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New Alveolinoidea (Foraminifera) from the Cenomanian of Oman
Cretaceous Research 50 (2014) 344e360
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New Alveolinoidea (Foraminifera) from the Cenomanian of Oman Piuz a, *, Christian Meister a, Vicent Vicedo b Andre a Departement de g eologie et pal eontologie, Mus eum d'histoire naturelle de la ville de Gen eve, Route de Malagnou 1, Case Postale 6434, CH-1211 Gen eve 6, Switzerland b Museu de Ci encies Naturals de Barcelona (Paleontologia), Parc de la Ciutadella s/n, 08003 Barcelona, Spain
a r t i c l e i n f o
a b s t r a c t
Article history: Received 5 February 2014 Accepted in revised form 11 April 2014 Available online 21 June 2014
The first alveolinoidean appearing in the Cenomanian Natih Formation of Oman (Adam foothills and southern edge of Jabal Akhdar) are studied in detail. Morphological analysis results in the creation of one new family, Myriastylidae, two new genera, Myriastyla and Alveocella, and four new species, M. omanensis, M. grelaudae, A. wernliana, and Cisalveolina nakharensis. These four new taxa have a short stratigraphic extension restricted to the uppermost part of Natih E unit and are dated early middle Cenomanian by neighboring foraminifers and ammonite levels. © 2014 Elsevier Ltd. All rights reserved.
Keywords: Tethys Oman Natih Cenomanian Foraminifera Alveolinoidea
1. Introduction During middle Cretaceous, wide shallow-water carbonate platform systems developed on the Arabian plate. In Oman, this succession was described as the Natih Formation and is classically attributed to the upper Albian to lower Turonian (Simmons and Hart, 1987; Smith et al., 1990; Scott, 1990; Kennedy and Simmons, 1991; Philip et al., 1995; Van Buchem et al., 2002; Homewood et al., 2008). The Natih Fm. shows rich associations of large foraminifera that changes through time and characterizes different lithostratigraphical units in which that formation is subdivided. One of the most abundant and important group of larger foraminifera in the Natih Fm. is the Alveolinoidea (superfamily Alveolinoidea Ehrenberg, 1839). The Late Cretaceous alveolinoids of the Caribbean and western Tethys paleobioprovinces are well known ^cheux, 1984, (see Reichel, 1933, 1937, 1941, 1947; Colalongo, 1963; Pe 2002; Schroeder and Neumann, 1985; Hottinger et al., 1989; Fleury and Fourcade, 1990; Calonge et al., 2002; Vicedo et al., 2009, 2011, 2013; Vicedo and Serra-Kiel, 2011 among others), but the representative of this group in the south and southwest margin of the Tethys call for detailed architectural studies.
* Corresponding author. Tel.: þ41 22 418 63 65. E-mail addresses: [email protected] (A. Piuz), [email protected] (C. Meister), [email protected] (V. Vicedo). http://dx.doi.org/10.1016/j.cretres.2014.04.009 0195-6671/© 2014 Elsevier Ltd. All rights reserved.
Numerous specimens of alveolinoids appearing in the Omani Natih Fm. series have been analyzed and revealed notable differences with other Cenomanian genera and species. The aims of this paper are to describe the new taxa of alveolinoids found in the studied material of Oman, and give a tentative age and distribution considering the biostratigraphical and paleobiogeographical context. 2. Material and methods The material of this study was collected in two field trips in Oman, which were carried out in 2009 and 2012. The Omani Natih Fm. is very well exposed in extensive outcrops in the northern part of the country, particularly in the southern side of chennec et al., Jabal Akhdar and in the Adam Foothills (Be 1992a,b). Fig. 1 gives the geographic location of studied field sections (Fig. 2). They are located in Jabal Madar, Jabal Madmar, Jabal Khaydalah and Jabal Qusaybah or Fitri (Adam foothills), plus Wadi Mi'Aidin and Wadi Nakhr (southern side of Jabal Akhdar). Larger foraminifera were found in hard limestone mainly made up of muddy microfacies (Fig. 3). Several thin sections were made in order to develop the detailed architectural analysis (nomenclature follows Hottinger, 2006). More than a thousand sections of alveolinoids have been photographed and compared, coming from thin section as well as polished rock samples. The material figured in this paper (Table 1) is housed in the micropaleontological
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Fig. 1. Geographical and geological setting of the studied localities.
um d’histoire naturelle de Gene ve” (MHNG collections of the “Muse ncies Naturals de Barcelona” (MGB numbers) and “Museu de Cie numbers). Ammonites (Meister and Piuz, in prep.) are housed in the um d'histoire naturelle de Gene ve”. “Muse 3. Geological settings During the Cretaceous, the Sultanate of Oman was part of an extensive carbonate platform complex of 1000 km wide and 1200 m thick (Droste and Van Steenwinkel, 2004). The Aptian (Granier, 2008) to Turonian Wasia group (defined by Steineke and Bramkamp, 1952) consist of the Nahr Umr Formation (defined by Owen and Nasr, 1958) at the base, and the Natih Formation (introduced by Glennie et al., 1974 as substitute to the “Wasia Limestone Formation” used formerly, e.g. Tschopp, 1967) at the top. The Natih Fm. rests conformably on the Nahr Umr Fm. and is chennec overlain in regional unconformity by the Muti Fm. (Be et al., 1992a). Intense erosion has removed the Natih Fm. in the chennec et al., 1992a). northeast of Jabal Akhdar and Saih Hatat (Be The upper Albian/Turonian Natih Formation consists of mainly mud-supported and some grain-supported limestone (with local rudist development) alternating with intraplatform basin organic rich calcareous shales. Deposition was interrupted several times by subaerial exposure with emersion and incision (Immenhauser laud et al., et al., 2000; Droste and Van Steenwinkel, 2004; Gre 2006, 2010; Homewood et al., 2008). Outcrop sedimentology of the Natih Fm. is detailed by Homewood et al. (2008) with an extensive list of references.
3.1. Lithostratigraphy chennec et al. For the geological maps of the studied area, Be (1992a,b) separated the Natih Formation into a lower (thickbedded shallow-marine limestone) and an upper (clayey and foetid limestone with planktonic foraminifera) mappable member. The upper one corresponded to the Fitri Formation of Rabu (1988), a term now abandoned. On their side, based on subsurface log signature, petroleum geologists subdivided the Natih Fm. into seven informal “members” (reservoir units) designated by the lowercase letters “a” to “g” from top to base (Hughes Clarke, 1988; Scott, 1990). Although labeled in a reverse stratigraphical order, the recombination of these subsurface informal units into outcropping lithostratigraphic “members” got soon extensively used (e.g. Philip et al., 1995; Van Buchem et al., 1996, 2002, 2011; Homewood et al., 2008). Even if lithological properties and boundaries can locally be confusing (see below), for evident practical reasons we use them here as informal units, in uppercase letters “A” to “G” (as in many previous publications), with reservations due to their informal status and lack of rock outcrop comprehensive description. Well recognizable in the north (southern side of Jabal Akhdar) and in the west of the Adam foothills (Jabal Qusaybah, J. Nadah, J. Salakh, J. Khaydalah, J. Madmar), they gradually lose their distinctive character eastward. Various hard grounds mark disconformities along the Natih Fm., some being easily recognizable in the field (5a, 6a, 7a, 8a in Fig. 2) and commonly used for correlation between sections in the Adam foothills (see Van Buchem et al., 1996, 2002, 2011;
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Homewood et al., 2008). The Natih E-D boundary is marked by a typical distinctive iron enriched ochre layer in most of the field sections (surface 5a of Van Buchem et al., 1996, 2002) and indicates the last occurrence of the new alveolinoids described in this paper. This major disconformity allows good correlations in laud et al., the studied area (Van Buchem et al., 1996, 2002; Gre 2006). The ammonites (Acompsoceras beds and Neolobites beds, see below) found along the transect (Fig. 2) and used to date the alveolinoids, allow some observations about lithostratigraphical units Natih A and B. Following the sedimentary succession between the two biostratigraphical markers, the thick series of intrashelf basin lumachellic interbedded calcareous shale and limestones (Natih B) in J. Qusaybah, gets thinner eastward and passes to shelf facies environment with corals in J. Khaydalah and J. Madmar above which some lumachelles are present just below the Neolobites beds (Fig. 2). In the eastern sections (J. Khaydalah, J. Madmar), above the top of Natih C (above surface 8a, Fig. 2), the lithofacies obviously differs from Natih B of the western sections (J. Qusaybah, J. Nadah). Some authors (e.g. Van Buchem et al., 2002, Fig. 8, Homewood et al., 2008, enclosure III) seem, eastward, to attribute it to Natih A. Does it correspond (facies e fossil content e age) to the Natih A known in the western sections? Ammonite data give new constrains for these correlations, but a comprehensive definition of the outcropping Natih lithostratigraphic units is now necessary before going any further on this point. 3.2. Biostratigraphy The age of the strata enclosing the new taxa is based on ammonites and foraminifers which give the following biostratigraphical data. 3.2.1. Ammonites The Natih Formation is locally dated by ammonite bearing levels (Kennedy and Simmons, 1991; Van Buchem et al., 1996, 2002; Meister and Piuz, 2013; Meister and Piuz, in prep.), but no ammonites have been found together with the new alveolinoids. Though, two ammonite levels (see below) refine dating these strata. The Neolobites beds are found in the same field sections (Fig. 2) as the new alveolinoids, while the Acompsoceras beds are found in lithostratigraphically correlated neighboring field sections (see remarks above) where the strata with the new alveolinoids are not outcropping. Neolobites beds: The well-known Neolobites beds (found in Natih B-A in Jabal Madmar, Jabal Khaydalah, Jabal Salakh and Jabal Qusaybah, Fig. 2, Meister and Piuz, in prep.) contain the higher Neolobites found in our series and indicate the earliest part of the late Cenomanian, several tens of meters above the samples concerned in this study (see Fig. 2). These beds contain Neolobites vibrayeanus (Orbigny), Turrilites costatus Lamarck, Calycoceras guerangeri (Spath), Cunningtoniceras sp. and a nautilus: Angulithes sp. This ammonite association is recognizable along the southern Tethys margin from Morocco to Oman and accurately indicates the lower part of the Calycoceras guerangeri Zone (Meister and Piuz, 2013 cum biblio). Acompsoceras beds: The slightly older Acompsoceras beds (found in the lowest part of Natih B in Jabal Salakh, Jabal Qusaybah, Fig. 2; Meister and Piuz, in prep.) indicate a middle Cenomanian age. Indeed, these beds contain Acompsoceras renevieri (Sharpe) and some Engonoceratidae (Neolobites). Acompsoceras renevieri, recorded from Europe, Russia, north and west Africa, Madagascar and Arabian peninsula, is a rather long-ranging taxon that corresponds to a time interval from the early Cenomanian
(Mantelliceras mantelli Zone) to the middle Cenomanian (Acanthoceras rhotomagense Zone) (see Kennedy and Juignet, 1993). re is known in the southern Tethys Neolobites fourtaoui Pervinquie margin and ranges from middle Cenomanian (Acanthoceras rhotomagense e A. jukesbrownei Zones) to the base of the late Cenomanian (Calycoceras guerangeri Zone).
3.2.2. Foraminifers Recent studies regarding microfossils of the Natih Fm. include those of Glennie et al. (1974), Simmons and Hart (1987), Rabu (1988), Smith et al. (1990), Kennedy and Simmons (1991), chennec et al. (1992a,b), Philip et al. (1995). The new species Be detailed in this study are the first alveolinoids appearing in the upper part of Natih E unit. They disappear together with most orbitolinids around or at the surface 5a (Natih E-D boundary) in all sections except Wadi Mi'Aidin where orbitolinids are found even above the last occurrence of alveolinids. Their stratigraphic extension comprises the distinctive overlap of orbitolinids and alveolinids (O.O.A. considered for the Adam Foothills) noted by Smith et al. (1990 p. 38; see also Simmons and Hart, 1987), in the upper part of Natih E unit. This interval is proposed as middle Cenomanian, mainly based on the presence of (little illustrated) Merlingina cretacea and Chrysalidina gradata which are (following the range chart of Schroeder and Neumann, 1985) absent during the early Cenomanian (see however e.g. Saint-Marc, 1977, 1982, for C. gradata, and Hamaoui, 1966, 1979, for M. cretacea). Other foraminifers used by Smith et al. (1990) to date this O.O.A. interval are middle Cenomanian alveolinids some of which (partially illustrated) are most probably the new taxa described in this paper, while their questionable Pseudorhapydionina laurinensis is not illustrated. In our field sections (Fig. 2), doubtful sections of M. cretacea are present together with C. gradata some meters below the first occurrence of the new alveolinoids. Associated with the new alveolinoids, the ramp limestone facies reveal, Biconcava bentori, Chrysalidina gradata, Cuneolina gr pavonia, Dicyclina sp., Haplophragmoides sp., Montcharmontia compressa, Nezzazata spp. (N. gr simplex, N. gr gyra), various orbitolinids (under study), diverse and abundant miliolids (Quinqueloculina spp.), Spiroloculina spp, Spiroplectammina sp., Trocholina arabica, and various dasyclad algae. The O.O.A. is followed (during Natih E-D-C) by other alveolinid species close to Decastroia Vicedo & Serra-Kiel which disappear toward the Natih C/B boundary in all sections (probably due to paleoenvironmental changes) except in Wadi Mi'Aidin where they are found higher in the series.
3.3. Age of the new alveolinoids The biostratigraphical data given above by ammonites and foraminifers allow proposing an early middle Cenomanian age (Acanthoceras rhotomagense ammonite zone) for the stratigraphic extension of the new alveolinoids. Stratigraphically below the new species, the first occurrence of M. cretacea and C. gradata are the main arguments (see above) to place the base of the middle Cenomanian, while the Acompsoceras beds, close to the last alveolinids, are not younger than the A. rhotomagense ammonite zone. Regarding the thickness of the sedimentary pile between these two points, the latter zone seem especially well developed in the Natih Fm. Note however that the data of Bulot et al. (in prep), as presented in Homewood et al. (2008, Fig. 5), propose the loweremiddle Cenomanian boundary at the Natih E-D boundary, data that if proven will change the age of the new species to (latter part? of the) early Cenomanian.
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Fig. 2. Field sections and localization of studied samples.
3.4. Paleobiogeography At present, the new specimens described below are only known from northern Oman (Jabal Akhdar and Adam foothills) which suggest that the Arabian platform could be a distinctive paleobioprovince during Cenomanian times, at least for porcellaneous complex large foraminifera. Endemism in alveolinoids is supported by many studies (e.g. Hottinger et al., 1989; Fleury and Fourcade, 1990; Vicedo et al., 2009). Further studies dealing with alveolinoids of the Middle East Cenomanian are required to develop biostratigraphy and paleobiogeography and to understand the relationships with other representatives of this group in the western
Tethys. In particular, confirming the presence or absence of Praealveolina Reichel, 1933, in Oman, genus widely cited in several previous papers and company's reports but not identified in the materials examined in this study. The Decastroia morphotypes, appearing in upper stratigraphical levels (Decastroia spp. in Fig. 2), merit to be studied as well, and compared to those of the type locality of Socotra (Yemen). 4. Systematic descriptions rouard, 1896 Suborder Miliolina Delage and He Superfamily Alveolinoidea Ehrenberg, 1839
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Fig. 2. (continued).
Family Alveolinidae Ehrenberg, 1839 Alveocella new genus Etymology: “With small alveoles”, from the Latin [alueus] cavity, and [cella] suffix used as diminutive. Type species: Alveocella wernliana new species. Diagnosis: Oval to fusiform shells, wall porcelaneous, successive chambers with planispiral involute coiling, apertural face with two to three rows of apertures extending from pole-to-pole. Chambers are subdivided by septula disposed in an alternate mode from one chamber to the other. Preseptal passage is
constant and always obvious. One to two rows of postseptal alveoles, extending from pole-to-pole, communicate through supplementary foramina with the previous chamber. Differential diagnosis: Alveocella differs from Praealveolina Reichel, 1933 and Archaealveolina Fourcade, 1980 in having alternate septula from one chamber to the next. Alveocella differs from Cisalveolina Reichel, 1941 in having postseptal alveoles. Alveocella is different from Decastroia Vicedo & Serra-Kiel, 2011 by the absence of floors in equatorial area, the alternate mode of the septula and the presence of alveoles. Alveocella has some features in common with the Oligocene Bullalveolina Reichel, 1936 and with the
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CampanianeSantonian Subalveolina Reichel, 1936, especially the alternate mode of the septula, the multiple apertures, and alveoles. Though, Bullalveolina bulloides (d'Orbigny) mainly differs by the distribution of the apertures in the apertural face. Bullalveolina shows main apertures in a lower row and intercalated supplementary apertures above; contrarily, supplementary and main apertures are vertically aligned in Alveocella. Moreover, Bullalveolina differs from Alveocella by its slightly umbilicate subspherical test, the coiling of its first whorls (typically streptospiral), the absence of septula in its first chambers, and its large preseptal passage. Subalveolina also differs from Alveocella by the arrangement of the apertures in the apertural face and by the nature of the alveoles. Subalveolina has one row of main apertures alternating with smaller intercalated apertures which connect with the small postseptal alveoles. In contrast, in Alveocella the main and supplementary apertures are not intercalated, thus, alveoli and chamberlets are aligned. Moreover, Subalveolina has larger alveoles, and supplementary chamberlets that appear below the main floor in polar regions. Alveocella wernliana new species (Figs. 3e7) Etymology: Dedicated to Professor R. Wernli, micropaleontologist at the University of Geneva. Holotype: Specimen illustrated in Fig. 4.6 (sample ap561-h) deposited in the micropaleontological collection of the Natural History Museum of Geneva n MHNG2013-42a
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Paratypes: Specimens illustrated in Fig. 4.1 (sample ap561-i), 4.3 (sample ap561-k), 5.11 (sample ap561-f), deposited in the micropaleontological collection of the Natural History Museum of Geneva n MHNG2013-43, MHNG2013-44a and MHNG2013-45 Type locality: Wadi Nakhr, southern edge of Jabal Akhdar, Oman. Coordinates: N23 09.330 E05712.264 Type level: Upper Natih E unit, lower middle Cenomanian. Diagnosis: Oval to fusiform dimorphic shells. The megalospheric generation starts with a rounded to oval proloculus of 400e460 mm followed by a flexostyle of a quarter of a whorl. Following chambers are arranged planispirally with 7e8 whorls in adult shells. Apertural face has two to three rows of apertures extending from poleto-pole. One row of main foramina connect chamberlets of successive chambers, one or two rows of supplementary foramina connect the postseptal alveoles with the previous chamber. One to two rows of alveoles appear since the second whorl. Axial sections show 11e14 chamberlets per quadrant at the fourth whorl. The maximum equatorial diameter observed is around 2.4 mm and the axial length is 3.6 mm. Larger specimens (up to 6 mm) with similar morphological characteristics are very rare and may belong to the microspheric generation although their juvenarium has not been observed (Fig. 7). Occurrence: This species is actually only known in the upper part of Natih E unit (lower middle Cenomanian) in the southern edge of Jabal Akhdar and Adam foothills, Oman.
Fig. 3. Typical muddy microfacies with alveolinoids in upper Natih E unit. Alveocella wernliana n. gen. n. sp., sample ap397, lower middle Cenomanian, Jabal Madmar, Adam foothills, Oman. See bar for scale.
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Table 1 um d'histoire naturelle de Gene ve” List of the material deposited in the “Muse ncies Naturals de Barcelona” (MGB numbers). (MHNG numbers) and “Museu de Cie Fig. 3 4
5
6
7 8
9
11
No 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 1 2 3 4
Sample
Collection Nr.
AP397-a AP561-i AP561-l AP561-k AP397-a AP561-f AP561-h AP561-c AP384-a M-11 M-11 M-11 M-11 AP384-j AP397-c AP561-i AP561-h AP561-m AP397-f AP397-f AP561-f AP561-n AP561-p AP561-f M11 M11 AP384-i AP384-e AP397-d AP561-o AP561-i AP561-n AP384-c AP561-f AP341-a AP561-b AP561-m AP561-d AP561-p AP561-f AP561-o AP384-j AP384-a AP561-j M-17 AP561-j AP561-k AP561-p AP561-c Ma-10 AP561-m AP561-g M-16 AP561-d AP561-h AP561-b AP561-c AP561-i AP561-i AP561-c AP561-c AP561-c AP561-d AP561-m AP561-c AP561-h AP384-i AP561-c AP561-l AP561-j AP561-i AP561-l AP561-p AP341-h
MHNG2013-52 MHNG2013-43 MHNG2013-50 MHNG2013-44a MHNG2013-52 MHNG2013-45 MHNG2013-42a MHNG2013-53 MHNG2013-54 MGB 59774 LP05.14 MGB 59774 LP01.10 MGB 59774 LP04.11 MGB 59774 LP04.22 MHNG2013-55 MHNG2013-56 MHNG2013-43 MHNG2013-42 MHNG2013-47 MHNG2013-57 MHNG2013-57 MHNG2013-45 MHNG2013-58 MHNG2013-49 MHNG2013-45 MGB 59774 LP03.11 MGB 59774 LP06.11 MHNG2013-46 MHNG2013-59 MHNG2013-60 MHNG2013-61 MHNG2013-43 MHNG2013-58 MHNG2013-62 MHNG2013-45 MHNG2013-63 MHNG2013-64 MHNG2013-47 MHNG2013-65 MHNG2013-49 MHNG2013-45 MHNG2013-61 MHNG2013-55 MHNG2013-54 MHNG2013-66 MGB 59780 LP03.01 MHNG2013-66 MHNG2013-44b MHNG2013-49 MHNG2013-53 MGB, 59824 LP02.11 MHNG2013-47 MHNG2013-51 MGB 59779 LP06.03 MHNG2013-65 MHNG2013-42b MHNG2013-64 MHNG2013-53 MHNG2013-43 MHNG2013-43 MHNG2013-53 MHNG2013-53 MHNG2013-53 MHNG2013-65 MHNG2013-47 MHNG2013-53 MHNG2013-42 MHNG2013-46 MHNG2013-53 MHNG2013-50 MHNG2013-66 MHNG2013-43 MHNG2013-50 MHNG2013-49 MHNG2013-67
Table 1 (continued ) Fig.
Status Paratype Paratype
Holotype 12
13
Paratype
14
Holotype
Paratype
Paratype
No
Sample
Collection Nr.
Status
5 6 7 8 9 10 11 12 13 14 3 4 6 7 8 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 1 2 3 4 5 6 7 8 9 10 11
AP561-g AP561-k M-11 AP561-m AP561-l AP561-f AP561-o AP561-l AP561-d AP561-a AP561-f AP561-j AP561-k AP561-d AP561-f Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 AP341-h AP341-h AP561-l Ma-10 AP561-p AP384-j AP561-f AP384-j AP561-k AP561-m AP561-h
MHNG2013-51 MHNG2013-44 MGB 59774 LP03.01 MHNG2013-47 MHNG2013-50 MHNG2013-45 MHNG2013-61 MHNG2013-50 MHNG2013-65 MHNG2013-68 MHNG2013-45 MHNG2013-66 MHNG2013-44 MHNG2013-65 MHNG2013-45 MGB 59824 LP02.03 MGB 59824 LP03.12 MGB 59824 LP03.16 MGB 59824 LP04.27 MGB 59824 LP05.02 MGB 59824 LP06.08 MGB 59824 LP05.01 MGB 59824 LP04.05 MGB 59824 LP06.10 MGB 59824 LP04.14 MGB 59824 LP05.03 MGB 59824 LP06.12 MGB 59824 LP04.07 MGB 59824 LP06.09 MGB 59824 LP05.06 MGB 59824 LP02.04 MGB 59824 LP02.01 MHNG2013-67 MHNG2013-67 MHNG2013-50 MGB 59824 LP04.27 MHNG2013-49 MHNG2013-55 MHNG2013-45 MHNG2013-55 MHNG2013-44b MHNG2013-47 MHNG2013-42b
Paratype
Paratype Holotype Paratype
Paratype
Paratype
Paratype Holotype Holotype Paratype Holotype Paratype Paratype
Cisalveolina Reichel, 1941 Type species: Cisalveolina fallax Reichel, 1941 Description: Porcelaneous, subglobular shells with planispirally arranged chambers. The simple aperture extends from pole-to-pole and consists in a narrow, slitlike opening. Chamber lumen is subdivided into chamberlets by mean of septula, which alternate in position from one chamber to the next. Preseptal and postseptal passages connect all chamberlets of the same chamber. Cisalveolina nakharensis new species (Figs. 8 and 9) Etymology: In allusion to the origin of the material. Holotype: Specimen figured in Fig. 8.6 (sample ap561-k) deposited in the micropaleontological collection of the Natural History Museum of Geneva n MHNG2013-44b Paratypes: Specimen figured in Fig. 8.10 (sample ap561-m), 9.2 (sample ap561-h) deposited in the micropaleontological collection of the Natural History Museum of Geneva n MHNG2013-47 and MHNG2013-42b
Paratype Holotype
Type locality: Wadi Nakhr, southern edge of Jabal Akhdar, Oman. Coordinates: N23 09.330 E05712.264 Type level: Upper part of Natih E unit, lower middle Cenomanian.
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Fig. 4. Alveocella wernliana n. gen. n. sp. from Wadi Nakhr (1e3, 5e7) and Wadi Mi'Aidin (9e12), southern edge of Jabal Akhdar; Jabal Madmar (4) and Jabal Khaydalah (8), Adam foothills; Oman. Upper Natih E unit, lower middle Cenomanian Scale bar 1 mm. Axial and sub-axial sections. 1e3, 5e7 from sample ap561; 4 from sample ap397; 8 from sample ap384. 9e12, from sample M-11. Abbreviations: alv, alveole; chl, chamberlet; fl, felxostyle; gl, glomerulus; m f, main foramen; p, proloculus; pr p, preseptal passage; s, septum; s f, supplementary foramen; sl, septulum.
Diagnosis: Subglobular shell-shape and dimorphism restricted to the early stages of growth. The megalospheric generation starts with a subspherical proloculus of around 150e200 mm in diameter followed by a flexostyle of at least half a whorl. Following chambers are slightly streptospiral to planispirally arranged. The maximum diameter observed in adult specimens is around 2.3 mm with 7e8 whorls. Septula appear in the first whorl. Postseptal passage is always located in the upper half of chamber height. Axial sections show 8e10 chamberlets per quadrant at the fourth whorl. Specimens of the microspheric generation are less abundant and are characterized by a
small streptospiral glomerulus. Aperture is a basal (interiomarginal) single and low (about ¼ to ½ of the chamber height) slit for the whole width of the test. A short undulating upper lip is often visible. Differential diagnosis: C. nakharensis differs from C. lehneri by its bigger size (2.3 mm of maximum diameter for megalospheric forms of C. nakharensis and 1.9 mm for those of C. lehneri), by its bigger megalosphere (150e200 mm and 110e140 mm respectively), and by its less developed early streptospiral growth (either in megalospheric or microspheric forms).
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Fig. 5. Alveocella wernliana n. gen. n. sp. from Jabal Khaydalah (1, 14e15) and Jabal Madmar (2, 6e7), Adam foothills; Wadi Nakhr (3e5, 8e11) and Wadi Mi'Aidin (12e13), southern edge of Jabal Akhdar; Oman. Upper Natih E unit, lower middle Cenomanian. Scale bar 1 mm. Equatorial and sub-equatorial sections. 1, 14e15 from sample ap384; 2, 6e7 from sample ap397; 3e5, 8e11 from sample ap561; 12e13 from sample M-11. Abbreviations: alv, alveole; fl, flexostyle; chl, chamberlet; p, proloculus; s, septum; s f, supplementary foramen; sl, septulum.
C. nakharensis is different from C. fraasi by having a smaller maximum diameter in megalospheric forms (2.3 mm for the former and 2.7 mm for the latter) and by showing a smaller megalosphere (150e200 mm for C. nakharensis and 200e370 mm for C. fraasi). The early streptospiral chamber arrangement is similar in both species, affecting only to the two first whorls. Occurrence: C. nakharensis is actually only recognized in the upper part of Natih E unit (lower middle Cenomanian) in the southern edge of Jabal Akhdar and Adam foothills, Oman.
Myriastylidae new family Type genus: Myriastyla new genus Diagnosis: Thick, porcelaneous wall and subspherical to axially elongated shells. Adult chambers are involute and planispirally arranged. The endoskeleton consists of longitudinal ridges (in the direction of growth) supporting each one row of pillars. The pillars are aligned in the direction of growth and alternate in position (staggered rows) from pole-to-pole. This structure permits the communication of the protoplasm within the whole
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Fig. 6. Alveocella wernliana n. gen. n. sp. from Jabal Madmar (1), Jabal Khaydalah (5, 14), and Jabal Madar (7), Adam foothills; and Wadi Nakhr (2e4, 6, 8e13), southern edge of Jabal Akhdar; Oman. Upper Natih E unit, lower middle Cenomanian. Scale bar 1 mm for pictures 1e2, 5e8, 14; 0.5 mm for pictures 3e4, 9e13. Equatorial, sub-equatorial and tangential sections. 1 from sample ap397; 2e4, 6, 8e13 from sample ap561; 7 from ap341; 5, 14 from sample ap384. Abbreviations: alv, alveole; m f, main foramen; pr p, preseptal passage; s, septum; s f, supplementary foramen; sl, septulum.
Fig. 7. Tangential section of probable microspheric specimen of Alveocella wernliana n. gen. n. sp. in wackestone microfacies with miliolids, nezzazatids and orbitolinids. Sample ap384, upper Natih E unit (lower middle Cenomanian), Jabal Khaydalah, Adam foothills, Oman. See bar for scale.
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Fig. 8. Cisalveolina nakharensis n. sp. from Jabal Madar (1), Jabal Khaydalah (2), Jabal Madmar (9), Adam foothills; Wadi Nakhr (3, 5e8, 10e11) and Wadi Mi'Aidin (4, 12), southern edge of Jabal Akhdar; Oman. Upper Natih E unit, lower middle Cenomanian. Scale bar 1 mm. Axial and sub-axial sections. 1 from sample ap341; 2 from sample ap384; 3, 5e8 from sample ap561; 4 from sample M-17; 9 from sample Ma-10; 12 from sample M-16. Abbreviations: chl, chamberlet; f, foramen; g, glomerulus; p, proloculus; po p, postseptal passage; s, septum; sl, septulum.
space of the chamber. Multiple apertures arranged in a single row; supplementary apertures may appear polewards. Remarks: The particular architecture of the morphotypes grouped in this new family, showing rows of pillars and planispiral chamber arrangement, has not permitted to attribute them to any of the families described within the superfamily Alveolinoidea. The diagnosis of the family Alveolinidae Ehrenberg, 1839 was emended by Hottinger et al. (1989) who stated “[…]. Chambers subdivided by longitudinal partitions (septula) producing completely separate chamber compartments (chamberlets) connected by an open space below the apertural face (preseptal passage). […]”. As it is pointed out above and in contrast to Alveolinidae Ehrenberg, 1839, and also to Rhapydioninidae Keijzer, 1945, the rows of pillars in myriastylids
facilitate the communication in the whole space of the chamber. No “true” compartments (chamberlets) result from that structure. Thus, a canal-shaped preseptal passage (as in alveolinids) connecting all the chamber lumen is not present as it is supposed that it was not necessary for the living organism. The morphotypes of the new family cannot be attributed to the family Fabulariidae Ehrenberg, 1839, because the latter include specimens with milioline coiling (at least in early growth stages) and a fixed apertural axis (Drobne, 1984; Hottinger et al., 1989). Myriastyla new genus Etymology: From the Greek [murios] very numerous, and [stulos] column, pillar.
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Fig. 9. Cisalveolina nakharensis. n. sp. from Wadi Nakhr (1e13, 15e17), southern edge of Jabal Akhdar; and Jabal Khaydalah (14), Adam foothills; Oman. Upper Natih E unit, lower middle Cenomanian. Scale bar 1 mm, unless specified (7e8, 12). Equatorial, oblique and tangential sections. 1e13, 15e17 from sample ap561, 14 from sample ap384. Abbreviations: chl, chamberlet; po p, postseptal passage; s, septum; sl, septulum.
Type species: Myriastyla omanensis new species Diagnosis: Dimorphic, subglobular to axially elongated shells constituted by numerous chambers with a planispiral-involute arrangement. Subglobular shells show a single row of multiple foramina in interiomarginal position extending from pole-to-pole. Supplementary apertures appear polewards, mainly in axially elongated forms (as in alveolinids). The embryo of the megalospheric generation consists of a subspherical proloculus followed by a flexostyle. The embryo of the microspheric generation has not been observed. Chambers show an endoskeleton that consists of longitudinal ridges supporting each a single row of pillars, as in
some fabulariids. The pillars, disposed in parallel rows aligned in the direction of growth, are alternating in position (staggered rows) from pole-to-pole (Fig. 10). Myriastyla omanensis new species (Figs. 11 and 12) Etymology: In allusion to the origin of the material in the mountains of Oman. Holotype: Specimen illustrated in Fig. 11.3 (sample ap561-p) deposited in the micropaleontological collection of the Natural History Museum of Geneva n MHNG2013-49.
Fig. 10. Basic internal structure of Myriastyla n. gen. Stereograph, shematic, not to scale.
Fig. 11. Myriastyla omanensis n. gen. n. sp. from Wadi Nakhr (1e3, 5e6, 8e14) and Wadi Mi'Aidin (7), southern edge of Jabal Akhdar; and Jabal Madar (4), Adam foothills; Oman. Upper Natih E unit, lower middle Cenomanian. Scale bar 1 mm. Axial, sub-axial and oblique sections. 1e3, 5e6, 8e14 from sample ap561; 4 from sample ap341; 7 from sample M-11. Abbreviations: ch, chamber; fl, flexostyle; m a, main aperture; m f, main foramen; p, proloculus; pi, pillar; pi r, pillar ridge; s, septum; s f, supplementary foramen.
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Fig. 12. Myriastyla omanensis n. gen. n. sp. from Wadi Nakhr (1e8), southern edge of Jabal Akhdar, Oman. Upper Natih E unit, lower middle Cenomanian. Scale bar 1 mm. Equatorial, oblique and tangential sections. All sections from sample ap561. Abbreviations: pi, pillar; pi r, pillar ridge; s, septum; s f, supplementary foramen.
Paratypes: Specimens illustrated in Fig. 11.2 (sample ap561-l), 11.5 (sample ap561-g), deposited in the micropaleontological collection of the Natural History Museum of Geneva n MHNG2013-50 and MHNG2013-51. Type locality: Wadi Nakhr, southern edge of Jabal Akhdar, Oman. Coordinates: N23 09.330 E05712.264. Type level: Upper Natih E unit, lower middle Cenomanian. Diagnosis: Subglobular shells. Dimorphism not observed. Maximum equatorial diameter observed is around 2.5 mm with 7e8 planispiral whorls. The megalospheric generation starts with a subspheric proloculus between 0.13 and 0.3 mm in diameter followed by a short flexostyle canal. The endoskeleton appears early during the ontogeny, starting right after the flexostyle. Microspheric embryo has not been identified. Multiple apertures consist of a row of round openings in interiomarginal position extending from poleto-pole. Supplementary apertures appear at the poles. The chamber roof is thick and always visible. Occurrence: This species is only known in the upper part of the Natih E unit (lower middle Cenomanian) in the southern edge of Jabal Akhdar and Adam foothills, Oman. Myriastyla grelaudae new species (Fig. 13) laud, geologist of EGID Etymology: Given in honour of Carine Gre (Bordeaux, France) with a big experience on the Cenomanian carbonates of Oman. Holotype: Specimen illustrated in Fig. 13.4 (sample Ma-10) deposited in the micropaleontological collection of the Museu de ncies Naturals de Barcelona (MGB 59824 LP04.27). Cie Paratypes: Specimens illustrated in Fig. 13.2, 13.5, 13.9, and 13.17 (all from sample Ma-10) deposited in the micropaleontological
collection of the Natural History Museum of Barcelona (collection numbers MGB 59824 LP03.12, MGB 59824 LP05.02, MGB 59824 LP06.10, and MGB 59824 LP02.01 respectively). Type locality: Jabal Madmar, Adam foothills, Oman, Coordinates: N 22 260 48.8200 , E57 350 28.7400 . Type level: Upper Natih E unit, lower middle Cenomanian. Diagnosis: Dimorphic, axially elongated shells. The megalospheric generation begins with a subspherical proloculus between 0.2 and 0.4 mm in diameter followed by a short flexostyle. The maximum equatorial diameter observed is around 1.7 mm with 8 spiral whorls and an axial length of 3.2 mm. Index of elongation of about 1.8e2. The endoskeleton appears in the first chamber after the flexostyle. The embryo of the microspheric generation has not been adequately observed, but the specimens of this generation have been identified by their size or by the early stages of growth (tightly coiled). The maximum equatorial diameter is up to 1.8 mm with more than 10 whorls and an axial length up to 7 mm. The index of elongation is about 4. Multiple apertures consisting of a row of round openings in interiomarginal position extending from pole-to-pole. Several levels of supplementary apertures appear polewards. Differential diagnosis: Myriastyla grelaudae n. sp. differs from the type species M. omanensis n. sp. mainly by having larger megalospheres (0.2e0.4 mm and 0.1e0.3 mm respectively) and by having more whorls with the same equatorial diameter (at a diameter of 1.7 mm there are 8 whorls in M. grelaudae n. sp. and 6 whorls in M. omanensis n. sp.). Moreover, M. grelaudae n. sp. is axially elongated in contrast to the subglobular morphology of M. omanensis n. sp. Occurrence: This species is only known in the upper part of the Natih E unit (lower middle Cenomanian) in Jabal Madmar (Adam foothills).
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Fig. 13. Myriastyla grelaudae n. sp. from Jabal Madmar, Adam foothills, Oman. Upper Natih E unit, lower middle Cenomanian. Microspheric? (1e2, 17) and megalospheric (3e16) specimens. Scale bar 1 mm. Axial, subaxial and subequatorial sections. All specimens from sample Ma-10. Abbreviations: fl, flexostyle; m f, main foramen; p, proloculus; pi, pillar; pi r, pillar ridge; s, septum; s f, supplementary foramen.
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Fig. 14. Drawings of Myriastyla omanensis n. gen. n. sp. (1e3, 5), M. grelaudae n. sp. (4), Alveocella wernliana n. gen. n. sp. (6-8), Cisalveolina nakharensis n. sp. (9-11). See table 1 for sample number. Abbreviations: alv, alveole; g, glomerulus; m f, main foramen; r, ridge; pi, pillar; po p, postseptal passage; pr p, preseptal passage; pi r, pillar ridge; p, proloculus; s, septum; s f, supplementary foramen; sl, septulum.
5. Conclusions Four new taxa (Fig. 14) appear as the first alveolinoidean in the upper part of the Natih E unit of Oman in the Adam foothills and southern side of Jabal Akhdar. Alveocella wernliana n. gen. n. sp. is characterized by the alternate mode of the septula, and the presence of postseptal alveoles. Cisalveolina nakharensis n. sp. shares many characteristics with C. fraasi but is older in age and has a smaller size. Myriastyla omanensis n. gen. n. sp. and M. grelaudae n.
sp. have a particular endoskeleton that consists of parallel longitudinal (in the direction of growth) ridges supporting each a single row of pillars. Pillars are disposed in staggered rows from pole-topole. Due to their noteworthy morphological features, different from all known alveolinids, it has been necessary to create a new family e Myriastylidae e within the superfamily Alveolinoidea Ehrenberg. The four taxa described in this paper appear together in the same levels and have (at least in the studied sections) a short
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vertical range corresponding to the first alveolinoid e top of Natih E unit (5a typical iron enriched layer). They have an important stratigraphic (lower middle Cenomanian) and paleobiogeographic (hitherto only known in the Middle East) significance, and bring new data to evolution lineages of the alveolinoids. Acknowledgments Best thanks to Prof. R. Wernli and Dr D. Dufour for sharing their knowledge and experience. Thanks to P.-A. Proz for the confection of the numerous thin sections, and to the Paul Broennimann Foundation. Salim Omar Al-Ibrahim, Director General of Minerals (Ministry of Commerce and Industry of Oman) and Ali Al Rajhi, Director of Survey and Research are thanked for their logistic laud are also support. Dr. Philippe Razin and Dr. Carine Gre acknowledged for sharing their expertise in the Omani carbonate deposits and logistic support during field work. Thanks to Prof. Josep Serra-Kiel for his very useful comments about alveolinids. Thanks to an anonymous reviewer, Prof. B. Granier and the editor in chief handling this manuscript E. Koutsoukos for their helpful remarks and comments. References chennec, F., Roger, J., Le Me tour, J., Wyns, R., 1992a. Geological map of Seeb, Sheet Be NF 40-03, scale 1/250 000, with Explanatory notes. Sultanate of Oman, Ministry ans, France, of Petroleum and Minerals, Directorate of Minerals, BRGM, Orle pp. 1e104. chennec, F., Wyns, R., Roger, J., Le Metour, J., Chevrel, S., 1992b. Geological map of Be Nazwa, Sheet NF 40-07, scale 1/250 000, with Explanatory notes. Sultanate of Oman. Ministry of Petroleum and Minerals, Directorate of Minerals, BRGM ans, France, pp. 1e91. Orle Calonge, A., Caus, E., Bernaus, J.M., Aguilar, M., 2002. Praealveolina (Foraminifera) species: a tool to date Cenomanian platform sediments. Micropaleontology 48 (1), 53e66. Colalongo, M.L., 1963. Selliaveolina viallii n. gen. n. sp. di Alveolinide Cenomaniano dell'Appennino meridionale. Giornale di Geologia 30 (2), 361e370. Drobne, K., 1984. Periloculina slovenica, B form, from the Paleocene of Majevica Mt. (Yugoslavia) and the new family Fabuliriidae. Razprave SAZU 25, 1e31. Droste, H., Van Steenwinkel, M., 2004. Stratal geometries and patterns of platform carbonates: The Cretaceous of Oman. In: Eberli, G., Masaferro, J.L., Sarg, J.F.R. (Eds.), Seismic Imaging of Carbonate Reservoirs and Systems. American Association of Petroleum Geologists, Memoir 81, pp. 185e206. res): Fleury, J.J., Fourcade, E., 1990. La superfamille Alveolinacea (Foraminife matique et essai d'interpre tation phyloge ne tique. Revue de MicroSyste ontologie 33 (3e4), 241e268. pale Glennie, K.W., Boeuf, M.G.S., Hughes Clarke, M.W., Moody-Stuart, M., Pilaar, W.F.H., Reinhardt, M., 1974. Geology of the Oman Mountain. Royal Dutch Geological and Mining Society Transactions 31, 1e423. Granier, B., 2008. Holostratigraphy of the Kahmah regional Series in Oman, Qatar, ologie, CG2008_A07, pp. 1e33. and the United Arab Emirates. Carnets de Ge laud, C., Razin, P., Homewood, P.H., Schwab, A.M., 2006. Development of inGre cisions on a periodically emergent carbonate platform (Natih Formation, Late Cretaceous, Oman). Journal of Sedimentary Research 76, 647e669. laud, C., Razin, P., Homewood, P., 2010. Channelized systems in an inner Gre carbonate platform setting: Differentiation between incisions and tidal channels (Natih Formation, Late Cretaceous, Oman). In: van Buchem, F.S.P., Gerdes, K.D., Esteban, M. (Eds.), Mesozoic and Cenozoic Carbonate Systems of the Mediterranean and the Middle East e Stratigraphic and Diagenetic Reference Models, Geological Society, London, Special Publications, 329, pp. 163e186. Hamaoui, M., 1966. Microfossils from Cenomanian sections in the Negev. Geological Survey of Israel Report Pal 3/66, pp. 1e12. l'e tude du Ce nomano-Turonien d'Israe €l, comHamaoui, M., 1979. Contribution a ontologiques avec quelques re gions me soge ennes. The se paraisons micropale Pierre et Marie Curie (Paris 6e ), pp. 1e121. Universite laud, C., Droste, H., Vahrenkamp, V., Mettraux, M., Homewood, P., Razin, P., Gre Mattner, J., 2008. Outcrop sedimentology of the Natih Formation, northern Oman: A field guide to selected outcrops in the Adam foothills and Al jabal al Akhdar areas. Geoarabia 13 (3), 39e120. Hottinger, L., Drobne, K., Caus, E., 1989. Late Cretaceous, larger, complex miliolids (Foraminifera) endemic in the Pyrenean Faunal Province. Facies 21, 99e134. Hughes Clarke, M.W., 1988. Stratigraphy and rock-unit nomenclature in the oil producing area of interior Oman. Journal of Petroleum Geology 11, 5e60. Hottinger, L., 2006. Illustrated glossary of terms used in foraminiferal research. ologie [Notebooks on Geology], Brest, Memoir 2006/02 (CG2006_ Carnets de Ge M02), pp. 1e126. http://dx.doi.org/10.4267/2042/5832.
Immenhauser, A., Creusen, A., Esteban, M., Vonhof, H.B., 2000. Recognition and interpretation of polygenic discontinuity surfaces in the Middle Cretaceous Shu'aiba, Nahr Umr, and Natih Formations of northern Oman. GeoArabia 5, 299e322. Kennedy, W.J., Juignet, P., 1993. A revision of the ammonite faunas of the type Cenomanian. 4. Acanthoceratinae (Acompsoceras, Acanthoceras, Protacanthoceras, Cunningtoniceras and Thomelites). Cretaceous Research 14, 145e190. Kennedy, W.J., Simmons, M.D., 1991. Mid-Cretaceous ammonites and associated microfossils from the Central Oman Mountains. Newsletters on Stratigraphy 25, 127e154. Meister, C., Piuz, A., 2013. Late Cenomanian e Early Turonian ammonites of the southern Tethys margin from Morocco to Oman: Biostratigraphy, paleobiogeography and morphology. Cretaceous Research 44, 83e103. Meister C., Piuz A., (in preparation). Cretaceous ammonites from Oman (Adam foothills). Owen, R.M.S., Nasr, S.M., 1958. Stratigraphy of the Kuwait-Basra area. 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Bureau de Recherches Ge oline ce nomanienne du Basin du Beausset. Eclogae Reichel, M., 1933. Sur une Alve Geologicae Helvetiae 26 (2), 269e280. olines. Me moires de la Socie te Pale ontologique Reichel, M., 1937. Etude sur les Alve Suisse 57 and 59, 1e147. olines du Cre tace supe rieur. Eclogae Reichel, M., 1941. Sur un nouveau genre d'Alve Geologicae Helvetiae 34 (2), 255e260. re nouveau du Reichel, M., 1947. Multispirina iranensis n. gen. n. sp., foraminife tace supe rieur de l'Iran. Me moires de la Socie te Pale ontologique Suisse 65, Cre 1e13. partition stratigraphique des grands Foraminife res benthiSaint-Marc, P., 1977. Re nomanien et du Turonien dans les re gions ques de l'Aptien, de l'Albien, du Ce diterrane ennes. Revista Espanola Micropaleontologia 9, 317e325. me oe cologique et pale obioge ographique de Saint-Marc, P., 1982. Distribution pale res benthiques du Ce nomanien. 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Late Aptian to Turonian stratigraphy of the eastern Arabian Plate-depositional sequences and lithostratigraphic nomenclature. Petroleum Geoscience 17, 211e222. Vicedo, V., Aguilar, M., Caus, E., Hottinger, L., 2009. Fusiform and laterally compressed alveolinaceans (Foraminiferida) from both sides of the Late Cretaceous €ontologie 253 (2e3), 229e247. Atlantic. Neues Jahrbuch für Geologie und Pala Vicedo, V., Calonge, A., Caus, E., 2011. Cenomanian rhapydioninids (Foraminiferida): Architecture of the shell and Stratigraphy. Journal of Foraminiferal Research 41 (1), 38e49. Vicedo, V., Serra-Kiel, J., 2011. Decastroia razini n. gen. n. sp. e A new alveolinacean (foraminifera from the Cenomanian of Socotra Island (Yemen). GeoArabia 16 (3), 17e26. Vicedo, V., Caus, E., Frijia, G., 2013. Late Cretaceous alveolinaceans (larger foraminifera) of the Caribbean palaeobioprovince and their stratigraphic distribution. Journal of Systematic Palaeontology 11 (1), 1e25.
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New Alveolinoidea (Foraminifera) from the Cenomanian of Oman Piuz a, *, Christian Meister a, Vicent Vicedo b Andre a Departement de g eologie et pal eontologie, Mus eum d'histoire naturelle de la ville de Gen eve, Route de Malagnou 1, Case Postale 6434, CH-1211 Gen eve 6, Switzerland b Museu de Ci encies Naturals de Barcelona (Paleontologia), Parc de la Ciutadella s/n, 08003 Barcelona, Spain
a r t i c l e i n f o
a b s t r a c t
Article history: Received 5 February 2014 Accepted in revised form 11 April 2014 Available online 21 June 2014
The first alveolinoidean appearing in the Cenomanian Natih Formation of Oman (Adam foothills and southern edge of Jabal Akhdar) are studied in detail. Morphological analysis results in the creation of one new family, Myriastylidae, two new genera, Myriastyla and Alveocella, and four new species, M. omanensis, M. grelaudae, A. wernliana, and Cisalveolina nakharensis. These four new taxa have a short stratigraphic extension restricted to the uppermost part of Natih E unit and are dated early middle Cenomanian by neighboring foraminifers and ammonite levels. © 2014 Elsevier Ltd. All rights reserved.
Keywords: Tethys Oman Natih Cenomanian Foraminifera Alveolinoidea
1. Introduction During middle Cretaceous, wide shallow-water carbonate platform systems developed on the Arabian plate. In Oman, this succession was described as the Natih Formation and is classically attributed to the upper Albian to lower Turonian (Simmons and Hart, 1987; Smith et al., 1990; Scott, 1990; Kennedy and Simmons, 1991; Philip et al., 1995; Van Buchem et al., 2002; Homewood et al., 2008). The Natih Fm. shows rich associations of large foraminifera that changes through time and characterizes different lithostratigraphical units in which that formation is subdivided. One of the most abundant and important group of larger foraminifera in the Natih Fm. is the Alveolinoidea (superfamily Alveolinoidea Ehrenberg, 1839). The Late Cretaceous alveolinoids of the Caribbean and western Tethys paleobioprovinces are well known ^cheux, 1984, (see Reichel, 1933, 1937, 1941, 1947; Colalongo, 1963; Pe 2002; Schroeder and Neumann, 1985; Hottinger et al., 1989; Fleury and Fourcade, 1990; Calonge et al., 2002; Vicedo et al., 2009, 2011, 2013; Vicedo and Serra-Kiel, 2011 among others), but the representative of this group in the south and southwest margin of the Tethys call for detailed architectural studies.
* Corresponding author. Tel.: þ41 22 418 63 65. E-mail addresses: [email protected] (A. Piuz), [email protected] (C. Meister), [email protected] (V. Vicedo). http://dx.doi.org/10.1016/j.cretres.2014.04.009 0195-6671/© 2014 Elsevier Ltd. All rights reserved.
Numerous specimens of alveolinoids appearing in the Omani Natih Fm. series have been analyzed and revealed notable differences with other Cenomanian genera and species. The aims of this paper are to describe the new taxa of alveolinoids found in the studied material of Oman, and give a tentative age and distribution considering the biostratigraphical and paleobiogeographical context. 2. Material and methods The material of this study was collected in two field trips in Oman, which were carried out in 2009 and 2012. The Omani Natih Fm. is very well exposed in extensive outcrops in the northern part of the country, particularly in the southern side of chennec et al., Jabal Akhdar and in the Adam Foothills (Be 1992a,b). Fig. 1 gives the geographic location of studied field sections (Fig. 2). They are located in Jabal Madar, Jabal Madmar, Jabal Khaydalah and Jabal Qusaybah or Fitri (Adam foothills), plus Wadi Mi'Aidin and Wadi Nakhr (southern side of Jabal Akhdar). Larger foraminifera were found in hard limestone mainly made up of muddy microfacies (Fig. 3). Several thin sections were made in order to develop the detailed architectural analysis (nomenclature follows Hottinger, 2006). More than a thousand sections of alveolinoids have been photographed and compared, coming from thin section as well as polished rock samples. The material figured in this paper (Table 1) is housed in the micropaleontological
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Fig. 1. Geographical and geological setting of the studied localities.
um d’histoire naturelle de Gene ve” (MHNG collections of the “Muse ncies Naturals de Barcelona” (MGB numbers) and “Museu de Cie numbers). Ammonites (Meister and Piuz, in prep.) are housed in the um d'histoire naturelle de Gene ve”. “Muse 3. Geological settings During the Cretaceous, the Sultanate of Oman was part of an extensive carbonate platform complex of 1000 km wide and 1200 m thick (Droste and Van Steenwinkel, 2004). The Aptian (Granier, 2008) to Turonian Wasia group (defined by Steineke and Bramkamp, 1952) consist of the Nahr Umr Formation (defined by Owen and Nasr, 1958) at the base, and the Natih Formation (introduced by Glennie et al., 1974 as substitute to the “Wasia Limestone Formation” used formerly, e.g. Tschopp, 1967) at the top. The Natih Fm. rests conformably on the Nahr Umr Fm. and is chennec overlain in regional unconformity by the Muti Fm. (Be et al., 1992a). Intense erosion has removed the Natih Fm. in the chennec et al., 1992a). northeast of Jabal Akhdar and Saih Hatat (Be The upper Albian/Turonian Natih Formation consists of mainly mud-supported and some grain-supported limestone (with local rudist development) alternating with intraplatform basin organic rich calcareous shales. Deposition was interrupted several times by subaerial exposure with emersion and incision (Immenhauser laud et al., et al., 2000; Droste and Van Steenwinkel, 2004; Gre 2006, 2010; Homewood et al., 2008). Outcrop sedimentology of the Natih Fm. is detailed by Homewood et al. (2008) with an extensive list of references.
3.1. Lithostratigraphy chennec et al. For the geological maps of the studied area, Be (1992a,b) separated the Natih Formation into a lower (thickbedded shallow-marine limestone) and an upper (clayey and foetid limestone with planktonic foraminifera) mappable member. The upper one corresponded to the Fitri Formation of Rabu (1988), a term now abandoned. On their side, based on subsurface log signature, petroleum geologists subdivided the Natih Fm. into seven informal “members” (reservoir units) designated by the lowercase letters “a” to “g” from top to base (Hughes Clarke, 1988; Scott, 1990). Although labeled in a reverse stratigraphical order, the recombination of these subsurface informal units into outcropping lithostratigraphic “members” got soon extensively used (e.g. Philip et al., 1995; Van Buchem et al., 1996, 2002, 2011; Homewood et al., 2008). Even if lithological properties and boundaries can locally be confusing (see below), for evident practical reasons we use them here as informal units, in uppercase letters “A” to “G” (as in many previous publications), with reservations due to their informal status and lack of rock outcrop comprehensive description. Well recognizable in the north (southern side of Jabal Akhdar) and in the west of the Adam foothills (Jabal Qusaybah, J. Nadah, J. Salakh, J. Khaydalah, J. Madmar), they gradually lose their distinctive character eastward. Various hard grounds mark disconformities along the Natih Fm., some being easily recognizable in the field (5a, 6a, 7a, 8a in Fig. 2) and commonly used for correlation between sections in the Adam foothills (see Van Buchem et al., 1996, 2002, 2011;
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Homewood et al., 2008). The Natih E-D boundary is marked by a typical distinctive iron enriched ochre layer in most of the field sections (surface 5a of Van Buchem et al., 1996, 2002) and indicates the last occurrence of the new alveolinoids described in this paper. This major disconformity allows good correlations in laud et al., the studied area (Van Buchem et al., 1996, 2002; Gre 2006). The ammonites (Acompsoceras beds and Neolobites beds, see below) found along the transect (Fig. 2) and used to date the alveolinoids, allow some observations about lithostratigraphical units Natih A and B. Following the sedimentary succession between the two biostratigraphical markers, the thick series of intrashelf basin lumachellic interbedded calcareous shale and limestones (Natih B) in J. Qusaybah, gets thinner eastward and passes to shelf facies environment with corals in J. Khaydalah and J. Madmar above which some lumachelles are present just below the Neolobites beds (Fig. 2). In the eastern sections (J. Khaydalah, J. Madmar), above the top of Natih C (above surface 8a, Fig. 2), the lithofacies obviously differs from Natih B of the western sections (J. Qusaybah, J. Nadah). Some authors (e.g. Van Buchem et al., 2002, Fig. 8, Homewood et al., 2008, enclosure III) seem, eastward, to attribute it to Natih A. Does it correspond (facies e fossil content e age) to the Natih A known in the western sections? Ammonite data give new constrains for these correlations, but a comprehensive definition of the outcropping Natih lithostratigraphic units is now necessary before going any further on this point. 3.2. Biostratigraphy The age of the strata enclosing the new taxa is based on ammonites and foraminifers which give the following biostratigraphical data. 3.2.1. Ammonites The Natih Formation is locally dated by ammonite bearing levels (Kennedy and Simmons, 1991; Van Buchem et al., 1996, 2002; Meister and Piuz, 2013; Meister and Piuz, in prep.), but no ammonites have been found together with the new alveolinoids. Though, two ammonite levels (see below) refine dating these strata. The Neolobites beds are found in the same field sections (Fig. 2) as the new alveolinoids, while the Acompsoceras beds are found in lithostratigraphically correlated neighboring field sections (see remarks above) where the strata with the new alveolinoids are not outcropping. Neolobites beds: The well-known Neolobites beds (found in Natih B-A in Jabal Madmar, Jabal Khaydalah, Jabal Salakh and Jabal Qusaybah, Fig. 2, Meister and Piuz, in prep.) contain the higher Neolobites found in our series and indicate the earliest part of the late Cenomanian, several tens of meters above the samples concerned in this study (see Fig. 2). These beds contain Neolobites vibrayeanus (Orbigny), Turrilites costatus Lamarck, Calycoceras guerangeri (Spath), Cunningtoniceras sp. and a nautilus: Angulithes sp. This ammonite association is recognizable along the southern Tethys margin from Morocco to Oman and accurately indicates the lower part of the Calycoceras guerangeri Zone (Meister and Piuz, 2013 cum biblio). Acompsoceras beds: The slightly older Acompsoceras beds (found in the lowest part of Natih B in Jabal Salakh, Jabal Qusaybah, Fig. 2; Meister and Piuz, in prep.) indicate a middle Cenomanian age. Indeed, these beds contain Acompsoceras renevieri (Sharpe) and some Engonoceratidae (Neolobites). Acompsoceras renevieri, recorded from Europe, Russia, north and west Africa, Madagascar and Arabian peninsula, is a rather long-ranging taxon that corresponds to a time interval from the early Cenomanian
(Mantelliceras mantelli Zone) to the middle Cenomanian (Acanthoceras rhotomagense Zone) (see Kennedy and Juignet, 1993). re is known in the southern Tethys Neolobites fourtaoui Pervinquie margin and ranges from middle Cenomanian (Acanthoceras rhotomagense e A. jukesbrownei Zones) to the base of the late Cenomanian (Calycoceras guerangeri Zone).
3.2.2. Foraminifers Recent studies regarding microfossils of the Natih Fm. include those of Glennie et al. (1974), Simmons and Hart (1987), Rabu (1988), Smith et al. (1990), Kennedy and Simmons (1991), chennec et al. (1992a,b), Philip et al. (1995). The new species Be detailed in this study are the first alveolinoids appearing in the upper part of Natih E unit. They disappear together with most orbitolinids around or at the surface 5a (Natih E-D boundary) in all sections except Wadi Mi'Aidin where orbitolinids are found even above the last occurrence of alveolinids. Their stratigraphic extension comprises the distinctive overlap of orbitolinids and alveolinids (O.O.A. considered for the Adam Foothills) noted by Smith et al. (1990 p. 38; see also Simmons and Hart, 1987), in the upper part of Natih E unit. This interval is proposed as middle Cenomanian, mainly based on the presence of (little illustrated) Merlingina cretacea and Chrysalidina gradata which are (following the range chart of Schroeder and Neumann, 1985) absent during the early Cenomanian (see however e.g. Saint-Marc, 1977, 1982, for C. gradata, and Hamaoui, 1966, 1979, for M. cretacea). Other foraminifers used by Smith et al. (1990) to date this O.O.A. interval are middle Cenomanian alveolinids some of which (partially illustrated) are most probably the new taxa described in this paper, while their questionable Pseudorhapydionina laurinensis is not illustrated. In our field sections (Fig. 2), doubtful sections of M. cretacea are present together with C. gradata some meters below the first occurrence of the new alveolinoids. Associated with the new alveolinoids, the ramp limestone facies reveal, Biconcava bentori, Chrysalidina gradata, Cuneolina gr pavonia, Dicyclina sp., Haplophragmoides sp., Montcharmontia compressa, Nezzazata spp. (N. gr simplex, N. gr gyra), various orbitolinids (under study), diverse and abundant miliolids (Quinqueloculina spp.), Spiroloculina spp, Spiroplectammina sp., Trocholina arabica, and various dasyclad algae. The O.O.A. is followed (during Natih E-D-C) by other alveolinid species close to Decastroia Vicedo & Serra-Kiel which disappear toward the Natih C/B boundary in all sections (probably due to paleoenvironmental changes) except in Wadi Mi'Aidin where they are found higher in the series.
3.3. Age of the new alveolinoids The biostratigraphical data given above by ammonites and foraminifers allow proposing an early middle Cenomanian age (Acanthoceras rhotomagense ammonite zone) for the stratigraphic extension of the new alveolinoids. Stratigraphically below the new species, the first occurrence of M. cretacea and C. gradata are the main arguments (see above) to place the base of the middle Cenomanian, while the Acompsoceras beds, close to the last alveolinids, are not younger than the A. rhotomagense ammonite zone. Regarding the thickness of the sedimentary pile between these two points, the latter zone seem especially well developed in the Natih Fm. Note however that the data of Bulot et al. (in prep), as presented in Homewood et al. (2008, Fig. 5), propose the loweremiddle Cenomanian boundary at the Natih E-D boundary, data that if proven will change the age of the new species to (latter part? of the) early Cenomanian.
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Fig. 2. Field sections and localization of studied samples.
3.4. Paleobiogeography At present, the new specimens described below are only known from northern Oman (Jabal Akhdar and Adam foothills) which suggest that the Arabian platform could be a distinctive paleobioprovince during Cenomanian times, at least for porcellaneous complex large foraminifera. Endemism in alveolinoids is supported by many studies (e.g. Hottinger et al., 1989; Fleury and Fourcade, 1990; Vicedo et al., 2009). Further studies dealing with alveolinoids of the Middle East Cenomanian are required to develop biostratigraphy and paleobiogeography and to understand the relationships with other representatives of this group in the western
Tethys. In particular, confirming the presence or absence of Praealveolina Reichel, 1933, in Oman, genus widely cited in several previous papers and company's reports but not identified in the materials examined in this study. The Decastroia morphotypes, appearing in upper stratigraphical levels (Decastroia spp. in Fig. 2), merit to be studied as well, and compared to those of the type locality of Socotra (Yemen). 4. Systematic descriptions rouard, 1896 Suborder Miliolina Delage and He Superfamily Alveolinoidea Ehrenberg, 1839
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Fig. 2. (continued).
Family Alveolinidae Ehrenberg, 1839 Alveocella new genus Etymology: “With small alveoles”, from the Latin [alueus] cavity, and [cella] suffix used as diminutive. Type species: Alveocella wernliana new species. Diagnosis: Oval to fusiform shells, wall porcelaneous, successive chambers with planispiral involute coiling, apertural face with two to three rows of apertures extending from pole-to-pole. Chambers are subdivided by septula disposed in an alternate mode from one chamber to the other. Preseptal passage is
constant and always obvious. One to two rows of postseptal alveoles, extending from pole-to-pole, communicate through supplementary foramina with the previous chamber. Differential diagnosis: Alveocella differs from Praealveolina Reichel, 1933 and Archaealveolina Fourcade, 1980 in having alternate septula from one chamber to the next. Alveocella differs from Cisalveolina Reichel, 1941 in having postseptal alveoles. Alveocella is different from Decastroia Vicedo & Serra-Kiel, 2011 by the absence of floors in equatorial area, the alternate mode of the septula and the presence of alveoles. Alveocella has some features in common with the Oligocene Bullalveolina Reichel, 1936 and with the
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CampanianeSantonian Subalveolina Reichel, 1936, especially the alternate mode of the septula, the multiple apertures, and alveoles. Though, Bullalveolina bulloides (d'Orbigny) mainly differs by the distribution of the apertures in the apertural face. Bullalveolina shows main apertures in a lower row and intercalated supplementary apertures above; contrarily, supplementary and main apertures are vertically aligned in Alveocella. Moreover, Bullalveolina differs from Alveocella by its slightly umbilicate subspherical test, the coiling of its first whorls (typically streptospiral), the absence of septula in its first chambers, and its large preseptal passage. Subalveolina also differs from Alveocella by the arrangement of the apertures in the apertural face and by the nature of the alveoles. Subalveolina has one row of main apertures alternating with smaller intercalated apertures which connect with the small postseptal alveoles. In contrast, in Alveocella the main and supplementary apertures are not intercalated, thus, alveoli and chamberlets are aligned. Moreover, Subalveolina has larger alveoles, and supplementary chamberlets that appear below the main floor in polar regions. Alveocella wernliana new species (Figs. 3e7) Etymology: Dedicated to Professor R. Wernli, micropaleontologist at the University of Geneva. Holotype: Specimen illustrated in Fig. 4.6 (sample ap561-h) deposited in the micropaleontological collection of the Natural History Museum of Geneva n MHNG2013-42a
349
Paratypes: Specimens illustrated in Fig. 4.1 (sample ap561-i), 4.3 (sample ap561-k), 5.11 (sample ap561-f), deposited in the micropaleontological collection of the Natural History Museum of Geneva n MHNG2013-43, MHNG2013-44a and MHNG2013-45 Type locality: Wadi Nakhr, southern edge of Jabal Akhdar, Oman. Coordinates: N23 09.330 E05712.264 Type level: Upper Natih E unit, lower middle Cenomanian. Diagnosis: Oval to fusiform dimorphic shells. The megalospheric generation starts with a rounded to oval proloculus of 400e460 mm followed by a flexostyle of a quarter of a whorl. Following chambers are arranged planispirally with 7e8 whorls in adult shells. Apertural face has two to three rows of apertures extending from poleto-pole. One row of main foramina connect chamberlets of successive chambers, one or two rows of supplementary foramina connect the postseptal alveoles with the previous chamber. One to two rows of alveoles appear since the second whorl. Axial sections show 11e14 chamberlets per quadrant at the fourth whorl. The maximum equatorial diameter observed is around 2.4 mm and the axial length is 3.6 mm. Larger specimens (up to 6 mm) with similar morphological characteristics are very rare and may belong to the microspheric generation although their juvenarium has not been observed (Fig. 7). Occurrence: This species is actually only known in the upper part of Natih E unit (lower middle Cenomanian) in the southern edge of Jabal Akhdar and Adam foothills, Oman.
Fig. 3. Typical muddy microfacies with alveolinoids in upper Natih E unit. Alveocella wernliana n. gen. n. sp., sample ap397, lower middle Cenomanian, Jabal Madmar, Adam foothills, Oman. See bar for scale.
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Table 1 um d'histoire naturelle de Gene ve” List of the material deposited in the “Muse ncies Naturals de Barcelona” (MGB numbers). (MHNG numbers) and “Museu de Cie Fig. 3 4
5
6
7 8
9
11
No 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 1 2 3 4
Sample
Collection Nr.
AP397-a AP561-i AP561-l AP561-k AP397-a AP561-f AP561-h AP561-c AP384-a M-11 M-11 M-11 M-11 AP384-j AP397-c AP561-i AP561-h AP561-m AP397-f AP397-f AP561-f AP561-n AP561-p AP561-f M11 M11 AP384-i AP384-e AP397-d AP561-o AP561-i AP561-n AP384-c AP561-f AP341-a AP561-b AP561-m AP561-d AP561-p AP561-f AP561-o AP384-j AP384-a AP561-j M-17 AP561-j AP561-k AP561-p AP561-c Ma-10 AP561-m AP561-g M-16 AP561-d AP561-h AP561-b AP561-c AP561-i AP561-i AP561-c AP561-c AP561-c AP561-d AP561-m AP561-c AP561-h AP384-i AP561-c AP561-l AP561-j AP561-i AP561-l AP561-p AP341-h
MHNG2013-52 MHNG2013-43 MHNG2013-50 MHNG2013-44a MHNG2013-52 MHNG2013-45 MHNG2013-42a MHNG2013-53 MHNG2013-54 MGB 59774 LP05.14 MGB 59774 LP01.10 MGB 59774 LP04.11 MGB 59774 LP04.22 MHNG2013-55 MHNG2013-56 MHNG2013-43 MHNG2013-42 MHNG2013-47 MHNG2013-57 MHNG2013-57 MHNG2013-45 MHNG2013-58 MHNG2013-49 MHNG2013-45 MGB 59774 LP03.11 MGB 59774 LP06.11 MHNG2013-46 MHNG2013-59 MHNG2013-60 MHNG2013-61 MHNG2013-43 MHNG2013-58 MHNG2013-62 MHNG2013-45 MHNG2013-63 MHNG2013-64 MHNG2013-47 MHNG2013-65 MHNG2013-49 MHNG2013-45 MHNG2013-61 MHNG2013-55 MHNG2013-54 MHNG2013-66 MGB 59780 LP03.01 MHNG2013-66 MHNG2013-44b MHNG2013-49 MHNG2013-53 MGB, 59824 LP02.11 MHNG2013-47 MHNG2013-51 MGB 59779 LP06.03 MHNG2013-65 MHNG2013-42b MHNG2013-64 MHNG2013-53 MHNG2013-43 MHNG2013-43 MHNG2013-53 MHNG2013-53 MHNG2013-53 MHNG2013-65 MHNG2013-47 MHNG2013-53 MHNG2013-42 MHNG2013-46 MHNG2013-53 MHNG2013-50 MHNG2013-66 MHNG2013-43 MHNG2013-50 MHNG2013-49 MHNG2013-67
Table 1 (continued ) Fig.
Status Paratype Paratype
Holotype 12
13
Paratype
14
Holotype
Paratype
Paratype
No
Sample
Collection Nr.
Status
5 6 7 8 9 10 11 12 13 14 3 4 6 7 8 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 1 2 3 4 5 6 7 8 9 10 11
AP561-g AP561-k M-11 AP561-m AP561-l AP561-f AP561-o AP561-l AP561-d AP561-a AP561-f AP561-j AP561-k AP561-d AP561-f Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 Ma-10 AP341-h AP341-h AP561-l Ma-10 AP561-p AP384-j AP561-f AP384-j AP561-k AP561-m AP561-h
MHNG2013-51 MHNG2013-44 MGB 59774 LP03.01 MHNG2013-47 MHNG2013-50 MHNG2013-45 MHNG2013-61 MHNG2013-50 MHNG2013-65 MHNG2013-68 MHNG2013-45 MHNG2013-66 MHNG2013-44 MHNG2013-65 MHNG2013-45 MGB 59824 LP02.03 MGB 59824 LP03.12 MGB 59824 LP03.16 MGB 59824 LP04.27 MGB 59824 LP05.02 MGB 59824 LP06.08 MGB 59824 LP05.01 MGB 59824 LP04.05 MGB 59824 LP06.10 MGB 59824 LP04.14 MGB 59824 LP05.03 MGB 59824 LP06.12 MGB 59824 LP04.07 MGB 59824 LP06.09 MGB 59824 LP05.06 MGB 59824 LP02.04 MGB 59824 LP02.01 MHNG2013-67 MHNG2013-67 MHNG2013-50 MGB 59824 LP04.27 MHNG2013-49 MHNG2013-55 MHNG2013-45 MHNG2013-55 MHNG2013-44b MHNG2013-47 MHNG2013-42b
Paratype
Paratype Holotype Paratype
Paratype
Paratype
Paratype Holotype Holotype Paratype Holotype Paratype Paratype
Cisalveolina Reichel, 1941 Type species: Cisalveolina fallax Reichel, 1941 Description: Porcelaneous, subglobular shells with planispirally arranged chambers. The simple aperture extends from pole-to-pole and consists in a narrow, slitlike opening. Chamber lumen is subdivided into chamberlets by mean of septula, which alternate in position from one chamber to the next. Preseptal and postseptal passages connect all chamberlets of the same chamber. Cisalveolina nakharensis new species (Figs. 8 and 9) Etymology: In allusion to the origin of the material. Holotype: Specimen figured in Fig. 8.6 (sample ap561-k) deposited in the micropaleontological collection of the Natural History Museum of Geneva n MHNG2013-44b Paratypes: Specimen figured in Fig. 8.10 (sample ap561-m), 9.2 (sample ap561-h) deposited in the micropaleontological collection of the Natural History Museum of Geneva n MHNG2013-47 and MHNG2013-42b
Paratype Holotype
Type locality: Wadi Nakhr, southern edge of Jabal Akhdar, Oman. Coordinates: N23 09.330 E05712.264 Type level: Upper part of Natih E unit, lower middle Cenomanian.
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Fig. 4. Alveocella wernliana n. gen. n. sp. from Wadi Nakhr (1e3, 5e7) and Wadi Mi'Aidin (9e12), southern edge of Jabal Akhdar; Jabal Madmar (4) and Jabal Khaydalah (8), Adam foothills; Oman. Upper Natih E unit, lower middle Cenomanian Scale bar 1 mm. Axial and sub-axial sections. 1e3, 5e7 from sample ap561; 4 from sample ap397; 8 from sample ap384. 9e12, from sample M-11. Abbreviations: alv, alveole; chl, chamberlet; fl, felxostyle; gl, glomerulus; m f, main foramen; p, proloculus; pr p, preseptal passage; s, septum; s f, supplementary foramen; sl, septulum.
Diagnosis: Subglobular shell-shape and dimorphism restricted to the early stages of growth. The megalospheric generation starts with a subspherical proloculus of around 150e200 mm in diameter followed by a flexostyle of at least half a whorl. Following chambers are slightly streptospiral to planispirally arranged. The maximum diameter observed in adult specimens is around 2.3 mm with 7e8 whorls. Septula appear in the first whorl. Postseptal passage is always located in the upper half of chamber height. Axial sections show 8e10 chamberlets per quadrant at the fourth whorl. Specimens of the microspheric generation are less abundant and are characterized by a
small streptospiral glomerulus. Aperture is a basal (interiomarginal) single and low (about ¼ to ½ of the chamber height) slit for the whole width of the test. A short undulating upper lip is often visible. Differential diagnosis: C. nakharensis differs from C. lehneri by its bigger size (2.3 mm of maximum diameter for megalospheric forms of C. nakharensis and 1.9 mm for those of C. lehneri), by its bigger megalosphere (150e200 mm and 110e140 mm respectively), and by its less developed early streptospiral growth (either in megalospheric or microspheric forms).
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Fig. 5. Alveocella wernliana n. gen. n. sp. from Jabal Khaydalah (1, 14e15) and Jabal Madmar (2, 6e7), Adam foothills; Wadi Nakhr (3e5, 8e11) and Wadi Mi'Aidin (12e13), southern edge of Jabal Akhdar; Oman. Upper Natih E unit, lower middle Cenomanian. Scale bar 1 mm. Equatorial and sub-equatorial sections. 1, 14e15 from sample ap384; 2, 6e7 from sample ap397; 3e5, 8e11 from sample ap561; 12e13 from sample M-11. Abbreviations: alv, alveole; fl, flexostyle; chl, chamberlet; p, proloculus; s, septum; s f, supplementary foramen; sl, septulum.
C. nakharensis is different from C. fraasi by having a smaller maximum diameter in megalospheric forms (2.3 mm for the former and 2.7 mm for the latter) and by showing a smaller megalosphere (150e200 mm for C. nakharensis and 200e370 mm for C. fraasi). The early streptospiral chamber arrangement is similar in both species, affecting only to the two first whorls. Occurrence: C. nakharensis is actually only recognized in the upper part of Natih E unit (lower middle Cenomanian) in the southern edge of Jabal Akhdar and Adam foothills, Oman.
Myriastylidae new family Type genus: Myriastyla new genus Diagnosis: Thick, porcelaneous wall and subspherical to axially elongated shells. Adult chambers are involute and planispirally arranged. The endoskeleton consists of longitudinal ridges (in the direction of growth) supporting each one row of pillars. The pillars are aligned in the direction of growth and alternate in position (staggered rows) from pole-to-pole. This structure permits the communication of the protoplasm within the whole
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Fig. 6. Alveocella wernliana n. gen. n. sp. from Jabal Madmar (1), Jabal Khaydalah (5, 14), and Jabal Madar (7), Adam foothills; and Wadi Nakhr (2e4, 6, 8e13), southern edge of Jabal Akhdar; Oman. Upper Natih E unit, lower middle Cenomanian. Scale bar 1 mm for pictures 1e2, 5e8, 14; 0.5 mm for pictures 3e4, 9e13. Equatorial, sub-equatorial and tangential sections. 1 from sample ap397; 2e4, 6, 8e13 from sample ap561; 7 from ap341; 5, 14 from sample ap384. Abbreviations: alv, alveole; m f, main foramen; pr p, preseptal passage; s, septum; s f, supplementary foramen; sl, septulum.
Fig. 7. Tangential section of probable microspheric specimen of Alveocella wernliana n. gen. n. sp. in wackestone microfacies with miliolids, nezzazatids and orbitolinids. Sample ap384, upper Natih E unit (lower middle Cenomanian), Jabal Khaydalah, Adam foothills, Oman. See bar for scale.
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Fig. 8. Cisalveolina nakharensis n. sp. from Jabal Madar (1), Jabal Khaydalah (2), Jabal Madmar (9), Adam foothills; Wadi Nakhr (3, 5e8, 10e11) and Wadi Mi'Aidin (4, 12), southern edge of Jabal Akhdar; Oman. Upper Natih E unit, lower middle Cenomanian. Scale bar 1 mm. Axial and sub-axial sections. 1 from sample ap341; 2 from sample ap384; 3, 5e8 from sample ap561; 4 from sample M-17; 9 from sample Ma-10; 12 from sample M-16. Abbreviations: chl, chamberlet; f, foramen; g, glomerulus; p, proloculus; po p, postseptal passage; s, septum; sl, septulum.
space of the chamber. Multiple apertures arranged in a single row; supplementary apertures may appear polewards. Remarks: The particular architecture of the morphotypes grouped in this new family, showing rows of pillars and planispiral chamber arrangement, has not permitted to attribute them to any of the families described within the superfamily Alveolinoidea. The diagnosis of the family Alveolinidae Ehrenberg, 1839 was emended by Hottinger et al. (1989) who stated “[…]. Chambers subdivided by longitudinal partitions (septula) producing completely separate chamber compartments (chamberlets) connected by an open space below the apertural face (preseptal passage). […]”. As it is pointed out above and in contrast to Alveolinidae Ehrenberg, 1839, and also to Rhapydioninidae Keijzer, 1945, the rows of pillars in myriastylids
facilitate the communication in the whole space of the chamber. No “true” compartments (chamberlets) result from that structure. Thus, a canal-shaped preseptal passage (as in alveolinids) connecting all the chamber lumen is not present as it is supposed that it was not necessary for the living organism. The morphotypes of the new family cannot be attributed to the family Fabulariidae Ehrenberg, 1839, because the latter include specimens with milioline coiling (at least in early growth stages) and a fixed apertural axis (Drobne, 1984; Hottinger et al., 1989). Myriastyla new genus Etymology: From the Greek [murios] very numerous, and [stulos] column, pillar.
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Fig. 9. Cisalveolina nakharensis. n. sp. from Wadi Nakhr (1e13, 15e17), southern edge of Jabal Akhdar; and Jabal Khaydalah (14), Adam foothills; Oman. Upper Natih E unit, lower middle Cenomanian. Scale bar 1 mm, unless specified (7e8, 12). Equatorial, oblique and tangential sections. 1e13, 15e17 from sample ap561, 14 from sample ap384. Abbreviations: chl, chamberlet; po p, postseptal passage; s, septum; sl, septulum.
Type species: Myriastyla omanensis new species Diagnosis: Dimorphic, subglobular to axially elongated shells constituted by numerous chambers with a planispiral-involute arrangement. Subglobular shells show a single row of multiple foramina in interiomarginal position extending from pole-to-pole. Supplementary apertures appear polewards, mainly in axially elongated forms (as in alveolinids). The embryo of the megalospheric generation consists of a subspherical proloculus followed by a flexostyle. The embryo of the microspheric generation has not been observed. Chambers show an endoskeleton that consists of longitudinal ridges supporting each a single row of pillars, as in
some fabulariids. The pillars, disposed in parallel rows aligned in the direction of growth, are alternating in position (staggered rows) from pole-to-pole (Fig. 10). Myriastyla omanensis new species (Figs. 11 and 12) Etymology: In allusion to the origin of the material in the mountains of Oman. Holotype: Specimen illustrated in Fig. 11.3 (sample ap561-p) deposited in the micropaleontological collection of the Natural History Museum of Geneva n MHNG2013-49.
Fig. 10. Basic internal structure of Myriastyla n. gen. Stereograph, shematic, not to scale.
Fig. 11. Myriastyla omanensis n. gen. n. sp. from Wadi Nakhr (1e3, 5e6, 8e14) and Wadi Mi'Aidin (7), southern edge of Jabal Akhdar; and Jabal Madar (4), Adam foothills; Oman. Upper Natih E unit, lower middle Cenomanian. Scale bar 1 mm. Axial, sub-axial and oblique sections. 1e3, 5e6, 8e14 from sample ap561; 4 from sample ap341; 7 from sample M-11. Abbreviations: ch, chamber; fl, flexostyle; m a, main aperture; m f, main foramen; p, proloculus; pi, pillar; pi r, pillar ridge; s, septum; s f, supplementary foramen.
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Fig. 12. Myriastyla omanensis n. gen. n. sp. from Wadi Nakhr (1e8), southern edge of Jabal Akhdar, Oman. Upper Natih E unit, lower middle Cenomanian. Scale bar 1 mm. Equatorial, oblique and tangential sections. All sections from sample ap561. Abbreviations: pi, pillar; pi r, pillar ridge; s, septum; s f, supplementary foramen.
Paratypes: Specimens illustrated in Fig. 11.2 (sample ap561-l), 11.5 (sample ap561-g), deposited in the micropaleontological collection of the Natural History Museum of Geneva n MHNG2013-50 and MHNG2013-51. Type locality: Wadi Nakhr, southern edge of Jabal Akhdar, Oman. Coordinates: N23 09.330 E05712.264. Type level: Upper Natih E unit, lower middle Cenomanian. Diagnosis: Subglobular shells. Dimorphism not observed. Maximum equatorial diameter observed is around 2.5 mm with 7e8 planispiral whorls. The megalospheric generation starts with a subspheric proloculus between 0.13 and 0.3 mm in diameter followed by a short flexostyle canal. The endoskeleton appears early during the ontogeny, starting right after the flexostyle. Microspheric embryo has not been identified. Multiple apertures consist of a row of round openings in interiomarginal position extending from poleto-pole. Supplementary apertures appear at the poles. The chamber roof is thick and always visible. Occurrence: This species is only known in the upper part of the Natih E unit (lower middle Cenomanian) in the southern edge of Jabal Akhdar and Adam foothills, Oman. Myriastyla grelaudae new species (Fig. 13) laud, geologist of EGID Etymology: Given in honour of Carine Gre (Bordeaux, France) with a big experience on the Cenomanian carbonates of Oman. Holotype: Specimen illustrated in Fig. 13.4 (sample Ma-10) deposited in the micropaleontological collection of the Museu de ncies Naturals de Barcelona (MGB 59824 LP04.27). Cie Paratypes: Specimens illustrated in Fig. 13.2, 13.5, 13.9, and 13.17 (all from sample Ma-10) deposited in the micropaleontological
collection of the Natural History Museum of Barcelona (collection numbers MGB 59824 LP03.12, MGB 59824 LP05.02, MGB 59824 LP06.10, and MGB 59824 LP02.01 respectively). Type locality: Jabal Madmar, Adam foothills, Oman, Coordinates: N 22 260 48.8200 , E57 350 28.7400 . Type level: Upper Natih E unit, lower middle Cenomanian. Diagnosis: Dimorphic, axially elongated shells. The megalospheric generation begins with a subspherical proloculus between 0.2 and 0.4 mm in diameter followed by a short flexostyle. The maximum equatorial diameter observed is around 1.7 mm with 8 spiral whorls and an axial length of 3.2 mm. Index of elongation of about 1.8e2. The endoskeleton appears in the first chamber after the flexostyle. The embryo of the microspheric generation has not been adequately observed, but the specimens of this generation have been identified by their size or by the early stages of growth (tightly coiled). The maximum equatorial diameter is up to 1.8 mm with more than 10 whorls and an axial length up to 7 mm. The index of elongation is about 4. Multiple apertures consisting of a row of round openings in interiomarginal position extending from pole-to-pole. Several levels of supplementary apertures appear polewards. Differential diagnosis: Myriastyla grelaudae n. sp. differs from the type species M. omanensis n. sp. mainly by having larger megalospheres (0.2e0.4 mm and 0.1e0.3 mm respectively) and by having more whorls with the same equatorial diameter (at a diameter of 1.7 mm there are 8 whorls in M. grelaudae n. sp. and 6 whorls in M. omanensis n. sp.). Moreover, M. grelaudae n. sp. is axially elongated in contrast to the subglobular morphology of M. omanensis n. sp. Occurrence: This species is only known in the upper part of the Natih E unit (lower middle Cenomanian) in Jabal Madmar (Adam foothills).
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Fig. 13. Myriastyla grelaudae n. sp. from Jabal Madmar, Adam foothills, Oman. Upper Natih E unit, lower middle Cenomanian. Microspheric? (1e2, 17) and megalospheric (3e16) specimens. Scale bar 1 mm. Axial, subaxial and subequatorial sections. All specimens from sample Ma-10. Abbreviations: fl, flexostyle; m f, main foramen; p, proloculus; pi, pillar; pi r, pillar ridge; s, septum; s f, supplementary foramen.
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Fig. 14. Drawings of Myriastyla omanensis n. gen. n. sp. (1e3, 5), M. grelaudae n. sp. (4), Alveocella wernliana n. gen. n. sp. (6-8), Cisalveolina nakharensis n. sp. (9-11). See table 1 for sample number. Abbreviations: alv, alveole; g, glomerulus; m f, main foramen; r, ridge; pi, pillar; po p, postseptal passage; pr p, preseptal passage; pi r, pillar ridge; p, proloculus; s, septum; s f, supplementary foramen; sl, septulum.
5. Conclusions Four new taxa (Fig. 14) appear as the first alveolinoidean in the upper part of the Natih E unit of Oman in the Adam foothills and southern side of Jabal Akhdar. Alveocella wernliana n. gen. n. sp. is characterized by the alternate mode of the septula, and the presence of postseptal alveoles. Cisalveolina nakharensis n. sp. shares many characteristics with C. fraasi but is older in age and has a smaller size. Myriastyla omanensis n. gen. n. sp. and M. grelaudae n.
sp. have a particular endoskeleton that consists of parallel longitudinal (in the direction of growth) ridges supporting each a single row of pillars. Pillars are disposed in staggered rows from pole-topole. Due to their noteworthy morphological features, different from all known alveolinids, it has been necessary to create a new family e Myriastylidae e within the superfamily Alveolinoidea Ehrenberg. The four taxa described in this paper appear together in the same levels and have (at least in the studied sections) a short
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vertical range corresponding to the first alveolinoid e top of Natih E unit (5a typical iron enriched layer). They have an important stratigraphic (lower middle Cenomanian) and paleobiogeographic (hitherto only known in the Middle East) significance, and bring new data to evolution lineages of the alveolinoids. Acknowledgments Best thanks to Prof. R. Wernli and Dr D. Dufour for sharing their knowledge and experience. Thanks to P.-A. Proz for the confection of the numerous thin sections, and to the Paul Broennimann Foundation. Salim Omar Al-Ibrahim, Director General of Minerals (Ministry of Commerce and Industry of Oman) and Ali Al Rajhi, Director of Survey and Research are thanked for their logistic laud are also support. Dr. Philippe Razin and Dr. Carine Gre acknowledged for sharing their expertise in the Omani carbonate deposits and logistic support during field work. Thanks to Prof. Josep Serra-Kiel for his very useful comments about alveolinids. Thanks to an anonymous reviewer, Prof. B. Granier and the editor in chief handling this manuscript E. Koutsoukos for their helpful remarks and comments. References chennec, F., Roger, J., Le Me tour, J., Wyns, R., 1992a. Geological map of Seeb, Sheet Be NF 40-03, scale 1/250 000, with Explanatory notes. Sultanate of Oman, Ministry ans, France, of Petroleum and Minerals, Directorate of Minerals, BRGM, Orle pp. 1e104. chennec, F., Wyns, R., Roger, J., Le Metour, J., Chevrel, S., 1992b. Geological map of Be Nazwa, Sheet NF 40-07, scale 1/250 000, with Explanatory notes. Sultanate of Oman. Ministry of Petroleum and Minerals, Directorate of Minerals, BRGM ans, France, pp. 1e91. Orle Calonge, A., Caus, E., Bernaus, J.M., Aguilar, M., 2002. Praealveolina (Foraminifera) species: a tool to date Cenomanian platform sediments. Micropaleontology 48 (1), 53e66. Colalongo, M.L., 1963. Selliaveolina viallii n. gen. n. sp. di Alveolinide Cenomaniano dell'Appennino meridionale. Giornale di Geologia 30 (2), 361e370. Drobne, K., 1984. Periloculina slovenica, B form, from the Paleocene of Majevica Mt. (Yugoslavia) and the new family Fabuliriidae. Razprave SAZU 25, 1e31. Droste, H., Van Steenwinkel, M., 2004. Stratal geometries and patterns of platform carbonates: The Cretaceous of Oman. In: Eberli, G., Masaferro, J.L., Sarg, J.F.R. (Eds.), Seismic Imaging of Carbonate Reservoirs and Systems. American Association of Petroleum Geologists, Memoir 81, pp. 185e206. res): Fleury, J.J., Fourcade, E., 1990. La superfamille Alveolinacea (Foraminife matique et essai d'interpre tation phyloge ne tique. Revue de MicroSyste ontologie 33 (3e4), 241e268. pale Glennie, K.W., Boeuf, M.G.S., Hughes Clarke, M.W., Moody-Stuart, M., Pilaar, W.F.H., Reinhardt, M., 1974. Geology of the Oman Mountain. Royal Dutch Geological and Mining Society Transactions 31, 1e423. Granier, B., 2008. Holostratigraphy of the Kahmah regional Series in Oman, Qatar, ologie, CG2008_A07, pp. 1e33. and the United Arab Emirates. Carnets de Ge laud, C., Razin, P., Homewood, P.H., Schwab, A.M., 2006. Development of inGre cisions on a periodically emergent carbonate platform (Natih Formation, Late Cretaceous, Oman). Journal of Sedimentary Research 76, 647e669. laud, C., Razin, P., Homewood, P., 2010. Channelized systems in an inner Gre carbonate platform setting: Differentiation between incisions and tidal channels (Natih Formation, Late Cretaceous, Oman). In: van Buchem, F.S.P., Gerdes, K.D., Esteban, M. (Eds.), Mesozoic and Cenozoic Carbonate Systems of the Mediterranean and the Middle East e Stratigraphic and Diagenetic Reference Models, Geological Society, London, Special Publications, 329, pp. 163e186. Hamaoui, M., 1966. Microfossils from Cenomanian sections in the Negev. Geological Survey of Israel Report Pal 3/66, pp. 1e12. l'e tude du Ce nomano-Turonien d'Israe €l, comHamaoui, M., 1979. Contribution a ontologiques avec quelques re gions me soge ennes. The se paraisons micropale Pierre et Marie Curie (Paris 6e ), pp. 1e121. Universite laud, C., Droste, H., Vahrenkamp, V., Mettraux, M., Homewood, P., Razin, P., Gre Mattner, J., 2008. Outcrop sedimentology of the Natih Formation, northern Oman: A field guide to selected outcrops in the Adam foothills and Al jabal al Akhdar areas. Geoarabia 13 (3), 39e120. Hottinger, L., Drobne, K., Caus, E., 1989. Late Cretaceous, larger, complex miliolids (Foraminifera) endemic in the Pyrenean Faunal Province. Facies 21, 99e134. Hughes Clarke, M.W., 1988. Stratigraphy and rock-unit nomenclature in the oil producing area of interior Oman. Journal of Petroleum Geology 11, 5e60. Hottinger, L., 2006. Illustrated glossary of terms used in foraminiferal research. ologie [Notebooks on Geology], Brest, Memoir 2006/02 (CG2006_ Carnets de Ge M02), pp. 1e126. http://dx.doi.org/10.4267/2042/5832.
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