serie NOVA TERRA nº 49

113 Series in the western central part of the CIZ ( Ugidos et al., 1997b; Valladares et al., 2000 ), and Douro Group in Portugal ( Sousa, 1982 ). The older units aremore frequent towards SWand the younger Cambri- an units towards NE. The local names and their distribution are summa- rized by Rodríguez Alonso et al. (2004b) . The Upper Unit shows greater lithological variety than the Lower Unit although it is mainly pelitic. The basal part of the Upper Unit is separated from the deposits of the Lower Unit by an angular unconformity ( Rodríguez Alonso et al., 2004b ). The record of tectonic activity consists of discontinuous accumulations of megabreccias, olistostromes and chaotic deposits, whichmay be accom- panied by some episodes of volcanism. Deposition took place in sedi- mentary environments ranging from turbiditic platform to offshore siliciclastic – carbonate turbiditic platform. This mixed platform is better developed towards Extremadura and Montes de Toledo. The rest of the Upper Unit includes gray, dark-gray and black shales, conglomerates and sandstones, together with discontinuous and minor interbedded layers of limestone, olistostromes, phosphates, and volcanic and volcanoclastic rocks. The sedimentary facies of the Upper Unit are more diverse and re fl ect a more complex evolution than those of the Lower Unit. Deposition took place on turbiditic slopes, mixed platform (carbonate – siliciclastic), siliciclastic platform, and even transitional marine-continental platform environments along the southern bound- ary of the CIZ ( Pieren, 2000; Pieren et al., 1991 ). The fossil record found in this unit places the Proterozoic – Cambrian transition in the Upper Alcudian or Ibor Group below the Pusa Group ( García Hidalgo, 1993; Liñán et al., 1984; San José et al., 1990 ), which is entirely Cambri- an. Pusa Shales were mostly deposited in shallowwaters, in a clear tran- sition from a turbiditic environment to a continental platform ( Simancas et al., 2004 ). The Pusa Group is conformably covered by transgressing sandstones deposited during the middle stages of the Early Cambrian. These fossil rich sediments, well-exposed in upright synclines south of Toledo (Azorejo Sandstones) and south of Salamanca (Tamames Sandstones), were deposited on shallow marine platforms, and are followed by car- bonates formed in a shallow shelf (Navalucillos Limestones in Montes de Toledo and Tamames Limestones in Salamanca) ( Díez Balda, 1986; Table 1 Whole rock major and trace element data of Lower Alcudian greywackes (Late Ediacaran). CIA-13 CIA-14 CIA-15 CIA-16 CIA-17 CIA-18 CIA-19 CIA-20 CIA-21 CIA-22 CIA-23 CIA-24 SiO 2 71.18 71.4 71.3 73.31 71.96 70.98 70.38 72.48 66.31 64.58 66.93 70 Al 2 O 3 13.15 13.48 13.05 12.19 12.77 12.65 13.71 12.67 14.79 15.83 15.53 13.27 Fe 2 O 3 4.92 5.03 4.99 5.08 5.01 4.92 5.28 5.05 5.47 6.26 5.19 4.53 MnO 0.035 0.047 0.046 0.066 0.047 0.036 0.044 0.057 0.066 0.064 0.051 0.065 MgO 1.91 1.86 1.97 1.74 1.77 1.49 1.73 1.58 2.02 2.36 1.93 1.5 CaO 0.27 0.59 0.48 0.27 0.28 0.29 0.38 0.76 1.29 0.74 0.47 1.45 Na 2 O 2.89 3.25 2.97 2.84 2.81 2.79 2.99 3 2.96 2.81 3.08 3.44 K 2 O 1.92 1.85 1.85 1.53 1.79 1.84 1.9 1.75 2.95 3.22 3.21 2.39 TiO 2 0.723 0.841 0.745 0.71 0.703 0.67 0.753 0.731 0.629 0.747 0.699 0.763 P 2 O 5 0.17 0.2 0.18 0.13 0.13 0.16 0.14 0.14 0.15 0.17 0.16 0.15 LOI a 2.24 2.36 2.4 2.2 2.22 2.21 2.37 2.51 3.16 3.24 2.69 2.89 Total 99.42 100.9 99.99 100.1 99.49 98.02 99.68 100.7 99.79 100 99.93 100.5 CIA 66 63 64 65 65 65 65 62 60 64 63 56 Sc 12 13 12 12 12 12 13 12 11 14 12 10 Be 2 2 2 2 2 2 2 2 3 3 3 2 V 94 99 97 94 95 93 97 94 72 93 84 85 Cr 80 100 90 80 90 80 80 90 60 80 80 90 Co 11 16 18 14 15 15 14 15 13 16 17 16 Ni 40 40 40 30 40 40 40 40 30 40 40 20 Cu 40 40 50 10 30 40 30 30 30 30 30 20 Zn 80 230 90 100 90 110 80 80 100 110 100 70 Ga 17 19 17 15 17 17 18 16 19 24 22 17 Rb 73 73 71 59 76 69 76 66 103 129 127 81 Sr 91 122 100 102 98 108 106 106 211 152 187 226 Y 25.5 31.6 26 25.6 25.1 25.2 25.9 26.6 35.5 40.3 31.6 23.3 Zr 226 360 243 218 228 192 209 293 223 243 237 307 Nb 10.9 12.7 10.5 9.8 10.4 9.7 11 10.2 13.7 15.4 13.5 11.2 Cs 3 3.2 3.1 2.6 3.2 2.7 3.1 2.7 5.7 6.4 6.4 4.1 Ba 395 446 422 341 363 422 451 400 740 778 834 679 Hf 5.5 8.5 5.9 5.4 5.7 4.7 5.2 6.6 5.8 6.2 5.8 7.2 Ta 0.8 0.88 0.78 0.74 0.76 0.73 0.81 0.79 1.06 1.16 1 0.83 Pb 12 14 15 20 14 12 12 15 67 17 16 20 Th 8.62 9.7 8.13 7.97 8.47 7.77 8.79 8.6 10.9 12.8 11.1 11 U 2.39 2.87 2.59 2.12 2.46 2.32 2.55 2.57 3.45 3.89 3.26 2.82 Al 2 O 3 /Na 2 O 4.6 4.1 4.4 4.3 4.5 4.5 4.6 4.2 5.0 5.6 5.0 3.9 Al 2 O 3 /TiO 2 18.2 16.0 17.5 17.2 18.2 18.9 18.2 17.3 23.5 21.2 22.2 17.4 SiO 2 /Al 2 O 3 5.4 5.3 5.5 6.0 5.6 5.6 5.1 5.7 4.5 4.1 4.3 5.3 K 2 O/Na 2 O 0.7 0.6 0.6 0.5 0.6 0.7 0.6 0.6 1.0 1.1 1.0 0.7 Rb/Sr 0.80 0.60 0.71 0.58 0.78 0.64 0.72 0.62 0.49 0.85 0.68 0.36 Ti/Zr 19.18 14.00 18.38 19.52 18.48 20.92 21.60 14.96 16.91 18.43 17.68 14.90 Ti/Nb 398 397 425 434 405 414 410 430 275 291 310 408 La/Sc 2.53 2.55 2.30 2.28 2.43 2.28 2.30 2.56 3.04 2.82 2.93 3.34 La/Th 3.52 3.41 3.39 3.43 3.44 3.53 3.40 3.57 3.06 3.09 3.17 3.04 Th/U 3.61 3.38 3.14 3.76 3.44 3.35 3.45 3.35 3.16 3.29 3.40 3.90 Th/Nb 0.79 0.76 0.77 0.81 0.81 0.80 0.80 0.84 0.80 0.83 0.82 0.98 Th/Sc 0.72 0.75 0.68 0.66 0.71 0.65 0.68 0.72 0.99 0.91 0.93 1.10 Zr/Sc 18.83 27.69 20.25 18.17 19.00 16.00 16.08 24.42 20.27 17.36 19.75 30.70 Co/Th 1.28 1.65 2.21 1.76 1.77 1.93 1.59 1.74 1.19 1.25 1.53 1.45 Oxides are in weight percent (wt.%). Trace elements are in parts per million (ppm). CIA: Chemical Index of Alteration ( Nesbitt and Young, 1982 ). Oxides in molar proportions. a Loss on ignition. 19 J.M. Fuenlabrada et al. / Tectonophysics 681 (2016) 15 – 30