High-resolution sequence stratigraphy of the Upper Cretaceous-Lower ...

Arabian Journal of Geosciences (2017) 10:531 https://doi.org/10.1007/s12517-017-3319-z

ORIGINAL PAPER

High-resolution sequence stratigraphy of the Upper Cretaceous-Lower Paleogene succession, Gabal Qreiya area, Upper Egypt Ahmed R. M. El-Younsy 1 & Nageh A. Obaidalla 1 & Emad R. Philobbos 1 & Abdelhamid M. Salman 1 Received: 29 October 2016 / Accepted: 30 November 2017 # Saudi Society for Geosciences 2017

Abstract The Upper Cretaceous-Lower Paleogene succession at Gabal Qreiya area that covers six rock units, Quseir, Duwi, Dakhla, Tarawan, Esna, and Thebes formations, is reviewed through a high-resolution sequence stratigraphic analysis. Six third-order depositional sequences and their associated surfaces and systems tracts are recognized based on stratigraphic, sedimentological, and high-resolution foraminiferal studies. The pre-Campanian sequence, comprising the Quseir Formation, was accumulated in inner neritic paleodepths, on marginal to shallow subtidal shelf. The Lower Campanian sequence that covers the Duwi Formation was accumulated in oscillating settings between inner to middle neritic paleodepths, on a shallow subtidal shelf. The Upper Campanian-Maastrichtian sequence that covers the lower part of the Dakhla Formation was accumulated in outer neritic-upper bathyal to middle neritic paleodepths, on a deep subtidal shelf to a shallow subtidal shelf. The Danian sequence that covers the middle part of the Dakhla Formation was accumulated in oscillating conditions between upper bathyal and middle neritic paleodepths, on a deep subtidal and a shallow subtidal shelf. The Selandian-Thanetian sequence that comprises the upper part of the Dakhla, Tarawan, and the lower part of the Esna formations was accumulated in fluctuating conditions from upper bathyal to middle neritic paleodepths, on a deep subtidal to a shallow subtidal shelf. The Ypresian sequence that includes the main parts of Esna and Thebes formations was accumulated in fluctuating settings among middle bathyal and middle neritic paleodepths, on a deep subtidal to a shallow subtidal shelf. Most of the sequence boundaries coincide with the global sea-level curve whereas some of them suggest a local tectonic event. Keywords Sequence stratigraphy . Systems tracts . Facies analysis . Depositional environments . Paleobathymetry

Introduction and geologic setting The Upper Cretaceous-Lower Paleogene mixed Siliciclastic, carbonate, and phosphorite succession (~ 218 m thick) exposed at Gabal Qreiya area, Upper Egypt, is characterized by pronounced facies variations, wide-ranging ages, distinct depositional changes, and obvious sedimentation breaks. This is owing to the interplay between the relative sea-level fluctuations and tectonic events. Extensive numerous sedimentological, stratigraphical, and paleontological studies at Gabal Qreiya area, Upper Egypt, were carried out including Said

* Ahmed R. M. El-Younsy [email protected] 1

Geology Department, Faculty of Science, Assiut University, P.O. Box: 71516, Assiut, Egypt

(1962, 1990), Abdel Razik (1972), El-Naggar (1970), Faris (1974, 1984, 1997), Faris et al. (1985), Soliman et al. (1986), Bandel et al. (1987), Hendriks and Luger (1987), Hendriks et al. (1987, 1990), Luger (1988), Luger and Gröeschke (1989), Hamama and Kassab (1990), Kassab and Hamama (1991), Luger et al. (1998), Tantawy (1998, 2003, 2006), Keller (2002), Keller et al. (2002), Berggren and Ouda (2003), Dupuis et al. (2003), Knox et al. (2003), Ouda and Aubry (2003), Speijer (2003), Soliman and Obaidalla (2010), and Aubry and Salem (2013). In spite this, no detailed sequence stratigraphic studies for exposed succession have been published in the studied area. Therefore, the current work aims to provide high-resolution sequence stratigraphic studies of the Upper Cretaceous-Lower Paleogene succession at Gabal Qreiya area, Upper Egypt, based on integrated and detailed sedimentological and biostratigraphical studies to throw more light on the relative sea-level fluctuations.

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Geologically, the studied area is distinguished by a relatively low-lying monotonous plain covered by Plio-Pleistocene sediments overlying Upper Cretaceous-Lower Paleogene strata together with conspicuous mountains such as Gabal El Sarai (590 m, a.s.l.), Gabal Aras (525 m, a.s.l.), Gabal Abu Had (640 m, a.s.l.), and Gabal Qreiya (615 m, a.s.l.). Gabal Qreiya area (latitude 26° 21− N; longitude 33° 01− E) is located to the southern end of Gabal Abu Had at the entrance of Wadi Qena in the eastern side of the upper Nile Valley, about 50 km northeast of Qena City (Fig. 1). The sedimentary sequence exposed at Gabal Qreiya is composed of different rock units belonging to the late Cretaceous-early Paleogene age. Generally, the surface structural setting of the area shows an overall structural simplicity and faults represent the main structural features affecting the area.

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Materials and methods In order to realize the goals of this work, the following objectives have been carried out: 1. A composite stratigraphic section from Gabal Qreiya area was measured and sampled in detail for recognizing and interpreting the lithological aspects, facies varieties,

Fig. 1 Geological map of the studied area (after the EGPC/CONOCO, 1987, Assiut sheet)

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planktonic and benthonic foraminiferal content, and nature of surface contacts. About 80 thin sections were prepared and examined for their composition and litho- and microfacies assemblages to reconstruct the depositional environments. The terminology of carbonate rocks is based on the classification introduced by Dunham (1962), while the classification of sandstone is based on Pettijohn (1975) and Pettijohn et al. (1987). The general paleoenvironmental reconstructions of Wilson (1975) and Flügel (2004) were applied. Identified the benthonic foraminiferal assemblages to estimate the paleodepths based on Berggren and Aubert (1975) and Van Morkhoven et al. (1986). Planktonic foraminiferal zonation was carried out in order to identify the timelines and hiatuses, based on Caron (1985), Li and Keller (1998), and Berggren and Pearson (2005). The identified benthonic and planktonic foraminifera were photographed using the scanning electron microscope (JSM 5400 LD) at Assiut University, Egypt. The studied succession was classified according to the modern approach of high-resolution sequence stratigraphy, using all available sedimentological and stratigraphical information, which enabled to throw light on the relative sea-level fluctuations.


Stratigraphic outline of the studied succession Lithostratigraphically, the Upper Cretaceous-Lower Paleogene succession at Gabal Qreiya is differentiated into six rock units arranged stratigraphically as follows from older: Quseir, Duwi, Dakhla, Tarawan, Esna, and Thebes formations (Table 1 and Fig. 2). This succession offers an excellent chance to study the recognizable rock units with its vertical enclosing lithofacies changes: Quseir Formation was termed by Youssef (1957) and represented the base of the low-lying plateaus capped by the Duwi Formation. It consists of varying color shales alternating with sandstone and siltstone beds and topped with about 10– 20-cm-thick glauconitic band (Plate 1a, b). In the studied area, the exposed thickness of this formation attains about 57 m (Fig. 2). Duwi Formation was defined by Youssef (1957). It overlies Quseir Formation and underlies Dakhla Formation. It consists of a succession of phosphorites interbedded with sandstones, shales, and marlsand capped by about 15–30-cm-thick conglomeratic band (Plate 1c, d). In the studied area, the measured thickness of this formation attains about 18 m (Fig. 2).

Table 1

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Dakhla Formation that was termed by Said (1962) is represented by about 83 m thick of the siliciclastic facies which underlain by the phosphate deposits of Duwi Formation and overlain by the carbonate facies of Tarawan Formation (Fig. 2). Abdel Razik (1972) subdivided the Dakhla Formation into two members: Hamama Marl Member at base and Beida Shale Member at top (Table 1). In the present work, the Hamama Marl Member (~ 28 m thick) represents the basal part of Dakhla Formation and rests unconformably on Duwi Formation by a conglomeratic band. It is composed of pale gray marl alternating with dark gray calcareous shales (Fig. 2 and Plate 1c). The Beida Shale Member (~ 55 m thick) conformably overlies the Ham ama Ma rl M emb er an d u nd erli es Ta ra wan Formation. It is characterized by greenish-gray, laminated shales, gray calcareous shales, claystones, and marls with a marker bed of thin brown friable and fissile gray shale bands (~ 30 cm thick) at its middle part (Fig. 2 and Plate 1e, f, g). Tarawan Formation (Awad and Ghobrial 1965) conformably overlies the Dakhla Formation and underlies the Esna

Lithostratigraphic correlation of the different proposed rock units of the Upper Cretaceous-Lower Paleogene succession at the studied area

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Fig. 2 Measured stratigraphic sections showing the lithostratigraphic units at the studied area

Formation. It attains about 8 m thick and is made up of massive, snow white, fossiliferous, moderately hard chalky, and argillaceous limestone (Fig. 2 and Plate 1e). Esna Formation was first introduced by Beadnell (1905) and reviewed by Said (1962) to describe the siliciclastic facies at Gabal Oweina area, Upper Egypt. In the studied area, the Esna Formation (~ 42 m thick) conformably overlies the Tarawan Formation and underlies the Thebes Formation. Abdel Razik (1972) subdivided the Esna Formation into two members: ElHanadi Member at base and El-Shaghab Member at top,

while Aubry et al. (2007) added the Abu Had Member at the top of the Esna Formation for the alternating shales and limestone at the transition between the monotonous shales of the Esna and the massive limestones of the Thebes (Table 1). In the current work, El-Hanadi Member (~ 8 m thick) represents the basal part of the Esna Formation, conformably overlies the Tarawan Formation, and composed of marl and calcareous shale. El Shaghab Member (~ 24 m thick) conformably overlies El-Hanadi Member and composed of claystones, shales, and marls with a conspicuous brown friable


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Plate 1 a A field photograph showing the contact between the Quseir Formation below and the Duwi Formation above, Section 1. b A field photograph showing a glauconitic band separating the uppermost part of the Quseir Formation below and the Duwi Formation above, Section 1. c A field photograph showing the contact between the Duwi Formation below and the Hamama Marl Member above, Section 1. d A field photograph showing a conglomeratic band separating the uppermost part of the Duwi Formation below and the Hamama Marl Member

above, Section 1. e A field photograph showing a general view of Dakhla, Tarawan, Esna, and Thebes formations, Section 2. f A field photograph showing the conformable Cretaceous/Paleocene contact near the lowest part of the Beida Shale Member, Section 2. g A field photograph showing the conformable Danian/Selandian strata at the middle part of the Beida Shale Member, Section 2. h A field photograph showing the conformable Paleocene/Eocene contact within Esna Formation, Section 2

phosphatic clayey band (~ 80 cm thick) near its lower part. Abu Had Member (~ 10 m thick) conformably overlies El Shaghab Member and underlies the Thebes Formation. It is composed of marls and calcareous shales (Fig. 2 and Plate 1e, h). Thebes Formation (Said 1960) forms the upper escarpment face and plateau surface. It conformably overlies the Esna Formation with a gradational contact and consists of thin to medium laminated limestone (~ 10 m thick) with chert interbeds in the lower part (Fig. 2 and Plate 1e, h). Biostratigraphically, the exposed rock units of Gabal Qreiya area are rich with both planktonic and benthonic foraminiferal fauna of very good preservation(Plates 2a–t and 3a– o), excluding Quseir and Duwi formations which contain only benthonic foraminifera especially the agglutinated ones. The planktonic foraminiferal zonation and datum levels of the

present work are shown in Fig. 3. The lower part of the Hamama Marl Member (~ 8 m thick) of the Dakhla Formation is characterized by the presence of the Globotruncana aegyptiaca Zone of Late Campanian age, followed upward by the presences of Gansserina gansseri, Pseudoguembelina hariaensis, and P. palpebra zones assign to Maastrichtian age. The lowermost part of the Beida Shale Member (~ 2 m thick) is characterized by the occurrence of Plummerita hantkeninoides Zone of latest Maastrichtian age. The middle part of this member is marked by the presences of Guembelitriacretacea, Parvularugoglobigerina eugubina, Parasubbotina pseudobulloides, Subbotina triloculinoides, Praemurica inconstans, P. uncinata, Morozovella angulata, Igorina albeari/Praemurica carinata, Igorina albeari, and Globanomalina pseudomenardii/ Parasubbotina variospira zones that defined a Danian-Selandian age. The upper part

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Plate 2 a Globotruncana aegyptiaca (Nakkady), sample no. R13; b, c Gansserina gansseri (Bolli), sample no. R21; d Pseudoguemblina hariaensis (Nederbragt), sample no. R24; e Pseudoguemblina palpebra (Brönnimann and Brown), sample no. R26; f Plummerita hantkeninoides (Brönnimann), sample no. B3; g Parasubbotina pseudobulloides (Plummer), sample no. B8; h Subbotina triloculinoides (Plummer), sample no. B10; i Praemurica inconstans (Bolli), sample no. B12; j Praemuricauncinata (Bolli), sample no. B16; k Morozovella angulata (White), sample no. B18; l Igorinaalbeari (Cushman and Bermŭdez),

sample no. B22; m Praemurica carinata (El-Naggar), sample no. B19; n Globanomalina psendomenardii (Bolli), sample no. B29; o Acarinina subsphaerica (Subbotina), sample no. B32; p Acarinina soldadoensis (Brönnimann), sample no. B38; q Morozovella velascoensis (Cushman), sample no. B39; r Acarinina sibaiyaensis (El Naggar), sample no. B42; s Pseudohastigerina wilcoxensis (Cushman and Ponton), sample no. B49 and t Morozovella formosa (Bolli), sample no. B60

of Beida Shale Member (~ 10 m thick) and the lower part of Tarawan Formation (~ 4 m thick) is characterized by the occurrence of the Acarinina subsphaerica Zone of the late Selandian-early Thanetian. The upper part of Tarawan Formation (~ 4 m thick) and the lower part of Esna Formation (El-Hanadi Member,~ 8 m thick) that are characterized by the occurrence of the Acarinina soldadoensis/ Globanomalina pseudomenardii and Morozovella velascoensis zones indicate early-late Thanetian age. The rest of the Esna Formation (~ 34 m thick) is characterized by the occurrence of the Acarinina sibaiyaensis, Pseudohastigerina wilcoxensis/ M o ro z o v e l l a v e l a s c o e n s i s , M . s u b b o t i n a e , a n d M. formosa zones point to the early Ypresian age. The Thebes Formation is characterized by the occurrence of the Morozovella aragonensis/M. subbotinae Zone of the late Ypresian age (Figs. 3 and 4).

Paleobathymetry The Upper Cretaceous-Lower Paleogene succession comprises little abundance and low species diversity of benthonic foraminifera relative to planktonic foraminifera. Benthonic foraminifera is generally used to deduce paleodepths and consequently to realize relative sea-level fluctuations (Sliter 1968; Sliter and Baker 1972; Berggren 1974; Berggren and Aubert 1975; Aubert and Berggren 1976; Van Morkhoven et al. 1986; Lüning et al. 1998; Speijer 2003; Obaidalla et al. 2009; Sprong et al. 2012). In the present investigations, several distinctive benthonic foraminiferal assemblages have been available depending on the scheme of Berggren and Aubert (1975) and Van Morkhoven et al. (1986). These foraminiferal assemblages (Plate 3a–o) and their paleobathymetric interpretation (Fig. 4) are as follows:


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Plate 3 a Haplophragmoides calculus (Cushman and Waters), sample no. Q13; b Lagena sulcata (Walker and Jacob), sample no. Q40; c Tritaxia midwayensis (Cushman), sample no. Q46; d Anomalina umboniferus (Schwager), sample no. R12; e Rectuvigerina striata (Schwager), sample no. R18; f cibicidoides alleni (Plummer), sample no. B10; g Angulogavelinella avimelechi (Reuss), sample no. B15; h Stensioina beccariiformis (White), sample no. B18; i Gavelinella

rubiginosus(Cushman), sample no. B25; j Dorothia bulletta (Carsey), sample no. B31; k Nuttalides truempyi (Nuttall), sample no. B48; l Marginulinopsis tuberculata (Plummer), sample no. B59; m Gaudryina soldadoensis (Cushman and Renz), sample no. B60; n Bolivina midwayensis (Cushman), sample no. R21 and o Gyroidinoides girardanus (Reuss), sample no. B29

1- The pre-Campanian Shale of the Quseir Formation is characterized by the presence of Haplophragmoides calculus (Cushman and Waters) benthonic assemblage, which points to inner neritic paleodepths (~ 10–50 m) setting (Fig. 4).

2- The lower Campanian shale and marl of the Duwi Formation are characterized by the presence of Lagenasulcata (Walker and Jacob) and Tritaxia midwayensis (Cushman) benthonic assemblage, which points to inner to middle neritic paleodepths (~ 40–80 m) setting (Fig. 4).

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Fig. 3 The timelines are based on planktonic foraminiferal zonation on the Campanian-Ypresian times identified in the studied stratigraphic sections. The time in million years (Ma) after Caron (1985), Li and Keller (1998), and Berggren and Pearson (2005)

3- The Upper Campanian-Maastrichtian of the Hamama Marl Member is characterized by the occurrence of Anomalina umboniferus (Schwager), Rectuvigerinastriata (Schwager), and Bolivina midwayensis (Cushman) benthonic assemblage, which points to outer neritic-upper bathyal paleodepths (~ 150–600 m) setting, coincides with increase in the P/B ratio of ~ 30–80% (Fig. 4). 4- The Danian part of the Beida Shale Member is characterized by the occurrence of Angulogavelinella avimelechi (Reuss), cibicidoides alleni (Plummer), and Stensioina beccariiformis (White) benthonic assemblage, which points to outer neritic-upper bathyal paleodepths (~ 180– 600 m) setting, this agrees with the increase in P/B ratio (40–80%). By the end of the Danian time, a noticeable decrease in the P/B ratio (25%) is observed that points to middle neritic paleodepths (~ 90 m) setting (Fig. 4). 5- The Selandian-Thanetian strata which cover the upper part of the Beida Shale Member, Tarawan Formation, and the lower part of the Esna Formation (El-Hanadi Member) are characterized by the different proportions of the occurrence of Gavelinella rubiginosus (Cushman), Gyroidinoides girardanus (Reuss), and

Dorothiabulletta (Carsey) benthonic assemblage. The proportion percentage of this assemblage in the upper part of the Beida Shale Member ranges between 30 and 70% that point to outer neritic-upper bathyal paleodepths (~ 150–500 m) settings. It increased upward in the Tarawan Formation reaching ~ 70–85% and indicates upper bathyal paleodepths (~ 500–600 m) setting, this agrees with the increase in P/B ratio, whereas the lower part of the Esna Formation (El-Hanadi Member) is characterized by the decreasing percentage of about 30% and refers to outer to middle neritic paleodepths (~ 200–90 m) setting, coincides with a declination in the P/B ratio of ~ 30% (Fig. 4). 6- The Ypresian strata which occupy the middle and upper parts of the Esna Formation and the lower part of the Thebes Formation are characterized by varied proportion of the Nuttalides truempyi (Nuttall), Marginulinopsis tuberculata (Plummer), and Gaudryina soldadoensis (Cushman and Renz) benthonic assemblage. The middle part of the Esna Formation (El-Shaghab Member) that contains high percentage ~ 70–90% of this assemblage points to bathyal paleodepths (~ 400–650 m) setting. It decreases upward in the upper part of the Esna Formation (Abu Had Member) reaching about 40% and


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Fig. 4 Litho- and bio-stratigraphy, range chart of the index planktonic foraminiferal species, Planktonic/Benthonic (P/B) ratios, and paleobathymetry (based on benthonic foraminiferal assemblages) in the Upper Cretaceous-Lower Paleogene succession at the studied area (for symbols, see Fig. 2)

points to outer neritic paleodepths (~ 100–200 m) setting, then decreases in the Thebes Formation up to 20% and points to middle neritic paleodepths (~ 80 m) setting (Fig. 4).

Facies analysis and depositional environments On the basis of detailed field observations in addition to the vertical variations in the lithofacies, microfacies, and biofacies of the studied succession at Gabal Qreiya area, the depositional environments for the different rock units were interpreted. Quseir Formation (~ 57 m thick) represents the oldest rock unit exposed in the studied area. It consists of greenish-gray and black shales enriched with agglutinated benthonic foraminifera of low species diversity, alternating with calcareous glauconitic quartz arenite, ferruginous siltstone, and ferruginous quartzarenite microfacies. This points to the deposition under marginal to shallow marine condition (Fig. 5 and

Plate 4a–c) in inner neritic paleodepths (~ 50 m) setting under an adverse environmental stress. Duwi Formation (~ 18 m thick) overlies the Quseir Formation. It is dominated by calcareous glauconitic phosphatic quartz arenite, calcareous phosphoarenite, oyster floatstone, siliceous phosphoarenite, and benthonic foraminiferal marl microfacies. This indicates shallow subtidal shelf (Fig. 5 and Plates 4e, f and 5a) in inner to middle neritic paleodepths (~ 40–80 m) setting. Hamama Marl Member of the Dakhla Formation (~ 28 m thick) unconformably overlies the Duwi Formation and marked by pale gray bioclastic foraminiferal marl intercalated with foraminiferal calcareous shales. Its base is dominated by bioclastic foraminiferal marl (~ 5 m thick) that characterized with low abundance and diversity of planktonic and benthonic foraminifera, marks deposition in a shallow subtidal setting. It is followed upward by foraminiferal calcareous shales (~ 4 m thick) that characterized with adequate abundance and diversity of planktonic and benthonic foraminifera, indicates deposition in a deep shallow subtidal setting. Then topped with a

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Fig. 5 Litho- and micro-facies types and its depositional environments of the studied Upper Cretaceous-Lower Paleogene succession at the studied area (for symbols, see Fig. 2)

bioclastic foraminiferal marl (~ 19 m thick) dominated by high abundance planktonic foraminifera (60 to 80%) with diverse benthonic foraminifera indicates deposition in a deep subtidal shelf under bathyal paleodepths (~ 600 m) setting and terminated with low diversity planktonic and benthonic foraminiferal (P/B ratios 30%) point to deposition in a shallow subtidal shelf (Fig. 5 and Plate 5c–e). Followed upward by the Beida Shale Member (~ 55 m thick) conformably underlies Tarawan Formation. It composes of shales, calcareous shales claystones, and marl with variable proportion of planktonic and benthonic foraminiferal types. This reveals repeated relatively oscillation from shallow to deep subtidal shelf in middle neritic to upper bathyal paleodepths (~ 80–600 m) setting (Fig. 5). Tarawan Formation (~ 8 m thick) conformably overlies Dakhla Formation and consists of yellowish chalky

limestones, mainly dominated by bioclastic foraminiferal wackestone and bioclastic foraminiferal packstone microfacies, points to a deep subtidal shelf in upper bathyal paleodepths (~ 500–600 m) setting (Fig. 5 and Plates 5f and 6a, b). Esna Formation (~ 42 m thick) conformably overlies Tarawan Formation and composes of marl, shale, claystone, and calcareous shale enriched with planktonic and benthonic foraminiferal types. The lower part of this unit (El-Hanadi Member) consists of bioclastic foraminiferal marl and foraminiferal calcareous shale with moderate percentage of planktonic and benthonic foraminiferal (~ 30%) indicates deposition in shallow subtidal shelf. The middle part of this unit (El-Shaghab Member) consists of phosphatic clay, foraminiferal marl, foraminiferal shale, and claystone enriched with well-preserved, high proportion of planktonic foraminiferal


types (70 to 90%) together with deep marine benthonic foraminifera points to deposition in deep subtidal shelf under bathyal water paleodepths(~ 650 m), followed upward by

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bioclastic foraminiferal marl and foraminiferal calcareous shale (Abu Had Member), generally characterized by low to moderate foraminiferal content and diversity with P/B (~

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Plate 4

a A photomicrograph showing ferruginous siltstone, Quseir Formation (sample Q8,PPL). b A photomicrograph showing ferruginous quartzarenite, Quseir Formation (sample Q22,PPL). c A photomicrograph showing calcareous glauconitic quartzarenite, Quseir Formation (sample Q25, PPL). d A photomicrograph showing an arenaceous glauconitic, separating the Quseir Formation below and the Duwi Formation above (sample Q31, PPL). e A photomicrograph showing calcareous glauconitic phosphatic quartzarenite, Duwi Formation (sample Q36, PPL). f A photomicrograph showing an oysteral floatstone within Duwi Formation (sample R3, XPL)

40%) indicating deposition in shallow subtidal shelf (Fig. 5 and Plate 6 c, d). Thebes Formation (~ 10 m thick) conformably overlies Esna Formation. It is generally represented by thin to medium laminated limestone, dominated by bioclastic foraminiferal wackestone microfacies with low abundance of planktonic and benthonic foraminifera that point to deposition in shallow subtidal shelf under water circulation in middle neritic paleodepths (~ 80 m) setting (Fig. 5 and Plate 6e, f).

Third-order depositional sequences The term “sequence” was originally defined by Mitchum et al. (1977) as “a stratigraphic unit composed of a relatively conformable succession of genetically related strata bounded at its top and base by unconformities or their correlative conformities.” Sequence stratigraphy concepts are used to provide a chronostratigraphic framework for the correlation and mapping of sedimentary facies in the depositional system for regional and local exploration (Emery and Myers 1996). A high-resolution sequence stratigraphic interpretation of the exposed Upper Cretaceous-Lower Paleogene succession at Gabal Qreiya area has been achieved based on integrated and detailed sedimentological and biostratigraphical studies. Six third-order depositional sequences were defined as follows: pre-Campanian sequence QsSQ0, Lower Campanian sequence DwSQ1, Upper Campanian-Maastrichtian sequence DkSQ2, Danian sequence DkSQ3, Selandian-Thanetian sequence Dk/T/EsSQ4, and Ypresian sequence Es/ThSQ5, separated by five well-defined sequence boundaries (SB1, SB2, SB3, SB4, and SB5). A complete description of the recognized depositional sequences, including their boundaries, nature of other bounding surfaces, paleoenvironmental changes across these surfaces, and systems tracts with the integrated lithofacies and biofacies data, is given below in stratigraphic order (Fig. 6).


with a glauconitic band (~ 10–20 cm thick) at the top of the Quseir Formation, marked an unconformable sequence boundary SB1 (Fig. 6 and Plates 1b and 4d). This sequence initiates by greenish gray, black shales enriched with benthonic foraminifera alternating with siltstones and sandstones sediments (~ 57 m thick) of inner neritic paleodepths (~ 10–50 m) setting, on marginal to shallow subtidal shelf indicating the transgressive systems tract/ highstand system tract TST/HST, since it is difficult to delineate the maximum flooding surface MFS separating the TST and HST deposits (Fig. 6).

The lower Campanian sequence DwSQ1 The second depositional sequence DWSQ1 coincides with the Lower Campanian Duwi Formation about 18 m thick (Fig. 6). The precise age of this sequence is difficult to determine because of the absence of any diagnostic planktonic foraminifera. This sequence is delimited at its base by the previous remarkable unconformable sequence boundary SB1 and terminated by the occurrence of an irregular surface with a conglomeratic band (~ 15–30 cm thick) separating the phosphatic facies of the Duwi formation at base from Hamama Marl Member at top, marking an unconformable sequence boundary SB2 (Fig. 6 and Plates 1d and 5b). The lowstand systems tract (LST) has not been recognized in this sequence. In this case, the transgressive surface (TS) at the base of the transgressive systems tract (TST) coincides with the sequence boundary SB1. This surface records the beginning of the transgressive facies during the early Campanian marine invasion across the studied area. This causes deposition of phosphatic facies alternately with shales and marls sediments (~ 14 m thick) on a shallow subtidal shelf, rich with benthonic foraminifera indicates inner to middle neritic paleodepths (~ 40–80 m) setting. It points to the transgressive systems tract (TST) sediments (Fig. 6). This is overlain by a gray shale thinly band (~ 50 cm thick) flooded with benthonic foraminiferal assemblage assigned to the maximum flooding surface MFS, which is overlain by siliceous phosphoarenite and black shale facies (~ 4 m thick) of a very shallow subtidal sediments contains few benthonic foraminifera indicate inner neritic paleodepths (~ 40 m) setting, assigned to the highstand system tract HST (Fig. 6).

The pre-Campanian sequence QsSQ0 The upper Campanian-Maastrichtian sequence DkSQ2 The first depositional sequence QsSQ0 coincides with the preCampanian Quseir Formation about 57 m thick (Fig. 6). It is difficult to define the exact age of this sequence since it is barren of any diagnostic planktonic foraminifera. This sequence is recognized by the presence of an irregular surface

The third depositional sequence DkSQ2 comprises both the Hamama Marl Member (~ 28 m thick) and the lowest part of the Beida Shale Member (~ 2 m thick) of the Dakhla Formation (Fig. 6). It represents the Late


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Plate 5 a A photomicrograph showing calcareous phosphoarenite, Duwi Formation (sample Q42, PPL). b A photomicrograph showing an intraformational conglomerate, separating the Duwi Formation from the Hamama Marl Member (sample R9, PPL). c, d, e Photomicrographs

showing bioclastic foraminiferal marl, Hamama Marl Member, Dakhla Formation (samples R11, R22, and B4, respectively, PPL). f A photomicrograph showing bioclastic foraminiferal wackestone, Tarawan Formation (sample B34, PPL)

Campanian G. aegyptiaca Zone (~ 9 m thick) followed upward by the Maastrichtian G. gansseri, P. hariaensis, P. palpebra, and P. Hantkeninoides zones (~ 21 m thick) that extends from ~ 70.4 Ma to ~ 65.0 Ma (Fig. 3). It is initiated with the previous significant sequence boundary SB2, and ended by a change from shale with low abundance and ratios of P/B below and

claystone above with high abundance and ratios of P/B, indicating no stratigraphic gap and referring to a conformable sequence boundary SB3 (Figs. 3 and 6), correlated to Cretaceous/Paleocene (K/P) unconformity in other parts of Egypt (e.g., Said and Sabry 1964; ElNaggar 1966; El-Younsy et al. 2015 at Gabal Oweina; Philobbos et al. 2013; Salman 2013 at Wadi Tarfa).

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Plate 6 a, b Photomicrographs showing bioclastic foraminiferal packstone, Tarawan Formation. Some foraminiferal chambers are filled with calcareous clay, embedded in a micritic groundmass (sample B36; a PPL and XPL). c, d Photomicrographs showing phosphatic foraminiferal shale, Esna Formation, note the simple lamination preserved foraminifera and phosphatic materials embedded in a micritic groundmass (samples B43 and B44, respectively, PPL). e, f Photomicrographs showing bioclastic foraminiferal wackestone, Thebes Formation (samples B62 and B63, respectively, PPL)

This sequence starts with a relatively thin band (~ 15–30 cm thick) made of an intraformational phosphatic conglomerate reflecting a very shallow subtidal facies of a lowstand systems tract (LST) bounded below by the sequence boundary (SB2) and above by a significant transgressive surface (TS), points to the beginning of sea level rise during the late Campanian at the studied area. It is overlain by a succession of marl and calcareous shales (~ 22.5 m thick) with high diversity planktonic and benthonic foraminifera (P/B 30–80%) of outer neritic to upper bathyal paleodepths (~ 150–600 m) setting, on a deep subtidal shelf defining the transgressive systems tract TST. Followed upward by marl and calcareous shales (~ 7 m thick), of low diversity planktonic and benthonic foraminifera (P/B ratios 30%) of middle neritic paleodepths (~ 80 m) setting, on a shallow subtidal shelf, signifying the highstand system tract (HST) at the latest Maastrichtian time. This major faunal turnover reflects the maximum flooding surface MFS (Figs. 4, 5, and 6).

The Danian sequence DkSQ3 The fourth depositional sequence DkSQ3 constitutes the lower part of the Beida Shale Member (~ 23 m thick) of the Dakhla Formation (Fig. 6). It encompasses the Danian G. cretacea, P. eugubina, P. pseudobulloides, S. triloculinoides, P. inconstans, P. uncinata, M. angulata, and I. albeari/P. carinata zones that extend from ~ 65.0 to ~ 59.7 Ma (Fig. 3). It is delineated at its base by the conformable sequence boundary SB3, and ended by the presence of thin brown and gray shale bands (~ 30 cm thick) represents a conformable sequence boundary SB4 (Figs. 3 and 6), correlative to their unconformities Danian/Selandian (D/S) boundary in other parts in Egypt or outside (e.g., El-Younsy et al. 2015 at Gabal Oweina and El-Azabi and Farouk 2011 at the Kharga Oasis of the Western Desert, Egypt; Thomsen and Heilmann-Clausen 1985 in Denmark). This sequence begins with shales, calcareous shales, and claystones (~ 18 m thick) enriched with high diversity of


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Fig. 6 Sequence stratigraphic interpretations based on facies and its depositional environments and foraminiferal analyses of the Upper Cretaceous-Lower Paleogene succession at the studied area (for symbols, see Fig. 2)

planktonic and benthonic foraminifera (P/B ratios 40–80%) of outer neritic to upper bathyal paleodepths (~ 180–600 m) setting, on a deep subtidal shelf indicating the transgressive systems tract TST. Therefore, its base (SB3) coincides with the transgressive surface (TS) indicating the absence of lowstand deposits. Followed upward by shale sediments (~ 5 m thick) characterized by scarcity of planktonic and benthonic foraminifera (P/B ratios 25%) of middle neritic paleodepths (~ 90 m) setting, on a shallow subtidal shelf, representing the highstand system tract HST. It denotes the advent of a sea level fall during the latest Danian time. The MFS coincides with the maximum abundance of planktonic foraminifera (P/B ratios 80%) and marks a change from deepening-upward to shallowing-upward biofacies deposits (Figs. 4, 5, and 6).

The Selandian-Thanetian sequence Dk/T/EsSQ4 The fifth depositional sequence Dk/T/EsSQ4 comprises the upper part of the Beida Shale Member (~ 30 m thick) of the Dakhla Formation, Tarawan Formation (~ 8 m thick) and the

lower part of the Esna Formation (El-Hanadi Member, ~ 8 m thick). It represents the middle to late Paleocene I. albeari, G. pseudomenardii/P. variospira, A. subsphaerica, A. soldadoensis/G. pseudomenardii, and M. velascoensis zones that extend from ~59.7 to ~ 55.3 Ma (Figs. 3 and 6). The base of this sequence is marked by the previously described conformable sequence boundary SB4, while its top, near the lower part of the Esna Formation, is characterized by a continuous sedimentation during the Paleocene/Eocene contact delineated a conformable sequence boundary SB5 at the brown phosphatic clayey band (~ 80 cm thick) which is correlative to their unconformity in other parts in Egypt (ElYounsy et al. 2015 at Gabal Oweina and El-Dawy et al. 2016 at the Kharga Oasis of the Western Desert). This sequence starts with shales, claystones, and calcareous shales (~ 30 m thick) followed upward by bioclastic foraminiferal wackestone and bioclastic foraminiferal packstone microfacies (~ 8 m thick) enriched with well-preserved planktonic and benthonic foraminifera (P/B ratios 30–85%) of outer neritic to upper bathyal paleodepths (~ 150–600 m) setting, on

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a deep subtidal shelf denotes the transgressive systems tract TST. Thus, its base (SB4) coincides with the transgressive surface (TS) indicating the absence of lowstand deposits (Fig. 6). This confirms the beginning of a sea-level rise during Selandian time in the studied area that reaches its maximum at the bathymetrically deepest interval with maximum frequency of planktonic foraminifera (P/B ratios 85%) at the upper bathyal paleodepths (~ 600 m) setting, on deep subtidal shelf marked the MFS. It is overlain by marl and calcareous shale of El-Hanadi Member (~ 8 m thick) that characterized by moderate diversity of planktonic and benthonic foraminifera (P/B ratios 30%) of outer-middle neritic paleodepths (~ 200–90 m) setting, on a shallow subtidal shelf, indicating the highstand system tract HST. It marks the fall in relative sea level during the latest Thanetian time (Figs. 4, 5, and 6).

The Ypresian sequence Es/ThSQ5 The sixth depositional sequence Es/ThSQ5 which represents the uppermost sequence in the studied stratigraphic sections (44 m) occupies El Shaghab (~ 24 m thick) and Abu Had (~ 10 m thick) members of the Esna Formation and the lower 10 m of the Thebes F o r m a t i o n ( F i g . 6 ) . I t c o n t a i n s t h e Yp r e s i a n A. sibaiyaensis, P. wilcoxensis/M. velascoensis, M. subbotinae, M. formosa, and M. aragonensis/M. subbotinae zones ranging from ~ 55.3 to ~ 52.0 Ma (Fig. 3). This sequence is delineated at its base by the previously described conformable sequence boundary SB5while its top is not reached (Fig. 6). Generally, its lower limit is a compound surface consisting of both the sequence boundary SB5 and the transgressive surface (TS) due to the absence of lowstand deposits denoting the base of the transgressive systems tract TST. The deposits of this transgressive systems tract TST start with claystones, calcareous shales, marls, and shales (~ 24 m thick) enriched with well-preserved planktonic and benthonic foraminifera (P/B ratios ~ 70–90%) point to a gradually deepening sea reaching middle bathyal paleodepths (~ 650 m) setting, on a deep subtidal shelf during this transgressive systems tract. The gradually deepening sea during the Ypresian time reaches its maximum with high proportions of planktonic foraminifera (P/B ratios 90%) marked the MFS. Followed upward by the highstand systems tract (20 m thick), that represents the uppermost recorded systems tract. It is composed of calcareous shale and marl (~ 10 m thick) followed upward by bioclastic foraminiferal wackestone (~ 10 m thick) of low diversity of planktonic and benthonic foraminifera (P/B ratios ~ 40–20%) of outer to middle neritic paleodepths (~ 200–80 m) setting, on a shallow subtidal shelf sign to a fall in sea level (Figs. 4, 5, and 6).

Sea-level changes and discussion The changes in relative sea-level and sediment supply clearly reflect the construction of a sedimentary succession. Sea-level changes are either attributed to the true eustatic sea-level variation (Vail et al. 1991) or to the changing morphology of the basin due to tectonics (Cloetingh 1988). Depending on the detailed and integrated investigations of the studied sedimentological and biostratigraphical analyses, more details about sea-level changes during the studied Upper Cretaceous-Lower Paleogene succession are acquired. A distinct history for each studied depositional sequence (QsSQ0, DwSQ1, DkSQ2, DkSQ3, Dk/T/EsSQ4, and Es/ThSQ5) is clearly noticed from the sea-level fluctuation curves deduced from both the sedimentary facies analysis and the paleobathymetry in the studied section (Fig. 7), compared with the global sea-level curve given by Haq et al. (1988). During both the pre-Campanian depositional sequence (QsSQ0) which is represented by the Quseir Formation and the Lower Campanian depositional sequence (DwSQ1) which is represented by the Duwi Formationthe sea-level fluctuation shows a slight coincidence to the global sea-level curve of Haq et al. (1988). The basal sequence boundary SB1 was attributed to sea-level fall during the pre-Campanian, whereas the upper sequence boundary SB2 was coincident with the global sea-level fall besides local tectonic event that inferred from the presence of conglomeratic band. A general parallelism with the global sea-level curve of Haq et al. (1988) is predictable during the Upper Campanian-Maastrichtian depositional sequence (DkSQ2), the Danian depositional sequence (DkSQ3), the Selandian-Thanetian depositional sequence (Dk/T/EsSQ4), and the Ypresian depositional sequence (Es/ ThSQ5). Accordingly, the three conformable sequence boundaries (SB3, SB4, and SB5) are considered to have been generated during three major episodes of lowered global sea level (the latest Maastrichtian, the latest Danian, and the latest Thanetian times).

Conclusions A high-resolution sequence stratigraphic analysis of the Upper Cretaceous-Lower Paleogene succession at Gabal Qreiya area led to the recognition of six third-order depositional sequences and their associated surfaces and systems tracts. This analysis was based on detailed and integrated stratigraphic, sedimentological, and high-resolution planktonic and benthonic foraminiferal data, which helped in giving some details about the characteristics and paleoenvironments of the identified sequences. The pre-Campanian depositional sequence QsSQ0 which covered the Quseir Formation was laid down in inner neritic paleodepths (~ 10–50 m), on marginal to shallow subtidal


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Fig. 7 Sea-level changes deduced from the facies and its depositional environments and the paleobathymetry analyses of the Upper Cretaceous-Lower Paleogene succession at the studied area, compared with the global sea-level curve of Haq et al. (1988) (for symbols, see Fig. 2)

shelf consisting of transgressive/highstand systems tracts TST/HST due to the difficulty of identifying MFS separating them. The Lower Campanian depositional sequence DwSQ1 which consisted of the Duwi Formation was laid down in a sea oscillating between inner to middle neritic paleodepths (~ 40–80 m), on a shallow subtidal shelf consisting of both the transgressive and highstand systems tracts. The Upper Campanian-Maastrichtian sequence DkSQ2 which covered the lower part of the Dakhla Formation was laid down in environmental conditions ranging from outer neritic-upper bathyal paleodepths (~ 150–600 m), on a deep subtidal shelf, to middle neritic paleodepths (~ 80 m), on a shallow subtidal shelf comprising the lowstand, transgressive, and highstand systems tracts. The Danian depositional sequence DkSQ3 which covered the middle part of the Dakhla Formation was accumulated in a gradually deepening sea reaching upper bathyal paleodepths (~ 600 m), on a deep subtidal shelf, followed by middle neritic paleodepths (~ 90 m), on a

shallow subtidal shelf exhibiting transgressive and highstand systems tracts. The Selandian-Thanetian depositional sequence Dk/T/ EsSQ4 whichcomprised the upper part of the Dakhla, Tarawan and the lower part of the Esna formations was accumulated in an oscillating conditions between upper bathyal paleodepths (~ 600 m), on a deep subtidal shelf and middle neritic paleodepths (~ 90 m), on a shallow subtidal shelf showing transgressive and highstand systems tracts. The Ypresian depositional sequence Es/ThSQ5 which consisted of the main parts of Esna and Thebes formations was accumulated in fluctuating settings among the middle bathyal paleodepths (~ 650 m), on a deep subtidal shelf and middle neritic paleodepths (~ 80 m), on a shallow subtidal shelf revealing transgressive and highstand systems tracts. The identified depositional sequences (QsSQ0, DwSQ1, DkSQ2, DkSQ3, Dk/T/EsSQ4, and Es/ThSQ5) generally coincide with the global sea-level curve of Haq et al. (1988). Accordingly, five sequence boundaries, separating the above sequences mentioned, were documented. Three sequence

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boundaries (SB3, SB4, and SB5), which traced along the Maastrichtian/Danian, Danian/Selandian, and Paleocene/ Eocene contacts were conformable boundaries, exhibiting no significant hiatus. They were correlative to unconformities in other parts of Egypt formed during three major episodes of lowered global sea level, whereas the other two sequence boundary SB1and SB2 are unconformable boundaries coinciding with the global sea-level fall. The sequence boundary (SB2) suggests a local tectonic event as a significant control on sedimentation. A similar work was made by El-Younsy et al. (2015) at Gabal Oweina area to the south of the present study. They determined six third-order depositional sequences and their associated surfaces and systems tracts. As well, they stated that some of the boundaries were coincided with global sealevel falls, while the others related to a local sea-level fall due to a morphological change of the basin as a result of local tectonic in the area.

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