serie NOVA TERRA nº 49

112 the Centro-Extremeño Anticline or Río Zujar Dome) and has been previously referred to as Lower Alcudian ( San José et al., 1990 ); Domo Extremeño Group in the Montes de Toledo, Extremadura and Alcudia ( Alvarez Nava et al., 1988 ); Lower Series in the Western Central area of the CIZ ( Ugidos et al., 1997b; Valladares et al., 2000, 2002 ); and Beiras Group in Portugal ( Silva et al., 1988 ). The thickness of this unit is unknown since its lower boundary remains unexposed, but the sequences exceed 4000 m. The metasedimentary rock series consists of a monotonous succession of shales and sandstones with some inter- bedded conglomerates and volcanoclastic layers, mainly in its upper part. The sediments of the Lower Unit have been interpreted as laid down in submarine fans, slopes and channels ( San José et al., 1990; Valladares et al., 2000 ), but evidence of shallower depositional environ- ments have also been found ( Rodríguez Alonso et al., 2004b ). As a whole, this sedimentary sequence is considered as a set of turbidites deposited in a prograding synorogenic clastic wedge fi lling a back-arc basin ( Rodríguez Alonso et al., 2004b ). Based on the presence of Cloudina carinata (Late Ediacaran, Cortijo et al., 2010 ) and other types of microfossils ( Jensen et al., 2007; Vidal et al., 1994a, 1994b ), the Lower Unit is Neoproterozoic in age. In the area, where the samples CIA-13 to CIA-20 were collected ( Figs. 2 and 3 b), the Lower Alcudian starts with shales, silts and thin beds of sandstones, which become thicker and more abundant in the middle part; the upper part is charac- terized by the presence of polygenic conglomerates (with greywackes, vein quartz, and metamorphic and granodioritic cobbles) and pebbly mudstones alternating with shales and sandstones ( García-Hidalgo et al., 1993 ). The whole sequence is interpreted as the progradation of a turbiditic fan, where the upper part was not deep, and thus it also shows outer shelf deposits. The samples were taken in the interval a of thick Bouma sequences within the middle part. In the Agudo – Valdemanco Anticline the absence of marker layers, such as the men- tioned conglomerates, has not allowed the distinction of different parts within the Lower Alcudian turbidites, but the samples CIA-21 to CIA-24 were collected in the a interval of very well exposed thick Bouma sequences. The Upper Unit has been given different names by different authors on different anticlines: Upper Alcudian or Ibor Group, Pusa Formation or Río Huso and Valdelacasa Groups ( Alvarez Nava et al., 1988; San José et al., 1990; Vidal et al., 1994a ) in the Centro-Extremeño and Alcudia anticlines, and the “ Montes de Toledo ” region; the Middle and Upper a) Valdelacasa Anticline b) Fig. 3. Synthetic stratigraphic columns of the Valdelacasa and Alcudia Anticlines (modi fi ed after Vidal et al., 1999 ). The location of the analyzed samples is shown. Color legend as in Fig. 2 . 18 J.M. Fuenlabrada et al. / Tectonophysics 681 (2016) 15 – 30