Journal of African Earth Sciences 159 (2019) 103580 Contents lists available at ScienceDirect Journal of African Earth Sciences journal homepage: www.elsevier.com/locate/jafrearsci New findings of eocene nautiloids from north Western Desert, Egypt T ∗ Mohamed F. Aly , Sherief A. Sadek Geology Department, Faculty of Science, Cairo University, Giza, Egypt ARTICLE INFO ABSTRACT Keywords: The Tertiary marine succession of the north Western Desert, Egypt, is rich in vertebrates, molluscs and other Nautiloids invertebrates, but nautiloids are less abundant. Five nautiloid species, are reported herein: Eutrephoceras sp., Sharks Aturoidea parkinsoni, Aturia aturi, Aturia cf. alabamensis and, Aturia cf. gujaratensis. They are collected and Tertiary identified from the lowermost part of Gebel Minqar Tebaghbagh area. The studied section is located 90 km to the Siwa oasis east of Siwa Oasis at the south of western side of the Qattara Depression. The recovered specimens are mostly Western desert crushed, partially fragmented internal molds, mostly showing badly preserved suture lines and dorsal to sub- Egypt central siphuncles. The nautiloids occur in abundance in random orientation through a clastic-dominated suc- cession. They are mostly represented by middle-aged and mature specimens. Recently, the lower part of Gebel Tabaghbagh was assigned to Late Eocene. 1. Introduction southwest of Aswan city, south Western Desert, Hewaidy and Azzab, 2002 described and identified five nautiloid species of the Paleocene The north western Desert of Egypt is almost a plain area. The only age from the Kurkur Formation. Those are Deltoidonautilus polymorphus characteristic features are the Marmarica Limestone plateau and the Hewaidy and Azzab, Deltoidonautilus sp. 1, Deltoidonautilus sp. 2, Eu- Qattara Depression where lower and upper Miocene beds are well ex- trephoceras desertorum (Quaas) and Cimmomia sp. van Vliet and Abu el posed. The area of Gebel Minqar Tabaghbagh is a newly discovered Khair (2010) reported the co-occurrence of the Late Eocene echinoid fossiliferous area in that region. Gebel Minqar Tabaghbagh is a perfect Conoclypeus sp. and nautiloid shells of Aturia sp. from the west-south Miocene outcrop of 150 m thick located 100 km east of Siwa Oasis. It west part of Qattara Depression. Hewaidy et al. (2019) described six represents the southern scarp of the plateau very near to the southern Paleogene nautiloid species from the Kharga Oasis, Western Desert tip of Qattara Depression (Fig. 1). However no much attention has been Egypt (five of Paleocene and one of Eocene ages). given for such rough area. Few workers have stepped later on; Sadek The aim of the present work is to record and systematically describe (2005), van Vliet and Abu el Khair (2010), Antar (2011) and Zalmout a new occurrence of some nautiliod species from the Tertiary rocks of et al. (2012). Egypt. These nautiliods are recovered from the lowermost glauconitic The basal part of section (17.5 m thick) is mainly shales and siltstones beds at the base of Minqar Tabaghbagh, east of Siwa Oasis. greenish sandy siltstone beds with minor limestone intercalations. The glauconitic sandy siltstones are characterized by abundance of several 2. Geologic setting nautiloid internal molds. These beds are highly abundant with the Late Eocene vertebrates, including giant archaic whales, sirenian remains The described nautiloids herein was collected and identified from and shark teeth (van Vliet and Abu el Khair, 2010; Antar, 2011; 17.5 m thick interval of glauconite and glauconitic siltstone and sand at Zalmout et al., 2012). the base of Minqar Tabaghbagh (Fig. 2). That is similar to the base of Few occurrences of Tertiary nautiloids have been reported from the Daba'a Formation that described by Norton (1967). The glauconitic Egypt (see Table 1). Cuvillier (in Hume, 1965) recorded the lower Eo- sand and siltstone facies appears to be continuous laterally in an east- cene Nautilus cf. mokattamensis Foord from Gebel Gurna. Aturia ziczac west direction (Shata, 1955; Albritton et al., 1990; Zalmout et al., (Sowerby) was described by Zittel as being associated with the Ypresian 2012). Albritton et al. (1990) stated that the Daba'a Formation is pre- molluscs between Dakhla and Farafra Oasis (in Hume, 1965). Fleming dominantly clastic in origin and contains calcareous sandstone and (1945) identified the Hercoglossa aegyptiaca Foord from the Ypresian- sandy limestone, and is a lateral equivalent of the Qasr el-Sagha For- Lutetian succession of Gebel Moqattam. In the area of Kurkur Oasis, mation, Fayum farther to the east. ∗ Corresponding author. E-mail addresses: [email protected] (M.F. Aly), [email protected] (S.A. Sadek). https://doi.org/10.1016/j.jafrearsci.2019.103580 Received 12 June 2019; Received in revised form 12 July 2019; Accepted 7 August 2019 Available online 08 August 2019 1464-343X/ © 2019 Elsevier Ltd. All rights reserved. M.F. Aly and S.A. Sadek Journal of African Earth Sciences 159 (2019) 103580 Fig. 1. Location map of the study area (Modified after Zalmout et al., 2012). Table 1 Paleogene nautiloids species reported from Egypt. All are from the Western Desert unless otherwise noted. Species Age Reported by Distribution in Egypt Nautilus cf. mokattamensis Foord 1891 Lower Eocene Cuvillier (in Hume, 1965) Mokattam, Cairo Aturia ziczac (Sowerby 1812) Zittel (in Hume, 1965) Dakhla and Farafra Oasis Hercoglossa aegyptiaca Foord 1891 Fleming (1945) Mokattam, Cairo Deltoidonautilus polymorphusHewaidy and Azzab, 2002 Paleocene Hewaidy and Azzab, 2002 Kurkur Oasis, southwest of Aswan city, south Western Desert Deltoidonautilus sp. 1 Deltoidonautilus sp. 2 Eutrephoceras desertorum (Quaas) Cimmomia sp Cimomia kurkurensis Hewaidy et al., (2019) Paleocene Hewaidy et al. (2019) Kharga Oasis, Western Deltoidonautilus hassani Hewaidy et al., (2019) Desert, Egypt Eutrephoceras desertorum (Quaas, 1902) Aturia sp. Aturoidea sp. Cimmomia sp Eocene Eutrephoceras sp. Late Eocene Present work Siwa Oasis, North Western Desert Aturoidea parkinsoni (Edwards, 1849) Aturia aturi (Basterot, 1825) Aturia cf. alabamensis (Morton, 1834) Aturia cf. gujaratensis Halder (2012) Stratigraphically, Said (1990) named the Upper Eocene shales and probably of Priabonian (beds 7–8; Fig. 2). The exposures are small hills limestones found in the southern part of the western margin of the of glauconitic sand and siltstones with iron oxides capped by gray shale. Qattara Depression as Daba'a Formation. In the west, the Eocene strata are overlained by Miocene strata, which subdivided into the Moghra, Mamura, Gebel Khashab and Marmarica formations (Tawadros, 2001). 3. Material and methods In the east, the Miocene strata unconformably overlie Oligocene rocks. The depression floor is at many places covered with Quaternary aeolian The present work is focused on the Eocene nautiloids collected from and alluvial fan deposits that form a sabkha deposits (van Vliet and Abu Gebel Tabaghbagh, north Western Desert. This material consists of el Khair, 2010). some 35 nautiloid internal molds, mostly replaced by Barite. They are The studied section in the area under study is 62 m thick and can be mostly crushed, portions of the body chamber, showing badly preserved subdivided into two major units. The upper Mamura Formation (Lower suture lines and dorsal to subcentral siphuncles in poorly preserved Miocene) and the lower Daba'a Formation (Upper Eocene-Oligocene). specimens. The nautiloids occur in abundance in random orientation The described nautiloids are collected from the base of the Tabaghbagh through the glauconitic siltstone beds rich in iron oxide nodules. They escarpment to the west-south west part of Qattara Depression. All the are mostly represented by middle-aged and mature specimens. fossils came from one level, about 70 m below the sea level that is most Conventions: Dimensions are given in millimeters: D = diameter; Wb = whorl breadth; Wh = whorl height; U = umbilicus. Figures in 2 M.F. Aly and S.A. Sadek Journal of African Earth Sciences 159 (2019) 103580 Measurements (in mm): Specimen D Wb Wh Wb/Wh U Siwa/01/CUGM 44 (100) 22 (50) 26 (59) 0.85 Occluded Siwa/02/CUGM 55 (100) 27 (49) 32 (58) 0.84 Occluded Description. The studied specimens are juveniles consisting only of one or two whorls. Broadly lenticular internal molds. Sculpture of fine, close-set equal spiral lirae. Siphuncle is completely not preserved on the studied specimens. Umbilicus closed in the described specimens. The suture line appears poorly preserved but straight to some extent. Remarks. The studied specimens are very similar to the Eutrephoceras dekayi (Morton, 1834) from North America, that figured by Landman et al. (1983, Fig. 4a) in their smooth ornamentation of shell and the sharply rounded flanks along with the broadly rounded venter. Eutrephoceras sp. has been recorded from the Paleocene of Victoria by Teichert (1947) and by McGowran (1959) from the Early and Middle Miocene of South Australia and from the Middle Miocene of Victoria, respectively. The incomplete specimens and the preservational state, along with the bad preservation of the suture lines supporting open nomenclature of the present species. Family Hercoglossidae Spath, 1927. Genus Aturoidea Vredenburg, 1925 Type-species: Nautilus parkinsoni Edwards (1849). Aturoidea parkinsoni (Edwards, 1849) Fig. 3. 1-4 1849 Nautilus parkinsoni Edwards, S. 49, Taf. 7. 1951 Aturoidea aff. parkinsoni Edwards, Miller, Fig. 15 A. Material. Four complete internal molds (Siwa/03/CUGM - Siwa/06/ CUGM), and five crushed and incomplete specimens; all specimens are compressed, deformed and replaced completely with barite (Siwa/07/ CUGM - Siwa/11/CUGM). Measurements (in mm). Specimen D Wb Wh Wb/Wh U Fig. 2. Columnar Stratigraphic section of Daba'a Formation showing the nau- Siwa/03/CUGM 42 (100) 25 (59) 23 (55) 1.08 9 (21) tiloid beds. Siwa/04/CUGM 49 (100) 27 (49) 23 (58) 1.17 14 (28) Siwa/05/CUGM 70 (100) 42 (60) 50 (71) 0.84 Occluded Siwa/06/CUGM 77 (100) 37 (48) 43 (56) 0.86 Occluded brackets are dimensions as a percentage of the diameter. Depository. All the collected specimens are housed at the Museum of the Geology Department, Cairo University, Giza, Egypt and are Description.