Cretaceous diatoms biostratigraphy and taxonomy ...

Cretaceous diatoms biostratigraphy and taxonomy from the North-eastern Sinai, Egypt Abdelfattah Ali Zalat Geology Department, Faculty of Science, Tanta University, Tanta 31527, Egypt email: [email protected]

ABSTRACT: Diatom occurrence, abundance, and biostratigraphic position are documented from subsurface Albian - Maastrichtian succession penetrated by the Raad-1 Well, drilled at the north-eastern Sinai, Egypt. The examined stratigraphic section is differentiated into four lithostartigraphic units from base to top: Kharita Formation (Albian), Halal Formation (Cenomanian), Wata Formation (Turonian) and Sudr Formation (Santonian to Maastrichtian). Well to moderately-preserved marine diatom assemblage included 87 species and varieties representing 37 genera have been identified. The assemblage is mainly dominated by planktonic taxa rather than periphytic forms. Most of the encountered diatom species have long stratigraphic ranges, except 39 taxa are belonged to Cretaceous period, and taxonomically enumerated. Two diatom biozones are recognized based on the distribution and stratigraphic occurrence of the Cretaceous diatoms in the studied section. Amblypyrgus campanellus Zone is characteristic the lower part of the succession (Kharita Formation), and point to Lower Cretaceous. Gladius antiques Zone is encountered from Halal, Wata and the lower part of Sudr Formations, and denotes the Upper Cretaceous age. The Albian / Cenomanian boundary is placed at the last occurrence of Albian diatom taxa and the first appearance of Late Cretaceous diatom forms. The microfloral content and lithological characters of the examined section reflect a shallow marine environment prevailed during the Early Cretaceous, which changed to be more deeply environment in the Late Cretaceous. Keywords: fossil marine diatoms, Cretaceous, biostratigraphy, taxonomy, Sinai

INTRODUCTION

In Egypt, the Cretaceous rocks are widely distributed and well exposed at several localities in Sinai, and in the Eastern and Western Deserts. Literature on the Cretaceous succession of Sinai is copious and including of geology, stratigraphy, macro and micropaleontology studies. Among these relevant works are El Shinnawi (1967), El Shazly et al. (1974), Bartov et al. (1980), Eyal et al. (1981), Kora and Hamama (1987), Allam and Khalil (1988), Cherif et al. (1989), Andrawis (1990), Jenkins (1990), Moustafa and Khalil (1987; 1990), Kassab (1991), Orabi (1992), Kora et al. (1994), May (1991), Kassab and Ismael (1994; 1996), Hewaidy et al. (1998), Kassab and Obaidalla (2001), El-Hedeny (2002), Aly et al. (2005), and many others. Most of the published micropaleontological works on the Cretaceous sediments of the northern Sinai have focused on the foraminifers, nannofossils and palynomorphs. The biostratigraphic zonations and the delineation of the Cretaceous stratigraphic boundaries based upon the microfossil groups in Sinai have been dealt by many authors (e.g., Said and Barakat 1957; El-Beialy 1993; Shahin 1993; Zarif 1997 and Ismail 1999). None of the previous studies dealt with the Cretaceous diatoms from Egypt. Diatoms are abundant and diverse group in all aquatic environments. They offer important information to reconstruct paleoenvironments and clarify stratigraphic relationships (Mann 1999). They are known from the Lower Cretaceous (Harwood et al. 2007) to Recent and represent useful tools as biostratigraphic, paleoenvironmental, and paleoclimatic indicators (Stoermer and Smol 1999). Because they form siliceous

skeletons, diatoms also constitute key elements of the contemporary silica cycle. Marine diatoms began to widespread and diversify early in the Cretaceous Period and by the Campanian (74.5–84 Ma) included relatively diverse centric and rare araphid pennate forms (Strelnikova 1990; Harwood and Nikolaev 1995). Calculations of various authors estimate the number of Cretaceous diatom genera to be around 80 (Harwood and Nikolaev 1995), and the number of species to exceed 300 (Strelnikova 1975, 1990; Sims et al. 2006). Most published Cretaceous diatom studies are descriptive and taxonomic, with little or no stratigraphic control (e.g., Hanna 1927; 1934; Jousé 1949; 1951; 1955; Krotov and Schibkova 1959; Strelnikova 1966; 1971; 1974; 1975; Barron 1985; Harwood 1988; Dell’Agnese and Clark 1994; Nikolaev et al. 2001; Tapia and Harwood 2002; Davies 2006). Nevertheless, general trends in Upper Cretaceous diatom biostratigraphy and evolution can be found in Strelnikova (1974) and a review of Cretaceous diatoms was presented by Harwood and Nikoleav (1995). The distribution of diatoms in many Cretaceous rock units around the world indicates that they were already abundant, widespread and diverse by the end of the Cretaceous. Although several studies recorded Cretaceous diatoms from marine deposits in many regions, there are no studies carried out on the Cretaceous diatoms from Egypt. This may be a result of their apparent scarcity and the limited number of diatomists looking at Cretaceous sediments of Egypt. The main target of the present study is to record for the first time in Egypt the diatom taxa from the Cretaceous sediments of the Raad-1 Well, north-eastern Sinai and to evaluate the use of these taxa in biostratigraphy and palaeoenvironmental interpretation.

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Abdelfattah Ali Zalat: Cretaceous diatoms biostratigraphy and taxonomy from the North-eastern Sinai, Egypt

anticlines at the Late Cretaceous and Early Tertiary levels; 3) NNW-SSE-trending normal faults at the Oligocene and Early Miocene levels; and 4) NNW-SSE-trending transform faults during the Late Miocene (Alsharhan and Salah 1996). Each of these major tectonic elements has affected dramatically the structure and tectonic evolution of the north Sinai area. Therefore, the northern part of the Sinai is characterized by several major folds, which are fractured along fault structures. Both tectonic structures run in NE-SW-directions. They continue to the west, across the Gulf of Suez (Kuss and Malchus 1988) and to the Negev and Lebanon (Wolfart 1967) further to the northeast. Folding started during Late Cretaceous times in the Levant, spanning an area described as the ‘Syrian Arc System’ by Said (1962). Synsedimentary tectonic movements have been seen since the Late Cenomanian (Kuss and Malchus 1988) and characterize the unstable shelf areas; the stable cratonal shelf continues further to the south.

TEXT-FIGURE 1

Location map of the studied Raad-1 Well.

GEOLOGICAL SETTING OF THE STUDY AREA

The Sinai Peninsula is bounded by the Suez Canal and Gulf of Suez rifted basin to the west, the transform Dead Sea-Aqaba rift to the east and the Mediterranean passive margin to the north. It is triangular in shape and occupies an area of almost 60 000km2 (text-fig. 1). It is separated geographically from Africa by the Suez Canal and the Gulf of Suez. The southern sector of the Sinai Peninsula is occupied by rigid Precambrian basement rocks that reach elevations of 2640m in Jebel Katherine (Said 1962). The central and northern sectors of the Sinai are covered with a northward-draining limestone plateau with a series of northeast-trending anticlinal and synclinal mountains that follow the Syrian Arc System. Farther north, a broad tract of sand dunes runs parallel to the Mediterranean coast and the Bardwail Lake and ranging in elevation from 10 to 1000m. The sedimentation in north Sinai during the Mesozoic was influenced mainly by the Arabo-Nubian Massif and the Tethys Sea. During the Cretaceous, Egypt was part of a broad Tethyan Seaway with open marine circulation to the Indo-Pacific in the east and the Atlantic– Caribbean–Pacific to the west. Shallow seas covered continental regions in North Africa, Europe, the Middle East and the Ural region (Luning et al. 2004). During the mid- Cretaceous, northern Sinai was a carbonate ramp that developed along the southern margin of the Tethyan Ocean (Wanas 2008). The studied area represents part of this ramp. The area has been tectonically active from the Early Cretaceous to the Eocene owing to regional compression in north-eastern Egypt (Shaaban et al. 2006). Four main tectonic trends reflect the influence of regional tectonic movements on the northern Sinai: 1) ENE-WSW-trending normal faults at the Triassic, Jurassic and Early Cretaceous levels; 2) NE-SW trending

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The stratigraphic section in North Sinai ranges in age from Precambrian to Recent and varies in thickness, lithology areal distribution and depositional settings (Alsharhan and Salah 1996). The lithostratigraphic units have been defined from examination of several measured sections and subsurface cores, electric logs tied to microfaunal and palynological studies of ditch samples and thin sections (Shata 1956; Said 1962; 1990; Neev 1975; 1977; Beyth 1981; Zaghloul and Khidr 1992; EGPC 1994). However, the Cretaceous deposits have a wide distribution in northern Sinai. They form the bulk of the anticlinal ridges in many places. The Cretaceous sequence in the studied area is subdivided into four lithostratigraphic units. The first unit is related to the Early Cretaceous and namely Kharita Formation, which is followed by Cenomanian transgressive marine beds of Halal Formation, the Turonian carbonate and marly facies of Wata Formation and the Santonian–Maastrichtian chalky limestone of Sudr Formation. LITHOSTRATIGRAPHY

The studied stratigraphic succession of the Raad-1 Well is differentiated into the following formal rock units from bottom to top: Kharita, Halal, Wata and Sudr formations (text-fig. 3). Kharita Formation

According to El-Gezeery and O’Conner (1975), the oil companies use the term Kharita Formation for the Albian sediments in the Western Desert, where it corresponds to Ramis Group. In the studied Raad-1 Well, the formation underlies the Cenomanian Halal Formation. It is composed mainly of white to gray hard limestone with hard, fine to medium grained sandstone, marl and shale intercalation. The formation includes the interval from the depth 1224 to 1310m, with thickness of about 86m. Generally, the formation comprises poorly non-diagnostic taxa, except some frequently diatom species, which belong to Albian age. Halal Formation

This Formation is exposed in northern and central Sinai; it was first described at Gebel Halal (Moon and Sadek 1921; Awad and Said 1966). It overlies the Albian Kharita Formation and underlies the Turonian Wata Formation. It represents the first marine transgression during the Cenomanian in northern Sinai and is correlative with the Raha Formation in central Sinai (Ghorab 1961). It is also equivalent to the Mazera Formation in the Makhtesh Ramon, Negev (Arkin and Braun 1965). In the studied well, it includes the interval from the depth 1032 to 1224m,

Micropaleontology, vol. 59, nos. 2–3, 2013

TEXT-FIGURE 2 Stratigraphic framework of Cretaceous rocks in different areas of Egypt (after Said 1990, Issawi et al. 1999, Nagm et al. 2010). with thickness of about 192m. The formation is underlain by the Kharita Formation and overlain by the Wata Formmation. It is composed mainly of limestones with minor interbedded shales. The age of this formation is assumed to be Cenomanian (Andrawis 1990 and Khalil 1993). The lower part of the formation (1098-1224m) contains poor non age diagnostic nannoplankton, while the upper part (1032 to 1098m) dominates by the nannoplankton assemblage points to Late Cenomanian age. Wata Formation

The Wata Formation was previously introduced in the Egyptian lithostratigraphy by Ghorab (1961) for the Turonian succession exposed at Wadi Wata in central Sinai. It is equivalent to the Ora Shale and the Gerofit Formation of the Judea Group in the Makhtesh Ramon, Negev (Arkin and Braun, 1965). In the studied Raad-1 Well, this formation unconformably overlies the Halal Formation and unconformably underlies the Sudr Formation. It includes the interval from the depth 933 to 1032m, with

a thickness of about 99m. The unit is composed mainly of shale with some limestone intercalation. Cherif et al. (1989) studied the Wata Formation in West central Sinai and suggested middle to late Turonian age to this formation. In the Raad-1 Well, Andrawis (1990) recognized the benthic foraminifera Discorbis turonicus zone, which indicate a Turonian age for this interval. Freund and Raab (1969) and Khalil (1993) are recorded Turonian ammonites and other macrofossils from this unit. The calcareous nannoplankton assemblage confirms the Turonian age for this formation. Sudr Formation

Ghorab (1961) used the term Sudr Formation for the Campanian-Maastrichtian chalky limestone and argillaceous limestone sequence at the type locality in Wadi Sudr (west-central Sinai). Awad and Said (1966) are indicated the chalky limestone is of wide geographic distribution and is known in both the Stable and Unstable shelf areas of Egypt. In the studied well,

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it includes the interval from depth 870 to 933m, with a thickness of about 63m. It is composed mainly of limestones, white, rarely grayish white, moderately hard, chalky, slightly argillaceous and fossiliferous. The formation forms a distinct rock unit, which contrasts with the underlying Wata Formation. On the bases of planktonic foraminiferal evidence (Andrawis 1990; Khalil 1993 and Zarif 1997) and the calcareous nannoplankton assemblage, the formation was considered to be Santonian Maastrichtian age. MATERIAL AND METHODS

This study is based on the investigation of 44 ditch and core samples obtained from the Cretaceous succession penetrated by Raad 1-Well, which was drilled by General Petroleum Company (GPC) in 1987. This well is located in north-eastern part of Sinai and is delineated by latitude 31° 10’ 45" N and longitude 34° 12’ 02" E (text-fig. 1). The lithological log of the formations penetrated together with thickness and position of the examined samples are shown in text-figure 2. In the early phase of this work, part of the material was processed for calcareous nannoplankton. Standard siliceous microfossil preparation techniques (Battarbee et al. 2001) with 20% HCl and 30% H2O2 were performed on 5 grams of each studied sample to extract fossil diatoms. A combination of rinsed, settling and decantation with distilled water were applied to concentrate the diatoms from the sediments. Residues were stored in plastic vials and protected from fungal growth by the addition of a few drops of formaldehyde. Slides were prepared by drying the residues onto 22 × 50 mm coverslips that were then mounted onto glass slides with Naphrax optical adhesive. Three slides were prepared of each sample and examined in detail using a Carl Zeiss photomicroscope with normal 63x and 100x oil immersion objective. Diatom identification was based on the preceding references of Cretaceous diatoms (e.g. Strelnikova 1974; Hajós and Stradner 1975; Fenner 1982; Barron 1985; Harwood 1988; Gersonde and Harwood 1990; Harwood and Nikolaev 1995; Dell’Agnese and Clark 1994; Tapia and Harwood 2002; and Davies 2006). Other Cenozoic diatom references were used to identify the caved and reworked forms (e.g. Hustedt 1930-1966; Hendey 1964; Andrews 1976; Abbott and Andrews 1979; Abbott 1980; Fenner 1984, 1985). The relative abundance and preservation of the identified taxa that belong to Cretaceous period were tabulated in Figs. 4. Quantitative analyses of the encountered diatom taxa were based on counts of 500 specimens per sample, and recorded as follows: A: abundant (more than 50 specimens per one traverse), C: common (21-50 specimens per one traverse), F: frequent (11-21 specimens per one traverse), R: rare (1-10 specimens per one traverse); Preservation of diatoms was determined qualitatively as follows: G (well preserved) = finely silicified forms present and no alternation of frustules observed; M (moderately preserved) = finely silicified forms present with alternation; P (poorly preserved) = finely silicified forms rare and the robust forms dominant.

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DIATOM BIOSTRATIGRAPHY RESULTS

The subsurface Cretaceous sediments of the Raad-1 Well in the north-eastern Sinai contain abundant and well to moderately preserved diatom taxa. The identified assemblage is composed principally of mixture of Cretaceous taxa with forms ranging up to the Tertiary. A total of 87 diatom species belonging to 37 genera were identified. Of these 39 species are characteristic of Cretaceous period and some of them having stratigraphic ranges extend to Tertiary (text-fig. 4). However, the remaining taxa are considered to be caved and coming from the overlying Tertiary sediments. Two diatom biozones are recognized based on the distribution and stratigraphic occurrence of diatoms in the studied section. These biozones may represent a starting point to aid the application of diatom biostratigraphy to Cretaceous strata in Egypt. As well as, the associated diatoms assemblages may reflect environmental changes and depositional conditions, and provide important stratigraphic context for the studied succession. Gladius antiquus Range Zone

This zone was recognized by Tapia and Harwood (2002) to define the stratigraphic interval between the first occurrence of Basilicostephanus sp. 1 up to the last occurrence of Gladius antiquus Forti et Schulz. In the present study this zone is defined as the interval from the last occurrence of Albian diatoms Amblypyrgus campanellus to last occurrence of Gladius antiquus Forti et Schulz and other Upper Cretaceous taxa. The associated assemblage is represented by frequent to common occurrence of such Upper Cretaceous taxa as Acanthodiscus vulcaniformis, Aulacodiscus sp. cf. Breviprocessus, Actinoptychus packi, Coscinodiscus morenoensis, Hemiaulus arcticus, H. bipons, H. danicus, H. danosuecicus, H. echinulatus, H. kittonii, H. orthocera, H. polymorphus,H. polymorphus var. Frigid, H. praelegans, H. sporialis, Stephanopyxis biseriata, S. grunowii, S. schenkii, S. hannai, S. superb, S. turris, Incisoria lanceolata, Rhizosolenia cretacea, Endictya lunyacsekii, Goniothecium odontella and Paralia ornate. This zone is assigned to Upper Cretaceous (Cenomanian –Santonian). The age of the Gladius antiquus Zone here is based on a similar age recorded by nannoplankton, palynology and foraminifera from the Halal and Wata Formations (Zarif 1997). Amblypyrgus campanellus Range Zone

This zone is recognized in the present study to define the stratigraphic interval between the first to last occurrence of Amblypyrgus campanellus. This Zone is recorded from the lower part of the studied section comprising Kharita Formation with thickness of about 86m (text-fig. 4). The lower boundary of this zone is defined by the first occurrence of marker species associated with other Lower Cretaceous taxa. The upper boundary is represented by last appearance of Lower Cretaceous taxa and first appearance of Gladius antiques associated with Upper Cretaceous species. The association is included Amblypyrgus campanellus, Crossophialus gyroscolus, Cypellachaetes sp., Hyalotrochus incompositus, Hyalotrochus radiates. According to Gersonde and Harwood (1990), the diatom assemblage of this zone is assigned to Early Cretaceous (Albian age). The diatom assemblage recovered in studied section has rather close similarities with the Aptian-Albian assemblages from Albian sediments, Weddell Sea, Antarctica by Gersonde and Harwood (1990)


TEXT-FIGURE 3 Lithostratigraphic section of the studied Raad-1 Well.

DISCUSSION

The well to moderately-preserved diatom taxa reported from the subsurface Cretaceous sediments of north-eastern Sinai offer a new perspective on the early history of these groups that was previously not available from Egypt due to the paucity of material and poor preservation of available materials and there is no Egyptian scientists dealt with this group. A total of 87 diatom taxa in 37 genera are documented. Of these 39 species are characteristic of Cretaceous period. The preceding Cretaceous diatom studies are illustrated that the number of diatom species has apparently progressed through the Mesozoic; increasing from four species in the Jurassic to almost 25 in the Aptian, 45 in the Albian, to more than 300 species in 60 genera by the lat-

est Cretaceous (Hanna 1927; 1934; Strel’nikova 1974; 1975; Hajos and Stradner 1975; Fenner 1982; 1985; Bergstresser and Krebs 1983; Harwood 1988; Gersonde and Harwood 1990; Harwood and Nikolaev 1995; Takahashi et al. 1999; Nikolaev and Harwood 2000; Nikolaev et al. 2001; Tapia and Harwood 2002). From these numbers it is apparent those marine siliceous phytoplanktons were well established by the end of the Early Cretaceous. Diatoms became a complex, diverse, and widespread group by Late Cretaceous time. Most of the previous works on the Cretaceous diatoms are descriptive, and there are no markers taxa can be distinguished for biozonation, in particular for the Lower Cretaceous. Since most

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of the diatom species in the Cretaceous continue into the Tertiary. However, there are some taxa are considered to be limited to Cretaceous time, some of these forms are characteristic of Early Cretaceous, particularly Aptian-Albian age, such as Crossophialus gyroscolus Harwood and Gersonde, Hyalotrochus radiatus Harwood and Gersonde, Hyalotrochus incompositus Harwood and Gersonde. More than 85% of the Late Cretaceous diatom species continued into the Paleocene and the floral composition of the dominant genera did not change across the Cretaceous/Tertiary boundary (Harwood 1988). The diatom assemblage recovered from the Kharita Formation was moderately preserved with low numbers encountered taxa. The assemblage has rather close similarities with the Aptian-Albian assemblage from Albian sediments, Weddell Sea, Antarctica by Gersonde and Harwood (1990). The common occurrence of Amblypyrgus campanellus associated with frequently occurrence of Crossophialus gyroscolus, Hyalotrochus radiatus, Hyalotrochus incompositus, confirms the Albian age for Kharita Formation. This is documented with palynomorphos taxa reported by Zarif (1997). Tapia and Harwood (2002) reported the last occurrence of these taxa point to the end of Lower Cretaceous. Therefore, the Albian/ Cenomanian boundary is situated at depth 1224m and can be delineated by the last occurrence of the Albian diatoms and the first occurrence of Late Cretaceous species which belong to genera Aulacodiscus, Acanthodiscus, Actinoptychus, Coscinodiscus, Hemiaulus, and Stephanopyxis. According to Harwood and Gersonde (1990), the early Cretaceous diatoms may have been restricted to continental margins and interior seas, areas where resting spore formation is most common. The Cenomanian Halal Formation yielded common diatom taxa. While no good recovery for diatoms are available from the Wata and Sudr formations, except some frequently to rare and moderately preserved forms in Wata Formation. The significant and common diatom species recorded from the Cenomanian sediments are: Acanthodiscus vulcaniformis, Aulacodiscus sp. cf. breviprocessus, Actinoptychus packi, Archepyrgus sp. aff. A. melosiroide, Coscinodiscus morenoensis, Gladius antiques, Hemiaulus arcticus, H. bipons, H. danicus, H. danosuecicus, H. echinulatus, H. kittonii, H. orthocera, H. polymorphus, H. polymorphus var. frigida, H. praelegans, H. sporialis, Pterotheca danica, Stephanopyxis biseriata, S. grunowii, S. schenkii, S. hannai, S. schenckii, S. superb, S. turris, Incisoria lanceolata, Rhizosolenia cretacea, Endictya lunyacsekii, Goniothecium odontella and Paralia ornate, in addition some taxa having long stratigraphic range. The first appearance of the genus Gladius should be sufficient to recognize the base of the Cenomanian. The Gladius antiques Zone was recognized by Tapia and Harwood (2002) to denote the beginning of the Late Cretaceous. Therefore, the occurrence of Gladius antiques in the samples of Halal and Wata Formations confirms the Late Cretaceous age for these rock units in the studied area. Many caved diatoms coming from the overlying Tertiary sediments were recorded. The more dissolution - resistant valves such as Xanthiopyxis spp. with other resting spore type commonly dominate the assemblage, and the geographically widely distributed species Thalassionema nitzschioides, Thalassionema nitzschioides var. parva, Thalassiothrix longissima and Chaetoceras spp. among others are common to frequent.

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The Albian/Cenomanian boundary

The Albian/Cenomanian stage boundary separates the Lower and Upper Cretaceous Series. The international Commission on stratigraphy has defined the base of the Cenomanian Stage by the first occurrence of the planktonic foraminifera Rotalipora globotruncanoides Sigal (Gale et al. 1996). Kennedy et al. (2004) concluded that the base of the Cenomanian corresponds to the first occurrence of planktonic foraminifera Rotalipora globotruncanoides along with the coexistence of Rotalipora appenninica, Rotalipora gandolfii, Rotalipora tehamensis. In conclusion, the Albian/Cenomanian boundary in the present work is determined accurately by means of diatom taxa, where the datum is delineated at the level of the last occurrence of Albian diatoms and first common occurrence of the Gladius antiques, associated with other significant Upper Cretaceous taxa at the base of Cenomanian Halal Formation. PALEOENVIRONMENTAL INTERPRETATION

The Cretaceous sedimentary succession in the Raad-1 Well begins at the base with deposition of the Albian Kharita Formation, which consists of limestone with sandstone, marl and shale intercalation. The recovery of marine diatom assemblage from the examined samples suggests a general neritic marine environment during the Albian time. Harwood and Gersonde (1990) suggested that the early Cretaceous diatoms may have been restricted to continental margins and interior seas, areas where resting spore formation is most common. The Albian/Cenomanian transition is noteworthy for paleoenvironmental changes that took place during the Cretaceous greenhouse period. An oceanic anoxic event evidently occurred in the latest Albian in the Atlantic and Tethyan regions (OAE 1d, Strasser et al. 2001; Wilson and Norris 2001), and oxygen isotope records from lower Cenomanian strata in mid-latitude areas suggests a rapid cooling event (Stoll and Schrag 2000). The Cenomanian Halal Formation is made up of limestones with minor interbedded shales. Samples of the lower part of this formation contain common diatom taxa with rare occurrence of calcareous nannoplankton. The dominance of marine diatoms indicates that the deposition of the early Cenomanian sediments took place in a warm, shallow neritic marine environment with normal marine salinity. Toward the top of Late Cenomanian Halal Formation, the relative abundance of diatom taxa decreased with increasing in the abundance of calcareous nannoplankton and foraminiferal tests. This may suggest that a deep marine environment of neritic condition prevailed during the Late Cenomanian. The well developed carbonate facies of the Halal Formation indicates a major marine transgression during the Cenomanian age, which covering the clastic sediments of the Early Cretaceous. The Late Cretaceous Sea continued its transgression during the Turonian age and led to the deposition of Wata Formation, which is characterized by dominance of shale and limestone intercalation. The microfloristic content of Wata Formation indicates high abundance of calcareous nannoplankton with frequently occurrence of diatom taxa. The microfloral content and lithological characters of the Wata Formation reflect a predominant shallow, open marine depositional environment of neritic conditions. The shallowing of the sea, which started during the Late Turonian due to the crustal uplift of the sea floor, continued throughout the Coniacian. According to Lewy (1975), in the Late Coniacian time, Sinai was slightly tilted southwestwards, and


TEXT-FIGURE 4 Stratigraphic distribution of the significant Cretaceous diatoms in the Raad-1 Well.

the uplifted northeastern part of it was eroded exposing the Coniacian and the Late Turonian strata. The Santonian Maastrichtian sediments of Sudr Formation are composed mainly of limestones of chalky nature, which are rich in calcareous nannoplankton with planktonic foraminiferal tests and containing low numbers of diatom taxa. The microfloral and faunal characters with lithological nature of the Sudr Formation indicate that the deposition of this unit took place in a deep marine environment.

TAXONOMY

A taxonomic study of the identified Cretaceous diatom taxa is reported briefly. The recent classification proposed by Round et al. 1990 and Nikolaev and Harwood 1996, 1998 were used in the present work. Taxa are systematically arranged, where each taxon is generally accompanied by the authority used in identification, its relative abundance, occurrence, distribution and known geologic age. Others taxa characteristic the overlying Tertiary rocks are represented in the List of reworked taxa.

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Kingdom: Protista Haeckel 1866 Subkingdom: Protoctista Hogg 1860 Phylum: Chrysophyta Pascher 1914 Class: Coscinodiscophyceae Round et al. 1990 Subclass: Archaegladiopsophycidae Nikolaev and Harwood 1998 Order: Stephanopyxales Nikolaev and Harwood 1998 Family: Stephanopyxidaceae Nikolaev 1988 Genus: Stephanopyxis Ehrenberg 1844 Stephanopyxis biseriata Strelnikova 1974 Stephanopyxis biseriata Strelnikova 1974, p. 60, pl. 7, figs. 8-9; Fenner 1985, p. 738, pl. 13, figs. 4-5.

Occurrence: Rare in the Halal Formation and very rare in the Wata Formation. Distribution: Late Cretaceous of western Siberia (Strelnikova 1974).

Known geologic age: Late Cretaceous – Oligocene. Stephanopyxis turris (Greville and Arnott) Ralfs in Pritchard 1861 Stephanopyxis turris (Greville and Arnott) RALFS in PRITCHARD 1861. – HUSTEDT 1930-1966, p. 304, fig. 104. – HAJÓS and STRADNER 1975, 926, Pl. 1, figs. 13-15. – BARRON 1985; pl. 10.3, fig. 5. – HARWOOD 1988, p. 88, pl. 19, figs. 26, 27. – NIKOLAEV et al. 2001: 14, Pl. 7, figs. 5-6. – TAPIA and HARWOOD 2002, pl.9, figs. 9-10.

Occurrence: Common to frequent in the Halal Formation and very rare in the Wata and Sudr Formations. Distribution: Late Cretaceous - Early Paleocene of Seymour Island, eastern Antarctic Peninsula (Harwood 1988), Middle Eocene - Oligocene of south Atlantic, Equatorial Pacific and Indian Oceans (Fenner 1984), Late Miocene - Early Pliocene of Virginia USA (Andrews 1980) and Miocene - Pliocene of the Atlantic margin of USA (Abbott 1980). Known geologic age: Late Cretaceous – Pliocene.

Known geologic age: Late Cretaceous. Stephanopyxis grunowii Grove and Sturt 1888

Plate 2, figure 3

Order: Gladiales Nikolaev and Harwood 1996 Family: Gladiaceae Nikolaev and Harwood 1996 Genus: Gladius Forti and Schulz 1932

Stephanopyxis grunowii Grove and Sturt 1888. – ABBOTT and ANDREWS 1979, p. 252, pl. 5, fig. 29; pl. 8, fig. 7. – TAPIA and HARWOOD 2002, pl. 7, fig. 5.

Gladius antiquus Forti and Schulz 1932

Occurrence: Frequent to rare in the Halal Formation and very rare in the Wata Formation.

Gladius antiquus FORTI and SCHULZ 1932, p. 242, text-fig. 3, fig. 6. – GERSONDE and HARWOOD 1990, p. 373, pl. 7, figs. 1, 2; pl. 8, figs. 1, 2, 5, 6; pl. 15, figs. 6, 7; pl. 17, fig. 12. – TAPIA and HARWOOD 2002, pl.1, fig.2.

Distribution: Late Cretaceous-Early Paleocene of Seymour Island, eastern Antarctic Peninsula (Harwood 1988), Middle Miocene of south Carolina and Georgia, USA (Abbott and Andrews 1979), Miocene-Pliocene of the Atlantic margin of USA (Abbott 1980) and Middle Eocene-Oligocene of south Atlantic, Equatorial Pacific and Indian oceans (Fenner 1984). Known geologic age: Late Cretaceous-Pliocene. Stephanopyxis hannai Hajós 1975

Plate 1, figure 10

Occurrence: Frequent in the Halal Formation and very rare in the Wata Formation. Distribution: Albian of northwest Germany (Forti and Schulz 1932) and Late Aptian – Early Albian of Weddell Sea margin, Antarctica (Gersonde and Harwood 1990); Albian to pre-Campanian (Late Cenomanian to Late Santonian?) of Canada Tapia and Harwood (2002).

Plate 2, figure 1

Known geologic age: Albian - Santonian.

Stephanopyxis hannai Hajós 1975 in HAJÓS and STRADNER 1975, p. 925, pl. 2, figs. 9, 10. – HARWOOD 1988, p. 88, pl. 19, figs. 20-21.

Gladius antiquus var. tenuis Gersonde and Harwood 1990

Occurrence: Frequent in the Halal Formation and very rare in the Wata and Sudr Formations.

Gladius antiquus var. tenuis GERSONDE and HARWOOD 1990, p. 373, pl. 7, figs. 3,4,10,11,15; pl. 8, figs. 3,4,7. – TAPIA and HARWOOD 2002, pl.1, fig.1.

Distribution: Late Cretaceous of south Pacific Ocean (Hajos and Stradner 1975) and Late Cretaceous of Seymour Island, eastern Antarctic Peninsula (Harwood 1988). Known geologic age: Late Cretaceous. Stephanopyxis superba (Greville) Grunow 1884 Cresswellia superba GREVILLE 1861 Stephanopyxis superba (Greville) GRUNOW 1884. – HAJÓS and STRADNER 1975, p. 926, figs. 11, 12; Harwood 1988, p. 88, pl. 19, fig. 25. – TAPIA and HARWOOD 2002, pl. 6, figs. 4-5.

Occurrence: Frequent to rare in the Halal Formation and very rare in the Wata Formation. Distribution: Late Cretaceous – Early Paleocene of Seymour Island, eastern Antarctic Peninsula (Harwood 1988) and Middle Eocene-Oligocene of south Atlantic, Equatorial Pacific and Indian Oceans (Fenner 1984).

312

Plate 1, figure 11

Occurrence: Frequent in the Halal Formation and very rare in the Wata Formation. Distribution: Albian of northwest Germany (Forti and Schulz 1932) and Late Aptian – Early Albian of Weddell Sea margin, Antarctica (Gersonde and Harwood 1990); Albian to pre-Campanian (Late Cenomanian to Late Santonian?) of Canada (Tapia and Harwood 2002). Known geologic age: Albian - Santonian. Genus: Calyptosporium Harwood and Gersonde 1990 Calyptosporium exasperatum Harwood and Gersonde 1990

Plate 1, figure 12 Calyptosporium exasperatum HARWOOD and GERSONDE 1990, p.407, Pl. 5, Figs. 1-11.


Occurrence: Rare in the Kharita Formation.

Genus: Cypellachaetes Harwood and Gersonde 1990

Distribution: Early Albian of Weddell Sea margin, Antarctica (Gersonde and Harwood 1990).

Cypellachaetes sp.

Known geologic age: Early Albian.

Occurrence: Few specimens of this species are observed rarely in the Kharita Formation.

Genus: Amblypyrgus Gersonde and Harwood 1990

Distribution: Albian of the eastern Weddell Sea, Antarctica (Harwood and Gersonde 1990).

Amblypyrgus campanellus Gersonde and Harwood 1990

Plate 1, figures 1–5 Amblypyrgus campanellus GERSONDE and HARWOOD 1990, p. 369, pl. 12, figs. 1-9; pl. 15, figs. 4, 5, 9, 10, 12, 13; pl. 19, figs. 3, 4 Stephanopyxis turris var. campanella FORTI and SCHULZ 1932, p. 246, text-fig. 5.

Occurrence: Rare in the Kharita Formation. Distribution: Late Aptian – Early Albian of Weddell Sea margin, Antarctica (Gersonde and Harwood 1990). Known geologic age: Late Aptian - Early Albian. Amblypyrgus sp.

Occurrence: Rare in the Kharita and Halal Formations.

Known geologic age: Albian. Subclass: Coscinodiscophycidae Round and Crawford in Round et al. 1990 Order: Melosirales Crawford in Round et al. 1990 Family: Endictyaceae Crawford in Round et al. 1990 Genus: Endictya Ehrenberg 1845 Endictya lunyacsekii Pantocsek 1889 Endictya lunyacsekii PANTOCSEK 1889. – HARWOOD 1988, p. 80, pl. 19, figs. 15, 16

Distribution: Late Cretaceous - Early Paleocene of Seymour Island, eastern Antarctic Peninsula (Harwood 1988). Occurrence: Rare in the Halal and Wata Formations.

Genus: Crossophialus Harwood and Gersonde 1990 Crossophialus gyroscolus HARWOOD and GERSONDE 199

Plate 1, figure 7 Crossophialus gyroscolus HARWOOD and GERSONDE 1990, p. 409, pl. 3, figs. 4-6.

Occurrence: Frequent to rare in the Kharita Formation.

Known geologic age: Late Cretaceous – Paleocene. Genus: Acanthodiscus Pantocsek 1892 Acanthodiscus vulcaniformis Jousé 1951 Acanthodiscus vulcanifornts Jousé, 1951 in HARWOOD 1988, p. 79, pl. 10, figs. 8-12.– Chasea ornata HAJÓS and STRADNER, 1975, p. 928, pl. 5, figs. 4, 5; pl. 27, fig. 4.

Distribution: Early Albian of the eastern Weddell Sea, Antarctica (Harwood and Gersonde 1990).

Occurrence: Rare in the Halal Formation

Known geologic age: Early Albian.

Distribution: Late Cretaceous of south Pacific Ocean (Hajos and Stradner 1975) and Late Cretaceous - Early Paleocene of Seymour Island, eastern Antarctic Peninsula (Harwood 1988).

Genus: Hyalotrochus Harwood and Gersonde 1990 Hyalotrochus incompositus Harwood and Gersonde 1990

Known geologic age: Late Cretaceous –Paleocene.

Plate 1, figure 9

Acanthodiscus sp.

Hyalotrochus incompositus Harwood and Gersonde 1990, p. 410, pl. 4, figs. 5 -10.

Occurrence: Few specimens belonging to this species occur only very sporadically in the Halal Formation.

Occurrence: Rare in the Kharita Formation Distribution: Early Albian of the eastern Weddell Sea, Antarctica (Harwood and Gersonde 1990). Known geologic age: Early Albian. Hyalotrochus radiatus Harwood and Gersonde 1990

Plate 1, figure 8

Order: Paraliales Crawford in Round et al. 1990 Family: Paraliaceae Crawford 1988 Genus: Paralia Heiberg 1863 Paralia sulcata (Ehrenberg) Cleve 1873 Paralia sulcata (Ehrenberg) CLEVE 1873. – HENDEY 1964, p. 73, pl. 23, fig.5. – ABBOTT and ANDREWS 1979, p. 247, pl. 4, figs. 27-28. – HARWOOD 1988: 85, figs. 16.8-9. – TAPIA and HARWOOD 2002, pl. 9, fig.13.

Hyalotrochus radiatus HARWOOD and GERSONDE 1990, p. 410, pl. 4, figs. 1-4; pl. 11, figs.7, 8.

Occurrence: Frequent to rare in the Halal Formation.

Occurrence: Rare in the Kharita Formation

Distribution: Late Cretaceous of western Siberia (Strelnikova 1974), Late Cretaceous - Early Paleocene of Seymour Island, eastern Antarctic Peninsula (Harwood 1988), Middle Eocene Oligocene of south Atlantic, Equatorial Pacific and Indian Oceans (Fenner 1984), Middle Miocene of south Carolina and Georgia USA (Abbott and Andrews 1979), Miocene - Early

Distribution: Early Albian of the eastern Weddell Sea, Antarctica (Harwood and Gersonde 1990). Known geologic age: Early Albian.

313


Pliocene of Virginia USA (Andrews 1980) and Holocene sediments of Lake Timsah, Egypt (Zalat 1997).

lantic, Equatorial Pacific and Indian Oceans (Fenner 1984) and Holocene sediments of Lake Timsah, Egypt (Zalat 1997).

Known geologic age: Late Cretaceous – Recent.

Known geologic age: Cretaceous – Recent.

Order: Coscinodiscales Round and Crawford in Round et al. 1990 Family: Coscinodiscaceae Kützing 1844 Genus: Coscinodiscus Ehrenberg 1838

Subclass: Biddulphiophycidaea Round and Crawford in Round et al. 1990 Order: Hemiaulales Round and Crawford in Round et al. 1990 Family: Hemiaulaceae Heiberg 1863 Genus: Hemiaulus Ehrenberg 1844

Coscinodiscus morenoensis Hanna 1927 Coscinodiscus morenoensis Hanna 1927. – HAJÓS and STRADNER 1975, p. 927, pl. 3, figs. 6, 7; pl. 4, fig. 2; pl. 24, figs. 1-3; pl. 25, figs. 1-5. – HARWOOD 1988, p. 80, pl. 10, figs. 15, 16.

Occurrence: Rare in the Halal Formation. Distribution: Late Cretaceous of south Pacific Ocean (Hajos and Stradner 1975) and Late Cretaceous - Early Paleocene of Seymour Island, eastern Antarctic Peninsula (Harwood 1988). Known geologic age: Late Cretaceous – Paleocene. Genus: Aulacodiscus Ehrenberg 1844 Aulacodiscus sp. cf. breviprocessus Strelnikova 1974 Aulacodiscus breviprocessus Strelnikova 1974, p. 76, pl. 25, figs. 1-4; Harwood 1988, p. 79, pl. 12, fig. 3.

Occurrence: Rare in the Halal Formation. Distribution: Late Cretaceous of western Siberia (Strelnikova 1974) and Late Cretaceous - Early Paleocene of Seymour Island, eastern Antarctic Peninsula (Harwood 1988).

Hemiaulus bipons (Ehrenberg) Grunow in Van Heurck 1882

Plate 2, figure 11 Hemiaulus bipons (Ehrenberg) Grunow in Van Heurck 1882; Harwood 1988, p. 82, pl. 13, figs. 5-11.

Occurrence: Frequent to rare in the Halal, Wata and Sudr Formations. Distribution: Late Cretaceous - Early Paleocene of Seymour Island, eastern Antarctic Peninsula (Harwood 1988). Known geologic age: Late Cretaceous – Paleocene. Hemiaulus danicus Grunow 1878 Hemiaulus danicus GRUNOW 1878. – HUSTEDT 1930, p.877, fig. 521. – HAJÓS and STRADNER 1975, p. 931, pl. 5, figs. 10-11. – SCHRADER and FENNER 1976, p. 983, pl. 10, figs. 11, 12. – HARWOOD 1988, p. 82, pl. 13, figs. 16, 17.

Occurrence: Frequent in the Halal formation and very rare in the Wata and Sudr Formations.

Family: Heliopeltaceae H. L. Smith 1872 Genus: Actinoptychus Ehrenberg 1841

Distribution: Late Cretaceous of south Pacific Ocean (Hajos and Stradner 1975), Late Cretaceous of western Siberia (Strelnikova 1974), Eocene – Oligocene of south Atlantic, Equatorial Pacific and Indian Oceans (Fenner 1984) and Late Cretaceous - Early Paleocene of Seymour Island, eastern Antarctic Peninsula (Harwood 1988).

Actinoptychus packi Hanna 1927

Known geologic age: Late Cretaceous – Oligocene.

Known geologic age: Late Cretaceous – Paleocene.

Plate 2, figure 4–5 Actinoptychus packi Hanna 1927. – HAJÓS and STRADNER 1975, p.928, pl. 5, figs. 23-24; pl. 29, figs. 1-4; pl. 30, figs. 1-4. – HARWOOD 1988, p. 79, pl. 9, figs. 7, 8.

Occurrence: Frequent to rare in the Halal, Wata and Sudr Formations. Distribution: Late Cretaceous of south Pacific Ocean (Hajos and Stradner 1975) and Late Cretaceous - Early Paleocene of Seymour Island, eastern Antarctic Peninsula (Harwood 1988). Known geologic age: Late Cretaceous – Paleocene. Actinoptychus senarius Ehrenberg 1843 Actinoptychus senarius Ehrenberg 1843. – ANDREWS 1976, p. 15, pl. 4, figs. 7-8; ABBOTT and ANDREWS 1979, p. 232, pl. 1, fig. 11. Actinoptychus undulatus (Bailey) Ralfs 1861. – HUSTEDT 1930– 1966, p. 475-478, fig. 264.

Occurrence: Frequent to rare in the Halal, Wata and Sudr Formations. Distribution: It is reported from beds of Cretaceous age to a common occurrence in modern habitat, as well as from the Middle Miocene of south Carolina and Georgia, USA (Abbott and Andrews 1979), Miocene – Pliocene of the Atlantic margin of USA (Abbott 1980), Middle Eocene – Oligocene of south At-

314

Hemiaulus echinulatus Jousé 1949

Plate 2, figure 12 Hemiaulus echinulatus Jousé 1949. – STRELNIKOVA 1974, p.100, pl. 44, figs. 15-23. – HAJÓS and STRADNER 1975, p. 931, pl. 5, figs. 21, 22. – FENNER 1985, p.731, fig. 14.10. – HARWOOD 1988, p. 82, pl. 13, fig. 4. – TAPIA and HARWOOD 2002, pl. 7, figs. 7-8.

Occurrence: Frequent to rare in the Halal Formation and very rare in the Wata and Sudr Formations. Distribution: Late Cretaceous of south Pacific Ocean (Hajos and Stradner 1975), Late Cretaceous of western Siberia (Strelnikova 1974) and Late Cretaceous of Seymour Island, eastern Antarctic Peninsula (Harwood 1988). Known geologic age: Late Cretaceous. Hemiaulus kittonii Grunow 1884

Plate 2, figure 7 Hemiaulus kittonii Grunow 1884. – STRELNIKOVA 1974, p.96, pl. 42, figs. 12-24. – SCHRADER and FENNER 1976, p. 984, pl. 10, fig. 19. – BARRON 1985, pl.10.2, fig. 8. – HARWOOD 1988, p. 83, pl. 13, fig. 15. Hemiaulus altus Hajós in HAJÓS and STRADNER 1975, p. 931, pl. 5, fig. 17-19.


Occurrence: Common to rare in the Halal Formation, and very rare in the Wata Formation. Distribution: Late Cretaceous of western Siberia (Strelnikova 1974), Late Cretaceous - Early Paleocene of Seymour Island, eastern Antarctic Peninsula (Harwood 1988) and Oligocene of the Norwegian Sea (Schrader and Fenner 1976). Known geologic age: Late Cretaceous – Oligocene.

WOOD 1988, p. 84, pl. 15, figs. 7-10. – TAPIA and HARWOOD 2002, pl. 5, fig. 7.

Occurrence: Rare in the Halal Formation. Distribution: Late Cretaceous of Siberia (Strelnikova 1971) and Late Cretaceous of Seymour Island, eastern Antarctic Peninsula (Harwood 1988). Known geologic age: Late Cretaceous.

Hemiaulus orthoceras Strelnikova 1974 Hemiaulus orthoceras STRELNIKOVA 1974, p. 103, pl. 45, figs. 20-24. – FENNER 1985, p. 732, pl. 13, figs. 16-18

Occurrence: Rare in the Halal and Wata Formations. Distribution: Late Cretaceous of western Siberia (Strelnikova 1974). Known geologic age: Late Cretaceous. Hemiaulus polymorphus Grunow 1884

Plate 2, figure 9 Hemiaulus polymorphus Grunow 1884. – HUSTEDT 1930-1966, p. 880, fig. 526.

Genus: Pterotheca Grunow in Van Heurck 1883 Pterotheca danica (Grunow) Forti 1909 Pterotheca danica (Grunow) Forti 1909. – GOMBOS and CIESIELSKI 1983, p. 603, pl. 13, figs. 1-3, 9. – HARWOOD 1988, p. 86, pl. 18, fig. 12.

Occurrence: Rare in the Halal and Wata Formations. Distribution: Late Cretaceous – Early Paleocene of Seymour Island, eastern Antarctic Peninsula (Harwood 1988) and Late Eocene – Early Miocene of southwest Atlantic (Gombos and Ciesielski 1983). Known geologic age: Late Cretaceous – Miocene.

Occurrence: Frequent to rare in the Halal Formation, and very rare in the Wata Formation.

Pterotheca sp.

Plate 1, figure 6 Distribution: Oligocene of the Norwegian Sea (Schrader and Fenner 1976) and Miocene – Pliocene of the Atlantic margin of USA (Abbott 1980).

Occurrence: Rare in the Halal formation.

Known geologic age: Late Cretaceous – Pliocene. Hemiaulus polymorphus var. frigida Grunow 1884

Order: Triceratiales Round and Crawford in Round et al. 1990 Family: Plagiogrammaceae De Toni 1890 Genus: Incisoria Hajós 1975

Plate 2, figure 8

Incisoria lanceolata Hajós and Stradner 1975

Hemiaulus polymorphus var. frigida Grunow 1884. – HUSTEDT 1930, p. 881, fig. 525. – STRELNIKOVA 1974, p. 103, pl. 45, figs. 1-19. – ABBOTT and ANDREWS 1979, p. 245, pl. 4, fig. 15. – HARWOOD 1988, p. 83, pl. 14, fig. 7. – TAPIA and HARWOOD 2002, pl. 5, fig. 8.

Incisoria lanceolata HAJÓS and STRADNER 1975, p. 937, pl. 13, figs. 22, 25; pl. 36, figs. 5. – HARWOOD 1988, p. 84, pl. 12, figs. 18, 19; pl. 17, fig. 4.

Occurrence: Frequent to rare in the Halal Formation and very rare in the Wata Formation. Distribution: Late Cretaceous - Early Paleocene of Seymour Island, eastern Antarctic Peninsula (Harwood 1988) and Middle Miocene of south Carolina and Georgia, USA (Abbott and Andrews 1979).

Occurrence: Rare in the Halal Formation. Distribution: Late Cretaceous of south Pacific Ocean (Hajós and Stradner 1975) and Late Cretaceous of Seymour Island, eastern Antarctic Peninsula (Harwood 1988). Known geologic age: Late Cretaceous. Incisoria sp.

Known geologic age: Late Cretaceous – Miocene.

Occurrence: Rare in the Halal Formation.

Hemiaulus praelegans Jousé 1951

Subclass: Rhizosoleniophycidae Round and Crawford in Round et al. 1990 Order: Rhizosoleniales Silva 1962 Family: Rhizosoleniaceae De Toni 1890 Genus: Rhizosolenia Ehrenberg 1841

Hemiaulus praelegans Jousé 1951. – HAJÓS and STRADNER 1975, p.932, pl. 6, figs. 12, 14. – HARWOOD 1988, p. 83, pl. 13, figs. 19, 20.

Occurrence: Rare in the Halal Formation and very rare in the Wata Formation. Distribution: Late Cretaceous of south Pacific Ocean (Hajós and Stradner 1975) and Late Cretaceous - Early Paleocene of Seymour Island, eastern Antarctic Peninsula (Harwood 1988).

Rhizosolenia cretacea Hajós and Stradner 1975

Known geologic age: Late Cretaceous – Paleocene.

Occurrence: Rare in the Halal and Wata Formations.

Hemiaulus sporalis Strelnikova 1971 Hemiaulus sporalis STRELNIKOVA 1971, p. 48, pl. 3, figs. 1-10. – STRELNIKOVA 1974, p. 95, pl. 41, figs. 1-10; pl. 42, figs. 1-11. – HAJÓS and STRADNER 1975, p. 932, Pl. 29, figs. 5, 6. – HAR-

Rhizosolenia cretacea HAJÓS and STRADNER 1975 , p. 929, pl. 7, fig. 7; pl. 31, figs. 4-6. – BARRON 1985, p. 141, pl. 10.3, fig.1. – HARWOOD 1988, p. 87, pl. 19, fig. 8.

Distribution: Late Cretaceous of south Pacific Ocean (Hajós and Stradner 1975) and Late Cretaceous –Early Paleocene of Seymour Island, eastern Antarctic Peninsula (Harwood 1988).

315


Known geologic age: Late Cretaceous – Paleocene. Subclass: Chaetocerotophycidae Round and Crawford in Round et al. 1990 Order: Chaetocerotales Round and Crawford in Round et al. 1990 Family: Chaetocerotaceae Ralfs in Pritchard 1861 Genus: Chaetoceros Ehrenberg 1844 Chaetoceros diadema (Ehrenberg) Gran 1897 Chaetoceros diadema (Ehrenberg) Gran 1897. – HENDEY 1964, p. 128, pl. 10, fig. 1.

Occurrence: Frequent to rare in the Halal and Wata Formations. Distribution: Common in Arctic Seas, Norwegian Seas, all parts of the North Sea, English Channel, Irish Sea and North Atlantic (Hendey 1964). Known geologic age: Not diagnostic. Chaetoceros didymum Ehrenberg 1845 Chaetoceros didymum Ehrenberg 1845. – HENDEY 1964, p. 125, pl. 17, fig. 2.

Occurrence: Frequent to rare in the Kharita, Halal and Wata Formations. Distribution: All parts of the North Sea, Norwegian and Danish Seas, Baltic, English Channel, and North Atlantic Ocean (Hendey 1964).

983, pl. 6, figs. 1, 2, 4. – BARRON 1985, p.141, pl. 10.2, fig. 13. – HARWOOD 1988, p. 82, pl. 10, figs. 21, 22. Gonothecium odontellum Ehrenberg. – STRELNIKOVA 1974, p. 116, pl. 55, figs. 1-12, pl. 56, figs. 1-5.

Occurrence: Sporadically in the Halal, Wata and Sudr formations. Distribution: Late Cretaceous of western Siberia (Strelnikova 1974), Late Cretaceous of south Pacific Ocean (Hajós and Stradner 1975), Late Cretaceous – Early Paleocene of Seymour Island, eastern Antarctic Peninsula (Harwood 1988), Oligocene – Miocene of the Norwegian Sea (Schrader and Fenner 1976) and Miocene –Pliocene of the Atlantic margin of USA and Virginia, USA (Abbott 1980 and Andrews 1980). Known geologic age: Late Cretaceous – Pliocene. Genus: Xanthiopyxis Ehrenberg 1844 Xanthiopyxis cf. granti Hanna 1927

Plate 2, figure 6 Xanthiopyxis granti Hanna. – HAJÓS and STRADNER 1975, p.927, pl. 4, figs. 16, 17; pl. 26, figs. 4, 5; pl. 35, fig.7.

Occurrence: Frequent in the Halal Formation and very rare in the Wata and Sudr Formations.

Known geologic age: Not diagnostic.

Distribution: Cretaceous of California, USA (Hanna 1927), Upper Cretaceous of South Pacific Ocean (Hajós and Stradner, 1975).

Chaetoceros spp.

Known geologic age: Upper Cretaceous.

Remarks: Many Chaetoceros forms appeared as fragments and could not be identified as to species.

Xanthiopyxis oblonga Ehrenberg 1844

Occurrence: Common to rare in the examined Formations. Genus: Goniothecium Ehrenberg 1841 Goniothecium odontella Ehrenberg 1844 Goniothecium odontella Ehrenberg 1844. – HAJÓS and STRADNER 1975, p. 935, pl. 10, figs. 11-12. – SCHRADER and FENNER 1976, p.

Xanthiopyxis oblonga Ehrenberg 1844. – SCHRADER and FENNER 1976, p. 1003, pl. 39, figs. 9, 10; pl. 40, fig. 5.

Occurrence: Frequent in the Halal Formation and very rare in the Wata and Sudr Formations. Distribution: Cretaceous of California, USA (Hanna 1927), Miocene of the Norwegian Sea (Schrader and Fenner 1976) and

PLATE 1 All figures magnified ´1200, except figures.1-3 ´630. 1-5 Amblypyrgus campanellus Gersonde and Har-

wood;

Gersonde;

6 Pterotheca sp.;

10 Gladius antiquus Forti and Schulz;

7 Crossophialus gyroscolus Harwood and Ger-

11 Gladius antiquus var. tenuis;

sonde; 8 Hyalotrochus radiatus Harwood and Ger-

sonde; 316

9 Hyalotrochus incompositus Harwood and

12 Calyptosporium exasperatum.

Abdelfattah Ali Zalat

micropaleontology, vol. 59, nos. 2–3, 2013

Plate 1

317


Middle Eocene – Oligocene of south Atlantic, Equatorial Pacific and Indian Oceans (Fenner 1984). Known geologic age: Cretaceous – Miocene. List of reworked taxa

Actinocyclus octonarius Ehrenberg 1837 Actinoptychus clevei A. Schmidt 1886 Asteromphalus symmetricus Schrader and Fenner 1976 Chaetoceros diadema (Ehrenberg) Gran 1897 Chaetoceros didymum Ehrenberg 1845 Cocconeis sp. Coscinodiscus argus Ehrenberg 1838 Coscinodiscus descrescens Grunow 1878 Coscinodiscus eccentricus Ehrenberg 1840 Coscinodiscus gigas var. diorama (Schmidt) Grunow 1884 Coscinodiscus lineatus Ehrenberg 1838 Coscinodiscus nitidus Gregory 1857 Coscinodiscus nodulifer A. Schmidt 1878 Coscinodiscus oculus-iridis Ehrenberg 1839 Coscinodiscus oligocenicus Jousé 1974 Coscinodiscus perforatus Ehrenberg 1844 Denticula sp. Dossetia hyalina Andrews 1976 Dossetia temperei Azpeitia 1911 Endictya oceanica Ehrenberg 1845 Epithemia adnata (Kützing) Brébisson 1838 Grammatophora marina (Lyngbye) Kützing 1844 Hemiaulus arcticus Grunow 1884 Hemiaulus danosuecicus Cleve-Euler 1951 Hemidiscus cuneiformis Wallich 1860 Navicula sp. aff. pennata Schmidt 1874 Podosira stelliger (Bailey) Mann 1907 Pyrgupyxis oligocaenica (Jousé) Schrader 1976 Rhaphoneis angulata Fenner 1976 Rhaphoneis parilis Hanna 1932 Rhaphoneis scalaris Ehrenberg 1845 Rhaphoneis surirella (Ehrenberg) Grunow in Van Heurck 1880 Rhizosolenia barboi Brun 1894 Rhizosolenia hebetata forma semispina (Hensen) Gran 1908 Rhizosolenia praebarboi Schrader 1973 Rhizosolenia styliformis Brightwell 1858

Riedelia claviger (A. Schmidt) Schrader and Fenner 1976 Sceptroneis sp. Stephanopyxis schenkii Kanaya 1959 Terpsinoe americana (Bailey) Ralfs 1861 Thalassionema hirosakiensis (Kanaya) Schrader 1973 Thalassionema lineatum Jousé 1971 Thalassionema nitzschioides Grunow in Van Heurck 1881 Thalassionema nitzschioides var. parva Heiden 1928 Thalassiosira oestrupii (Ostenfeld) Proskina-Lavrenko 1956 Thalassiothrix longissima Cleve and Grunow 1880 Xanthiopyxis papillosus Hajós 1968 Xanthiopyxis sp. CONCLUSION

The subsurface Cretaceous sedimentary succession in the Raad-1 Well, north-eastern Sinai is differentiated into four rock units, which are arranged from older to younger: Kharita, Halal, Wata and Sudr formations. Diatom analysis of forty-four ditch and core samples collected from these rock units yielded well to moderately preserve 87 marine diatom taxa belonging to 37 genera. The recognized diatom assemblage is composed mainly of mixed Cretaceous and Tertiary taxa. Most of the encountered diatom species have long stratigraphic ranges, except 39 taxa are belonged to Cretaceous period. Two diatom biozones are recognized based on the distribution and stratigraphic occurrence of the Cretaceous diatoms in the studied section. Amblypyrgus campanellus Zone characterizes the lower part of the succession (Kharita Formation), and point to Lower Cretaceous. Gladius antiques Zone comprizes Halal, Wata and the lower part of Sudr Formations, and denotes the Upper Cretaceous age. The precise location of the Cenomanian - Albian boundary is determined based on the last occurrence of Albian diatom taxa such as Amblypyrgus campanellus Gersonde and Harwood, Crossophialus gyroscolus Harwood and Gersonde, Hyalotrochus radiatus Harwood and Gersonde, Hyalotrochus incompositus Harwood and Gersonde, and first appearance of Late Cretaceous diatom forms belonging to the genera Gladius, Aulacodiscus, Acanthodiscus, Actinoptychus, Coscinodiscus, Hemiaulus, and Stephanopyxis. The paleoenvironmental construction of the Cretaceous sediments of the Raad-1 well, north-eastern Sinai is interpreted using the microfloral content and lithological characters of the examined section. It can be

PLATE 2 All figures magnified ´1200. 1 Stephanopyxis hannai Hajós

8 Hemiaulus polymorphus var. frigida Grunow;

2 Stephanopyxis schenckii Kanaya;

9 Hemiaulus polymorphus Grunow;

3 Stephanopyxis grunowii Gove and Staurt; 4-5 Actinoptychus packi Hanna;

318

10 Hemiaulus arcticus Grunow; 11 Hemiaulus bipons (Ehrenberg) Grunow;

6 Xanthiopyxis cf. granti Hanna;

12 Hemiaulus echinulatus Jousé;

7 Hemiaulus kittonii Grunow;

13 Hemiaulus danosuecicus Cleve-Euler.

Abdelfattah Ali Zalat

micropaleontology, vol. 59, nos. 2–3, 2013

Plate 2

319


concluded that a shallow marine environment prevailed during the Early Cretaceous, which changed to be more deeply environment in the Late Cretaceous. ACKNOWLEDGMENTS

I would like to thank Prof. A. Allam, Helwan University and Dr. Nadia Zarif, General Petroleum Company, Egypt for providing me the investigated samples.

Cenomanian–Turonian exposures in West–Central Sinai, Egypt. Revue de Micropaléontologie, 31: 243–262. DAVIES, A., 2006. “High resolution palaeoceanography and palaeoclimatology from mid and high latitude Late Cretaceous laminated sediments.” Unpubl. PhD thesis, University of Southampton, School of Ocean and Earth Science. DELL’AGNESE, D. J. and CLARK, D. L., 1994. Siliceous microfossils from the warm Late Cretaceous and early Cenozoic Arctic Ocean. Journal of Paleontology, 68: 31–47.

REFERENCES ABBOTT, W. H., 1980. Diatoms and stratigraphically significant silicoflagellates from the Atlantic margin coring project and other Atlantic margin sites. Micropaleointology, 26: 49–80.

EGPC, 1964. Oligocene and Miocene rock stratigraphy of the Suez region. Cairo: Egyptian General Petroleum Cooperation, 142 pp.

ABBOTT, W. H. and ANDREWS, D. W., 1979. Middle Miocene marine diatoms from the Hawthorn Formation of the Ridgeland Trough, South Carolina and Georgia. Micropaleointology, 25: 225–271.

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