Sequence stratigraphy of the Maastrichtian-Paleocene succession at the Dakhla Oasis, Western Desert, Egypt

Accepted Manuscript Sequence stratigraphy of the Maastrichtian-Paleocene succession at the Dakhla Oasis, Western Desert, Egypt Abdel Galil A. Hewaidy, Sherif Farouk, Youssef S. Bazeen PII:

S1464-343X(16)30387-9

DOI:

10.1016/j.jafrearsci.2016.11.028

Reference:

AES 2741

To appear in:

Journal of African Earth Sciences

Received Date: 17 May 2016 Revised Date:

20 September 2016

Accepted Date: 22 November 2016

Please cite this article as: Hewaidy, A.G.A., Farouk, S., Bazeen, Y.S., Sequence stratigraphy of the Maastrichtian-Paleocene succession at the Dakhla Oasis, Western Desert, Egypt, Journal of African Earth Sciences (2017), doi: 10.1016/j.jafrearsci.2016.11.028. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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ABSTRACT The Maastrichtian-Paleocene succession at the Dakhla Oasis is marked by the presence of a typical Nile Valley Facies represented by the Dakhla and Tarawan formations in Edmonstone and Qur El Malik sections in the central and western parts of the oasis, while a mixed Nile Valley and Garra Al-Arbain facies represented by Dakhla, Kurkur and Tarawan formations in Teneida section in the eastern part of the oasis adjacent to the Abu Tartur Plateau. These sections were examined for their foraminiferal contents, lithologic characters and stratigraphic boundaries. The distribution of foraminifera in the studied sections is variable and inconstant, as the planktonics are concentrated only at certain levels, which may be considered as a time intervals of transgression and maximum flooding surfaces. Eight planktonic biozones are distinguished in this work; of theses two are of Maastrichtain age and six are of Paleocene age. Eight 3rd order depositional sequences are recognized in the studied Maastrichtian-Paleocene succession based on the time stratigraphic boundaries released from the planktonic foraminifera and sea level changes which are released from the paleoecologic interpretations. The distinguished sequences are subdivided into their systems tracts based on the paleobathymetric interpretations of P/B% and benthic biofacies analysis. These sequences are bounded by eight sequence boundaries (SB A - SB H) represented by unconformity surfaces and depositional hiatuses. The correlation of the sequence boundaries of the established depositional sequences with the eustatic sea level curve, suggesting that these depositional sequences were resulted from the interplay of eustatic sea-level changes and local tectonic activities.

ACCEPTED MANUSCRIPT Sequence Stratigraphy of the Maastrichtian-Paleocene Succession at the Dakhla Oasis, Western Desert, Egypt 1 Abdel Galil A. Hewaidy , Sherif Farouk2 and Youssef S. Bazeen1

1. Introduction: The Dakhla Oasis lies about 300 km west of the Nile, between longitudes 28°15`- 29°40` E and latitudes 25°00` - 26°00` N (Fig. 1). The oasis and adjacent areas were subjected to many geological investigations since 1883 when Zittel gave the first geological information about the south Western Desert. This is followed by several paleontological and stratigraphical studies (e.g., Le Roy, 1953; Hermina et al., 1961; Awad & Ghobrial, 1965; El-Naggar, 1966; Abbass & Habib, 1969; Issawi, 1972; Barthel & Herrmann- Degen, 1981; Luger, 1985; Anan & Sharabi, 1988; Hermina, 1990; Hewaidy, 1990; ElAzabi & El-Araby, 2000; Schnack, 2000; Tantawy et al., 2001; Hewaidy et al., 2006; El-Azabi & Farouk, 2011; Hewaidy et al., 2014 and Farouk & El-Sorogy, 2015). Few of these studies were concerned with the sequence stratigraphy of this area (e.g., El-Azabi & El-Araby, 2000; Schnack, 2000; Hewaidy et al., 2006 and El-Azabi & Farouk, 2011). The main objectives of this study are: 1- Establishing a biostratigraphic framework for the Maastrichtian-Paleocene succession exposed at Dakhla Oasis based on planktonic foraminiferal zonation. 2- Study the environments of deposition of the studied successions based on foraminiferal content and lithological characters. 3- Interpretation of the studied succession in terms of sequence stratigraphy.

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2. Material and methods: Three sections representing the Maastrichtian-Paleocene successions in the Dakhla Oasis were measured, sampled, and studied at Edmonstone, Qur El Malik, and Teneida. A total of 749 rock samples were collected from the three studied sections. The studied samples were prepared for foraminiferal studies following the normal techniques. The foraminiferal species were picked and the different planktonic and benthonic foraminiferal species were identified and counted. The different foraminiferal parameters as planktonic/benthic ratios (P/B %) and diversity were calculated. The benthic foraminiferal species are subjected to cluster analysis using Minitab computer program in order to figure out the relation between the different associated groups and subdivide them into biofacies assemblages. Bathymetric range for the different benthic foraminiferal species and assemblages, planktonic/benthic ratio (P/B %) and diversity, expressed by the total number of the species, were employed to establish the paleodepth curve. The distribution of the identified planktonic foraminiferal species was utilized in planktonic foraminiferal biostratigraphic classification of the studied

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1. Geology Department, Faculty of Science, Al-Azhar University, Cairo, Egypt, [email protected]; [email protected]. 2. Petroleum Research Institute, Cairo, Egypt. ABSTRACT The Maastrichtian-Paleocene succession at the Dakhla Oasis is marked by the presence of a typical Nile Valley Facies represented by the Dakhla and Tarawan formations in Edmonstone and Qur El Malik sections in the central and western parts of the oasis, while a mixed Nile Valley and Garra Al-Arbain facies represented by Dakhla, Kurkur and Tarawan formations in Teneida section in the eastern part of the oasis adjacent to the Abu Tartur Plateau. These sections were examined for their foraminiferal contents, lithologic characters and stratigraphic boundaries. The distribution of foraminifera in the studied sections is variable and inconstant, as the planktonics are concentrated only at certain levels, which may be considered as a time intervals of transgression and maximum flooding surfaces. Eight planktonic biozones are distinguished in this work; of theses two are of Maastrichtain age and six are of Paleocene age. Eight 3rd order depositional sequences are recognized in the studied Maastrichtian-Paleocene succession based on the time stratigraphic boundaries released from the planktonic foraminifera and sea level changes which are released from the paleoecologic interpretations. The distinguished sequences are subdivided into their systems tracts based on the paleobathymetric interpretations of P/B% and benthic biofacies analysis. These sequences are bounded by eight sequence boundaries (SB A - SB H) represented by unconformity surfaces and depositional hiatuses. The correlation of the sequence boundaries of the established depositional sequences with the eustatic sea level curve, suggesting that these depositional sequences were resulted from the interplay of eustatic sea-level changes and local tectonic activities.

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3. Lithostratigraphy: The stratigraphic successions exposed in the study area are represented by two main facies types: Nile Valley Facies and Garra El-Arbain Facies (Isswai, 1972). These facies are described in detail below within the context of their corresponding Maastrichtian-Paleocene rock units.

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3.1. Nile Valley Facies: this facies is widely distributed in the study area and subdivided into two formations: Dakhla Formation at the base and Tarawan Formation at the top.

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3.1.1. Dakhla Formation: The term Dakhla Shale was first introduced by Said, 1962 to describe 230 m thick of shales and mudstones overlying the Duwi Formation and underlying the Tarawan Formation. According to Awad and Ghobrial, 1965, the Dakhla Formation is subdivided into three formal members the Mawhoob Shale Member at base, the Beris Oyster Mudstone Member at middle, and the Kharga Shale Member at top. The Mawhoob Shale Member describes the basal fissile black shales overlying the Duwi Formation and underlying the Beris Oyster Mudstone Member of the same formation. It consists of grey to black fissile calcareous silty shales inerbedded with siltstone. It is assigned to the early Maastrichtian age based on its foraminiferal content (CF7 Zone). The Beris Oyster Mudstone Member represents the middle subdivision of the Dakhla Formation. It consists of grey to reddish grey shale intercalated with argillaceous limestone, sandstone, and siltstone enriched in Exogyra overwegi of the middle Maastrichtian age. The Kharga Shale Member is overlain by the Tarawan Formation. It consists of pale to dark grey to green calcareous, partly glauconitic, and phosphatic shale intercalated with siltstone, sandstone, and limestone. At the middle part of the Kharga Shale Member, a phosphatic conglomeratic band with 20-30cm thick, represents erosional disconformity defines the well-established hiatus at the Cretaceous/Paleogene boundary. This band is equivalent to Bir Abu Minqar Horizon given by Barthel and Herrmann-Degen, 1981 in the Farafra – Dakhla stretch. Therefore, the member is subdivided into lower Kharga Shale unit of late Maastrichtian age and upper Kharga Shale unit of Paleocene age (Luger, 1985).

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3.1.2. Tarawan Formation: The Tarawan Formation forms the top scarp faces of the plateaus surrounding the Dakhla Oasis. It unconformably overlies the Dakhla Formation. This unconformity is indicated by the presence of irregular surface with bioturbated marl to silty clay with limestone nodules, and ferruginous sandstone at the top of the Dakhla Formation. It is composed mainly of chalk and chalky limestone with few marl and shale intercalations. The chalk is snow white to yellowish white, hard, thickly bedded, and wall forming. This formation is assigned to the late Paleocene age (P4 Zone).

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3.2. Garra El-Arbain facies: in the study area, this facies is represented by the Kurkur Formation (Issawi, 1968). It is only recorded in the eastern part of the study area at Teneida section close to Abu-Tartur plateau. 3.2.1. Kurkur Formation: In the study area, it is recorded as a thin tongue at the unconformity surface (K/P boundary) between the two parts of the Kharga Shale Member at Teneida section. The Kurkur Formation occurs as a thin tongue on top of the unconformity surface in Gabal Gifata section to the north of Mut in Dakhla oasis, where it is again overlain by shales of the Kharga Shale Member (Hermina, 1990). The same observation was noted by Hewaidy, 1990, at Beris-Doush area. It is composed of brown to dark brown, hard, argillaceous, fossiliferous, dolomitic and oolitic limestone with silty shale and marl intercalations. The age of the Kurkur Formation vary from place to place; it is assigned to the planktonic foraminiferal P4 Zone in Abu Tartur Plateau (El-Deftar et al., 1978), to P3 - P4 zones in the Garra-Kurkur stretch (Hewaidy, 1994), to P2 Zone in G. El-Borga (Hewaidy and Soliman, 1993) and to P1c Zone in the present study.

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succession based on the schemes of Li et al., 1999 and Huber et al., 2008 for the Maastrichtian and that of Keller et al., 1995; Keller et al., 2002; Berggren and Pearson, 2005 and Wade et al., 2011 for the Paleocene. The biostratigraphic studies, biofacies analysis, and detailed field study are integrated to build a sequence stratigraphic framework for the studied succession.

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5. Paleobathymetry: The paleobathymetric analyses for the studied sediments are based on the estimation of the different foraminiferal parameters as planktonic/benthic ratio (P/B %), diversity and benthic foraminiferal biofacies and associations.

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5.1. Planktonic/benthic ratio (P/B %): The planktonic/benthic ratio was considered as a useful tool in determining the paleodepth providing that normal marine conditions prevailed during the time of deposition, and dissolution has not affected the sample material (Van der Zwaan et al., 1990). This ratio is expressed as (P/B %= P x 100\ (P+B). This ratio has a low value in the shallow marine waters and generally increases with depth until the Carbonate Compensation Depth (CCD). Olsson and Nyong, 1984 argued that the inner shelf (10-50 m depth) is characterized by low planktonic percentages (1-5%) with low species diversity and high benthic percentages; the middle shelf depth (50-100m) is characterized by 8-25% planktonic foraminifera and higher species diversity; the outer shelf depth (100–200m) is marked by 30-70% planktonic foraminiferal assemblage; whereas the continental slopes (200-800m) are characterized by 90% planktonic foraminifera. Generally, in the studied interval, the planktonic/benthic ratio varies greatly from 0-70%, which indicates fluctuation in the environment from very shallow inner shelf to outer shelf environments (Figs. 8, 10 and 12).

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5. 2. Species diversity: The diversity is expressed by the total number of species recorded at the sample. In general, the diversity is low at shallow waters and increases with increasing depth from middle to outer shelf depths and then decreases again in deeper marine waters because the diversity is controlled by nutrient availability

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4. Foraminiferal biostratigraphy: Several zonal schemes for the Late Cretaceous and Paleogene planktonic foraminifera were proposed in many parts of the world. The planktonic zones used here are based on the schemes of Li and Keller, 1998a; Li et al., 1999 and Huber et al., 2008 for the Maastrichtian part and that of Toumarkine and Luterbacher, 1985; Keller et al., 1995; Keller et al., 2002; Berggren and Pearson, 2005 and Wade et al., 2011 for the Paleocene part (Fig. 2). Eight planktonic biozones are recorded in this work. Two biozones are recorded in the Maastrichtian part; CF7 and CF3 based on the first appearance of Gansserina gansseri (Bolli) and Pseudoguembelina hariaensis Nederbrahgt respectively; separated by nondiagnostic/barren intervals (Figs. 3-5). The FAD of the Gansserina gansseri is recorded at the base of all the studied sections within the lower part of the Dakhla Formation followed by an interval barren from the diagonstic planktonic foraminifera. In contrast to, GSSP and the standard zonations (e.g., Huber et al., 2008) where this species appears at the uppermost Campanian, it appears in the Middle East area lately within the lower Maastrichtian (Farouk, 2014). The FAD of the Pseudoguembelina hariaensis ,which marks the CF3 Zone, is recorded within the Dakhla Formation at Beris/Kharga members contact at Teneida and Edmonstone sections (Figs. 3-4). Several late Maastrichtian marker planktonic foraminiferal species are first appeared at the lower boundary of CF3 as Rugoglobigerina reicheli Brönnimann, Globotruncana esnehensis Nakkady, and Racemiguembelina powelli Smith and Pessagno. For the Paleocene part, six biozones have been recorded; P1c, P1d, P2, P3a, P3b and P4. The FAD of the Globanomalina compressa and/or Parasubbotina varianta (P1c) is recorded at the base of the Kurkur Formation. The lower boundary of P1d Zone, marked by the FAD of the Praemurica trinidadensis, is documented at the base of the upper Kharga Shale unit of the Dakhla Formation at Teneida and Edmonstone sections (Figs. 3-4). P1d/P2 and P2/P3a zonal boundaries are marked by the FAD of Praemurica uncinata and Morozovella angulata respectively. These zones are recorded within the upper Kharga Shale unit at the three studied sections, while the P3a/P3b zonal boundary is recorded only at Edmonstone section (Figs. 3-5) and marked by the FAD of the Igorina albeari. The The FAD of the Globanomalina pseudomenardii marking the base of P4 Zone is recorded within the uppermost part of the Dakhla Formation at Tenieda and Edmonstone sections and at the Dakhla/Tarawan formational boundary at Qur El Malik section. Berggren and Pearson, 2005 subdivided P4 Zone into three subzones (Fig. 2). In the present study, it is difficult to follow this subdivion due to the poor preservation and rarity of the planktonic foraminifera within this interval.

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5.3. Benthic foraminiferal biofacies: Benthic foraminiferal taxa show definite specific environmental preferences and can be used to reconstruct past environments. Bathymetric ranges for the different benthic foraminiferal species were determined based on reviewing previous literatures and shown on Fig. 6. The benthic foraminiferal assemblages have been identified, counted and converted into percentages (Figs. 9, 11 and 13); the species with maximum percentages less than 4% were neglected from the final dataset. Cluster analysis by Minitab computer software was performed on this final dataset. Seven clusters or groups were obtained (Fig. 7). The clustered taxa are separated into environmentally dependent groups which considered as biofacies assemblages. The dominant taxa in each biofacies were used to identify paleoenvironments inhabited by the biofacies assemblage (Fig. 6). The following is the detailed description for these biofacies associations:

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5.1. Ammobaculites khargaensis Biofacies: This biofacies includes the coarse agglutinated species of the genera Ammobaculites, Haplophragmoides, Ammoastuta, Flabillammina, and Cribrostomoides (Fig. 7). The most dominant species in this biofacies are Ammobaculites khargaensis (61% of the assemblage in this biofacies) and Haplophragmoides calcula (15% of the assemblage in this biofacies). This biofacies is considered as mixohaline assemblage and interpreted as of littoral environment with fresh water supply (Berggren, 1974a; Hewaidy and Cherif, 1984; Luger, 1985; Cherif and Hewaidy, 1986; Hewaidy, 1990; Hewaidy, 1994; Hewaidy, 1997 and Leckie and Olson, 2003). This biofacies is commonly represented at the Maastrichtian part of the Dakhla Formation (Figs. 8, 10 and 12).

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5.2. Haplophragmoides excavata Biofacies: This biofacies is characterized by the dominance of Haplophragmoides excavata (41%), H. glabra (16%), Bathysiphon eocenicus (8%), and Ammobaculites subcretaceous (7%), Trochammina simplex (6%), and other rare foraminiferal species as Ammomarginulina aubertae, Ammobaculites expansus and Trochammina deformis (Fig. 7). This biofacies is referred to a very shallow littoral environment (Berggren, 1974a; Luger, 1985; Cherif and Hewaidy, 1986; Hewaidy, 1990; Hewaidy et al., 2014 and Hewaidy, 1997). This biofacies is commonly represented at the Paleocene part of the Dakhla Formation at Edmonstone and Qur El Malik sections (Figs. 8, 10 and 12).

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which is frequent at shelf and decreases toward the shore and the bathyal regions (Olsson and Nyong, 1987). In the present study, the diversity changes from low to high diversities indicating variation in the environment of deposition and nutrient availability from restricted lagoonal and littoral environments to deeper marine environment of an outer neritic conditions (Figs. 8, 10 and 12).

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5.4. Anomalinoides aegyptiaca Biofacies: This biofacies is characterized by a well-diversified and highly abundant benthic foraminiferal assemblage. It includes some species of inner to middle neritic environments, while others are of outer neritic environment. The species of the inner to middle neritic environments are Anomalinoides aegyptiaca (13.7%), Lacosteina maquawilensis (12%), Discorbis pseudoscopos (10%), Elhasaella alanwoodi (9%), Orthokarstenia oveyi (8%), and Eouvigerina aegyptiaca (2.5%). The outer neritic environment species are Angulogavelinella abudurbensis (7%) and Anomalinoides affinis (2.8%). These frequent species are associated with some less frequent species as Bulimina prolixa, Cibicidoides pseudoperlucidus, Gaudryina spp., Lenticulina pseudosecans, L. rotulata, Neobulimina canadensis, Orthokarstenia esnehensis, Spiroplectinella spp., Vaginulina spp., Valvalabamina depressa, Valvulineria aegyptiaca and Cibicidoides decoratus (Fig. 7). Such assemblage is referred to the Midway Fauna Type of Berggren and Aubert, 1975 of deep inner to middle neritic environments (Berggren, 1974a; Luger, 1985; Hewaidy, 1994; Speijer, 1994; Hewaidy, 1997; Speijer

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5.3. Trochammina rainwateri Biofacies: This biofacies is dominated by the Trochammina rainwateri (43%), T.umiatensis (16.5%), T. diagonis (13%), and Insculptarenula texana (8.5%), these in addition to other less frequent species as T. bohemi and Reophax texanus. This assemblage is interpreted as deeper littoral environment with normal marine water (Berggren, 1974a; Luger, 1985; Hewaidy, 1997 and Hewaidy et al., 2014). This biofacies is represented at the Maastrichtian part of the Dakhla Formation at the three studied sections (Figs. 8, 10 and 12).

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5.5. Cibicidoides pseudoacuta Biofacies: This biofacies includes a well-diversified and highly abundant faunal association. It includes some species of middle neritic to bathyal environments and others of outer neritic to bathyal environments. The species of the middle neritic to bathyal environments are Anomalinoides zitteli (22%), A. praeacutus (7%), Gyroidinoides girardana (7%), Oridorsalis plummerae (2.5%), and Siphogeneroides eleganta (1.7%). An outer neritic to bathyal species are Cibicidoides pseudoacuta (26%), Pulsiphonina prima (5%), Valvalabamina planulata (5%), and Marginulinopsis tuberculata (4%). These frequent species are associated with some less common species as, Orthokarstenia higazi, Osangualaria plummerae, Pseudonodosaria manifesta, Bulimina strobila, Loxostomoides applinae, and Trifarina esnaensis. This assemblage coexisted in an outer neritic environment (Berggren, 1974a; Hewaidy, 1994; Speijer, 1994; Hewaidy, 1997; Speijer and Schmitz, 1998; El-Dawy and Hewaidy 2003 and Sprong et al., 2012) as being further supported by the higher percentage of the planktonic/benthic ratio (60-70%). It is more commonly represented at the Paleocene part of the Dakhla Formation at the three studied sections (Figs. 8, 10 and 12).

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and Schmitz, 1998 and El-Dawy and Hewaidy 2003). This biofacies is mainly represented in the Maastrichtian part of the Dakhla Formation at the three studied sections (Figs. 8, 10 and 12).

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5.7. Neoeponides duwi Biofacies: The most dominant species in this biofacies is the Neoeponides duwi (about 99.3%) and Zeauvigerina aegyptiaca (0.7%). Neoeponides duwi assemblage is interpreted as deep inner-middle neritic environments with water depth ranging from 30-70m (Hewaidy, 1994; Speijer and Schmitz, 1998; Schnack 2000; Speijer, 2003 and Sprong et al., 2012). This biofacies is only represented at the lower Paleocene Kurkur Formation at Teneida section (Fig. 8).

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6. Sequence Stratigraphy Eight 3rd order depositional sequences are distinguished in this work, of these; three are recognized in the Maastrichtian and five in the Paleocene. These sequences are bounded by eight sequence boundaries (SB A - SB H) represented by unconformity surfaces and depositional hiatuses. The systems tracts of the analyzed sequences are recognized and differentiated based on sea level changes interpreted from the paleobathymetric analysis of the different foraminiferal parameters as P/B % and benthic biofacies. The majority of these sequences are represented by transgressive systems tracts (TST) and highstand systems tracts (HST) while the lowstand systems tracts are missing in most of the recognized sequences except at the (DS E) at Edmonstone section. The following is a brief description of the recognized depositional sequences and their sequence boundaries and systems tracts.

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Depositional Sequence A: Lower Maastrichtian Dakhla sequence (DS A) DS A includes the whole thickness of the Mawhoob Shale Member of the Dakhla Formation. It attains about 21m thick at Teneida section, 50m thick at Edmonstone section, and 80m thick at Qur El Malik section (Figs. 8, 10 and 12). It is bounded at base by sequence boundary A (SB A) which is represented by the Duwi/Dakhla formational boundary (El-Azabi and El-Araby, 2000; Hewaidy et al., 2006 and El-Azabi and Farouk, 2011). This boundary is represented by a sharp contact between the Duwi and Dakhla formations and the presence of a phosphatic bed with reworked phosphate debris and some conglomerate granules. The sequence boundary A (SB A) is coinciding with a major eustatic sea-level fall recorded at the early Maastrichtian (Haq et al., 1988 and Hardenbol et al., 1998). This boundary is an amalgamated surface as a result of fusing a transgressive surface (TS) with sequence boundary (SB A) due to the absence of the (LST). The Lower Maastrichtian Dakhla sequence covers the interval of the early Maastrichtian Gansserina gansseri (CF7) Zone and the lower part of the overlying nondiagnostic/barren interval.

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5.6. Cibicides farafraensis Biofacies: This biofacies is characterized by the dominance of the following species: Cibicides farafraensis (24.8%), Cibicidoides howelli (18%), C. pharaonis (13.5%), Epistomina esnaensis (11.9%), Lenticulina midwayensis (8.7%), Pyramidulina spp. (8.6%), Alabamina wilcoxensis (5%), Bolivina cretosa (2.3%) and Rotalia calcariformis (2.2%). This assemblage is referred to the Midway Fauna Type of Berggren and Aubert, 1975 and donates middle to outer neritic environments (Berggren, 1974a; Speijer, 1994; Speijer and Schmitz, 1998 and El-Dawy and Hewaidy 2003). This biofacies is recorded at the upper Paleocene part of the Dakhla Formation at Edmonstone section (Fig. 10).

ACCEPTED MANUSCRIPT This sequence can be subdivided into two systems tracts as follows:

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HST: In the upper part of the depositional sequence DS A, the absence of planktonic forams coupled with the high dominance of the Ammobaculites khargaensis biofacies with low diversity suggest a drop in the relative sea level which indicate a regressive phase of a highstand systems tract (HST). These highstand deposits include the top part of the Mawhoob Shale Member of the Dakhla Formation (Figs. 8, 10 and 12). It is composed of progradational parasequence set of grey to green shales and clays intercalated with calcareous siltstone. The calcareous siltstone interbeds, which represent the deeper conditions during the parasequence, become thinner and fewer upwardly indicating a regressive phase. This systems tract is suggested to be deposited in a littoral environment with very few oscillations to shallow inner neritic environment as a result of dramatic drop in the relative sea level (Figs. 8, 10 and 12).

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Depositional Sequence B: Middle Maastrichtian Dakhla sequence (DS B)

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This depositional sequence is represented by the Beris Oyster Mudstone Member of the Dakhla Formation. It is delineated at base by the sequence boundary B (SB B) which is represented by the Mawhoob/Beries members boundary (El-Azabi and El-Araby, 2000; El-Azabi and Farouk, 2011). The sequence boundary B (SB B) is coinciding with the eustatic sea-level fall recorded at the middle Maastrichtian (Haq et al., 1988 and Hardenbol et al., 1998). This sequence boundary is characterized by the presence of bioturbated siltstone to silty shale with reworked and fragmented megafossils and shark teeth at the top of the Mawhoob Shale Member. The exact age of this sequence is difficult to determine as its sediments are barren of any diagnostic planktonic foraminifera. The Exogyra overwegi Zone that marks the Beris Oyster Mudstone Member is characteristic of the middle Maastrichtian age in the Western Desert of Egypt (Hermina, 1967). This sequence could be tentatively attributed to the middle Maastrichtian Zone CF4, which marks the same biostratigraphic interval in the deeper parts of the Dakhla Basin (Tantawy et al., 2001 and Hewaidy et al., 2006). This sequence can be subdivided into two systems tracts as follows:

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TST: This transgressive systems tract consists of littoral to shallow inner neritic shales and mudstones intercalated with argillaceous and fossiliferous limestone and siltstone ledges enriched in Exogyra overwegi (Figs. 8, 10 and 12). The presence of Exogyra overwegi indicates water depth not exceed 30 m. With regarding to its foraminiferal content, this systems tract is characterized by very low planktonic/benthic ratio (0-10%) with benthic assemblage dominated by Ammobaculites khargaensis biofacies and Trochammina rainwateri biofacies. Also, the Anomalinoides aegyptiaca biofacies occurs in some deeper intervals. The maximum flooding surface (MFS) is placed at the transition from deeper facies with maximum abundance of Exogyra overwegi below to shallower facies above.

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HST: It is composed of progradational parasequence set of black fissile shale with minor greyish siltstone interbeds (Figs. 8, 10 and 12). This systems tract is marked by a complete absence of any planktonic forms. The foraminiferal content is represented by scarce foraminiferal tests belonging to the simple-walled agglutinated genera Ammobaculites and Haplophragmoides of restricted littoral and lagoonal environments.

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At Qur El Malik section, the middle Maastrichtian Dakhla sequence (DS B) is represented only by the deepening-up deposits of the transgressive systems tract (TST) while the progradational facies of the highstand systems tract (HST) are missing and consequently the maximum flooding surface is being amalgamated with the overlying sequence boundary (Fig. 12).

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TST: It is composed of white to greenish marl at Teneida and Edmonstone sections (Figs. 8 and 10) while at Qur El Malik section, it is composed of grey to greenish marly shale with siltstone intercalations (Fig 12). It is characterized by high planktonic/benthic ratio (60%), high diversity (45-60 species) with high dominance of Anomalinoides aegyptiaca biofacies and some elements of Cibicidoides pseudoacuta biofacies (Figs. 9, 11 and 13). Such conditions donate middle-outer neritic environments for this part and indicate that it was deposited during periods of relative sea level rise. The maximum flooding surface (MFS) is placed at the last occurrence of the planktonic foraminifera within this interval which corresponds to the maximum faunal abundance. This surface marks the transition from deepening upward to shallowing upward phases in facies trend.

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Depositional Sequence C: Upper Maastrichtian Dakhla sequence (DS C) DS C includes the lower unit of the Kharga Shale Member and falls within the interval of Pseudoguembelina hariaensis (CF3) Zone and the overlying barren interval. It attains about 98m thick at Teneida section, 50m at Edmonstone section, and 60m at Qur El Malik section. It is bounded at base by sequence boundary C (SB C) which is represented by the early/late Maastrichtian (Beris/Kharga members) contact. This boundary is characterized by the presence of intensive bioturbation at the top of Beris Mudstone Member indicating a break in sedimentation. This sequence boundary is coinciding with a short term sea level fall that occurred at the base of the Abathomphalus mayaroensis Zone (Haq et al., 1988). This sequence can be subdivided into two systems tracts as follows:

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HST: The regressive interval of this sequence is characterized by complete absence of any planktonic foraminifera and rare benthic foraminiferal species belonging to Trochammina rainwateri biofacies and Ammobaculites khargaensis biofacies (Figs. 8 and 10). It is composed mainly of grey shales and mudstones with very minor siltstone intercalations at base. Such conditions suggest deposition under very shallow water conditions of littoral environment and indicate a significant fall in the relative sea level. At Qur El Malik section, this systems tract is composed of white hard concretionary sandy and argillaceous limestone and vary-colored shales completely barren of foraminifera (Fig. 12).

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Depositional Sequence D: lower Paleocene Kurkur sequence (DS D) The lower Paleocene Kurkur sequence (DS D) comprises the whole interval of the Kurkur Formation. It falls within the interval of the Globanomalina compressa (P1c) Zone. It is recorded only at Teneida section with thickness of about 14.5m. It is bounded at base by sequence boundary D (SB D) which is represented by a regional unconformity recorded at the K/P boundary (Luger, 1985; Hewaidy, 1990; Hewaidy, 1994; Abd El-Kireem and Samir, 1995 and Tantawy et al., 2001). It coincides with Dakhla/Kurkur formational boundary and marked by the presence of a phosphatic conglomerate band with 20-30cm thick of Bir Abu Minqar Horizon which marks the Cretaceous/Paleogene boundary in the Western Desert of Egypt (Barthel and Herrmann-Degen, 1981). This unconformity is indicated by absence of the latest Maastrichtian planktonic (CF2) and (CF1) biozones and the earliest Paleocene planktonic (P1a) and (P1b) biozones. This hiatus appears to be related primarily to a major sea-level fall and secondarily to regional tectonic activity related to the Bahariya arch (Tantawy et al., 2001). This sequence can be subdivided into two systems tracts as follows:

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TST: The transgressive systems tract of the lower Paleocene Kurkur sequence (DS D) is characterized by a moderate planktonic/benthic ratio (10-35%), low diversity, and high dominance of the Neoeponides duwi biofacies that suggest inner-middle neritic environments (Hewaidy, 1994; Speijer and Schmitz, 1998; Speijer, 2003 and Sprong et al., 2012). The fast rise in the relative sea level directly after the K/P boundary, results in the amalgamation of transgressive surface (TS) and sequence boundary (SB) and the absence of the lowstand systems tract (LST). The maximum flooding surface (MFS) is placed at

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TST: This transgressive systems tract is composed of retrograditional parasequence set of pale, dark grey and green calcareous, phosphatic, fissile shale intercalated with calcareous siltstone, sandstone, and limestone belonging to Pseudoguembelina hariaensis (CF3) Zone. It is characterized by variation in planktonic/benthonic ratio (P/B %) ratio between beds with high ratio (25-60%) and others with very low ratio (0-7%). The benthic foraminiferal biofacies is represented by the oscillation between Anomalinoides aegyptiaca biofacies and/or Ammobaculites khargaensis biofacies and Trochammina rainwateri biofacies. This parasequence set was deposited during a relative sea-level rise and assigned to inner-middle neritic environments (Figs. 8 and 10). At Qur El Malik section, a pleohigh topographic conditions prevailed during deposition of this systems tract, as very low planktonic/benthic ratio (0-7%), low to moderate (5-15 species) diversity, and high dominance of Ammobaculites khargaensis biofacies and/or Anomalinoides aegyptiaca biofacies were prevailed reflecting deposition under littoral to shallow inner neritic environments (Figs. 12). This reflects a fluctuation in the relative sea level during the deposition of this systems tract and difference in the paleotopography indicated by the shallower facies towards Qur El Malik section. The maximum flooding surface (MFS) is placed at the top of thin calcareous siltstone band with last occurrence of the Maastrichtian planktonic foraminifera (Figs. 8 and 10). This surface separates innermiddle neritic shales intercalated with calcareous siltstone bands below from littoral to inner neritic grey to green fissile shales above.

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Depositional Sequence E: lower Danian Dakhla sequence (DS E) The lower Danian Dakhla sequence (DS E) covers the interval of the early Paleocene Praemurica trinidadensis (P1d) Zone and the most part of the Praemurica uncinata (P2) Zone and occupies the lower part of the upper Kharga Shale unit. It is composed of pale to dark grey and green calcareous phosphatic shale. This depositional sequence is bounded at base by sequence boundary E (SB E) which is represented by the Kurkur/Dakhla formational boundary at Teneida section and coincides with the CretaceousPaleogene (K/P) boundary at Edmonstone and Qur El Malik sections. The Cretaceous-Paleogene (K/P) boundary at Edmonstone and Qur El Malik sections lies at base of the Bir Abu Minqar Horizon within the Dakhla Formation, which separates the lower and upper units of the Kharga Shale Member. This boundary is marked by absence of the latest Maastrichtian planktonic (CF2) and (CF1) biozones and the earliest Paleocene planktonic (P1a), (P1b), and (P1c) biozones at Edmonstone section (Fig 10), while at Qur El Malik section, the magnitude of this hiatus is likely to be greater due to the absence of the Praemurica trinidadensis (P1d) Zone (Fig. 12). This sequence boundary matches well with the global sea level fall recorded at the base of the Praemurica trinidadensis (P1d) Zone (Haq et al., 1988 and Hardenbol et al., 1998). This depositional sequence includes three systems tracts as follows: LST: The lowstand systems tract (LST) of this depositional sequence is recorded only at the Edmonstone section (Fig.Fig 14 14). It is represented by a shallowing-up pattern characterized by the absence of planktonic foraminifera and high dominance of Trochammina rainwateri and Anomalinoides aegyptiaca biofacies which suggest a shallow inner neritic environment (Fig. 10).

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TST: The transgressive systems tract (TST) of this depositional sequence is represented by the deepest marine facies recorded in the study area. It is represented a deepening–up pattern characterized by rich faunal content with high planktonic/benthic ratio ranging from 50-70% and high diversity (60 species). The benthic foraminiferal biofacies is characterized by a well-diversified faunal assemblage dominated by Cibicidoides pseudoacuta biofacies (Figs. 8, 10 and 12). These indicate deposition under outer neritic environmental conditions. This systems tract corresponds to the planktonic zones Praemurica trinidadensis (P1d) and the lower part of Praemurica uncinata (P2) of the early Danian age.

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HST: Within the upper part of (P2) Zone at Edmonstone and Qur El Malik sections, the absence of planktonic forams and high dominance of Haplophragmoides excavata biofacies clearly delineate the regressive deposits of a highstand systems tract (HST). No obvious change in lithology was observed between this systems tract and the underlying transgressive systems tract (TST), so it is distinguished mainly based on the marked change in the different foraminiferal parameters as planktonic/benthic ratio, diversity, and benthic foraminiferal biofacies (Figs. 10 and 12). While at Teneida section due to the deposition in paleo-low as indicated from reduced thickness within the Praemurica uncinata (P2) Zone and deeper conditions, this systems tract has not been detected which result in continuous transgressive phase and the amalgamation of both transgressive systems tracts TST-E and TST-F (Fig. 8). The maximum flooding surface (MFS) which marks the end of transgression is placed before the marked drop in the planktonic foraminifera within this interval. This drop is also accompanied with a major change in the composition of the benthic assemblage indicating transition from outer neritic depths below to littoral above (Figs. 10 and 12).

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Depositional Sequence F: Upper Danian Dakhla sequence (DS F) DS F covers an interval within the upper Kharga Shale unit between sequence boundary F (SB F) at base and sequence boundary G (SB G) at top. The sequence boundary F (SB F) is indicated by the presence of a ledge of ferruginous sandy shale separates the pale to dark grey calcareous and phosphatic shale below and the grey to brownish glauconitic shale with sandstone and siltstone intercalations above. This ledge is

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the last occurrence of the planktonic foraminifera within this interval and coincides with the maximum abundance of the Neoeponides duwi. HST: It is characterized by the absence of planktonic foraminifera. It is dominated by Trochammina rainwateri biofacies, which reflect a shallow inner neritic environment. It is composed of green gypsiferous shale intercalated with brown argillaceous limestone band enriched in scattered oyster shells (Fig. 8Fig 8).

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Depositional Sequence G: Selandian Dakhla sequence (DS G) DS G occupies the uppermost part of the upper Kharga Shale unit at Edmonstone and Teneida sections including the upper Paleocene (Selandian) part of the Dakhla Formation with thickness of about 8m thick at Teneida section and 3.5m thick at Edmonstone section. It is delineated at base by the sequence boundary (SB G) which corresponds to the Danian/Selandian (D/S) boundary. In the study area, the Danian/Selandian (D/S) transition is characterized by a faunal break due to completely or partly absence of the Igorina albeari (P3b) Zone (Farouk and El-Sorogy, 2015). This sequence boundary is coinciding with the global sea level fall at the base of the Globanomalina pseudomenardii (P4) Zone (Haq et al., 1988). The DS G is composed of pale to dark grey to green calcareous shale.

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This depositional sequence (DS G) includes a transgressive systems tract (TST) only. TST: At Teneida section, this systems tract is characterized by high planktonic/benthic ratio (5070%), high diversity and high dominance of Cibicidoides pseudoacuta biofacies intercalated at middle with a barren interval from planktonic foraminifera and characterized by low diversity benthic assemblage belonginig to Haplophragmoides excavata biofacies. These donate an outer neritic environment changed to inner neritic environment during this systems tract (Fig. 8).

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At Edmonstone section, this systems tract is characterized by low planktonic/benthic ratio (0-18%) and the benthic foraminiferal biofacies is represented by Haplophragmoides excavata biofacies and

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associated with a planktonic and benthic foraminiferal turnover indicating transition from shallower conditions below to deeper conditions above. This boundary is a sub-marine erosional surface indicating a short-lived break in sedimentation coupled with a relative sea-level drop. The upper Danian sequence falls within the interval of the uppermost part of the Praemurica uncinata (P2) Zone to the Igorina albeari (P3b) Zone. This depositional sequence can be subdivided into two systems tracts as follows: TST: It is composed of a retrograditional parasequence set of grey to brownish glauconitic fissile shale with sandstone and siltstone intercalations. At Edmonstone section, it is characterized by change from beds with high planktonic/benthic ratio (35- 65%), high diversity (25-30 species), and the dominance of Cibicidoides pseudoacuta biofacies and Cibicides farafraensis biofacies to beds with only agglutinated foraminifera belonging to Haplophragmoides excavata biofacies. Such coniditions suggest oscillation in the environment of deposition from deep middle neritic to shallow inner neritic environments (Fig. 10). At Qur El Malik section, this systems tract started at a ledge of ferruginous sandy shale with low planktonic/benthic ratio (18%) and high dominance of Haplophragmoides excavata biofacies and Anomalinoides aegyptiaca biofacies. This suggests an inner neritic environment and marks the advent of transgression. This is followed by an interval barren from planktonic foraminifera and dominated by highly abundant low diversified simple-walled agglutinated benthic assemblage represented by Haplophragmoides excavata biofacies and Trochammina rainwateri biofacies that indicate a littoral environment (Fig. 12). This reflects the difference in the paleotopography and irregularity in the basin of deposition as indicated by shallower water conditions towards Qur El Malik section, which is considered as a paleo-high. HST: In the upper part of this depositional sequence, a marked decrease in the planktonic/benthic ratio (0-15%) is observed and indicates a slowing in the rate of relative sea level rise which interpreted as a regressive phase of highstand systems tracts (HST). The deposits of this systems tract are recorded only at Edmonstone section and included within the P3b Zone (Fig. 14). It is composed of grey to brownish glauconitic shale grades upward to sandy shale and sandstone (Fig. 10). This upward increase in the sand content confirms the shallowing upward characters within this systems tract. A relative sea level fall started at the P3b and topped by a regional hiatus between the Danian/Selandian (D/S) boundary which was reported in the stable shelf of the Western Desert (Farouk and El-Sorogy, 2015). The reported relative sea level fall within the P3b Zone is recorded from many parts in world (e.g. Hardenbol et al., 1998; Schmitz et al., 2011; Guasti et al., 2005; Sprong et al., 2011and Farouk and Faris 2013). This shallowing trend within P3b Subzone at the Danian/Selandian boundary may be correlated with the Latest Danian Event (LDE) which has been recorded in many parts of Egypt and Tunisia (Sprong et al., 2011; Sprong et al., 2012).

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Depositional Sequence H: Selandian Tarawan sequence (DS H) DS H comprises the upper Paleocene Tarawan Formation and falls within the interval of the Globanomalina pseudomenardii (P4) Zone. It attains about 24.5m thick at Teneida section, 14m thick at Edmonstone section, and 20m thick at Qur El Malik section (Figs. 8, 10 and 12). It is composed of snow white to yellowish white, hard, thickly bedded, and wall forming chalk and chalky limestone with few marl and shale intercalations. It is bounded at base by sequence boundary (SB H) which is represented by a regional unconformity recorded at the Dakhla/Tarawan formational boundary. This unconformity is marked by the presence of irregular surface marked by bioturbated marl to silty shale with ferruginous sandstone and Thalassinoides burrows at the Dakhla/Tarawan formational contact (Barthel and Herrmann-Degen, 1981; El-Azabi and El-Araby, 2000; El-Azabi and Farouk, 2011). These are interpreted as a result of burrowing at the top of the Dakhla Formation and then filled by the limestone of the Tarawan Formation. The Selandian Tarawan sequence (DS H) is represented only by a transgressive systems tract (TST) in the studied area.

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Cibicides farafraensis biofacies that assign this interval to inner neritic environment (Fig. 10). Further west in the study area at Qur El Malik section, the Danian/Selandian boundary coincides with the Dakhla/Tarawan formational contact (P3a/P4 zonal boundary) resulting in the amalgamation of both sequence boundaries SB G and SB H and consequently the absence of the Selandian Dakhla sequence (DS G).

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7. Correlations: Sequences and their sequence boundaries are interpreted to form in response to cycles of relative fall and rise of sea level (Van Wagoner, et al., 1990). The correlation of the relative sea level cycles to global and eustatic cycles charts help to understand whether these cycles formed as a result of the global eustacy or related to other local tectonics.

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Most sequence boundaries recognized in the study area are matching well with those from adjacent areas and global ones (Fig. 15). Small discrepancies were observed in some intervals which may be attributed to limited biostratigraphic resolution, or to local tectonics prevailed in the area under consideration during the studied time interval.

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The first sequence boundary SB A is recorded at the base of the Dakhla Formation at the three studied sections. It is coinciding with the major eustatic sea-level fall at the early Maastrichtian (Haq et al., 1988). It is marked by an unconformity surface recorded at the contact between the Duwi and the Dakhla formations (Hermina, 1990; El- Azabi & El-Araby, 2000; Tantawy et al., 2001; Hewaidy et al., 2006). It coincides with the sequence boundary SB 1 of El-Azabi and El-Araby, 2000 and Ca/MaKh1 of ElAzabi and Farouk, 2011. The Lower Maastrichtian Dakhla sequence (DS A) may be equivalent to Ma 1 sequence of Hardenbol et al., 1998 and UZA 4. 5 sequence of Haq et al., 1988.

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The sequence boundary (SB B), recorded at the contact between the Mawhoob and Beries members, is coinciding with the global sea level fall that occurred within the CF 4 Zone (Hardenbol et al., 1998). It may be correlated with SB 2 of El-Azabi and El-Araby, 2000 at west Dakhla Oasis and MaKh2 of El-Azabi and Farouk, 2011 at the Kharga Oasis. The strata across this sequence boundary exhibit a significant change in paleodepth from littoral below to inner neritic environment above. The Middle Maastrichtian Dakhla sequence (DS B) may correspond to TA1. 1 sequence of Haq et al., 1988.

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The sequence boundary (SB C) is recorded at the base of the lower Kharga Shale unit of the Kharga Shale Member. It may be equivalent to the global short-lived sea level fall that occurred at the base of the Abathomphalus mayaroensis Zone (Haq et al., 1988). It may be correlated with SB 3 of El-Azabi

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TST: At Teneida and Edmonstone sections, it is characterized by a moderate planktonic/benthic ratio (40%) with high percentages of Morozovella and Acarinina, and high dominance of Anomalinoides aegyptiaca biofacies, Cibicidoides pseudoacuta biofacies and Cibicides farafraensis biofacies that suggest a middle neritic environment (Figs. 8 and 10). At Qur El Malik section, this systems tract is characterized by higher planktonic/benthic ratio (50%) which denotes a deeper depositional conditions (middle-shallow outer neritic environment).

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The fourth sequence boundary (SB D) is defined at the base of the lower Paleocene Kurkur Formation. It is coinciding with the well-known hiatus recorded at the K/P boundary over the Western Desert of Egypt (e.g. El-Naggar, 1966; Abbass and Habib, 1969; Luger, 1985; Anan and Sharabi, 1988, Hermina, 1990; Hewaidy, 1990; Hewaidy, 1994; Abd El Kireem and Samir, 1995; El-Azabi and El-Araby, 2000; Tantawy et al., 2001). This hiatus is indicated by the absence of the Maastrichtian CF2 and CF1, in addition to the Paleocene P0, P1a and P1b biozones. It is attributed primarily to the major sealevel fall and secondarily to the regional tectonic activity of the Bahariya arch (Tantawy et al., 2001).This sequence boundary may be equivalent to the global sea level fall recorded at the latest Maastrichtian (Haq et al., 1988; Hardenbol et al., 1998). The sequence boundary (SB C) may be correlated with the sequence boundary Ma- Sin-Z given by Lüning et al., 1998 in central east Sinai.

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The sequence boundary (SB E) has been defined at the base of the upper Kharga Shale unit. At Edmonstone and Qur El Malik sections, the lower Paleocene Kurkur sequence (DS D) is missing and subsequently the sequence boundary (SB D) is fused with (SB E). This sequence boundary is correlated well with the global sea level fall that occurred at the base of the Praemurica trinidadensis (P1d) Zone recorded by Haq et al., 1988. It may be equivalent to SB 4 of El-Azabi and El-Araby, 2000 in the Dakhla Oasis; SB 3 of Hewaidy et al., 2006 in the Farafra Oasis; DaSin-3 of Lüning et al., 1998 in central east Sinai and Da 4 of Hardenbol et al., 1998 in the global sea level chart at the upper part of P1c Subzone. It may be correlated with the relative sea level fall detected by Speijer, 1994 at the P1c Subzone in the paleodepth curve established for Gabal Owiena based on benthic foraminiferal analysis.

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The Sixth sequence boundary (SB F) is recorded within the Upper Kharga Shale unit at Edmonstone and Qur El Malik sections near the top of the Praemurica uncinata (P2) Zone. It is marked by a ledge of ferruginous sandy shale interpreted as a sub-marine erosional surface. A planktonic and benthic foraminiferal turnover was noted across this boundary suggesting an abrupt transition from shallower to deeper conditions.

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The seventh sequence boundary (SB G) is defined at the base of the Globanomalina pseudomenardii (P4) Zone within the upper unit of the Kharga Shale Member. It is characterized by a faunal break due to completely or partly absence of the Igorina albeari (P3b) Zone. This sequence boundary coincides with the Danian/Selandian (D/S) boundary and matches with the global sea level fall that occurred at the base of the Globanomalina pseudomenardii (P4) Zone (Haq et al., 1988). The Danian/ Selandian sea-level fall have been recognized in various parts of Egypt (e.g. Lüning et al., 1998; Speijer, 2003; El-Azabi and Farouk, 2011; Sprong et al., 2012; Farouk and Faris, 2013; Farouk and ElSorogy, 2015). The sequence boundary (SB G) may be correlated to ThSin-2 given by Lüning et al., 1998; SelGal 2 sequence boundary given by Kuss et al., 2000 at the Galala plateaux and Sel 1 of Hardenbol et al., 1998 in their global sea level chart with minor modifications in age.

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The eighth sequence boundary (SB H) is represented by the unconformity recorded at the Dakhla/Tarawan formational boundary. This unconformity was recorded in many parts in the Western Desert of Egypt (Dakhla-south Farafra by Barthel and Herrmann-Degen, 1981; Dakhla area by El-Azabi and El-Araby, 2000; Farafra area by Hewaidy et al., 2006; Kharga Oasis by El-Azabi and Farouk, 2011). This sequence boundary may be correlated with the sequence boundaries SB5 of El-Azabi and ElAraby, 2000 in west Dakhla, with ThSin-3 of Lüning et al., 1998 in central east Sinai, and with ThKh5 of El-Azabi and Farouk, 2011 in Kharga Oasis. In summation, a correlation of the sequence boundaries established in this work for the Maastrichtian-Paleocene succession of the Dakhla Oasis with those postulated in the eustatic cycle charts of Haq et al., 1988 and Hardenbol et al., 1998 displays a good agreement. The sequence boundaries SB

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and El-Araby, 2000 at west Dakhla Oasis and MaGl 1 of Kuss et al., 2000 at the Galala plateaux. A marked change in the parasequence stacking pattern from progradational below to retrogradational above was observed across this boundary. This was indicated by an abrupt increase in planktonic/ benthic ratio and a marked change in benthic biofacies. The strata across this sequence boundary exhibit a significant change in paleodepth from littoral below to inner-middle neritic above. The Upper Maastrichtian Dakhla sequence (DS B) is equivalent to Ma 5 sequence of Hardenbol et al., 1998 and TA1. 2 sequence of Haq et al., 1988.

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7. Conclusions:

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A, SB B, SB C, SB D, SB E and SB G are correlated well with the global eustatic sea level charts (Fig. 15), which suggest a greater control of eustatic sea-level on sequence boundary formation. Discrepancies of sequence boundaries SB F and SB H with the global eustatic sea level charts (Fig. 15) reflect a greater control of local tectonics on the formation of these sequence boundaries. There is some correspondence between the sequence boundaries and depositional sequences recognized in this work and that recorded in the Dakhla Oasis (El-Azabi and El-Araby, 2000), in Farafra Oasis (Hewaidy et al., 2006), in Kharga Oasis (El-Azabi and Farouk, 2011). The correlation of the established sequence model with the sea level curve in central east Sinai given by Lüning et al., 1998 revealed the presence of a good correspondence in particular to the relative sea level fall associated with the sequence boundaries Ma- Sin-Z, DaSin-3 and ThSin-2. This reflects the regional conditions controlling the deposition of the studied interval. Although, there are some discrepancies such as that occur at the SB F sequence boundary which may be related to limited biostratigraphic resolution and the scarcity or lack of planktonic foraminifera in some intervals. Also, some of these discrepancies may be attributed to the local tectonics.

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References

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The Maastrichtian-Paleocene succession in the Dakhla Oasis is marked by the presence of two facies types: Nile Valley Facies; which is subdivided into the Dakhla Formation at base and the Tarawan Formation at top; and Garra Al Arbain Facies; which is represented by the Dakhla and Kurkur formations. The Nile Valley Facies is represented mostly in the western part of the Dakhla Oasis, while the Garra Al Arbain Facies is represented by a tongue of the Kurkur Formation which is fully represented in Abu Tartur Plateau on the eatern side of the studied area. Based on the lateral and vertical distribution of the identified foraminiferal species, the studied succession is subdivided into eight planktonic foraminiferal biozones. These are Gansserina gansseri Zone (CF7) of early Maastrichtian age, Pseudoguembelina hariaensis Zone (CF3) of late Maastrichtian age, Globanomalina compressa Zone (P1c), Praemurica trinidadensis Zone (P1d), Praemurica uncinata Zone (P2), Morozovella angulata Zone (P3a), and Igorina albeari Zone (P3b) of early Paleocene age, and Globanomalina pseudomenardii Zone (P4) of late Paleocene age. The sequence stratigraphic analysis of the Maastrichtian-Paleocene succession at the Dakhla Oasis, led to the recognition of eight third order depositional sequences. The recognized sequences were the result of primarily repeated rise and fall of relative sea level cycles. These sequences are bounded by eight sequence boundaries (SB A - SB H) based on the presence of unconformity surfaces and faunal breaks. The systems tracts of the distinguished sequences are recognized and differentiated based on the paleobathymetric analysis using different foraminiferal parameters (as P/B % and benthic biofacies) which have helped in constructing the relative sea level curve for the study area. Most of the distinguished sequences are represented by TST and HST systems tracts while the lowstand systems tract is totally missing except at the DS E in Edmonstone section. The established depositional sequences and sequence boundaries are correlated with the global and local sea level charts. This correlation suggested that, these depositional sequences are resulted mainly from eustatic sea-level changes coupled with local tectonic activities.

Abbass, H. L., and Habib, M. M., 1969: Stratigraphy of west Mawhoob area, south Western Desert, Egypt. Instit. Desert d’Egypt. Bull., 19(2): 47-107.

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Abd El-Kireem, M. R. and Samir, A. M., 1995: Biostratigraphic implications of the Maastrichtian- lower Eocene sequence at the North Gunna section, Farafra Oasis, Western Desert, Egypt. Marine Micropaleont., 26: 329-340.

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Anan, H. S., and Sharabi, S. A., 1988: Benthonic foraminifera from the Upper Cretaceous-Lower Tertiary rocks of the northwest Kharga Oasis, Egypt. M.E.R.C. Ain Shams University. Earth Sciences Series., 2: 191–218.

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Awad, G. A., and Ghobrial, M. G., 1965: Zonal stratigraphy of the Kharga Oasis. Geol. Surv. Paper., 34: 77. Cairo.

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Fig 1. Geological map of the Dakhla Oasis with location of the three studied sections. After Conoco, 1987. Fig 2. Planktonic foraminiferal zones identified from Tthe Maastrichtian-Paleocene succession exposed at the Dakhla Oasis and their equivalents proposed in the nearby areas. The age estimates and datum events are based on the standard planktonic foraminiferal zonal schemes of Li & Keller (1998a, b) and Li et al. (1999) for the Late Cretaceous and on the scheme of Keller et al. (1995) and Berggren & Pearson (2005) for the Paleocene.

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Fig 3. Distribution chart of the identified planktonic species at Teneida section.

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Fig 4. Distribution chart of the identified planktonic species at Edmonstone section.

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Fig 5. Distribution chart of the identified planktonic species at Qur El Malik section.

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Fig 6. Summary of paleobathymetrical preference of the most dominated benthic species. 1Berggren, 1974a; 2-Luger, 1985; 3-Speijer, 1994; 4-Cherif and Hewaidy, 1986; 5-Hewaidy, 1990; 6Hewaidy, 1994; 7-Hewaidy, 1997; 8-Speijer and Schmitz, 1998; 9-El-Dawy and Hewaidy 2003; 10Sprong et al., 2012; 11-Hewaidy, 1996; 12-Berggren, 1974b; 13-Speijer, 2003.

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Fig 7. Dendogram derived from cluster analysis of benthic foraminiferal species recorded in the three studied sections.

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Fig 8. Stratigraphic succession at Teneida section with the P/B ratio, diversity, benthic foraminiferal biofacies association, paleoenvironments, relative sea level, and sequence stratigraphic interpretation.

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Fig 9. Frequency chart of the identified benthic species at Teneida section.

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Fig 10. Stratigraphic succession at Edmonstone section with the P/B ratio, diversity, benthic foraminiferal biofacies association, paleoenvironments, relative sea level, and sequence stratigraphic interpretation. For legend see Fig.8.

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Fig 11. Frequency chart of the identified benthic species at Edmonstone section.

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Fig 12. Stratigraphic succession at Qur El Malik section with the P/B ratio, diversity, benthic foraminiferal biofacies association, paleoenvironments, relative sea level, and sequence stratigraphic interpretation. For legend see Fig.8.

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Fig 13. Frequency chart of the identified benthic species at Qur El Malik section.

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Fig 14. Correlation between the recorded depositional sequences at the three studied sections. For legend see Fig.8.

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Fig 15. Comparison between the established sequence boundaries and eustatic sea level curve of Haq et al., 1988, and other regional and local ones.

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Wade, B. S., Pearson, P. N., Berggren, W. A., and Pälike. H., 2011: Review and revision of Cenozoic tropical planktonic foraminiferal biostratigraphy and calibration to the geomagnetic polarity and astronomical time scale. Earth Sci. Reviews., 104: 111−142.

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1. The present paper includes a sequence stratigraphic classification for the MaastrichtianPaleocene succession in the Dakhla Oasis, Western Desert, Egypt. 2. This classification is based on detailed examination of three surface exposures for their physical boundaries and foraminiferal contents. 3. The main physical unconformity surfaces are used as sequence boundaries. 4. The planktonic foraminifera are used to build a chronostratigraphic outline for the Maastrichtian-Paleocene interval in the study area. 5. The benthonic foraminifera are used to build the sea-level curve for the MaastrichtianPaleocene time and then the systems tracts interpretations.