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31 quality of the analyses is high and the general precision is calculated at ∼0.01%, with higher precision (∼0.001%) for MnO and TiO 2 . The results of the analyses are included in Table 1 and plotted into the diagrams presented in Fig. 5. The geochemistry of major and trace elements in siliciclastic rocks is widely used to understand their nature and alteration degree, as well as to track provenance sources and tectonic setting for sedimentary basins (Holland, 1978; Nesbitt and Young, 1982; Taylor and McLennan, 1985; Bhatia, 1983; Bhatia and Crook, 1986; Herron, 1988; Floyd et al., 1991). Elements with a particularly stable behaviour (REE, Th, Cr, Co, Nb, Ti, Sc, Zr, Y, Hf) provide a basis for interpreting the conditions under which sedimentation of the Ediacaran Iberian series took place. 3.2. Results Samples collected in the Obejo-Valsequillo Domain (Serie Negra) display quite homogenous contents in major elements (Table 1). No significant differences from those of the Upper Continental Crust (UCC; Condie, 1993) can be observed, with the exception of CaO (avg. 0.8 wt %; UCC: 3.36 wt%). Low values for SiO 2 /Al 2 O 3 , K 2 O/Na 2 O, Al 2 O 3 / Na 2 O y Al 2 O 3 /Ti 2 O ratios (avg. 4.4, 0.8, 4.6 and 21.1, respectively), are similar to those of the Lower Alcudian greywackes (avg. 5.2, 0.7, 4.6 and 18.8, respectively; Fuenlabrada et al., 2016), and lay within the typical range for an upper continental crust provenance (4.5, 0.9, 4.5 and 24.2, respectively; Condie, 1993). Such ratios are consistent with an immature character for these metasedimentary rocks. The PIA values Fig. 4. Schematic stratigraphic columns of the Late Ediacaran series. (A) Lower Alcudian Series from the southern part of the Central Iberian Zone. (B) Serie Negra Group from the Obejo Valsequillo Domain (Ossa-Morena Complex). E. Rojo-Pérez et al. 3UHFDPEULDQ 5HVHDUFK ² Contrasting isotopic sources: CIZ - OMC boundary