Brachiopods from the Lower-Middle Cambrian Láncara Formation of the Cantabrian Mountains, Northwest Spain THOMAS WOTTE & MICHAL MERGL WOTTE, T. & MERGL, M., 2007:09:03. Brachiopods from the Lower-Middle Cambrian Láncara Formation of the Cantabrian Mountains, Northwest Spain. Memoirs of the Association of Australasian Palaeontologists 33, 101-122. ISSN 0810-8889. Micro- and macrobrachiopods from eight stratigraphic sections of the carbonate upper member of the Middle Cambrian Láncara Formation (comprising lower Beleño facies and upper Barrios facies) in the Cantabrian Mountains are analysed. They comprise ten species, two of which are new, assigned to nine genera, two of which are new. They are: Acrothele primaeva (de Verneuil & Barrande in de Prado, 1860), Acrothele sp., Eoobolidae gen. et sp. indet., Genetreta trilix gen. et sp. nov., Iberotreta sampelayoi gen. et sp. nov., Luhotreta? proclinis (Mergl & Elicki, 2004), Micromitra cf. sculptilis (Meek, 1873), Nisusia vaticina (de Verneuil & Barrande in de Prado, 1860), Trematobolus simplex (Vogel, 1962) and Yorkia zafrensis (Gil-Cid & Mélou, 1986). Stratigraphic distribution patterns of the brachiopod fauna mirror the drowning of the environment. Trematobolus simplex is exclusively found in the carbonates of the Beleño facies, whereas Nisusia vaticina and Yorkia zafrensis are typical representatives of the nodular limestones of the Barrios facies. The species of the genera Trematobolus, Nisusia and Yorkia demonstrate the affinity of the upper Láncara brachiopod association with faunas of the Siberian platform, New South Wales and some Avalonian terranes (Newfoundland, New Brunswick). Thomas Wotte ([email protected]), Geological Institute, Freiberg University of Mining and Technology, Bernhard-von-Cotta Street 2, D-09599 Freiberg, Germany; Michal Mergl ([email protected]), Department of Biology, University of West Bohemia at Plzeň, Klatovská 51, CZ-306 19, Plzeň, Czech Republic. Received 23 April 2007. Keywords: Brachiopoda, Middle Cambrian, Láncara Formation, Cantabrian Zone, Spain. THE IBERIAN MASSIF (Fig. 1A) has one and fossil content allow differentiation of this of the most complete Palaeozoic sedimentary formation into two members (Zamarreño 1972): successions in Europe (Gibbons & Moreno the lower member consists of dolomites and 2002). The approximately 2700 m thick Cambrian dolomitic limestones with a rather poor fossil succession in the Cantabrian Zone consists of three content represented by algae, archaeocyaths (only formations (Fig. 2). The lowermost formation, at the eastern part of the Cantabrian Zone) (e.g., the Herrería Formation, is characterised by Debrenne & Zamarreño 1970; Perejón & Moreno- claystones, sandstones and conglomerates, Eiris 2003) and trilobites (Sdzuy 1959). The representing a ?Neoproterozoic-Early Cambrian upper member of the Láncara Formation has been age. Within this siliciclastic succession, calcareous divided into two facies (Zamarreño 1972): the intercalations are sometimes observed. The fossil lower Beleño facies is characterised by coarsely content of the Herrería Formation consists of crystalline, grey to roan dolomitic limestones ichnofossils (e.g., van der Meer Mohr & Okulitch and limestones with a high content of glauconite 1967; Palacios & Vidal 1992), acritarchs (e.g., and echinoderm debris. The overlying Barrios Palacios & Vidal 1992; Vidal et al. 1999) and facies consists of reddish to purple limestones trilobites (e.g., Sdzuy 1961; Liñán et al. 1993). and nodular limestones with a highly diverse The sedimentary environment of the Herrería fossil content. Known faunal elements of the Formation is interpreted as a shallow marine upper member of the Láncara Formation include platform with occasional intertidal deltaic and trilobites (e.g., Sdzuy 1968; Sdzuy & Liñán 1993), fluviatile episodes (e.g., Rupke 1965; Aramburu brachiopods (de Verneuil & Barrande in de Prado et al. 1992). The carbonates of the Lower-Middle 1860; Sampelayo 1935), echinoderms (Schroeder Cambrian Láncara Formation overlie the Herrería 1973; Friedrich 1993), molluscs (Geyer 1986; Formation (Fig. 2). Differences in lithology Wotte 2006), sponge and chancelloriid remains 102 AAP Memoir 33 (2007) Fig. 1. A, simplified geological map of the Iberian Peninsula. B, generalised geological map of the Cantabrian Mountains (modified after Pérez-Estaún et al. 1988); Tr = Truebano section; Ge = Genestosa section; Ra = Rabanal section; LL = Láncara de Luna section; BL = Los Barrios de Luna section; Pe = Piedras Bermejas section; Ro = Rodiezmo section; Ve = Vegaservera section; PI = Porma section. (Sdzuy 1969; Clausen & Álvaro 2006), and in the siliciclastic material (Wotte et al. 2004; phosphatic small shelly fossils (van den Boogaard Wotte 2005). The environment of the Láncara 1983). The faunal and lithological transition Formation is interpreted as a transition from a from the Beleño into the Barrios facies is carbonate ramp to a mixed carbonate-siliciclastic gradual, characterised by a continuous change ramp (Wotte et al. 2004; Wotte 2005), with in the fossil content, and a successive increase supralittoral-littoral conditions in its western part AAP Memoir 33 (2007) 103 Schroeder (1973), Friedrich (1993) and Sdzuy (1993); and graptolites by Sdzuy (1974). Middle Cambrian-Tremadocian acritarchs were recorded by Fombella (1978, 1979). Aramburu et al. (1992) and Aramburu & García-Ramos (1993) interpreted the siliciclastic succession of the Oville Formation as shallow platform deposits of an intertidal and braid plain deltaic environment. BIOFACIES The upper member of the Láncara Formation contains a highly diverse fauna of trilobites, echinoderms, brachiopods, chancelloriid and sponge remains, but also molluscs and phosphatic small shelly fossils. Based on point counting analyses of thin sections, the vertical faunal distribution through the upper member of the Láncara Formation could be divided into four distinct faunal assemblages (Wotte et al. 2004; Wotte 2005; Fig. 3). For sections which were only documented but not intensively sampled, the vertical faunal succession was estimated on the basis of field data, and in comparison with the point-counted sections. The faunal assemblages of these sections are illustrated in Figure 3 as ‘assumed’. In almost all sections, the upper member of the Láncara Formation (except Genestosa; cf. Fig. 3) starts with an abrupt onset and a predominance of echinoderms, whereas trilobites and brachiopods are clearly less common. This biofacies is called faunal assemblage 1, and is equal with the Beleño facies of Zamarreño (1972). The base of faunal assemblage 2 is marked by a minimum of echinodermal remains, and characterises the base of the Barrios facies. The faunal content is either dominated by trilobites and brachiopods, or it shows nearly equal volumetric ratios of echinoderms, trilobites and brachiopods. Faunal assemblage 3 develops as part of a conformable continuum and is characterised by a further increase in the abundance of trilobites and brachiopods as well as a resurgence of Fig. 2. Simplified stratigraphic profile of the Cambrian echinoderm numbers. Faunal assemblages 1-3 of the Cantabrian Mountains (modified after Liñán et al. 1993 and Geyer & Landing 2004). also include chancelloriids, sponges, molluscs, and phosphatic small shelly fossils as minor faunal elements. In the Los Barrios de Luna section, this and shallow sublittoral environments in its eastern general faunal trend is characterised by a short region (Zamarreño 1972; Aramburu et al. 1992). and rapid decrease in echinoderms, trilobites and The overlying Middle Cambrian-Ordovician brachiopods, whereas further faunal elements Oville Formation consists of claystones and (e.g., chancelloriids, poriferids, molluscs) sandstones (Fig. 2). Sometimes quartzose beds show no distinct change. This specific portion, are observable in the uppermost part (Truyols characterised by Stromatactis-rich limestones, et al. 1990). No carbonate intercalations are represents faunal assemblage 4 (Fig. 3). present in this part of the succession. The fossil content of the Oville Formation is also relatively PREVIOUS WORK AND SAMPLE diverse: trace fossils were described by Gámez CHARACTERISTICS Vintaned et al. (2000); trilobites by Sdzuy (1961, The initial observations on brachiopods from 1968) and Gozalo et al. (2000); echinoderms by the studied area were presented by de Verneuil 104 AAP Memoir 33 (2007) Fig. 3. Distribution of the faunal assemblages within the studied sections. For sections not point-counted, acceptance of the faunal assemblages and definition of their boundaries are problematic (see text), and thus illustrated as ‘assumed’. Genestosa is the only locality where the faunal succession starts with faunal assemblage 2. Faunal assemblage 4 was only recorded at the Los Barrios de Luna section. For abbreviations of the sections see caption to Figure 1. & Barrande (in de Prado 1860), who discussed for the repository was not successful. Walcott and illustrated five brachiopod species. The type (1912) revised all species described by de material was not available to Walcott (1908, Verneuil & Barrande (in de Prado 1860). Finally, 1912) and has probably been lost; a recent search Sampelayo (1935) figured and commented on AAP Memoir 33 (2007) 105 section latitude longitude altitude [m] Truebano 42° 56´09. 9´´ N 006° 00´28. 4´´ W 1253 Genestosa 43° 00´22. 2´´ N 006° 00´41. 1´´ W 1265 Rabanal 42° 55´51. 4´´ N 005° 58´25. 3´´ W 1175 Láncara de Luna 42° 54´34. 8´´ N 005° 55´26. 5´´