See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/241554530 Ranges and basins in the Iberian Peninsula: Their contribution to the present topography Article in Geological Society London Memoirs · January 2006 DOI: 10.1144/GSL.MEM.2006.032.01.13 CITATIONS READS 45 1,503 2 authors, including: Jaume Vergés Geosciences Barcelona (Geo3Bcn) CSIC 305 PUBLICATIONS 9,296 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: Growth Strata in the Central Zagros fold-and-thrust belt, Dehdasht area View project MITE: Modeling the Iberian Topographic Evolution View project All content following this page was uploaded by Jaume Vergés on 21 May 2014. The user has requested enhancement of the downloaded file. Ranges and basins in the Iberian Peninsula: their contribution to the present topography JAUME VERGE´ S & MANEL FERNA` NDEZ Group of Dynamics of the Lithosphere (GDL), Institute of Earth Sciences ‘Jaume Almera’, CSIC, 08028 Barcelona, Spain (e-mail: [email protected]) Abstract: The Iberian Peninsula, at the western end of the Alpine–Himalayan Belt, displays a complex structure with mountain ranges of diverse structural trends and sedimentary basins between them. The Iberian Peninsula also shows an elevated mean topography, the highest in Europe. In this short paper, we investigate the Alpine evolution of the Iberian Peninsula since Mesozoic times, when Iberia was isolated as an independent plate. This occurred from Albian (formation of the northern plate boundary) to Oligocene times (end of the Pyrenean Orogeny). Iberia was squeezed between Africa and Europe during Tertiary times and all previously established Mesozoic extensional basins were inverted, as were some of the Hercynian structures. The opening of the Valencia Trough, cutting the eastern margin of the Iberian Peninsula, began in Oligocene times. Concomitant crustal and lithospheric stretching during the Neogene along the eastern margin of Iberia produced limited uplifts, some of which are still active. The modern topography of the Iberian Penin- sula was developed mainly as the result of three main tectonothermal mechanisms since late Palaeozoic times: variations in crustal den- sities, and possibly mantle depletion, inherited from the Hercynian Orogeny; crustal and lithospheric thickening during Tertiary compression; and upper mantle thinning during the Neogene–Quaternary. The Iberian Peninsula constitutes the westernmost segment of the between Africa and Iberia changes progressively from pure right- 12 000 km long Alpine–Himalayan Belt formed as a result of lateral strike-slip along the Gloria Fault to a diffuse transpressive the Tertiary closure of the Tethys Ocean during the collision of boundary from the Gorringe Bank to the Gulf of Cadiz region India, Arabia and Africa with Asia and Europe (e.g. Dercourt (e.g. Argus et al. 1989). et al. 1986). The present structure of the Iberian Peninsula developed through Rifting initiated during Triassic times (c. 250 Ma) and culmi- the interplay of several geodynamic processes related to the Atlan- nated in crustal break-up along the Atlantic margin (e.g. Ziegler, tic opening, the formation of two plate boundaries limiting the 1988, 1992). Continental break-up of the African Plate occurred Iberian Plate, the north–south Africa–Europe convergence, and during the Late Jurassic (c. 156 Ma). The Atlantic Ocean propa- the concomitant rapid retreat and consumption of the oceanic gated northwards through the proto-Azores–Gibraltar plate Tethyan realms. Different geodynamic processes related to these boundary, producing the continental rupture of the Iberian Plate large-scale tectonic events were to some extent coeval over particu- in Early Cretaceous times (c. 118 Ma; e.g. Srivastava et al. lar morphotectonic regions. Both the diversity of geodynamic 1990). The mid-Cretaceous northern boundary of the Iberian processes and their potential conjunction complicate the unravelling Plate formed along the oceanic lithosphere of the Atlantic Ocean of the evolution of the Iberian Plate in general and, in particular, the and its eastern continuation along the continental lithosphere of southern plate boundary between Iberia and Africa (Betic the Pyrenees (Fig. 1). Cordillera, Rif, Alboran Sea and Gulf of Cadiz tectonic units). Towards the end of Late Cretaceous (chron 33, 80 Ma) Africa This paper documents in brief the Alpine evolution of the onshore shifted its motion northwards, initiating convergence with Iberian Peninsula mountain ranges and sedimentary basins, Eurasia with the consumption of the Tethys Ocean (e.g. Dercourt emphasizing the geodynamic processes that created positive topo- et al. 1986). At the westernmost termination of the Alpine– graphic relief. This evolution took involved the following major tec- Himalayan Belt, the Iberian Plate underwent a protracted defor- tonic events: (1) formation of extensional Mesozoic basins at the mation phase, resulting in orogenic belts along the plate bound- intersection of the proto-Atlantic and the Tethys oceans; (2) gener- aries (Bay of Biscay–Pyrenees and Azores–Gibraltar) and ation of Late Cretaceous–Tertiary fold-and-thrust belts and basins severe intraplate deformation. Several large Tertiary sedimentary by the northwards motion of Africa; (3) formation of basins by basins developed on the Iberian Plate close to the bounding moun- Neogene extension along the eastern margin of the proto-Western tain chains (Friend & Dabrio 1996). Most of these basins began as Mediterranean. The paper concludes with the present topographic flexural basins and continued as intermontane basins during the configuration of the Iberian Peninsula and its heritage from Hercy- growth of the complex Iberian mountain system (Fig. 1). nian times including the relatively recent lithospheric thinning Iberia initially moved together with the African Plate, from latest along the Mediterranean province of Spain. Cretaceous to mid-Eocene times (chron 19, 42 Ma), deforming Two recently published books on the geology of Spain give a mainly the Bay of Biscay–Pyrenees plate boundary. From mid- detailed description of the mountains and basins documented in Eocene to the end of Oligocene times (chron 6c, 24 Ma), it moved this brief paper (Gibbons & Moreno 2002; Vera 2004). Andeweg independently and both plate boundaries were active. Subsequently, (2002) has also illustrated the evolution of the palaeostress field during the last 24 Ma, most of the deformation was accommodated in the Iberian Peninsula through the Cenozoic. along the complex and poorly understood plate boundary between Iberia and Africa, leading to the formation of the Betics, the Gibraltar Arc, and the Rif. The end of the Oligocene also coincided with exten- Mesozoic extensional basins sion along the proto-Western Mediterranean Sea, which affected the entire eastern margin of the Iberian Plate. This extension formed the Preceding the opening of the central Atlantic during mid-Jurassic oceanic lithosphere below the Liguro-Provenc¸al Basin north of times (chron BSMA at c. 170 Ma), the Iberian Peninsula (Iberian the Paul Fallot Fault. To the south of this fault, thinned lithosphere Plate) was deformed by large-scale stretching that resulted in below the Valencia Trough and Alboran Sea and oceanic lithosphere numerous extensional basins with different orientations. Rift below the Algeria Basin formed (Fig. 1). The present contact systems developed along the western margin of the Iberian Plate From:GEE,D.G.&STEPHENSON, R. A. (eds) 2006. European Lithosphere Dynamics. Geological Society, London, Memoirs, 32, 223–234. 0435-4052/06/$15.00 # The Geological Society of London 2006. 223 224 J. VERGE´ S & M. FERNA` NDEZ The separation between Europe and Africa for this period is about 240 km along this transect (e.g. Boccaletti et al. 1977; Olivet 1996; see position B for Africa in Fig. 2). The proposed position of Africa provides very little room for the restored Betic domain, thus creating a significant space problem, which has already been recognized (e.g. Andrieux et al. 1971; Mauffret et al. 1989; Frizon de Lamotte et al. 1991; Lonergan & White 1997; Spakman & Wortel 2000). Andrieux et al. (1971) proposed a model, still used with modifications by a number of workers, in which the Alboran Block was displaced towards the west by lateral extrusion during the north–south conver- gence of Africa and Iberia. Crustal and lithospheric thinning was the common process that formed the extensional basins. The thinned regions constituted weaker zones at the end of the Cretaceous just before the onset of Tertiary compression. Most of these extensional basins were tectonically inverted, preserving their original basin orientation. An extensive distribution of Triassic evaporites controls the geo- metry of the thrust system in both previous tectonic basins and structural highs, as in the case of the southern end of the Iberian Fig. 1. Map of Western Europe with location of principal orogenic chains related Chain along the Altomira thrust system (the western boundary to the Africa–Europe collision (based on Verge´s&Sa`bat 1999). The Pyrenean of the Iberian Range; Fig. 3). Range corresponds to the westernmost limit of the about 12 000 km long Q7 Alpine–Himalayan Belt. CCR, Catalan Coastal Ranges; B-C, Basco-Cantabrian thrust belt; CM, Cantabrian Mountains; P.F.F., Paul Fallot Fault. Alpine Orogeny: Tertiary compressive belts and sedimentary basins (offshore Galicia and Portugal;