P. Schmoldt, PhD - MTNet - DIAS

7.2. Betic Mountain Chain
part, represents a thick Palaeozoic shelf sequence of sediments, including Silurian graptolitic
black shale [Garcia-Alcalde et al., 2002] and Devonian carbonates [Colmenero
et al., 2002], both materials possessing the potential to form good electric conductors (see
Section 5 for details about electric conductivities), and extension-related volcanic rocks,
with a Proterozoic basement [Gibbons and Moreno, 2002a]. The Iberian Massif also
contains the Ossa-Morena Zone (OMZ in Fig. 7.1), located in the south-west of Spain,
which originates from the Cadomian orogeny and is therefore pre-Variscan [Gibbons and
Moreno, 2002a].
The Cantabrian Mountains were initially formed during Variscan orogeny and underwent
post-orogenic deformations during subsequent tectonic processes, whereas the Betics
and Pyrenees are due to Alpine orogeny, the result of successive collision of the Iberian
continental plate with Eurasia and Africa in Late Mesozoic – Cenozoic times [e.g. Dewey
et al., 1989; DeMets et al., 2006; Muñoz, 1992; Abalos et al., 2002; Azanon et al., 2002;
Capote et al., 2002; Gibbons and Moreno, 2002a; de Vicente and Vegas, 2009]. The intraplate
ranges are compressional mountain belts from Alpine orogeny (Spanish Central
System, CR in Fig. 7.1) and Tertiary orogeny (Iberian Ranges), separating the three major
Iberian basins, namely Duero, Ebro, and Tajo. Details about geologic settings of these intraplate
ranges and the Tajo Basin are given in Section 7.3, describing the regions around
the PICASSO Phase I study area more closely.
For the central Iberian Peninsula, a lithospheric thickness of around 110 km (±5 km)
has been inferred (cf. Sec. 7.3), diminishing towards the boundaries of the peninsula to
depths as shallow as 60 km at the Valencia Trough. The crust beneath the stable interior
has a typical continental structure with a thickness of 31 – 32 km and increased thickness
under the Alpine ranges [e.g. Capote et al., 2002]. Deep structures beneath the peninsula
are not well resolved since deep probing seismic studies are complicated due to Iberia’s
location on the edge of Europe. Seismic studies in this region, which, besides MT, have
the best potential to reveal deep-seated features, are challenged by the need to install and
maintain long-term stations in the Atlantic Ocean [e.g. Cloetingh et al., 2009] (cf. Sec.
7.3.2).
7.2. Betic Mountain Chain
The Betic Mountain Chain (also Betic Cordillera or Betics) is part of the arc-shaped
alpine Betic-Rif Cordilleras, stretching from the southeastern edge of the Iberian Peninsula
through the strait of Gibraltar down to the east of Morocco. The Betic-Rif Cordilleras
surround the Alboran Basin (also referred to as Alboran Domain and Alboran Microplate),
located beneath the western Mediterranean Sea. The Rif and Betic mountains are thrust
belts characterised by south-, west-, and north-vergent low angle thrust systems with tectonic
transportation directed away from the Alboran Basin [Seber et al., 1996]. The tectonic
setting of the Betic Cordillera is reasonably well known, and it is widely accepted
that the mountain chain was formed due to the collision of the African and Iberian plates
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