Nova Terra 52

1965) (Fig. 3). 2.1. Stratigraphic record of the Ediacaran series The Ediacaran series of the Schist and Greywacke Complex are di- vided in two groups: Lower Alcudian and Upper Alcudian (Redlin, 1955; Ovtracht and Tamain, 1970; Pieren, 2000) (Fig. 3). The Lower Alcudian is composed of a monotonous succession of turbidites, sub- divided from bottom to top into three formations: (1) shales and greywackes of the Coronada Formation, (2) greywackes, micro- conglomerates and shales of the Santa María del Zújar Formation, and (3) shales, diamictites and greywackes of the Orellana Formation (Pieren, 2000). The minimum thickness of the Lower Alcudian in the southern boundary of the Central Iberian Zone is 6000 m, since its bottom remains unexposed (Pieren, 2000) (Figs. 3 and 4). The maximum depositional age of the Lower Alcudian has been recently calculated at c. 565 ± 4 Ma using U-Pb geochronology in detrital zircons (Talavera et al., 2015; Linnemann et al., 2017). This age is equivalent to the age proposed for this sequence by means of pa- leontologic and stratigraphic evidence (Pieren, 2000). This sequence is unconformably overlain by the Upper Alcudian (Figs. 3 and 4), which is thinner and also includes layers of conglomerates and limenstones (Pieren, 2000). The geochemistry of the Lower Alcudian siliciclastic rocks (metagreywackes) in the southern sector of the Central Iberian Zone has been recently studied by Fuenlabrada et al. (2016). The oldest sedimentary series in the Obejo-Valsequillo Domain (Ossa-Morena Complex) is the Serie Negra (Carvalhosa, 1965) (Fig. 3). Although a precise separation is usually complicated in sectors affected by intense deformation and metamorphism, this series has been divided into two formations, from bottom to top: the Montemolín Formation and the Tentudía Formation (Eguíluz, 1988). The Montemolín Forma- tion is composed by metagreywackes, metasandstones, schists, micas- chists, quartzschists and black quartzites, with levels of amphibolites and amphibolic gneisses (Fig. 4). The precise age of this series is un- known, but its maximum depositional age has been estimated at c. 590 Ma (U-Pb geochronology in detrital zircons; Ordóñez Casado, 1998). The Tentudía Formation is composed by metasandstones, vol- canogenic metagreywackes, slates and phyllites, black quartzites, me- tacherts and layers of micaschists and limestones (Fig. 4). Its maximum depositional age has been calculated at c. 565–541 Ma (U-Pb geochro- nology in detrital zircons; Schäfer et al., 1993; Linnemann et al., 2008; Pereira, 2015). It is considered that, with the exception of the Mérida Massif, the Serie Negra exposed in the Obejo-Valsequillo Domain cor- responds to the upper part of the Tentudía Formation (Bandrés, 2001). Fig. 2. Geological map of the Iberian Massif showing the distribution of the allochthonous terranes in NW and SW Iberia (Díez Fernández and Arenas, 2015). Abbreviations: AF, Azuaga Fault; BAO, Beja-Ace- buches Ophiolite; CA, Carvalhal Amphibolites; CF, Canaleja Fault; CMU, Cubito-Moura Unit; CO, Cal- zadilla Ophiolite; CU, Central Unit; ET, Espina Thrust; HF, Hornachos Fault; IOMCO, Internal Ossa- Morena Complex Ophiolites; LLF, Llanos Fault; MLF, Malpica-Lamego Fault; OF, Onza Fault; OVD, Obejo Valsequillo Domain; PG–CVD, Puente Génave-Cas- telo de Vide Detachment; PRF, Palas de Rei Fault; PTF, Porto-Tomar Fault; RF, Riás Fault; VF, Viveiro Fault. Location of the geological map presented in Fig. 3 is shown. E. Rojo-Pérez et al. 3UHFDPEULDQ 5HVHDUFK ² Contrasting isotopic sources: CIZ - OMC boundary