Maastrichtian-Paleocene successions at Kharga-Dakhla stretch, Western Desert, Egypt: Paleoenvironmental and basin evolution interpretations

Journal Pre-proof Maastrichtian-Paleocene successions at Kharga-Dakhla stretch, Western Desert, Egypt: Paleoenvironmental and basin evolution interpretations Kamel H. Mahfouz, Amr A. Metwally PII:

S1464-343X(19)30386-3

DOI:

https://doi.org/10.1016/j.jafrearsci.2019.103731

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AES 103731

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Journal of African Earth Sciences

Received Date: 30 October 2019 Revised Date:

4 December 2019

Accepted Date: 4 December 2019

Please cite this article as: Mahfouz, K.H., Metwally, A.A., Maastrichtian-Paleocene successions at Kharga-Dakhla stretch, Western Desert, Egypt: Paleoenvironmental and basin evolution interpretations, Journal of African Earth Sciences (2020), doi: https://doi.org/10.1016/j.jafrearsci.2019.103731. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. 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. © 2019 Published by Elsevier Ltd.

Maastrichtian-Paleocene successions at Kharga-Dakhla stretch, Western Desert, Egypt: paleoenvironmental and basin evolution interpretations Kamel H. Mahfouz1, Amr A. Metwally2 1 Geology Department, Faculty of Science, Al-Azhar University, Assiut Branch, Egypt 2 Geology Department, Faculty of Science, Assiut University, Assiut 71516, Egypt Abstract Detailed field, litho-, bio-stratigraphic and paleoenvironmental studies on the MaastrichtianPaleocene successions exposed at El-Qasr, Abu Tartur, Gabal El-Aguz and Darb Gaga sections at Kharga-Dakhla region, Western Desert, Egypt are attempted. Three rock units are recognized; Dakhla, Kurkur and Tarawan formations. Eight calcareous nannofossil and ten planktonic foraminiferal zones are recorded and integrated to determine a precise age dating. Four benthonic foraminiferal biofacies (A, B, C and D) are reconstructed using the R-mode (species) hierarchical cluster analysis. These biofacies along with the relative abundance of the calcareous nannofossil species are used to interpret the paleoenvironmental conditions as well as the depositional settings prevailed during deposition of the studied successions. The integration of these data led to the identification of significant hiatuses which could be linked to two syn-sedimentary tectonic events (Tectonic Event I and II). Tectonic Event I at the Cretaceous/Paleogene (K/Pg) boundary has a regional effect and led to expose the southern part of the Tethys margin that is represented by the present study area. Throughout the Early Danian, the sedimentary basin could be divided into two sub-basins at El-Qasr and El-Aguz sections separated by two sub-marine paleohighs at the Abu Tartur and Darb Gaga sections which represented the northern extensions of the southern shallow Garra El-Arbain Facies. The effect of Tectonic event II initialized at Danian and continued through Thanetian. This event is restricted to the eastern part at Darb Gaga and El-Aguz sections forming an areal paleohigh at Darb Gaga and a sub-marine paleohigh at El-Aguz sections. Keywords: Maastrichtian - Paleocene; nannofossil and foraminifera; Paleoenvironment; Basin evolution; Syrian Arc Orogeny; Kharga-Dakhla region, Egypt. 1. Introduction During the Late Cretaceous-Early Paleogene time, Egypt was located at the southern margin of the Tethys Ocean (Fig. 1). This location provides the Egyptian sedimentary successions a great potential for important and key biologic events through this time interval. These events are preserved at well exposed sedimentary successions that deposited in two major sedimentary basins 1

at the middle and southern Egypt. These basins are represented by the Dakhla basin at the west and the Upper Nile basin towards the east. These two basins are separated by the Kharga uplift in between (Said, 1990). Major tectonic events affected these basins during the Late Cretaceous and continued during the Early Paleogene. These tectonics are synchronous with the opening of the North Atlantic Ocean which resulted in the forming of the well-known Syrian Arc fold system. This orogeny is one of the main factors that controlled formation of restricted marine basins that marked by anoxic conditions. The Maastrichtian-Paleocene successions that exposed at Kharga-Dakhla stretch represent a part of the Dakhla basin. These sequences are marked by vertical and lateral facies changes due to the combination between the Nile Valley Facies (deep marine facies) and Garra-El Arbain Facies (shallow marine facies) along the Kharga-Dakhla area (Issawi, 1972). As a consequence, considerable number of studies have been oriented to study the general geology, stratigraphy, micropaleontology and the sedimentology of the sequences along the Kharga-Dakhla district (e.g. Said; 1961, 1962; Hermina et al., 1961; Issawi, 1972; Omara et al., 1976; Hewaidy, 1983, 1990, 1994, Hewaidy and Cherif, 1984, Faris, 1984; Hendriks et al., 1987; Luger, 1988a; Hermina, 1990; Tantawy et al., 2001; Hewaidy et al., 2006, 2014, 2017, 2018, 2019a,b,c,d; Mahfouz, 2008; Obaidalla et al., 2008, 2015; El-Azabi and Farouk, 2011; Hewaidy and Ayyad 2015; Metwally 2015; El-Dawy et al., 2016, 2018; Abdelhady et al., 2018; Metwally and Mahfouz 2018). Most of these studies have experienced main problem related to the poor age determinations, in particular, of the Upper Cretaceous successions. Furthermore, there is a little attention has been given to the evolution of the sedimentary basin and its geometry during this time interval with the exception of the study of Metwally and Mahfouz (2018) which dealt with this subject across the Late PaleoceneEarly Eocene at Kharga-Baris oases. Thus, the objectives of the present study are to; (1) integrate calcareous nannofossil and planktonic foraminiferal zonal schames at the Dakhla and Tarawan formations in order to precisely age determination; (2) analyze quantitatively the calcareous plankton community which lead to reconstruct their abundance pattern and thus the paleoenvironmental conditions prevailed during deposition of the studied units. In addition to, study of the benthonic foraminiferal biofacies and its paleoenvironmental implications especially the agglutinated foraminifera at the levels that lacks calcareous nannoplankton; (3) determine the tectonic events and reconstruct the basin evolution based on the integration of the field, litho-, biostratigraphic and paleoenvironmental data. 2. Material and methods To reveal the objectives of the present study and understand the geological and paleoenvironmental conditions prevailed during deposition of the Maastrichtian-Paleocene successions at Kharga2

Dakhla stretch, four sections encompass the studied interval are sampled in details (Fig. 1). These sections are; Gabal El-Aguz section, located at ∼50 km north of Kharga Oasis (25° 50′ 97˝N, 30° 41′ 99˝E) with total thickness of ~77m thick (53 samples); Darb Gaga section, located at ~20 km north of Baris Oasis (24° 55′ 06˝N, 30° 47′ 75˝E) attains ~50m thick (55 samples), Abu Tartur section (25° 24′ 53˝N, 30° 03′ 78˝E) reaches ~85m thick (59 samples), and El-Qasr section, (25° 44′ 26˝N, 28° 52′ 46˝E) comprises ~249m thick (97 samples). A total of 264 rock samples are obtained from the four stratigraphic sections under investigation. These samples are subjected to calcareous nannofossil and foraminiferal analyses. For calcareous nannofossil analysis, all the samples are proceeded following the standard technique of smear slide preparation from raw sediments (Perch Nielsen, 1985; Bown and Young, 1998). Smear slides of each sample are examined under polarized microscope with 1250X magnification. The calcareous nannofossil taxa of the studied sections exhibit moderate to well preservation and generally abundant which allowed detailed quantitative analyses of the calcareous nannofossil assemblages. The quantitative analyses are achieved following the technique of Jiang and Gartner, 1986 by counting of ~300 individual. Whereas about 100 individual are counted in samples that displayed very low abundance. Nannofossil species richness is calculated as the total number of species that counted in each sample. The important nannofossil species are illustrated in Plate I. For foraminiferal analysis, ~200 gram from each sample is disaggregated in water with dilute hydrogen peroxide (H2O2). The samples are washed through a 63µm sieve and the obtained residues are dried. These processes are repetitive until clean surface of foraminiferal tests are recovered. The abundance of the foraminiferal species of the present study are vary. Representative splits of the residue are analyzed under binocular stereomicroscope. The foraminiferal species are picked out, identified and mounted on micro slides for permanent record. The total foraminiferal number and species richness of benthonic foraminifera are counted. Also, the planktonic/benthonic (P/B) and agglutinated/calcareous (A/C) percentages are also calculated. In addition, the paleobathymetry of the identified benthonic foraminiferal species are established (Table 1). To identify the different benthonic foraminiferal assemblage (biofacies) with similar distribution patterns, the R-mode (species) hierarchical cluster analysis is achieved using originPro 2017 computer software. The obtained data are used to reconstruct the paleoenvironmental setting of the studied units. Finally, based on the integration of all the obtained data, the sedimentary basin evolution during the Late Cretaceous-Early Paleocene time interval are achieved. Some of the most important agglutinated benthonic foraminiferal species are photographed by the Scanning Electron Microscope Unit (JSM 5400 LD) at Assiut University, Assiut, Egypt, and given in Plate II. All the figured specimens are 3

housed at the Museum of the Geology Department, Faculty of Science, Assiut University, Assiut, Egypt in the collection of Dr. Amr A. Metwally. 3. Results 3.1. Lithostratigraphy The Upper Cretaceous-Lower Paleogene successions are widely distributed in the central and southern parts of Egypt (Hermina, 1990). These successions are vertically and laterally changed which represent the two well-known Nile Valley Facies and Garra El-Arbain Facies of Issawi (1972). At the studied sections, three rock units are recognized; Dakhla and Tarawan formations belongs to the Nile Valley Facies and Kurkur Formation which represents the Garra El-Arbain Facies. Dakhla Formation (Said, 1961) The Dakhla Formation represents the lower scarp face expanded around the Dakhla and Kharga oases. It overlies the Duwi Formation and underlies the Tarawan or Kurkur formations. At the Dakhla-Kharga area, Awad and Ghobrial (1965) subdivided the Dakhla Formation into Mawhoob Shale, Beris Oyster Mudstone and Kharga Shale members. Also Lüger (1985) informally subdivided the Kharga Shale Member into Lower Kharga Shale and Upper Kharga Shale members which separated by Cretaceous/Paleogene (K/Pg) boundary. In the present study, the upper rock unit of the Dakhla Formation (Kharga Shale Member) and it’s subdivisions of Lüger (1985) are applied. The Lower Kharga Shale Member in the study area consists of thick succession of black to dark gray shale intercalated with silty marl beds of Late Maastrichtian age. It attains ~112m, ~68m, 26m and 30m thick at El-Qasr, Abu Tartur, Gabal El-Aguz and Darb Gaga sections respectively. At ElQasr, G. El-Aguz and Darb Gaga sections, the Lower Kharga Shale Member caped with a remarkable and well defined conglomeratic bed (Abu Minqar Horizon) that marks the K/Pg boundary (Fig 2: A, C, D and F). At Abu Tartur Section, the Lower Kharga Shale Member overlain by the Early Paleocene Kurkur Formation (Cherif and Hewaidy, 1987). The Upper Kharga Shale Member consists of grey shale and calcareous shale intercalated with limestone beds of Paleocene age. The maximum measured thickness of this member (~123m) is recorded at El-Qasr section, while it attains ~27m thick at G. El-Aguz and ~7m at Darb Gaga section. The Upper Kharga Shale Member at these sections is laterally facies changed to the Kurkur Formation at Abu Tartur section. Tarawan Formation (Awad and Ghobrial, 1965) 4

The Tarawan Formation consists of white to yellowish white chalky limestone, marl and limestone. It overlies the Dakhla Formation at El-Qasr section which represents the top rock unit of the sedimentary succession at this site (Fig 2. G). Towards east at G. El-Aguz and Darb Gaga sections, it overlies the Dakhla Formation and underlies the Esna Formation. The Tarawan Formation attaints ~23m at G. El-Aguz, ~13.5m at El-Qasr and Darb Gaga sections. Based on its calcareous plankton contents, it’s assigned to the Late Paleocene age. Based on the field observation, the contact between the Dakhla and Tarawan formations is marked by the occurrence of erosive surface at G. El-Aguz and Darb Gaga sections. This is documented by the presence of irregular and bioturbated surface at the base of the Tarawan Formation (Fig 2. B and E) at G. El-Aguz. At Darb Gaga section the presence of irregular surface, glauconitic rich sediments and plenty occurrence of pebbles are characteristics of the base of the Tarawan Formation (Fig 2. E). Kurkur Formation (Issawi, 1968) This rock unit is only represented at Abu Tartur section. It consists of ~17.5m thick of yellowish, well bedded, massive dolomitic limestone rich with bivalve shells. It overlies the Dakhla Formation at Abu Tartur section (Fig 2. H). At the northeastern scarps of the Dakhla Oasis, Hermina (1990) and Hewaidy et al., (2014) recorded the Kurkur Formation of the Paleocene age which unconformablly overlain the Dakhla Formation. 3.2. Biostratigraphy 3.2.1. Calcareous nannofossil zones The standard calcareous nannofossil zonal scheme proposed by Sissingh (1977) combined with the subdivisions proposed by Perch-Nielsen (1979, 1981) for the Late Maastrichtian are applied at the present study. The zonal scheme (NP) of Martini (1971) for the Early Paleogene are applied. In addition, the classification of Varol (1989) abbreviated as (NTp) for the division of Zone NP4 is also applied. The taxonomic species concept of Perch-Nielsen (1985) for the Cretaceous and Paleocene species in addition to Aubry et al. (2011) are adopted in the present study. Based on the Lowest Occurrence (LO) of the calcareous nannofossil marker species, eight zones are represented in the Late Maastrichtian-Paleocene interval at the studied sections. These zones are; Lithraphidites quadratus, Micula murus and M. prinsii covered the Late Maastrichtian, while Chiasmolithus danicus (NP3); Ellipsolithus macellus (NP4); Fasciculithus tympaniformis (NP5); Heliolithus kleinpellii (NP6) and Discoaster mohleri–Heliolithus riedelii (NP7/8) zones represent the Paleocene. 3.2.1.1 Maastrichtian zones 5

Lithraphidites quadratus Zone It is designated by Cěpek and Hay (1969) to represent the stratigraphic interval between the LO of L. quadratus and the LO of Nephrolithus frequens. However, N. frequens is a typical higher latitude species (e.g. Perch-Nielsen 1985), so, it is not relevant to use it as a zonal marker at low latitude sites. Furthermore, the former species is very rare at the studied samples. Consequently, the L. quadratus Zone is adopted and defined as the interval from the LO of the nominate taxon to the LO of Micula murus. L. quadratus Zone is recorded at El-Qasr section encompasses the lower 3m thick of the Lower Kharga Shale Member (Fig 3). This zone is the only calcareous nannofossil Zone recorded at Abu Tartur section covering ~26m thick of the Lower Kharga Shale Member (Fig 4). Whereas the overlying succession lacks any calcareous nannofossil as well as planktonic foraminiferal species. Micula murus Zone It represents the stratigraphic interval from the LO of M. murus to the LO of Micula prinsii. This zone attains ~107m thick at El-Qasr section to cover the main part of the Lower Kharga Shale Member. This zone is marked by the occurrence of three distinct barren intervals at different stratigraphic levels. It is marked by existence of calcareous nannofossil species at two stratigraphic levels (level 1: samples no. 9-18), and (level 2: samples no. 27-30). These levels are marked by relatively high abundance of the calcareous nannofossil species and notable occurrence of M. decussata especially at level 2 (Fig 3). Micula prinsii Zone It is recorded at El-Qasr section and covers the stratigraphic interval from the LO of M. prinsii to the LO of the incoming Paleocene species. This zone attains ~2m thick and unconformably overlain by the early Danian Chiasmolithus danicus (NP3) Zone (Fig 3). This indicates presence of a hiatus across the K/Pg boundary at El-Qasr section. It covers the interval which represented by the missed nannofossil zones Markalius inversus (NP1) and Cruciplacolithus tenuis (NP2). Generally this interval is marked by a significant hiatus at all studied sections but with different magnitudes. The K/Pg boundary hiatus is represented by the missing of NP1, NP2 and Chiasmolithus danicus (NP3) zones at El-Aguz section. 3.2.1.2 Paleocene zones Chiasmolithus danicus (NP3) Zone 6

It represents the interval between the LO of C. danicus and the LO of E. macellus. It is only recorded at El-Qasr section and attains ~6.5m thick and assigned to Danian age that covers the lowermost part of the Upper Kharga Shale Member. It is conformably overlain by E. macellus (NP4) Zone (Fig 3). Ellipsolithus macellus (NP4) It covers the stratigraphic interval between the LO of E. macellus to the LO of F. tympaniformis and represented by ~12m thick of the lower part of the Upper Kharga Shale Member at El-Qasr section. The NP4 Zone is assigned to Danian-Selandian age. It is marked by low calcareous nannofossil diversity and considers the latest Paleocene zone that recorded at El-Qasr section, while the overlying 110m thick of the succession are found scarce in its nannofossil content. Towards the east at G. El-Aguz section it is represented by ~26m thick which covers the lower part of the Upper Kharga Shale Member (Fig 5), while at Darb Gaga section, this interval is marked by its barren of calcareous plankton contents (Fig 6). At G. El-Aguz, the NP4 Zone is subdivided into five subzones following the classification of Varol (1989); NTp7A, NTp7B, NTp8A, NTp8B and NTp8C. The boundaries between these subzones are defined by the LO of C. edentulus (NTp7A/NTp7B), LO of Sphenolithus primus (NTp7B/NTp8A), LO of Lithoptychius ulii and L. billii (NTp8A/ NTp8B) which approximately define the Danian/Selandian (D/S) boundary and LO of L. janii, L. pileatus, F. involutus define the (NTp8B/ NTp8C). The NP4 Zone is conformably overlain by Fasciculithus tympaniformis (NP5) Zone at ElAguz section (Fig 5). Fasciculithus tympaniformis (NP5) It covers the interval from the LO of F. tympaniformis to the LO of H. kleinpellii. It attains ~2m thick which occupies the uppermost part of the Upper Kharga Shale Member at G. El-Aguz section, whereas at Darb Gaga it comprises ~2.5m thick of the lowermost part of the Tarawan Formation. The NP5 Zone of the Selandian age is conformably overlain by H. kleinpellii (NP6) Zone at Darb Gaga section, while it is unconformably overlain by Discoaster mohleri - Heliolithus riedelii interval Zone (NP7/8) at El-Aguz section (Figs 5and 6). Heliolithus kleinpellii (NP6) It encompasses the stratigraphic interval from the LO of H. kleinpellii to the LO of Discoaster mohleri. It is only recorded at Darb Gaga section within the middel part of the Tarawan Formation attaining ~2m thick. It is conformably overlain by D. mohleri – H. riedelii (NP7/8) Zone at Darb 7

Gaga section, while it is not recorded at G. El-Aguz section due to the presence of a hiatus across the Selandian/Thanetian transition (Figs 5and 6). Discoaster mohleri - Heliolithus riedelii interval Zone (NP7/8) This zone defined as the stratigraphic interval from the LO of D. mohleri to the LO of D. multiradiatus. It is assigned to Early Thanetian age and covers the topmost part of the Tarawan Formation comprises ~23m thick at G. El-Aguz and ~9m thick at Darb Gaga section (Figs. 5 and 6). 3.2.2. Planktonic foraminiferal zones Ten planktonic foraminiferal zones are identified covering the Late Maastrichtian-Paleocene transition. The zonal schemes of Caron (1985); Li and Keller (1998) for the Maastrichtian age and Berggren and Pearson (2005) for the Paleocene age are applied here with minor modifications. These proposed zones are briefly discussed from base to top as follows: 3.2.2.1. Maastrichtian planktonic foraminiferal zones In the present study, incomplete planktonic foraminiferal zonal scheme is recorded due to the presence of many barren intervals within the Upper Maastrichtian interval. Gansserina gansseri Zone This zone is introduced by Brönnimann (1952). In the present study, Gansserina gansseri Zone is only recorded at El-Qasr section (Fig. 7). It is defined as a Lowest-Occurrence Zone (LOZ) covering the interval from the lowest occurrence (LO) of Gansserina gansseri (Bolli) to the LO of Abathomphalus mayaroensis (Bolli). It is coeval to the Lithraphidites quadratus and the lower part of the Micula murus nannofossil zones. The Gansserina gansseri Zone is represented by the lower part of the Lower Kharga Member of Late Maastrichtian age. It attains ~53m thick at El-Qasr section. This zone is overlain by a barren interval, so the topmost level of this zone is not certainly defined. Pseudoguembelina palpebra Zone This zone is defined by Li and Keller (1998). It is defined herein as a Partial-Range Zone (PRZ) to cover the interval from the highest occurrence (HO) of G. gansseri (Bolli) to the LO of Plummerita hantkeninoides (Brönnimann). It is comparable to Micula prinsii nannofossil zone. This zone covers the Lower Kharga Shale Member and is recorded at El-Qasr and G. El-Aguz (~2m thick for each) sections of Late Maastrichtian age (Fig. 7 and 8). This zone is the latest Maastrichtian zone that recorded at El-Qasr section due to the missing of the Plummerita hantkeninoides Zone. At G. ElAguz, this zone is overlain and underlain by barren intervals. 8

3.2.2.2. Paleocene planktonic foraminiferal zones During the Paleocene, almost complete planktonic foraminiferal zonal scheme is recorded at the eastern parts of the study area (G. El-Aguz and Darb Gaga sections). Otherwise at the western parts at El-Qasr and Abu Tartur sections, many barren intervals are recorded reflecting varying paleoenvironmental and/or tectonic setting from east to west direction. Praemurica inconstans Zone (P1c) This zone is introduced by Berggren et al. (1995) as Globanomalina compressa/Praemurica inconstans-Praemurica uncinata Subzone (P1c). At the present study, the Praemurica inconstans Zone is defined as a LOZ of the nominate taxon from its LO to the LO of Praemurica uncinata (Bolli). It is equivalent to the NP3 nannofossil zone. The P1c Zone covers the lowermost part of Upper Kharga Shale Member (6.5m thick). It represents the earliest Paleocene planktonic foraminiferal zone which is only recorded at El-Qasr section, indicating a hiatus at the K/Pg boundary due to missing of the latest Maastrichtian Plummerita hantkeninoides Zone and the Early Paleocene P0, Pα, P1a and P1b planktonic foraminiferal zones. The P1c Zone is conformably overlain by the Praemurica uncinata (P2) Zone (Fig. 7). On the other hand, this zone is not recorded at the other studied sections (G. El-Aguz and Darb Gaga) due to hiatus across the K/Pg boundary. At Abu Tartur section, the shallow facies of Garra El-Arbain Facies may led to disappearance of any planktonic foraminiferal taxa at present study. Praemurica uncinata Zone (P2) This zone is presented by Berggren and Pearson (2005). It is defined herein as LOZ from the LO of P. uncinata (Bolli) to the LO of Morozovella angulata (White). It is coeval to NP4 nannofossil zone of Early Danian age. The Praemurica uncinata Zone comprises the lower part of the Upper Kharga Shale Member and is recorded at El-Qasr (~14m thick) and G. El-Aguz (~2.25m thick) sections, while it is not recorded in Darb Gaga section due to presence of a barren interval. At G. El-Aguz, the Early Paleocene P0, Pα, P1a, P1b and P1c planktonic foraminiferal zones are missing indicating also a hiatus across the K/Pg boundary. The P2 Zone is conformably overlain by the Morozovella angulata (P3a) Zone at G. El-Aguz section (Fig. 8), while it is overlain by a barren interval in ElQasr section. Morozovella angulata Zone (P3a) It is originally defined by Hillebrandt (1965). In the present study, it is defined as a LOZ from the LO of M. angulata (White) to the LO of Igorina albeari (Cushman and Bermúdez). This zone is coeval to the lower part of the NP4 nannofossil zone and is represented by the Upper Kharga Shale 9

Member of Danian age. This zone is only defined at G. El-Aguz section (~4.5m thick) which is conformably overlain by the Igorina albeari/Praemurica carinata (P3b) Zone. It is not recorded in the other three sections due to presence of barren intervals. Igorina albeari/Praemurica carinata Zone (P3b) It is originally defined by Obaidalla et al., (2009). The Igorina albeari/Praemurica carinata Zone is defined as Concurrent-Range Zone (CRZ) form the LO of I. albeari (Cushman and Bermúdez) to the HO of P. carinata (El Naggar). At the present study, this zone is equivalent to the middle part of the NP4 nannofossil zone. It is only recoded at G. El-Aguz section and attains ~7.30m thick of the Upper Kharga Shale Member of the latest Danian age. This zone is conformably overlain by the Igorina albeari (P3c) Zone (Fig. 8). While, it is not recorded at the other three sections due to presence of barren intervals. Igorina albeari Zone (P3c) It is defined as the Lowest-occurrence Subzone by Berggren and Pearson (2005). In the present study, it is defined as PRZ from the HO of P. carinata (El Naggar) to the LO of Globanomalina pseudomenardii (Bolli). It is only recorded at G. El-Aguz section which represented by ~3m thick of the Upper Kharga Shale Member that assigned to Early Selandian age. It is comparable to the middle part of the NP4 nannofossil zone. It is conformably overlain by the Globanomalina pseudomenardii/Parasubbotina variospira (P4a) Zone. Globanomalina pseudomenardii/Parasubbotina variospira Zone (P4a) This zone is defined as Concurrent-range Subzone by Berggren and Pearson (2005). In the present study, this zone is defined as a CRZ to cover the interval from the LO of G. pseudomenardii (Bolli) to the HO of P. variospira (Belford). The P4a Zone of Selandian age is equivalent to the upper part of the NP4, NP5 and the lower part of NP6 nannofossil zones. It is recorded at both G. El-Aguz and Darb Gaga sections (Figs. 8 and 9). At G. El-Aguz, this zone is represented by the uppermost part of the Upper Kharga Shale Member (~10.5m thick) and is unconformably overlain by Acarinina soldadoensis/Globanomalina pseudomenardii (P4c) Zone. While at Darb Gaga, this zone is represented by the lowermost part of Tarawan Formation (~3.25m thick) and is conformably overlain by the Acarinina subsphaerica (P4b) Zone. Acarinina subsphaerica Zone (P4b) This zone is defined as Partial-range Subzone Berggren et al (2000). In the present study, It is defined as PRZ from the HO of P. variospira (Belford) to the LO of Acarinina soldadoensis (Brönnimann). This zone is represented by the main part of the Tarawan Formation (~8.70m thick) 10

at both El-Qasr and Darb Gaga sections of Selandian-Thanetian age (Fig. 7 and 9). This zone is coeval to the upper part of the NP6 and lower part of NP7/8 nannofossil zones. At Darb Gaga section, the P4b Zone is conformably overlain by the Acarinina soldadoensis/Globanomalina pseudomenardii (P4c) Zone. At El-Qasr section, this zone represents the topmost part of the measured section. At G. El-Aguz section, this zone is absent due to the presence of a hiatus between Dakhla and Tarawan Formation. Acarinina soldadoensis/Globanomalina pseudomenardii Zone (P4c) This zone is defined as Concurrent-range Subzone by Berggren et al (1995). In the present study, it is defined as CRZ covering the interval from the LO of A. soldadoensis (Brönnimann) to the HO of the G. pseudomenardii (Bolli). It is equivalent to the NP7/8 nannofossil zone. The P4c Zone of the Thanetian age is represented the by topmost part of the Tarawan Formation at both G. El-Aguz (~23m thick) and Darb Gaga (~1.25m thick) sections (Figs. 8 and 9). 3.3. Benthonic foraminiferal biofacies Benthonic faunal assemblages and individual species have been used as indicator to the depositional settings and then relative sea level oscillations (e.g.; Berggren, 1974a, b; Berggren and Aubert, 1975; Luger, 1985 and 1988b; Hewaidy, 1997; Schnack, 2000; El Dawy, 2001; Speijer, 2003; Sprong et al., 2012; El-Dawy et al., 2016, 2018; Hewaidy et al., 2019b). The recorded benthonic foraminiferal species are subjected to R-mode (species) hierarchical cluster analysis to determine the depositional settings of the studied sections. Consequently, four benthonic foraminiferal biofacies; A, B, C and D are recognized (Fig. 10). The depositional setting of each benthonic foraminiferal biofacies is determined using the paleobathymetric setting of the most common benthonic foraminiferal species (Table 1). The identified biofacies indicate four major depositional settings. These biofacies are briefly described as follows; Biofacies A is represented by Haplophragmoides spp., Trochammina spp., Ammobaculites spp., Earlandammina bullata and Unitendina oblonga. The most dominant taxon in this biofacies is Haplophragmoides spp. which represent ~40% of the assemblage. Haplophragmoides spp. often occurs in organic rich mud under dysoxic conditions (Stassen et al., 2012). This assemblage is composed completely of arenaceous agglutinated foraminiferal species with low diversity. The biofacies A indicates deep littoral environment grading to very shallow inner neritic environment. This high percentage of agglutinated foraminifera may indicate shallower conditions with freshwater supply (Hewaidy, 1997). Biofacies B is marked by the dominance of the infaunal taxa including Pyramidulina spp., Orthokarstenia spp., Siphogeneroides eleganta, Eouvigerina spp., Marginulina spp., along with 11

Cibicidoides, pharaonics, Anomalinoides umbonifera, Anomalinoides susanaensis and Bathysiphon eoceincus. The dominance of the infaunal taxa reflect deposition under eutrophic and dysoxic environments (Jorissen et al., 1995). The percentage of inner-middle neritic taxa comprises ~45% such as Orthokarstenia spp., Eouvigerina spp., Cibicidoides, pharaonics, Anomalinoides umbonifera. While, the middle-outer neritic taxa represents ~55% including: Pyramidulina spp., Orthokarstenia spp., Siphogeneroides eleganta, Marginulina spp. and Bathysiphon eoceincus. Thus, the biofacies B indicates middle neritic environment. Biofacies C is characterized by the occurrence of Cibicidoides libycus, Gyroidinoides spp., Bulimina spp., Gaudryina spp., Cibicidoides proprius, Anomalinoides aegyptiaca, Anomalinoides praeacutus, Cibicidoides succedens, Spiroplectinella knebeli, Loxostomoides applinae, Cibicidoides decorates, Vaginulina spp. and Preabulimina spp. This assemblage consists mainly of epifauanl taxa which are distributed in oligotrophic and well‑oxygenated conditions (Jorissen et al., 1995). The dominance of this assemblage (~54%) reflects middle-outer neritic environment (e.g.; Anomalinoides aegyptiaca, Gyroidinoides spp., Bulimina spp., Anomalinoides praeacutus, Cibicidoides succedens, Loxostomoides applinae, Vaginulina spp.) and (~38%) of outer neriticupper bathyal environment (e.g. Cibicidoides libycus, Gaudryina spp., Spiroplectinella knebeli, Preabulimina spp.), while the reminder taxa (~8%) is of an inner neritic environment. So, the biofacies C suggests middle-outer neritic environment. Biofacies D is represented by Lenticulina spp., Anomalinoides grandis, Cibicidoides alleni, Anomalinoides midwayensis, Cibicidoides pseudoacutus, Anomalinoides zitteli,

Anomalinoides

acutus, Lagena spp., Cibicides farafraensis, Laevidentalina spp., Epiniodes lunatus, Osangularia expansa and Pseudoclavulina farafraensis. The taxa indicating middle-outer neritic environment represents ~47% (such as; Cibicidoides pseudoacutus, Anomalinoides zitteli, Pseudoclavulina farafraensis, Lenticulina spp.), and taxa of the outer neritic-upper bathyal environment is represented by ~28%. (Cibicidoides alleni, Lagena spp., Cibicides farafraensis, Osangularia expansa), while the inner-outer neritic environmental taxa constitutes ~25 (e.g. Anomalinoides grandis, Anomalinoides midwayensis, Laevidentalina spp.). Therefore, the biofacies D indicates an outer neritic environment. 4. Discussion 4.1. Paleoenvironmental interpretation The paleoenvironmental conditions that prevailed during deposition of the Upper MaastrichtianPaleocene sequences are inferred from the integration of field observation criteria, lithologic facies changes and the abundance patterns of the sensitive calcareous nannofossil environmental 12

indicators (Figs. 11-13) along with the calcareous benthonic and agglutinated foraminifera (Figs. 4, 9, 14-15). The palaeoecological preferences for the main calcareous nannofossil species that used in the present study with its supporting published references are given in Table 2. Based on the integration of the obtained data, two distinct intervals are recognized; Maastrichtian and Paleocene. The Maastrichtian paleoenvironmental history Generally, the Upper Maastrichtian sediments in the present study are represented by the lower part of the Dakhla Formation (Lower Kharga Shale Member) which mainly constitutes of thick successions of black to dark grey shale intercalated with silty marl beds which may reflects input of terrestrial fine grained sediments under very low oxygen conditions with rich contents of high organic matter. This interpretation is supported by the occurrence of sensitive paleoenvironmental faunal and floral indices. Regarding to the calcareous nannofossil, the Upper Maastrichtian sediments at El-Qasr section are deposited under normal marine conditions. This indicates by the relatively high species richness which ranging between ~20 and 30 species/sample (Fig. 11). In contrast, the Upper Maastrichtian interval at the rest of the studied sections is marked by scarcity of the calcareous plankton community. This reflects that this interval at these localities is marked by an extreme sea-level regression. The Late Maastrichtian nannofossil assemblage at El-Qasr section is dominated by the occurrence of Micula decussata (Fig. 11). Three remarkable peaks of M. decussata are recorded at El-Qasr section during the Late Maastrichtian, two of them including a prominent one (~60% of the total assemblages) are recorded within the M. murus Zone and the third (~35%) at the topmost part of M. prinsii Zone. During the peaks intervals of M. decussata, an overall sharp decrease of the nannofossil species diversity as well as planktonic foraminifera is observed (Figs. 7 and 11). This drop in species diversity is could be attributed to a periods of an extreme shallowing marine conditions not to enhancement of the diagenetic process. The massive occurrence of M. decussata is used by several authors as an indicator of badly preserved assemblage (Table 2) which is not match with our results since it occurs among well-preserved assemblage. Furthermore, if the massive occurrence of M. decussata reflects a diagenetic processes, the dissolution-susceptible species Biscutum constans and Cribrosphaerella ehrenbergii (Eshet and Almogi Labin, 1996) would be completely eliminated during these intervals which is not the case in the present study. Thus, the thriving of M. decussata indicates a paleoecological print rather than preservation index. Regarding the paleoecological conditions that prevailed during the deposition of peaks intervals of M. decussata, it marked by stressful conditions that could be represented by warm and oligotrophic 13

conditions. This interpretation is based on the criteria that introduced by Moshkovitz and Eshet (1989); Eshet et al. (1992); Tantawy (2003); Thibault and Gardin (2006). The warm climatic conditions during these intervals are expressed by the decreased abundance of the cool-water species (A. cymbiformis Ah. Octoradiata, N. frequens and K. magnificus) in associated with the sharp increase of M. decussata (Fig. 11). On the hand, increased oligotrophication during the intervals of M. decussata bloom is indicated by the dominance of the low-productivity indicators Eiffelithus spp. (mainly E. turriseiffelii) (up to ~15%), Prediscosphaera cretacea (up to ~18%) and Lithraphidites spp. (up to ~10%). In contrast, the high productivity markers including B. constans and T. saxea are occurred in an extremely low abundance which not exceeded than ~5% (Fig. 11). The results of the foraminiferal indices during the Late Maastrichtian interval are strongly supported the calcareous nannofossil interpretations. The Lower Kharga Shale Member at El-Qasr section is moderately rich with calcareous foraminiferal species which indicate normal open marine setting. It is characterized by moderately P/B% (~30-53 %), A/C (4-8%, except for sample no.9), benthonic species richness (up to 18 species). Also, the main benthonic foraminiferal assemblages are represented by biofacies B (~73%) except for sample no. 9 which constitutes of ~93% of biofacies A (Fig. 14). All these data, indicate that the Lower Kharga Shale Member at El-Qasr section was deposited in a middle neritic environmental setting. The thick succession of the Lower Kharga Shale Member that corresponds to Micula murus nannofossil zone and its equivalent Gansserina gansseri planktonic foraminiferal zone is characterized by partially barren interval of the calcareous planktonic foraminifera. This suggests deposition under very shallow conditions and/or restricted environmental marine conditions such as lagoon setting. On the other hand, the characteristics of the uppermost part of the Lower Kharga Shale Member (Micula prinsii, Pseudoguembelina palpepra nannofossil and planktonic foraminiferal zones) reflects return to normal marine conditions. It is marked by P/B ~15%, A/C ~4%, very rich benthonic foraminiferal assemblage biofacies B (~88%, such as; Eouvigerina aegyptaca, Orthokarstenia esnehensis and Anomalinoides umbonifera) which indicate a depositional of middle neritic environmental conditions. Toward the east at Abu Tartur, Darb Gaga and El-Aguz, the Upper Maastrichtian sequence is barren of calcareous foraminiferal species (planktonic and benthic) (Figs. 4, 9 and 15). This part constitutes of intercalated consecutive barren intervals and intervals completely rich with areaneous agglutinated foraminiferal species (A/C 100%) such as Haplophragmoides spp., Trochammina spp., Ammobaculites spp., Earlandammina bullata and Unitendina oblonga (biofacies A). The occurrence of these species might reflect a stressful environmental conditions most probably anoxia. The presence of certain taxa in high abundance such as Haplophragmoides spp. could 14

reflect intense dissolution in an anoxic environmental conditions (e.g. Alegret et al. 2005; Ernst et al. 2006) probably accompanied with change in food supply (e.g. Koutsoukos et al. 199; Gooday 2003). These conditions seem to be responsible for the termination of the calcareous plankton community due to the presence of restricted and/or isolated marine environments that characterize this part of the Western Desert of Egypt. Based on its biofacies content, these interval probably deposited under deep littoral-inner neritic environmental setting (Figs. 4, 9 and 15). At El-Aguz section, the Upper Maastrichtian interval marked by presence of distinct levels (sample no. 20 and 26-27) that characterized by flux of normal marine conditions. These levels marked by relatively high P/B ratio (~70%) and biofacies B of about 50%, biofacies C and D ~50% for each (Fig. 15) which indicate middle-outer neritic environmental conditions. Generally, at all the studied sections, the upper part of the Maastrichtian Dakhla Formation is composed of black shales with agglutinated foraminifera may be deposited in laggonal conditions except thin band of marl including deeper fauna and indicate oscillation in the sea-level. The Paleocene paleoenvironmental history The Paleocene sediments at the present study are marked by changing of the sediments regime from black shale (Lower Kharga Shale Member) which could reflect anoxic, stressful environmental conditions to grey shale and calcareous shale intercalated with limestone bands (Upper Kharga Shale Member). This may generally indicates return to normal marine setting. This reflects by the relatively high abundance and diversity of calcareous plankton assemblages. However, there is an obvious variation at the depositional setting along the studied sections from shallow marine westward to relatively deeper conditions eastward. According to the calcareous plankton assemblages, the Danian sediments at El-Qasr section is subdivided into two distinct intervals: The first one corresponds to the NP3 and lower part of NP4 nannofossil zones and it’s equivalent planktonic foraminiferal zones P1c and the lower part of P2 zones. The nannofossil assemblage composition of this interval reflects normal, relatively warm and mesotrophic marine conditions (Fig. 11). It is indicated by relatively high abundance of the warm-water species Coccolithus subpertusus (up to ~20%) and C. pelagicus (up to ~10%) in associated with relatively moderate values of the cool-water taxa Chiasmolithus spp. (up to ~15%) and Placozygus sigmoides (~10%). The mestrophic, normal marine conditions during this interval is indicated by the high abundance of Neochiastozygus spp. (up to ~20%) and Cruciplacolithus spp. (up to ~25%). This interpretation is based on the suggestion of Gibbs et al. (2006) and Self-Trail et al. (2012) for the paleoecological affinity of Neochiastozygus spp. and Gardin (2002) for Cruciplacolithus spp. Regarding the 15

foraminiferal analyses, these conditions are supported by increasing of the foraminiferal abundance (up to ~933 individual), high P/B% (~62-90), high benthonic species richness (~33 species), as well as low A/C% (~3-18). At the same time, the benthonic foraminiferal assemblages are represented by biofacies B (~30%), C (~20%) and D (~50%). All these data indicate middle-outer neritic environmental setting. The second Paleocene interval is corresponding to the uppermost part of the NP4 and P2 nannofossil and foraminiferal zones, it is distinguished by gradual declining of the species diversity (~10-12 species/sample) to disappear completely at the topmost part of NP4 Zone. Also, a sharp decline of the total foraminiferal number from ~933 to 412 is observed at the same level. This level is characterized by prominent increase of the pentalith Braarudosphaera bigelowii which reaches ~65% of the total calcareous nannofossil assemblage (Fig. 11). The prominent increase of B. bigelowii during this interval probably indicates a period of reduced salinity and increased freshwater influx. This is based on the suggestion of Bukry (1974), Wade and Bown (2006), Bartol et al. (2008) for the paleoecological interpretation for the enrichments of B. biglowii. At Abu Tartur section, the Paleocene sediments of Kurkur Formation (Garra-El Arbain facies) is marked by deposition under very shallow marine conditions. These conditions are inferred from the presence of the bivalve shells that characterized the massive limestone of Kurkur Formation as well as its barren contents of the calcareous plankton assemblages. Toward the east at El-Aguz section, there is a notable trend toward more open and normal marine conditions during the Paleocene. This enhancement is indicated by the relatively high abundance of the calcareous nannofossil species. The paleoenvironmental conditions that prevailed during the deposition of the Upper Kharga Shale Member at El-Aguz section reflect deposition in proper marine environments with relatively cool, mesotrophic to eutrophic conditions. This trend is reflected by the relatively high calcareous nannofossil species diversity (up to ~25 species/sample) and the dominance occurrence of the cool-surface water indicators Chiasmolithus spp. (up to ~15%), Placozigus sigmoides (up to ~15%), small Prinsius (up to ~25%) along with Neochiastozygus spp. (up to ~20%), and Cruciplacolithus spp. (up to ~15%) (Fig. 12). Also, the foraminiferal indices at the same interval exhibit high P/B (~75-85%), low A/C (~8%), dominance of biofacies D (~46%), biofacies C (~41%) beside the fairly representative of biofacies B (~13%) (Figs. 9, 12, 13 and 15). These data indicate an outer neritic environmental conditions. In contrast, at Darb Gaga section, only Tarawan formation is characterized by its faunal and floral contents, while the Upper Kharga Shale Member is entirely barren of the calcareous plankton which may indicates deposition in very shallow marine environments. 16

During the Late Paleocene Tarawan Formation, the nannofossil assemblage reflects warm and oligotrophic marine conditions at Darb Gaga and El-Aguz sections. It is marked by diversity assemblage (up to ~20 species/sample) and dominance occurrence of the warm oligotrophic indicators Coccolithus subpertusus, C. pelagicus (up to ~20% for each), Fasciculithus spp. (up to ~25%), Sphenolithus primus (up to ~30%) and Discoaster spp. (up to ~10%) (Fig. 12 and13). While the rest of the assemblage contains relatively low abundance of the cool and eutrophic taxa Chiasmolithus spp., Placozigus sigmoides, small Prinsius and Toweius eminens. Also, the Tarawan Formation is characterized by high P/B (~60-85%), low A/C (~3-5%). The dominance biofacies that comprises the Tarawan Formation at El-Qasr and Darb Gaga (biofacies D ~70-100%) reflects deeper setting (outer neritic) than its equivalent at the El-Aguz (biofacies D ~50%) which indicates middle-outer neritic setting. 4.2. Syn-sedimentary tectonic events The history of the Egyptian sedimentary basins during the Late Cretaceous-Early Paleogene is marked by major tectonic activities combined with sea-level change that controlled the deposition at these basins. The most acceptable and affective tectonic event is the Syrian Arc fold system (e.g. Obaidalla et al. 2006; Mahfouz 2013, El-Ayyat and Obaidalla 2013, 2016; Obaidalla et al., 2017, 2018, Metwally and Mahfouz 2018; Faris et al., 2018). This tectonic orogeny affected large parts of the southern Egyptian sedimentary basins. The rejuvenation of this orogeny could cause partial isolation of the shallow semi-restricted embayment of the Middle Campanian transgression from the Tethys (El-Hawat, 1997). The findings of the present study suggest that the effect of the Syrian Arc orogeny in forming isolated marine environments is not only restricted to the Maastrichtian but it is continued throughout the Lower Paleogene at the studied area. The successions under investigation are represented by marine sediments that deposited under variable environmental conditions. These successions are marked by variable thickness especially of the Dakhla Formation (e.g. the thickness the Upper Kharga Shale Member range from 123m thick at El-Qasr section to ~7m thick at Darb Gaga section, Fig. 16). Also, these successions have a vertical distinctive change of the style of the sedimentary regimes. Furthermore, regional and local unconformity surfaces are recoded within the rock units as well as at the formational boundaries. These unconformity surfaces are supported by field observations which associated with completely and/or partially missing of specific calcareous plankton zones. Also, the barren intervals which are recoded at different levels reflecting stressful environmental conditions interrupt the normal marine environmental conditions. All these evidences could reflect tectonic activity coupled with sea-level oscillation affected this part of the Dakhla basin during the Late Cretaceous/Paleogene time interval. These tectonic events might be responsible for formation of several paleo-structural highs 17

and lows. These activities could be linked to the Syrian Arc System. This orogeny affected the study area though two syn-sedimentary tectonic events (Tectonic Event I and II) during the Maastrichtian-Paleocene time interval (Fig. 16). Tectonic Event I: This event is corresponding to the K/Pg boundary which is considered as a regional tectonic event in Egypt. Tectonic event I is evidenced by distinctive change of style of the sedimentary regime from black shale intercalated with silty marl beds of the Lower Kharga Shale Member to light grey shale and calcareous shale intercalated with marl and limestone beds of the Upper Kharga Shale Member. Also, this event is documented by the occurrence of a conglomeratic bed (Abu Minqar Horizon) at El-Qasr, G. El-Aguz and Darb Gaga sections. The partial and/or complete missing of the Late Maastrichtian and Early Danian calcareous plankton foraminiferal and nannofossil zones supported also this tectonic event. At El-Qasr section, the K/Pg boundary is marked by notable hiatus expressed by partially missing of the topmost part of the latest Maastrichtian M. prinsii Zone as well as the absence of the earliest Danian zones Markalius inversus (NP1) and Cruciplacolithus tenuis (NP2) and its equivalent planktonic foraminiferal Plummerita hantkeninoides (CF1) zone of the Late Maastrichtian age and missing of Guembeltria cretacea (P0), Parvularugoglobigerina eugubina (Pα), Parasubbotina pseudobulloides (P1a), Subbotina triloculinoides (P1b) zones of Early Danian age. At El-Aguz section, the Late Maastrichtian barren interval is overlain by Praemurica uncinata (P2) Zone of Danian age due to missing of the Early Danian P0, Pα, P1a, P1b, Praemurica inconstans (P1c) zones. At Darb Gaga section, the detection of this event is lithologically based on the presences of the conglomeratic bed of Abu Minqar Horizon which separated the Lower Kharga Shale and the Upper Kharga Shale members. While at Abu Tartur section this hiatus is recorded at the base of Kurkur Formation, This hiatus is documented by Cherif and Hewaidy (1987). This event is most probably caused by the double effect of the tectonic activity and sea-level change. The extensive hiatus that characterize the K/Pg boundary in the Western Desert is largely attributed to the uplift of the Bahariya arch (Said, 1961; Abdel-Kireem and Samir, 1995; Ibrahim and Abdel Kireem, 1997; Tantawy et al., 2001) which could be considered as an echo of the Syrian Arc System (Almogi-Labin et al., 1990). Tectonic Event II: This event restricts to the eastern part of the study area at Darb Gaga and El-Aguz section. At Darb Gaga section, Tectonic event II is evidenced by the distinctive lithologic change from grey shale of the Upper Kharga Shale Member to white to yellowish limestone and chalky limestone of the Tarawan Formation. Furthermore, this event is documented by the occurrence of a glauconitic rich 18

sediments, pebbles and erosive surface at the base of the Tarawan Formation. This observation is supported by the totally absence of the Danian calcareous plankton zones as well as the missing of Early Selandian Igorina albeari (P3c) planktonic foraminiferal zone. This event initializes at the Danian/Selandian (D/S) boundary, with maximum magnitude toward south at Darb Gaga section and limited magnitude toward the north at El-Aguz sections. At G. El-Aguz section, this event is characterized by presence a minor sediments breakup through the (D-S) transition expressed by the absence of the Latest Danian Event (LDE) beds. Whereas the successive calcareous nannofossil bio-events that characterize and defined the D/S boundary at the base of the NTp8B Subzone (e.g. Aubry et al., 2012; Monechi et al., 2013; Metwally, 2019) as well as a complete planktonic foraminiferal zones are recorded. This tectonic event is recognized at several localities all over the Egyptian provinces (.g. Mahfouz 2013, El-Ayyat and Obaidalla 2013, 2016; Faris et al., 2018) which reflects the regional nature of this tectonic. Thereafter, the echo of the Tectonic event II is rejuvenated throughout the Selandian-Thanetian (ST) transition at G. El-Aguz section. It is marked by notable hiatus at the Dakhla/Tarawan formational boundary which marked by bioturbated and irregular surface at the base of Tarawan Formation. Also, It is documented by the partially missing of the upper part of Fasciculithus tympaniformis (NP5) and the absence of Heliolithus kleinpellii (NP6) calcareous nannofossil zones and missing of its equivalent Acarinina subsphaerica (P4b) planktonic foraminiferal zone. The hiatus around the (S-T) transition is well- notarized at several localities at Egypt (e.g. Strougo 1986; Kassab and Keheila 1994; Obaidalla et al., 2006: El-Ayyat and Obaidalla 2013, 2016; Faris et al., 2018). This indicates that this event is intensively affected the Egyptian sedimentary basins during this time interval and represent a regional unconformity recorded in the Western Desert of Egypt. At the same time, at Darb Gaga section, the deposition during this time interval seems to be more stable indicated by the complete occurrence of the S-T calcareous plankton zones. 4.3. Sedimentary basin evolution The study area is a part of the southern Tethys margin during the Upper Cretaceous-Lower Paleogene transition. So, the present study attempts to understand the mechanism in which the sedimentary basin is evolved. As mention above, the Upper Cretaceous-Lower Paleogene transition is subject to two syn-sedimentary tectonic events. These events are variable in its magnitude and effectively participated in the sedimentary basin evolution. Five phases are proposed to understand the sedimentary basin evolution. The interpretation of each phase is based on the integration data of the field observations, litho-, bio-startigraphic data, and quantitative analyses of the calcareous plankton as well as benthonic foraminiferal biofacies which is discussed earlier in details. 19

1- Maastrichtian phase a- During the Maastrichtian, the basin is received input of the terrestrial materials (mostly of black shale) rich with organic matter under very low oxygen conditions as indicated by its floral and faunal contents. b- Intensive detrital input characterizes the westward direction at El-Qasr section where a thick succession of the Upper Cretaceous is accumulated (~112m). This is most probably due to the uplift of the Gilf El Kebir Spur at the southwest of Dakhla which is suggested to be a possible source of the clastic material during Maastrichtian and continued to the Paleocene. Toward the east at Abu Tartur, El-Aguz and Darb Gaga, its thickness reduced to reach ~ 68m, 26m and 30m respectively (Fig. 17A). c- Except for El-Qasr section, these successions are almost barren of the calcareous plankton and rich with agglutinated foraminifera at distinct levels. At El-Qasr, the lower part as well as the uppermost part of the Dakhla Formation are deposited under middle neritic environment setting. Therefore, this phase reflects deposition under very shallow water depth (deep littoral– shallow inner neritic) at Abu Tartur, El-Aguz and Darb Gaga sections, while middle neritic depositional setting characterizes the deposition at El-Qasr section. 2- Cretaceous/Paleogene (K/Pg) phase a- A major uplift tectonic event which corresponding to Tectonic event I led to expose the Upper Cretaceous basin and continued to reach the Lower Paleogene sediments. b- This phase is marked by the presence of significant continental clastic sediments (conglomeratic bed of Abu Minqar Horizon) at El-Qasr, El-Aguz and Darb Gaga sections except for Abu Tartur area which may be interpreted as inter-fingering sub-basin during this time. This phase is documented by the absence of the Late Maastrichtian and Early Danian calcareous planktonic zones. Therefore, the sedimentary basin during the K/Pg boundary is marked by an areal paleohigh setting due to the double effect of Tectonic event I and sea-level regression which led to removal of the latest Maastrichtian and earliest Danian sediments (Fig. 17B). 3- Early Danian phase a- The sedimentary basin during this time interval is subsidence and received fine grains sediments of normal marine setting. b- The water paleodepth of the sedimentary basin during this phase is varied from middle-outer neritic at El-Qasr section to outer neritic at El-Aguz section. While it seems to be deep littoral– shallow marine inner neritic setting at Abu Tartur and Darb Gaga section. Consequently, the Early 20

Danian sedimentary basin (Fig. 17C) could be divided into two sub-basins at El-Qasr and El-Aguz sections (deep sedimentary facies of the Nile Valley Facies) separated by two sub-marine paleohighs at the Abu Tartur and Darb Gaga sections (shallow sedimentary facies of the Garra ElArbain Facies). The depositional setting of Abu Tartur section (Garra El-Arbain Facies) doesn't changed markedly during the Early Paleocene (submarine paleohigh) which characterized by deep littoral–shallow inner neritic environmental conditions. 4- Danian/Selandian (D/S) phase a- The shape of the sedimentary basin throughout this phase still as the same of the previous one (two sub-basins). At Darb Gaga section, the sedimentary basin is uplifted due to the effect of the Tectonic event II (Fig. 17D) which is documented by the occurrence of pebbles and irregular surface at the base of the Tarawan Formation, while this event is limited at El-Aguz section. b- During this phase, the west part of the basin is still received high detrital input of the terrestrial materials at El-Qasr section (Fig. 17E). This is documented by the massive accumulation of thick succession of the Dakhla Formation (upper part) represented by ~123m. While it is reduced in thickness toward the east to attain ~27m at El-Aguz and ~7m at Darb Gaga sections. So, the water paleodeth for the upper part of the Dakhla Formation (Lower Khrga Shale Member) is varied from middle-outer neritic at El-Qasr section to deep littoral–shallow inner neritic at the eastern part of the basin at Darb Gaga section. Hence, the D/S sedimentary basin represents an areal paleohigh due to the effect of the Tectonic event II which is intensively effected the eastward part at Darb Gaga section while it is limited at El-Aguz section which may be the depocenter of this sub-basin. This is also supported by the complete occurrence of the calcareous planktonic zones during this time interval. 5- Selandian/Thanetian (S/T) phase a- The S/T phase is marked by uplift of the sedimentary basin as a result of the effect of the echo of the Tectonic event II at G. El-Aguz section which led to form sub-marine paleohigh (Fig. 17F). This event is documented by the presence of irregular surface and biotrubation at the base of the Tarawan Formation. In contrast at Darb Gaga area, the basin seems to be more stable during this phase where a complete S/T calcareous plankton zones are recorded. The relatively stable nature of this part of the Dakhla basin is documented previously during the Late Paleocene/Early Eocene by Metwally and Mahfouz (2018). Thus, this part of the sedimentary basin could represent the more stable area during the Paleocene and continued to the Eocene.

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b- The water paleodepth of the sedimentary basin during this phase reflects deposition in an outer neritic at Darb Gaga section to middle-outer neritic at El-Aguz section. c- Moving westward at El-Qasr section, the sedimentary basin is subject to subsidence event (Fig. 17G) where the depositional setting changed from deep littoral–shallow inner neritic that characterize the Upper Kharga Shale Member to an outer neritic setting of the Tarawan Formation. 5. Conclusions Details field, litho-, bio-stratigraphic and paleoenvironmental studies are carried out for the Upper Cretaceous-Lower Paleogene successions at El-Qasr, Abu Tartur, Gabal El-Aguz and Darb Gaga sections, Kharga-Dakhla stretch, Western Desert, Egypt. Three rock units are recognized; Dakhla, Tarawan and Kurkur formations. The biostratigraphic analyses led to recognize eight calcareous nannofossil and ten planktonic foraminiferal zones. The integration of these data allow specific determination of the age dating for the Upper Cretaceous Lower Paleogene successions. The Rmode (species) hierarchical cluster analysis of the benthonic foraminiferal species led to determine four biofacies; A, B, C and D. The benthonic foraminiferal assemblages that corresponding to these biofacies with similar distribution patterns reflecting proper paleodepth for each biofacies. These biofacies along with the relative abundance of the calcareous nannofossil species are used to interpret the paleoenvironmental conditions that prevailed during the studied time interval. Based on the obtained data, the Maastrichtian-Paleocene successions at the studied area are subdivided into two intervals; Maastrichtian and Paleocene. The Maastrichtian interval at all studied sections that belonging to the Lower Kharga Shale Member deposited under stressful environment probably anoxia. This is indicated by the absence of calcareous plankton community and the dominance of the areaneous agglutinated foraminiferal species Haplophragmoides spp., Trochammina spp., Ammobaculites spp., Earlandammina bullata and Unitendina oblonga. While at El-Qasr section, the lower and the uppermost part of the Maastrichtian Lower Kharga Member deposited in middle neritic depositional setting under normal marine conditions. This is indicated by the presence of proper calcareous plankton marine community. The Paleocene interval that belonging to the Upper Kharga Shale Member reflects return to normal marine conditions eastward at El-Aguz section which deposited in middle to outer neritic environment. This is indicated by the relatively high abundance and diversity of the calcareous plankton assemblages across this interval. At El-Qasr and Darb Gaga (Upper Kharga Shale Member) and Abu Tartur (Kurkur Formation) sections, more stressful conditions affected this part of the Paleocene sediments which reflected deposition under deep littoral-inner neritic environment. On the other hand, the characteristic of the lower Danian sediments at El-Qasr section indicate 22

proper marine environment. The overall identified calcareous planktonic assemblages of the Late Paleocene Tarawan Formation probably indicate deposition in middle to an outer neritic setting, warm and oligotrophic environmental conditions. Several field observations, lithological and paleontological criteria which recorded during the Maastrichtian-Paleocene transition indicating a notable hiatuses as a consequences of two synsedimentary tectonic events (Tectonic Event I and II). The integration of the obtained data show a well view about the evolution of the Upper Cretaceous-Lower Paleogene sedimentary basin in the study area as a part of the southern Tethys margin. Due to the intensive input of the terrestrial materials enriched with organic matter, thick successions of black shale (Lower part of the Dakhla Formation) are deposited under very low oxygen conditions during the Late Maastrichtian transition indicating deep littoral setting interrupted with normal marine setting at some level especially at ElQasr section. Then the sedimentary basin during the K/Pg boundary is subject to uplift tectonic event (Tectonic event I) which led to form an areal paleohigh due to the double effect of the Tectonic event I and sea level regression. After this, the Early Danian sedimentary basin is subsidence and divided into two sub-basins. Eastward, the D/S sedimentary basin represents an areal paleohigh due to the intensively effect of the Tectonic event II at Darb Gaga section while it is limited at El-Aguz section which may be the depocenter of this sub-basin. At the same time, G. ElAguz section is subjected to uplift as an echo of the Tectonic event II which led to form submarine paleohigh while, the Darb Gaga area is more stable during this phase. Acknowledgments The authors deeply appreciate Prof. Mohamed G Abdelsalam (Editor-in-Chief) for editorial support. we are grateful to two anonymous reviewers, for their critical and useful comments during revision. References Abdelhady, A., Seuss, B., El-Dawy, M., Obaidalla, N., Mahfouz, K., Abdel Wahed, S., 2018. The Unitary Association method in biochronology and its potential stratigraphic resolving power: A case study from Paleocene-Eocene strata of southern Egypt. Geobios, 51, (4), 259-268. doi: 10.1016/j.geobios.2018.06.005. Abdel-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 Micropaleontology, 26, 329–340. Alegret, L., Ortiz, S., Arenillas, I., Molina, E., 2005. Palaeoenvironmental turnover across the Palaeocene/Eocene boundary at the Stratotype section in Dababiya (Egypt) based on benthic foraminifera. Terra Nova, 17, 526–536. Almogi-Labin, A., Flexer, A., Honigstein, A., Rosenfeld, A. and Rosenthal, E., 1990. Biostratigraphy and tectonically controlled sedimentation of the Maastrichtian in Israel and adjacent countries. Revista Española de Paleontología, 5, 41–52. 23

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Wei, W., Wise Jr., S.W., 1990. Biogeographic gradients of middle Eocene-Oligocene calcareous nannoplankton in the South Atlantic Ocean. Palaeogeography, Palaeoclimatology, Palaeoecology, 79, 29–61. Williams, J.R., Bralower, T.J., 1995. Nannofossil assemblages, fine-fraction stable isotopes, and the paleoceanography of the Valanginian–Barremian (Early Cretaceous) North Sea Basin. Paleoceanography, 10, 815–839. Wind, F.H., 1979. Maestrichtian-Campanian nannofloral provinces of the southern Atlantic and Indian Oceans. In: Talwani, M., Hay, W., Ryan, W.B.F. (Eds.), Deep Drilling Results in the Atlantic Ocean: Continental Margins and Paleoenvironment. American Geophysical Union, Washington, pp. 123–137. Table's captions Table 1: Summary of paleobathymetrical references of the most common benthonic foraminiferal species used in the present study. 1-El-Dawy and Hewaidy, 2003; 2-Speijer, 1994; 3-Hewaidy, 1997; 4-Speijer and Schmitz; 1998; 5-Sprong et al., 2012; 6- LeRoy, 1953; 7, Schnack, 2000; 8Stassen et al., 2009; 9- El Dawy et al., 2016, 10- El Dawy et al., 2018, 11- Mahfouz et al., 2018. Table 2: Published palaeoecological references of the calcareous nannofossil environmental indicators used in the present study across the Upper Cretaceous- Paleocene time interval. 1. Thierstein 1980; 2. Thierstein 1981, 3. Eshet and Almogi Labin, 1996; 4. Moshkovitz and Eshet, 1989; 5. Eshet et al. 1992, 6. Tantawy, 2003; 7. Thibault and Gardin, 2006; 8. Erba, 1990; 9. Erba et al., 1992; 10. Williams and Bralower, 1995; 11. Fisher and Hay, 1999; 12. Watkins et al., 1996; 13. Watkins and Self-Trail, 2005; 14. Lees, 2002; 15. Thierstein, 1976; 16. Wind, 1979; 17. Pospichal and Wise, 1990a, b; 18. Bralower, 2002; 19. Wei and Wise, 1990; 20. Firth and Wise, 1992; 21. Self-Trail et al., (2012) Figures captions Fig. 1: A. Location map of the study area; B, Simplified Late Maastrichtian palaeobiogeographic map shows the locations of the studied sections (modified after Philip and Floquet, 2000). Fig. 2: Field photographs showing: A. the Cretaceous/Paleogene (K/Pg) boundary at the base of a conglomerate bed within the Dakhla Formation at G. El-Aguz section, B. the Dakhla/Tarawan formational boundary with the irregular surface and bioturbation at the base of the Tarawan Formation at Gabal El-Aguz section, C. the Cretaceous/Paleogene (K/Pg) boundary at the base of a conglomerate bed within the Dakhla Formation at Darb Gaga section, D. reddish ferruginous conglomerate bed at Darb Gaga section, E. the Dakhla/Tarawan formational boundary with the erosive surface, pebbles and bioturbation at the base of the Tarawan Formation at Darb Gaga section, F. the Cretaceous/Paleogene (K/Pg) boundary at the base of a conglomerate bed within the Dakhla Formation at El-Qasr section, G. the Tarawan Formation at El-Qasr section, H. the Kurkur Formation at Abu Tartur section.

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Fig. 3: Litho-, bio-stratigraphy, range chart of the identified calcareous nannofossils throughout the K/Pg transition at El-Qasr section. Fig. 4: Litho-, bio-stratigraphy, range chart of the identified calcareous nannofossils and foraminiferal species, the foraminiferal indices and benthonic biofacies throughout the K/Pg transition at Abu Tartur section (for legend see figure 3). Fig. 5: Litho-, bio-stratigraphy, range chart of the identified calcareous nannofossils throughout the K/Pg transition at G. El-Aguz section (for legend see figure 3). Fig. 6: Litho-, bio-stratigraphy, range chart of the identified calcareous nannofossils throughout the K/Pg transition at Darb Gaga section (for legend see figure 3). Fig. 7: Litho-, bio-stratigraphy and range chart of the identified planktonic foraminiferal species across the K/Pg transition at El-Qasr section (for legend see figure 3). Fig. 8: Litho-, bio-stratigraphy and range chart of the identified planktonic foraminiferal species across the K/Pg transition at G. El Aguz section (for legend see figure 3). Fig. 9: Litho-, bio-stratigraphy, range chart of the identified foraminiferal species, the foraminiferal indices and benthonic biofacies throughout the K/Pg transition at Darb Gaga section (for legend see figure 3). Fig. 10: Dendrogram of the R-mode cluster analysis of the common benthonic foraminiferal taxa. Fig. 11: Relative abundance of the important nannofossil species and species richness of the nannofossil throughout K/Pg transition at El-Qasr section (for legend see figure 3). Fig. 12: Relative abundance of the important nannofossil species and species richness of the nannofossil throughout K/Pg transition at G. El Aguz section (for legend see figure 3). Fig. 13: Relative abundance of the important nannofossil species and species richness of the nannofossil throughout K/Pg transition at Darb Gaga section (for legend see figure 3). Fig. 14: Litho-, bio-stratigraphy, range chart of the benthonic foraminiferal species, the foraminiferal indices and benthonic biofacies across the K/Pg transition at El-Qasr section (for legend see figure 3). Fig. 15: Litho-, bio-stratigraphy, range chart of the benthonic foraminiferal species, the foraminiferal indices and benthonic biofacies across the K/Pg transition at G. El Aguz section (for legend see figure 3). Fig. 16: Litho- and bio-startigraphic correlation of the Maastrichtian-Paleocene successions at the study area. Fig. 17: Sketch showing the scenario of the sedimentary basin evolution throughout the Maastrichtian-Paleocene transition. 32

Fig. 17: (continued) Plate's captions Plate I. Light photomicroscope images of selected nannofossil species recorded from the Upper Cretaceous-Paleocene successions of the studied area: 1. Watznaueria barnesiae, sample no. 14, El-Qasr section; 2. Prediscosphaera cretacea, sample no. 3, El-Qasr section; 3. Arkhangelskiella cymbiformis, sample no. 1, El-Qasr section; 4. Micula decussata, sample no. 3, El-Qasr section; 5. Ahmuellerella octoradiata, sample no. 12, El-Qasr section; 6. Lithraphidites quadratus, sample no. 2, El-Qasr section; 7. Eiffellithus turriseiffelii, sample no. 12, El-Qasr section; 8. Biscutum constans, sample no. 16, El-Qasr section; 9. Micula murus, sample no. 12, El-Qasr section; 10. Micula prinsii, sample no. 49, El-Qasr section; 11. Chiasmolithus danicus, sample no.56, El-Qasr section; 12. Ellipsolithus macellus, sample no.40, El-Aguz section; 13. Chiasmolithus edentulus, sample no.43, El-Aguz section; 14. Sphenolithus primus, sample no.48, El-Aguz section; 15. Lithoptychius ulii, sample no.47, El-Aguz section; 16. Lithoptychius janii, sample no.53, El-Aguz section; 17. Lithoptychius pileatus, sample no.54, El-Aguz section; 18. Fasciculithus involutus, sample no.58, El-Aguz section; 19. Fasciculithus tympaniformis, sample no.42, Darb Gaga section; 20. Heliolithus kleinpellii, sample no.46, Darb Gaga section; 21. Discoaster mohleri, sample no.53, Darb Gaga section; 22. Discoaster falcatus, sample no.66, El-Aguz section; 23. Neochiastozygus junctus, sample no.54, Darb Gaga section; 24. Three specimens of Braarudosphaera bigelowii, sample no.62, El-Qasr section. Plate II. Scanning Electron Microscope (SEM) of selected agglutinated foraminiferal species recorded from the Upper Cretaceous-Paleocene successions of the studied area: 1. Ammobaculites junceus, sample no. 42, Abu Tartur section; 2. Ammobaculites khargaensis, sample no. 43, Abu Tartur section; 3. Ammobaculites subcretaceus, sample no. 9, Darb Gaga section; 4. Ammobaculites texanus, sample no. 6, El-Qasr section; 5. Ammobaculites stephensoni, sample no. 40, Abu Tartur section; 6. Bathysiphon eocenicus, sample no. 43, El-Aguz section; 7. Unitendina oblonga, sample no. 12, El-Aguz section; 8. Phenacophragma assurgens, sample no. 47, Abu Tartur section; 9. Earlandammina bullata, sample no.33, El-Aguz section; 10. Earlandammina bullata, sample no.12, El-Aguz section; 11. Haplophragmoides calculus, sample no.25, Darb Gaga section; 12. Haplophragmoides formosus, sample no.30, El-Aguz section; 13. Haplophragmoides kirki sample no.48, Abu Tartur section; 14. Trochammina bohemi, sample no.23, Abu Tartur section; 15. Trochammina deformis, sample no.9, Darb Gaga section; 16. Trochammina rainwateri, sample no. 31, El-Aguz section; 17. Trochammina simplex, sample no.27, Darb Gaga section.

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Table 1: Summary of paleobathymetrical references of the most common benthonic foraminiferal species used in the present study. 1-El-Dawy and Hewaidy, 2003; 2-Speijer, 1994; 3-Hewaidy, 1997; 4-Speijer and Schmitz; 1998; 5-Sprong et al., 2012; 6- LeRoy, 1953; 7, Schnack, 2000; 8- Stassen et al., 2009; 9- El Dawy et al., 2016, 10- El Dawy et al., 2018, 11- Mahfouz et al., 2018. Most common benthonic foraminiferal species Haplophragmoides spp. Ammobaculites spp. Trochammina spp. Anomalinoides umbonifera Cibicidoides proprius Epiniodes lunatus Cibicidoides pharaonis Eouvigerina spp. Orthokarstenia spp. Anomalinoides midwayensis Anomalinoides aegyptiaca Bulimina ovata / quadrata Anomalinoides zitteli Loxostomoides applinae Lenticulina spp. Cibicidoides succedens Siphogenerinoides eleganta Marginulina spp. Anomalinoides praeacutus Vaginulina spp. Bathysiphon spp. Pyramidulina spp. Cibicidoides pseudoacuta Gyroidinoides spp. Gaudryina spp. Cibicidoides alleni Lagena spp. Cibicidoides libycus Spiroplectinella spp. Preabulimina spp.

Coastal

Paleobathymetric range Neritic Inner Middle Outer

Upper Bathyal

Ref. 8,10 8,10 10 8,10 1,10 10 10 4,7 3,7 7,8 2,4 6 10 2,4,5 3, 7 8,9,10 2,4,5 4,7 8 7 7 4,7, 11 1,2,4,5,11 8,10 4,5 9,10 7,11 11 2,4,5,11 11

Table caption Table 2: Published palaeoecological references of the calcareous nannofossil environmental indicators used in the present study across the Upper Cretaceous- Paleocene time interval. 1. Thierstein 1980; 2. Thierstein 1981, 3. Eshet and Almogi Labin, 1996; 4. Moshkovitz and Eshet, 1989; 5. Eshet et al. 1992, 6. Tantawy, 2003; 7. Thibault and Gardin, 2006; 8. Erba, 1990; 9. Erba et al., 1992; 10. Williams and Bralower, 1995; 11. Fisher and Hay, 1999; 12. Watkins et al., 1996; 13. Watkins and Self-Trail, 2005; 14. Lees, 2002; 15. Thierstein, 1976; 16. Wind, 1979; 17. Pospichal and Wise, 1990a, b; 18. Bralower, 2002; 19. Wei and Wise, 1990; 20. Firth and Wise, 1992; 21. Self-Trail et al., (2012)

Upper Cretaceous

Paleocene

Nannofossil taxa C. subpertusus C. pelagicus P. sigmoides Chiasmolithus spp. Fasciculithus spp. S. primus Discoaster spp. Prinsius spp. T. eminens M. decussata E. turriseiffelii P. cretacea Lithraphidites spp. B. constans T. saxea W. barnesiae M. murus A. cymbiformis A. octoradiata K. magnificus N. frequens

Cool water

Warm water ■ ■

Low productivity

High productivity

Preservation

■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■

■

■ ■ ■ ■ ■ ■ ■ ■

■

References 18 18 17b 18 and 19 19 19 19 17, 18, 19, and 20 21 1, 2, 3, 4, 5, 6, and 7 3 and 7 3 and 7 3 and 7 3, 8, 9, 10, and 11 3 1, 6, 9, 10, 12, and 13 2, 7, and 12 2 2, 14, 15, 16 and 17a 2, 14, 15, 16 and 17a 2, 14, 15, 16 and 17a

Highlights

Field, litho-, bio-stratigraphic and paleoenvironmental studies were carried out. Eight calcareous nannofossils and ten planktonic foraminiferal zones are integrated. Four benthonic foraminiferal biofacies (A, B, C and D) are identified. Two syn-sedimentary tectonic events are recognized affecting the Dakhla basin. Five phases are proposed to interpret the sedimentary basin evolution.

Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

There are no financial interests/personal relationships which may be considered as potential competing interests

Dr. Kamel H. Mahfouz Geology Department, Faculty of Science, Al-Azhar University (Assiut branch), Egypt E-mail: [email protected]