Abyiad section; (14) Acarinina mayoensis (Brönnimann and Bermudez), ventral view, sample no. 30, the El Fashn Fm, G. Abyiad section; (15) Acarinina medizzai (Toumarkine and Bolli), ventral view, sample no. 76, the Qurn Member, the Beni Suef Fm, G. Abyiad section; (16) Acarinina pentacamerata (Subbotina), ventral view, sample no. 55, the El Fashn Fm, G. Abyiad section; (17) Acarinina piparoensis (Brönnimann and Bermudez), ventral view, sample no. 19, the Qarara Fm, G. Abyiad section; (18) Acarinina praetopilensis (Blow), ventral view, sample no. 30, the El Fashn Fm, G. Abyiad section; (19) Acarinina rohri (Brönnimann and Bermudez), ventral view, sample no. 1, the Gehannam Fm, Garabaa section; (20) Acarinina spinuloinflata (Bandy), ventral view, sample no. 47, the El Fashn Fm, G. Abyiad section. Bar scale 100 µm.
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Diversity 17 00116 g008
Figure 8. SEM photos of some planktonic species recorded in the studied sections. (1, 2) Acarinina topilensis (Cushman), ventral and dorsal views, sample no. 19, the Qararra Fm, G. Abyiad section; (3) Morozovelloides bandyi (Fleisher), ventral view, sample no. 9, the Qararra Fm, G. Abyiad section; (4) Morozovelloides coronatus (Blow), ventral view, sample no. 52, the El Fashn Fm, G. Abyiad section; (5) Morozovelloides crassatus (Cushman), ventral view, sample no. 47, the El Fashn Fm, G. Abyiad section; (6) Igorina broedermanni (Cushman and Bermudez), ventral view, sample no. 29, the El Fashn Fm, G. Abyiad section; (7) Dentoglobigerina cf. tripartite (Blow), ventral view, sample no. 2, the Qurn Member, the Beni Suef Fm, W. Bayad El Arab section; (8) Dentoglobigerina galavisi (Bermudez), ventral view, sample no. 67, the El Fashn Fm, G. Abyiad section; (9) Dentoglobigerina tripartite (Koch), ventral view, sample no. 22, the Tarbul Member, the Beni Suef Fm, W. Bayad El Arab section; (10) Dentoglobigerina venezuelana (Hedberg), ventral view sample no. 24, the Tarbul Member, the Beni Suef Fm, W. Bayad El Arab section; (11) Pseudohastigerina danvillensis (Howe and Wallace), ventral view, sample no. 73, the Qurn Member, the Beni Suef Fm, G. Abyiad section; (12) Pseudohastigerina micra (Cole), ventral view, sample no. 5, the Qarara Fm, G. Abyiad section; (13). Pseudohastigerina naguewichiensis (Myatliuk), ventral view, sample no. 7, the El Fashn Fm, W. Bayad El Arab section; (14) Turborotalia ampliapertura (Bolli), ventral view, sample no. 78, the Qurn Member, the Beni Suef Fm, G. Abyiad section; (15, 16) Turborotalia cerroazulensis (Cole), peripheral and ventral views, sample no. 43, the El Fashn Fm, G. Abyiad section; (17) Turborotalia centralis (Cushman and Bermudez), ventral view, sample no. 32, the El Fashn Fm, G. Abyiad section; (18) Turborotalia cocoaensis (Cushman, 1928), ventral view, sample no. 7, the El Fashn Fm, W. Bayad El Arab section; (19) Turborotalia frontosa (Subbotina), ventral view, sample no. 32, the El Fashn Fm, G. Abyiad section; (20) Turborotalia increbescens (Bandy), ventral view, sample no. 39, the El Fashn Fm, G. Abyiad section; (21) Turborotalia praecentralis (Blow), ventral view, sample no. 19, the Qarara Fm, G. Abyiad section; (22) Turborotalia possagnoensis (Toumarkine and Bolli), ventral view, sample no. 9, the Qarara Fm, G. Abyiad section; (23, 24) Chiloguembelitria oveyi (Ansary), side view, sample no. 24, the El Fashn Fm, G. Abyiad section; (25–27) Chiloguembelinia cubensis (Palmer), side view, sample no. 20, the Tarbul Member, the Beni Suef Fm, W. Bayad El Arab section; (28) Chiloguembelinia ototara (Finlay), side view, sample no. 10, the Qurn Member, the Beni Suef Fm, W. Bayad El Arab section; (29, 30) Streptochilus martini (Pijpers), side view, sample no. 10, the Qurn Member, the Beni Suef Fm, W. Bayad El Arab section; (31) Tenuitella angustiumbilicata (Bolli), ventral view, sample no. 72, the Qurn Member, the Beni Suef Fm, G. Abyiad section; (32) Morozovelloides coronatus (Cushman and Jarvis), ventral view, sample no. 9, the Qarara Fm, G. Abyiad section. Bar scale 100 µm.
Figure 8. SEM photos of some planktonic species recorded in the studied sections. (1, 2) Acarinina topilensis (Cushman), ventral and dorsal views, sample no. 19, the Qararra Fm, G. Abyiad section; (3) Morozovelloides bandyi (Fleisher), ventral view, sample no. 9, the Qararra Fm, G. Abyiad section; (4) Morozovelloides coronatus (Blow), ventral view, sample no. 52, the El Fashn Fm, G. Abyiad section; (5) Morozovelloides crassatus (Cushman), ventral view, sample no. 47, the El Fashn Fm, G. Abyiad section; (6) Igorina broedermanni (Cushman and Bermudez), ventral view, sample no. 29, the El Fashn Fm, G. Abyiad section; (7) Dentoglobigerina cf. tripartite (Blow), ventral view, sample no. 2, the Qurn Member, the Beni Suef Fm, W. Bayad El Arab section; (8) Dentoglobigerina galavisi (Bermudez), ventral view, sample no. 67, the El Fashn Fm, G. Abyiad section; (9) Dentoglobigerina tripartite (Koch), ventral view, sample no. 22, the Tarbul Member, the Beni Suef Fm, W. Bayad El Arab section; (10) Dentoglobigerina venezuelana (Hedberg), ventral view sample no. 24, the Tarbul Member, the Beni Suef Fm, W. Bayad El Arab section; (11) Pseudohastigerina danvillensis (Howe and Wallace), ventral view, sample no. 73, the Qurn Member, the Beni Suef Fm, G. Abyiad section; (12) Pseudohastigerina micra (Cole), ventral view, sample no. 5, the Qarara Fm, G. Abyiad section; (13). Pseudohastigerina naguewichiensis (Myatliuk), ventral view, sample no. 7, the El Fashn Fm, W. Bayad El Arab section; (14) Turborotalia ampliapertura (Bolli), ventral view, sample no. 78, the Qurn Member, the Beni Suef Fm, G. Abyiad section; (15, 16) Turborotalia cerroazulensis (Cole), peripheral and ventral views, sample no. 43, the El Fashn Fm, G. Abyiad section; (17) Turborotalia centralis (Cushman and Bermudez), ventral view, sample no. 32, the El Fashn Fm, G. Abyiad section; (18) Turborotalia cocoaensis (Cushman, 1928), ventral view, sample no. 7, the El Fashn Fm, W. Bayad El Arab section; (19) Turborotalia frontosa (Subbotina), ventral view, sample no. 32, the El Fashn Fm, G. Abyiad section; (20) Turborotalia increbescens (Bandy), ventral view, sample no. 39, the El Fashn Fm, G. Abyiad section; (21) Turborotalia praecentralis (Blow), ventral view, sample no. 19, the Qarara Fm, G. Abyiad section; (22) Turborotalia possagnoensis (Toumarkine and Bolli), ventral view, sample no. 9, the Qarara Fm, G. Abyiad section; (23, 24) Chiloguembelitria oveyi (Ansary), side view, sample no. 24, the El Fashn Fm, G. Abyiad section; (25–27) Chiloguembelinia cubensis (Palmer), side view, sample no. 20, the Tarbul Member, the Beni Suef Fm, W. Bayad El Arab section; (28) Chiloguembelinia ototara (Finlay), side view, sample no. 10, the Qurn Member, the Beni Suef Fm, W. Bayad El Arab section; (29, 30) Streptochilus martini (Pijpers), side view, sample no. 10, the Qurn Member, the Beni Suef Fm, W. Bayad El Arab section; (31) Tenuitella angustiumbilicata (Bolli), ventral view, sample no. 72, the Qurn Member, the Beni Suef Fm, G. Abyiad section; (32) Morozovelloides coronatus (Cushman and Jarvis), ventral view, sample no. 9, the Qarara Fm, G. Abyiad section. Bar scale 100 µm.
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Diversity 17 00116 g009
Figure 9. Stratigraphic range chart of the recorded planktonic foraminifera species and the proposed biozones in the Garabaa section. B means the base of the section.
Figure 9. Stratigraphic range chart of the recorded planktonic foraminifera species and the proposed biozones in the Garabaa section. B means the base of the section.
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Diversity 17 00116 g010
Figure 10. (a,b) Stratigraphic range chart of the recorded planktonic foraminifera species and the proposed biozones in the G. Abyiad section.
Figure 10. (a,b) Stratigraphic range chart of the recorded planktonic foraminifera species and the proposed biozones in the G. Abyiad section.
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Diversity 17 00116 g011
Figure 11. Stratigraphic range chart of the recorded planktonic foraminifera species and the proposed biozones in the Byad El Arab section.
Figure 11. Stratigraphic range chart of the recorded planktonic foraminifera species and the proposed biozones in the Byad El Arab section.
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Diversity 17 00116 g013
Figure 13. Histogram represents the percentages of the benthic foraminiferal groups (Arenaceous, Miliolina, Lagenina, and Rotaliina) in the studied sections ((A) Garabaa, (B) Gabal Abyiad, (C) Wadi Bayad El Arab).
Figure 13. Histogram represents the percentages of the benthic foraminiferal groups (Arenaceous, Miliolina, Lagenina, and Rotaliina) in the studied sections ((A) Garabaa, (B) Gabal Abyiad, (C) Wadi Bayad El Arab).
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Diversity 17 00116 g014
Figure 14. Statistical analysis of the foraminiferal assemblages in the three studied sections: (A,B) Gabal Abyiad section; (C) Wadi Bayad El Arab section; (D) Garabaa section.
Figure 14. Statistical analysis of the foraminiferal assemblages in the three studied sections: (A,B) Gabal Abyiad section; (C) Wadi Bayad El Arab section; (D) Garabaa section.
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Diversity 17 00116 g015
Figure 15. Ternary diagrams represent the distribution of the benthic foraminiferal assemblages in the studied rock units (after Murray [33]) ((A) Garabaa section, (B) Gabal Abyiad section, (C) Wadi Bayad El Arab section).
Figure 15. Ternary diagrams represent the distribution of the benthic foraminiferal assemblages in the studied rock units (after Murray [33]) ((A) Garabaa section, (B) Gabal Abyiad section, (C) Wadi Bayad El Arab section).
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Table 1. Planktonic groups (superfamilies, families, genera, and species) and distribution of species in the recorded biozones. Note that X means that the species is recoded; E11 = Morozovelloides lehneri Zone; E12 = Orbulinoides beckmanni Zone; E13 = Morovovelloides crassatus Zone; E14 = Globigerinatheka semiinvoluta Zone.
Table 1. Planktonic groups (superfamilies, families, genera, and species) and distribution of species in the recorded biozones. Note that X means that the species is recoded; E11 = Morozovelloides lehneri Zone; E12 = Orbulinoides beckmanni Zone; E13 = Morovovelloides crassatus Zone; E14 = Globigerinatheka semiinvoluta Zone.
SuperfamiliesFamiliesGeneraSpeciesBiozones
E11E12E13E14
GlobigerinoideaGlobigerinidaeCatapsydraxC. africanusx x
C. dissimilisx xx
C. howei xx
C. unicavus x
GloborotaloidesG. permicrus x
G. suteri xx
ParagloborotaliaP. nana xxx
ParasubbotinaP. griffinaeXX
P. inaequispiraXXXX
PseudoglobigerinellaP. cf. bolivarianaXX
GlobigerinaG. turgidaXX
GlobturborotalitaG. euapertura X
G. gnaukiXXXX
G. martiniXXXX
G. occlusaXXXX
G. ouachitensis XX
G. praebulloides XX
SubbotinaS. angiporoides XXX
S. corpulentaXXXX
S. eocaenaXXXX
S. hagniXXX
S. linapertaXXXX
S. minima XX
S. praeturritilinaXXX
S. yeguaensis XX
S. senni X
TurborotalitaT. carcoelleensis X
GlobigerinathekaG. barri XX
G. index XX
G. mexicanaXXX
G. rubriformis X
G. subconglobata XX
G. tropicalis XX
OrbulinoidesO. beckmanni X
TruncorotaloididaeAcarininaA. bullbrookiXXX
A. collectea XX
A. hayensiXXX
A. libyaensisXXX
A. mayaroensisXXX
A. matthewsaeXXX
A. medizzai XX
A. nicoli X
A. pentacamerataxxx
A. piparoensisxx
A. praetopilensisxxx
A. primitiva xx
A. rohrixxx
A. spinuloinflataxxx
A. topilensisxxx
MorozovelloidesM. bandyixxx
M. coronatusxxx
M. crassatusxxx
M. lehnerix
IgorinaI. broedermanixxx
GloboquadrinidaeDentoglobigerinaD. galavisi x
D. pseudovenezuelana xx
D. cf. tripartita xx
D. tripartita xx
D. venezuelana xx
HedbergellidaePseudohastigerinaP. danvillensis xx
P. micraxxxx
P. naguewichiensis xx
TurborotaliaT. ambliapertura x
T. bowerixx
T. cerroazulensisxxxx
T. centralisxxxx
T. cocoaensis xx
T. frontosa x
T. increbescens x
T. praecentralis x
T. pseudomayeri x
T. pomeroli x
T. possagnoensisx
HeterohelicoideaGuembelitriidaeChiloguembelitriaC. oveyi x
ChiloguembelinidaeChiloguembelinaC. cubensisx xx
C. cf. cubensis x
C. ototara xx
StreptochilusS. martini x
HeterohelicidaeBifarinaB. selseyensis x
GlobigerinitidaeTenuitellaT. angustiumbilicata xx
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Abu Bakr, S.; Abd El-Gaied, I.M.; Abd El-Aziz, S.M.; Sayed, M.M.; Mahmoud, A. Planktonic Foraminifera of the Middle and Upper Eocene Successions at the Northwestern and Northeastern Sides of the Nile Valley, Egypt: Stratigraphic and Paleoenvironmental Implications. Diversity 2025, 17, 116. https://doi.org/10.3390/d17020116

AMA Style

Abu Bakr S, Abd El-Gaied IM, Abd El-Aziz SM, Sayed MM, Mahmoud A. Planktonic Foraminifera of the Middle and Upper Eocene Successions at the Northwestern and Northeastern Sides of the Nile Valley, Egypt: Stratigraphic and Paleoenvironmental Implications. Diversity. 2025; 17(2):116. https://doi.org/10.3390/d17020116

Chicago/Turabian Style

Abu Bakr, Safaa, Ibrahim M. Abd El-Gaied, Sayed M. Abd El-Aziz, Mostafa M. Sayed, and Abdelaziz Mahmoud. 2025. "Planktonic Foraminifera of the Middle and Upper Eocene Successions at the Northwestern and Northeastern Sides of the Nile Valley, Egypt: Stratigraphic and Paleoenvironmental Implications" Diversity 17, no. 2: 116. https://doi.org/10.3390/d17020116

APA Style

Abu Bakr, S., Abd El-Gaied, I. M., Abd El-Aziz, S. M., Sayed, M. M., & Mahmoud, A. (2025). Planktonic Foraminifera of the Middle and Upper Eocene Successions at the Northwestern and Northeastern Sides of the Nile Valley, Egypt: Stratigraphic and Paleoenvironmental Implications. Diversity, 17(2), 116. https://doi.org/10.3390/d17020116

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