Famennian Rhynchonellides (Brachiopoda) from Deep-Water Facies of the Ougarta Basin (Saoura Valley, Algeria)
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Geol. Mag. 152 (6), 2015, pp. 1009–1024. c Cambridge University Press 2015 1009 doi:10.1017/S0016756814000697 Famennian rhynchonellides (Brachiopoda) from deep-water facies of the Ougarta Basin (Saoura Valley, Algeria) ∗ BERNARD MOTTEQUIN† , FATIMA ZOHRA MALTI‡, MADANI BENYOUCEF§, ∗∗ CATHERINE CRÔNIER¶, LOUISA SAMAR║, CARINE RANDON & DENISE BRICE†† †Institut Royal des Sciences Naturelles de Belgique, D. O. Terre et Histoire de la Vie, rue Vautier 29, B 1000 Brussels, Belgium ‡Université de Béchar, Faculté des Sciences et de la Technologie, BP 417, Béchar 08000, Algeria §Université de Mascara, Département des Sciences de la Terre, BP 305, Mascara 29000, Algeria ¶FRE 3298, Géosystèmes, Université Lille 1, Sciences de la Terre, 59655 Villeneuve d’Ascq Cedex, France ║ ∗∗ SONATRACH, Centre de Recherche et Développement, Boumerdès 35000, Algeria UMR 7207 CR2P Centre de Recherche sur la Paléobiodiversité et les Paléoenvironnements, Université Pierre et Marie Curie, Laboratoire de Micropaléontologie, 75252 Paris Cedex 05, France ††Université Catholique de Lille et Groupe ISA 48 boulevard Vauban, 59046 Lille Cedex, France (Received 9 April 2014; accepted 24 October 2014; first published online 10 April 2015) Abstract – In the Saoura Valley (Ougarta Basin, Saharan Algeria), the lower–upper Famennian part of the essentially shally Marhouma Formation is characterized by deep-water facies and includes horizons rich in ammonoids (goniatites and clymeniids) and blind to eye-reduced phacopide trilobites. They are also rich in small-sized and smooth rhynchonellide brachiopods, investigated here for the first time in order to detail their post-Kellwasser recovery. Rhynchonellides clearly predominate in the brachiopod assemblages (representing 90 % of the whole assemblage, with 10 species) composed otherwise of athyridides, orthides and spiriferides. Rhynchonellides are mostly represented by relatively flat leiorhynchids and rozmanariids consistent with poor oxygenation on the sea floor. One new species is described (Evanidisinurostrum saouraense sp. nov.); four genera, previously known only from the south-eastern margin of Laurussia, are reported for the first time from the northern margin of Gondwana: the leiorhynchid Sphaeridiorhynchus and the rozmanariids Leptoterorhynchus, Pugnaria and Novaplatirostrum. Keywords: Upper Devonian, Marhouma Formation, North Gondwana, brachiopods, Rhynchonellida, palaeoecology. 1. Introduction 2007). Brachiopods are of interest because they flour- ished along the northern margin of Gondwana in neritic Upper Devonian deposits were first recognized in facies sometimes unfavourable to ammonoids and con- the Saoura Valley (Algeria, Ougarta Basin) by Haug odonts, and are therefore valuable tools for biostrati- (1903) on the basis of cephalopods (goniatites and graphy in such palaeoenvironmental contexts, espe- clymeniids), which are particularly abundant in some cially regarding the Devonian–Carboniferous boundary levels (see also Menchikoff, 1930). The first compre- (Mottequin, Brice & Legrand-Blain, 2014). hensive study on the geology of this area was by Gau- This paper is the first comprehensive study of the tier (1906) and refined by Alimen et al. (1952), who diverse and small rhynchonellide brachiopods from described several important sections. The richness in the Famennian (Marhouma Formation) Saoura Valley ammonoids enabled Petter (1959) and Göddertz (1987) where they are the dominant element in the brachiopod to discriminate the zonation established by Wedekind assemblages, although they also occur in benthic com- (1908, 1926) in Germany and subsequently modified munities (cf. Crônier et al. 2013 for trilobites). Their by several authors (e.g. Korn, Klug & Reisdorf, 2000; diversity and palaeoecology are also discussed. Korn, 2004). Lower and Middle Devonian brachiopod faunas from the Ougarta were first described by Le Maître (1952) 2. Geological setting and material and revised in part by Boumendjel et al. (1997), Ouali Mehadji et al. (2004), and Brice et al. (2011) but, un- The material described in this paper comes from til recently, Upper Devonian brachiopods were poorly the Saoura Valley in the eastern part of the Ou- known (e.g. Brice, Legrand-Blain & Nicollin, 2005, garta Basin (Algerian Sahara), about 350 km SSW of Béchar (Fig. 1). The rhynchonellides were collected by F. Z. Malti in 2006–2008 during fieldwork for her ∗ Author for correspondence: [email protected] PhD thesis on the Marhouma Formation, a unit first http://journals.cambridge.org Downloaded: 01 Aug 2016 IP address: 157.193.5.232 1010 B. MOTTEQUIN AND OTHERS Figure 1. (a, b) Geographic locations of the Saoura Valley in the Ougarta Basin in Algeria. Abbreviations: b. – Béchar; m. – Morocco. (c) Location of studied sections (CA – Cheffar El Ahmar; St – Gara Diba; Ou – Ouarourout; Ze – Tamtert–Zereg). described by Poueyto (unpub. internal report, Société Ouali Mehadji et al.(2012); it is overlain by sandstones nationale de Recherche et d’Exploitation de Pétrole of the uppermost Famennian Ourarourout Formation en Algérie (SN-REPAL), 1965) and Bastien et al. (un- (Fabre, Kazi-Tani & Moussine-Pouchkine, 2005). pub. internal report, SN-REPAL, 1965) (e.g. Ouali Me- Member 1 consists of calcareous shales devoid of hadji et al. 2012 for more details), following a NNW– rhynchonellides; it is Late Frasnian in age (do Iβ)on SSE transect along the Saoura Valley and more par- the basis of goniatites (Manticoceras sp.) and entomo- ticularly in Ouarourout (30° 10 30 N; 2° 14 30 W), zoaceans (Casier, 1983). Gara Diba (30° 7 38 N; 2° 12 30 W), Cheffar El Ah- Member 2 includes silty shales with ‘griotte’ nod- mar (29° 57 25 N; 2° 7 15 W) and Tamtert-Zereg ules; it is divided into two submembers (a and b). The (29° 54 30 N; 1° 49 30 W) (Figs 1–3). She gathered term ‘griotte’ is applied to nodular to pseudonodular abundant and diverse marine macro- and microfaunas, limestones rich in ammonoid cephalopods (Benhamou including brachiopods, ammonoids (goniatites and cly- et al. 2004). Submember a comprises silty shales with meniids identified by D. Korn), trilobites, conodonts, numerous specimens of Evanidisinurostrum saour- and spores. aense sp. nov. in the Gara Diba section and a few Subdivisions of the Famennian Stage are those used Sphaeridiorhynchus sp. in the Cheffar El Ahmar sec- by Becker, El Hassani & Tahiri (2013, fig. 2) in align- tion in thin limestone lenses rich in horizontal burrows. ments between the conodont and ammonoid zonations The age of this submember cannot be precisely de- (see also Clausen, Weddige & Ziegler, 1993; Korn, termined due to the lack of conodonts and goniatites; 2002; Crônier et al. 2013). The acronyms do I to do the rhynchonellides suggest a possible early Famen- VI refer to successive Frasnian–Famennian cephalo- nian age. Submember b consists of alternating shales pod zones (Wedekind, 1908) with ‘do’ meaning Upper and ‘griotte’ limestone levels, sometimes in a succes- Devonian. sion of centimetre-thick beds. A limestone bed of this F.Z. Malti (unpub. PhD thesis, Oran University and submember in the Gara Diba section has produced the Abou Bekr Belkaid University, 2012) discriminated conodont Palmatolepis minuta subtilis in the interval four successive members in the Marhouma Formation spanning the P. triangularis to P. trachytera zones (do (Figs 2–3), the latter totalling about 260 m according to II). An interval of ‘griotte’ limestone in the Cheffar El http://journals.cambridge.org Downloaded: 01 Aug 2016 IP address: 157.193.5.232 Famennian rhynchonellides from the Saoura Valley 1011 Figure 2. Distribution of rhynchonellides, ammonoids, conodonts and palynomorphs within the Marhouma Formation in the Saoura Valley (Ougarta Basin, Algeria). Abbreviations: G. – Grandispora; P. – Palmatolepis; U. – Umbellasphaericum devonicum. Ahmar section produced Leptoterorhynchus sp. asso- ive of the middle–upper Palmatolepis expansa Zone ciated with Maenoceras; this rhynchonellide was pre- (upper–uppermost Famennian). This submember in the viously known from the middle Famennian. Tamtert–Zereg section is late Famennian on the basis Member 3 includes the ‘griotte’ limestone which of Platyclymenia Zone ammonoids. It has a diverse is divided into three submembers (a, b, c); one rhynchonellide fauna: Centrorhynchus sp., Leptoter- ‘griotte’ level produced several conodonts indicat- orhynchus sp., Phacoiderhynchus aff. antiatlasicus http://journals.cambridge.org Downloaded: 01 Aug 2016 IP address: 157.193.5.232 1012 B. MOTTEQUIN AND OTHERS Figure 3. Distribution of rhynchonellides within the Marhouma Formation in the Cheffar El Ahmar, Gara Diba, Ouarourout and Tamtert–Zereg sections. Sartenaer, 2000, Hadyrhyncha cf. hadyensis Havlícek,ˇ Order RHYNCHONELLIDA Kuhn, 1949 1979 and Novaplatirostrum sp. Superfamily RHYNCHOTREMATOIDEA Schuchert, 1913 Member 4 consists of shales with some ‘griotte’ Family TRIGONIRHYNCHIIDAE Schmidt, 1965 levels, but also sandy and silty deposits of turbiditic Subfamily TRIGONIRHYNCHIINAE Schmidt, 1965 origin; these are particularly thick at Ouarourout and Genus Centrorhynchus Sartenaer, 1970 Tamtert–Zereg. It has three submembers (a, b, c), but Type species. Camarotoechia baitalensis Reed, 1922, only the oldest submember produced rhynchonellides Famennian, Pamir. (Pugnaria sp.). Centrorhynchus sp. Figure 4a–b 3. Systematic palaeontology Material. One incomplete articulated specimen (Ze 2/8) from the Tamtert–Zereg section, Marhouma Form- The material described and figured here is housed at the ation, Member 3, Submember