Abstract
Three‐dimensional modeling that integrates fluvial sediment transport, crustal‐scale tectonic deformation, and lithospheric flexural subsidence is carried out to simulate the landscape and drainage evolution of the Ebro sedimentary basin (NE Iberia). The Ebro Basin underwent a long period of closed intramountain drainage as a result of tectonic topography generation at the Pyrenees, the Iberian Range, and the Catalan Coastal Range. In the late Oligocene, the Catalan Coastal Range underwent extension leading to the formation of the Valencia Trough (NW Mediterranean), but the Ebro Basin remained closed for nearly 15 Myr more before the Ebro River cut through the remnants of the topographic barrier. This drainage opening caused widespread basin incision that shaped spectacular outcrops of the syntectonic and posttectonic infill. Here we investigate the processes controlling these major drainage changes. The modeling results, constrained by a large data set on the tectonic and transport evolution of the area, predict a closed phase characterized by a large lake in the central eastern Ebro Basin. Dry climatic conditions probably lowered the lake level and contributed, together with rift flank uplift, to prolong this endorheic basin stage. The age and amount of reworked sediment after the opening are consistent with an onset of basin incision between 13 and 8.5 Ma as a result of lake capture by escarpment erosion and lake level rise associated with sediment accumulation and wetter climatic conditions. Sea level changes in the Mediterranean had no major impact in the large‐scale drainage evolution of the Ebro Basin.
Highlights
[2] Endorheic drainage basins are essential in understanding the evolution of sedimentary basins because they do not fit the notion that erosional products from orogens are carried to the oceans
The converging and partially synchronous tectonic shortening along the Pyrenees and the Iberian Range closed the western connection of the basin to the Atlantic Ocean in the earliest late Eocene, starting a long endorheic period of lacustrine deposition that lasted through the Oligocene and most of the Miocene [Riba et al, 1983]
[4] At the late Oligocene-early Miocene, the southeastern topographic barrier formed by the Catalan Coastal Range underwent tectonic inversion leading to the extensional reactivation of former reverse faults and producing rifting along the present Valencia Trough in NW Mediterranean [e.g., Bartrina et al, 1992]
Summary
[3] The formation of the Ebro foreland basin began during the Paleocene by flexural subsidence related to the growth of three surrounding Alpine ranges: the Pyrenees to the north (collisional orogenic chain), and the Catalan Coastal Range and Iberian Range to the SE and SW, GARCIA-CASTELLANOS ET AL.: TECTONICS, CLIMATE, AND DRAINAGE. [32] The numerical model applied here to study the drainage and sedimentary basin evolution is based on the approach developed by Garcia-Castellanos [2002] and incorporates planform numerical solutions to the following processes (Figures 6 and 7): (1) tectonic deformation is mainly driven by upper crustal thrust stacking and normal faulting; (2) surface transport is driven by the fluvial network as previously described; and (3) the mass redistribution resulting from (1) and (2) is compensated by regional isostasy (lithospheric flexure). [49] As the deposited sediments in the basin thicken, their deformation in the frontal part of the Pyrenean units produce a topographic barrier of increasing altitude, eventually producing deflections of the main rivers Such interaction between drainage networks and tectonic deformation in the External Sierras during middle Eocene to early Miocene times has been reported by Burbank and Verges [1994] and Arenas et al [2001]. This difference reflects the need for low precipitation rates (low R and KR in equation (3)) to avoid an earlier drainage opening in the model
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