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et al . 2000; Bandres et al . 2002; Expósito et al . 2003; Simancas et al . 2004; Díaz García 2006; Díez Fernández et al . 2019), all of which are collectively referred to as Cadomian Orogeny (cycle). The external section of Gondwana facing such subduction was involved in the Variscan cycle, whose onset and culmination may corre- spond to an extensional event that led to the opening of oceanic basins (e.g. Rheic Ocean; Linnemann et al . 2007, 2008; Nance et al . 2010), and the raise of the Variscan Orogen after their suturing (Matte 1991; Franke 2000; Ballèvre et al . 2009; Martínez Catalán et al . 2009), respec- tively. The Iberian Massif contains Cenozoic mountain ranges formed during the Alpine cycle (e.g. de Vicente and Vegas 2009). Some of them occur at the boundaries of the Iberian micro-plate (e.g. Pyrenees, Betics), while others occupy intra-plate positions. Both are the result of plate tectonics in the Mediterranean domain as well as of distributed strain upon Africa–Europe convergence (Dewey et al . 1989; Jolivet et al . 2008; de Vicente et al . 2018). The Mérida Massif is located in the SW part of the Iberian Massif (Figure 2). Previous studies have sug- gested that its composition and current structure is the result of Cadomian, Variscan, and Alpine tectonics (Gonzalo 1987, 1989; Bandrés 2001; Insúa Márquez et al . 2003). This massif includes an extensive exposure of Neoproterozoic and Lower Palaeozoic rocks (Figure 3), and represents a good opportunity to study Cadomian tectonics and the interference of subsequent orogenic cycles. Mapping of its bedrock geology has provided different outcomes over the years (Roso de Luna and Hernández Pacheco 1950; Gonzalo 1987; Bandrés 2001; Insúa Márquez et al . 2003). Although poorness of expo- sure may explain some variation, most of it seems to derive from contrasting criteria followed during map- ping. The Mérida Massif, although relatively small in size, is characterized by a significantly rich variety of rocks, making it difficult to establish coherent lithologi- cal groups to be mapped. Deformation in this area includes the development of foliations, folds, faults, and shear zones, some of which are coeval to pervasive metamorphism (Gonzalo 1987, 1989; Bandrés et al . 2000; Bandrés 2001). 3 . Tectonostratigraphy In this section, we provide a brief description of the main lithological associations we have established in the Mérida Massif (Figure 3). Grouping is focused on recog- nition of major tectonic blocks intervening in Cadomian and Variscan tectonics (Figure 4). Rocks included into each tectonostratigraphic unit meet the following grouping criteria: (i) similar structural position at regio- nal scale, (ii) the ensemble shows either continental or oceanic crust affinity, (iii) equivalent tectonometa- morphic evolution, and (iv) they are separated from other units by either a major mechanical boundary (i.e. fault or ductile shear zone) or a major stratigraphic dis- continuity (e.g. discordance). Age of protoliths alone was not taken as a grouping criteria, because the amalgama- tion of two tectonic blocks may juxtapose rocks of simi- lar age. Descriptions are given following normal chronological order according to their (meta-) sedimen- tary strata. Where bedding and age constrains are lack- ing, underlying units (as indicated by their main foliation) are described first. 3.1. Lower Gneiss Unit: Magdalena Gneisses This unit consists of penetratively deformed and strongly recrystallized metamorphic rocks, which range from intermediate to felsic orthogneisses (Figure 5(a)) and paragneisses (Figure 5(b)). Both contain abundant quartz and feldspar, although abundance in mica varies. Figure 2. Regional geological map of the Obejo-Valsequillo Domain showing the location of the Mérida Massif. Location of map in Figure 3 is indicated. INTERNATIONAL GEOLOGY REVIEW 3 Tectonostratigraphy of the Mérida Massif