Publication: On the tectonic origin of Iberian topography
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Publication Date
2009
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Elsevier
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Abstract
The present-day topography of the Iberian peninsula can be considered as the result of the MesozoicCenozo–ic
tectonic evolution of the Iberian plate (including rifting and basin formation during the Mesozoic and
compression and mountain building processes at the borders and inner part of the plate, during the Tertiary,
followed by Neogene rifting on the Mediterranean side) and surface processes acting during the Quaternary.
The northern-central part of Iberia (corresponding to the geological units of the Duero Basin, the Iberian Chain,
and the Central System) shows a mean elevation close to one thousand meters above sea level in average, some
hundreds of meters higher than the southern half of the Iberian plate. This elevated area corresponds to (i) the
top of sedimentation in Tertiary terrestrial endorheic sedimentary basins (Paleogene and Neogene) and
(ii) planation surfaces developed on Paleozoic and Mesozoic rocks of the mountain chains surrounding the
Tertiary sedimentary basins. Both types of surfaces can be found in continuity along the margins of some of the
Tertiary basins. The Bouguer anomaly map of the Iberian peninsula indicates negative anomalies related to
thickening of the continental crust. Correlations of elevation to crustal thickness and elevation to Bouguer
anomalies indicate that the dierent landscape units within the Iberian plate can be ascribed to dierent
patterns: (1) The negative Bouguer anomaly in the Iberian plate shows a rough correlation with elevation, the
most important gravity anomalies being linked to the Iberian Chain. (2) Most part of the so-called Iberian
Meseta is linked to intermediate-elevation areas with crustal thickening; this pattern can be applied to the two
main intraplate mountain chains (Iberian Chain and Central System) (3) The main mountain chains (Pyrenees
and Betics) show a direct correlation between crustal thickness and elevation, with higher elevation/crustal
thickness ratio for the Central Systemvs. the Betics and the Pyrenees. Other features of the Iberian topography,
namely the longitudinal pro le of the main rivers in the Iberian peninsula and the distribution of present-day
endorheic areas, are consistent with the Tertiary tectonic evolution and the change from an endorheic to an
exorheic regime during the Late Neogene and the Quaternary. Some of the problems involving the timing and
development of the Iberian Meseta can be analysed considering the youngest reference level, constituted by
the shallow marine Upper Cretaceous limestones, that indicates strong dierences induced by (i) the overall
Tertiary and recent compression in the Iberian plate, responsible for dierences in elevation of the reference
level of more than 6 km between the mountain chains and the endorheic basins and (ii) the eect of Neogene
extension in the Mediterranean margin, responsible for lowering several thousands of meters toward the East
and uplift of rift shoulders. A part of the recent uplift within the Iberian plate can be attributed o sostatic uplift in zones of crustal thickening.