Daniel Garcia-Castellanos

Catastrophic flood of the Mediterranean after the Messinian salinity crisis

The Mediterranean Sea became disconnected from the world’s oceans and mostly desiccated by evaporation about 5.6 million years ago during the Messinian salinity crisis. The Atlantic waters found a way through the present Gibraltar Strait and rapidly refilled the Mediterranean 5.33 million years ago in an event known as the Zanclean flood. The nature, abruptness and evolution of this flood remain poorly constrained. Borehole and seismic data show incisions over 250 m deep on both sides of the Gibraltar Strait that have previously been attributed to fluvial erosion during the desiccation. Here we show the continuity of this 200-km-long channel across the strait and explain its morphology as the result of erosion by the flooding waters, adopting an incision model validated in mountain rivers. This model in turn allows us to estimate the duration of the flood. Although the available data are limited, our findings suggest that the feedback between water flow and incision in the early stages of flooding imply discharges of about 108 m3 s-1 (three orders of magnitude larger than the present Amazon River) and incision rates above 0.4 m per day. Although the flood started at low water discharges that may have lasted for up to several thousand years, our results suggest that 90 per cent of the water was transferred in a short period ranging from a few months to two years. This extremely abrupt flood may have involved peak rates of sea level rise in the Mediterranean of more than ten metres per day.

Interplay between tectonics, climate, and fluvial transport during the Cenozoic evolution of the Ebro Basin (NE Iberia)

[1] 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. INDEX TERMS: 1625 Global Change: Geomorphology and weathering (1824, 1886); 1815 Hydrology: Erosion and sedimentation; 3210 Mathematical Geophysics: Modeling; 3344 Meteorology and Atmospheric Dynamics: Paleoclimatology; 8102 Tectonophysics: Continental contractional orogenic belts; KEYWORDS: Pyrenees, drainage evolution, lake, sediment budget, erosion, flexure

Lithospheric folding in Iberia

Integration of stress indicator data, gravity data, crustal kinematics data, and analysis of topography and recent vertical motions demonstrates the occurrence of consistently oriented spatial patterns of large-scale Alpine to recent intraplate deformation in Iberia. The inferred upper crustal and lithospheric deformation patterns and the timing of the associated expressions at or near the surface support the existence of a close coupling with plate boundary processes operating at the margins of Iberia. Patterns of lithosphere and upper crustal folds are oriented perpendicular to the main axis of present-day intraplate compression in Iberia inferred from structural analysis of stress indicator data and focal mechanism solutions. These findings suggest the presence of lithospheric folds, with wavelengths compatible with theoretical predictions of folding wavelengths of Variscan lithosphere. Stress-induced intraplate deformation set up by plate interactions is compatible with indications for the absence of present-day deep mantle-lithosphere interactions inferred from seismic tomography.

Messinian salinity crisis regulated by competing tectonics and erosion at the Gibraltar arc

The Messinian salinity crisis (5.96 to 5.33 million years ago) was caused by reduced water inflow from the Atlantic Ocean to the Mediterranean Sea resulting in widespread salt precipitation and a decrease in Mediterranean sea level of about 1.5 kilometres due to evaporation. The reduced connectivity between the Atlantic and the Mediterranean at the time of the salinity crisis is thought to have resulted from tectonic uplift of the Gibraltar arc seaway and global sea-level changes, both of which control the inflow of water required to compensate for the hydrological deficit of the Mediterranean. However, the different timescales on which tectonic uplift and changes in sea level occur are difficult to reconcile with the long duration of the shallow connection between the Mediterranean and the Atlantic needed to explain the large amount of salt precipitated. Here we use numerical modelling to show that seaway erosion caused by the Atlantic inflow could sustain such a shallow connection between the Atlantic and the Mediterranean by counteracting tectonic uplift. The erosion and uplift rates required are consistent with previous mountain erosion studies, with the present altitude of marine sediments in the Gibraltar arc and with geodynamic models suggesting a lithospheric slab tear underneath the region. The moderate Mediterranean sea-level drawdown during the early stages of the Messinian salinity crisis can be explained by an uplift of a few millimetres per year counteracted by similar rates of erosion due to Atlantic inflow. Our findings suggest that the competition between uplift and erosion can result in harmonic coupling between erosion and the Mediterranean sea level, providing an alternative mechanism for the cyclicity observed in early salt precipitation deposits and calling into question previous ideas regarding the timing of the events that occurred during the Messinian salinity crisis.

Crustal-scale cross-sections across the NW Zagros belt: implications for the Arabian margin reconstruction

Quantified balanced and restored crustal cross-sections across the NW Zagros Mountains are presented in this work integrating geological and geophysical local and global datasets. The balanced crustal cross-section reproduces the surficial folding and thrusting of the thick cover succession, including the near top of the Sarvak Formation (~90 Ma) that forms the top of the restored crustal cross-section. The base of the Arabian crust in the balanced cross-section is constrained by recently published seismic receiver function results showing a deepening of the Moho from 42 ± 2 km in the undeformed foreland basin to 56 ± 2 km beneath the High Zagros. The internal parts of the deformed crustal cross-section are constrained by new seismic tomographic sections imaging a ~50° NE-dipping sharp contact between the Arabian and Iranian crusts. These surfaces bound an area of 10800 km 2 that should be kept constant during the Zagros orogeny. The Arabian crustal cross-section is restored using six different tectonosedimentary domains according to their sedimentary facies and palaeobathymetries, and assuming Airy isostasy and area conservation. While the two southwestern domains were directly determined from well-constrained surface data, the reconstruction of the distal domains to the NE was made using the recent margin model of Wrobel-Daveau et al . (2010) and fitting the total area calculated in the balanced cross-section. The Arabian continental–oceanic boundary, at the time corresponding to the near top of the Sarvak Formation, is located 169 km to the NE of the trace of the Main Recent Fault. Shortening is estimated at ~180 km for the cover rocks and ~149 km for the Arabian basement, including all compressional events from Late Cretaceous to Recent time, with an average shortening rate of ~2 mm yr −1 for the last 90 Ma.

Numerical modeling of foreland basin formation: a program relating thrusting, flexure, sediment geometry and lithosphere rheology

Abstract An algorithm has been developed which allows the flexural deflection of the lithosphere to be calculated under thrust loading and the geometry of the sedimentary infill in the adjacent foreland basin. To that purpose we have considered arbitrarily shaped thrust-load systems moving towards the foreland, and surface processes denudating the orogen and filling the basin. The regional compensation of topographic loads is based on the assumption that the lithosphere behaves as a thin plate with either homogeneous (elastic, viscoelastic) behavior or more realistic depth-dependent elastic–plastic rheology. When using heterogeneous rheology, the program calculates the flexural behavior as a function of crustal geometry and thermal regime of the lithosphere, thus relating the basin infill geometry with the deep lithosphere properties. We show some examples where the geometry of the basin and sedimentary infill (e.g. onlap/toplap patterns) are generated assuming different lithosphere rheologies and synthetic tectonic contexts which support the applicability of the model to study the formation and evolution of foreland basins.

Modelling the Middle Pleistocene uplift in the Ardennes–Rhenish Massif: thermo-mechanical weakening under the Eifel?

Abstract Middle Pleistocene uplift in the Eifel has been interpreted as the isostatic response of the lithosphere to a deep buoyant hot body. The spatial and temporal distribution of the uplift in the Ardennes–Rhenish Massif Region has recently been constrained by new data of river incision that have been compiled in this work. The uplift distribution can be reproduced using a thin elastic plate model and assuming that the uplift is created by a deep buoyant load, the distribution of which coincides with the weakening. Models incorporating a lithospheric weakening provide a better fit of the observed uplift than models with homogeneous flexural rigidity. These results are confirmed by numerical experiments using a depth-dependent elasto-plastic plate rheology, linking the flexural model with the thermo-mechanical structure of the lithosphere.

Role of the 3D distributions of load and lithospheric strength in arcuate orogenic arcs: poly-stage subsidence in the Carpathians foredeep.

Abstract It has been widely documented that the depth of foredeeps does not always reflect the topography of the neighboring orogens. In many cases, the topographic load is insufficient to explain basin subsidence. Such is the case of the SE Carpathians where an anomalously deep (almost 13 km) foreland basin has evolved since the Middle Miocene (Badenian). A peculiar feature of this basin is its position relative to the orogen. In contrast to typical foredeeps, which deepen towards the belt, the maximum depth of this basin is 10–20 km out of the orogen. The subsidence in the Carpathians Bend foreland is characterized by two stages: the first is Middle Miocene (Badenian) in age and is related to NE–SW extension when fault-bounded basins were formed. Modeling shows that the foreland underwent small pre-orogenic uniform thinning. The modeling also predicts

Deep structure of the Vøring Margin: the transition from a continental shield to a young oceanic lithosphere

The present-day lithospheric structure across the Norwegian Margin in the Voring region is presented. The Voring Margin is characterized by the presence of large volume of magmatic underplating, thick Mesozoic basins, and prominent crustal thinning. Results from recent deep seismic experiments in the Voring Basin and Voring Marginal High and 3-D gravity modelling have been implemented in a regional 2-D lithospheric transect that runs from the Norwegian Caledonian Belt to the oceanic domain, crossing the transition between the Precambrian Fennoscandian/Baltic shield and the Cenozoic northern North Atlantic oceanic lithosphere. The modelling approach integrates elevation, gravity, geoid and heat flow data under the assumptions of thermal steady-state and local isostasy. The results confirm and refine the major trends of the crustal geometry which is characterized by a Moho depth varying from about 45 km beneath the Caledonian thrusts, to 30 km beneath the Trondelag Platform, to 20–14 km beneath the Voring Basin and to 13 km in the oceanic domain. The lithosphere thins from the Norwegian Caledonian Belt (190 km thick) to the oceanic domain (<60 km) in a stepwise manner reflecting the progressive seawards migration of lithospheric deformation since the Paleozoic. Our lithospheric thickness results are different from those predicted by post-rift lithospheric cooling models. In the oceanic domain, observed residual bathymetry (∼600 m) is interpreted as the remaining effect of a deep seated thermal perturbation during the upper Cretaceous which would also produce a heat flow anomaly of ∼15 mW m−2. Alternatively, residual bathymetry can be interpreted in the absence of thermal anomalies as produced by depletion of the sublithospheric mantle extending down to 130–230 km depth depending on the density contrast (10–30 kg m−3).

Geophysical and geological constraints on the evolution of the Guadalquivir foreland basin, Spain

Abstract This paper presents a compilation and reinterpretation of available geophysical and geological data recently acquired for the ENE-WSW Guadalquivir foreland basin, located on the northern margin of the Betic orogen in southern Iberia. The data include seismic reflection and refraction profiles, well logs, gravity, geoid, surface heat-flow data and field observations. The deep structure of the southern Iberian margin is characterized by large variations in crustal thickness and high heat-flow values, which result in a very low lithospheric rigidity for the whole area. Geoid and gravity data show that deformation affected the crust and the lithospheric mantle differently, producing anomalous mass distributions that could act as subsurface loads. Seismic sequence analysis of the basin infill has permitted the re-assessment of the depositional sequential arrangement of the sediments deposited from Late Langhian-Early Serravallian to Messinian. They are arranged in six sequences and do not show any E-W progradational pattern indicating that during this period the acting loads moved essentially in a NNW direction. A careful analysis of the southern border of the basin shows that the ‘so-called olistostromes’ correspond to lateral diapirs of squeezed Triassic evaporites and internally imbricated Miocene wedges. We discuss the results obtained in terms of palaeo-geographic environments, time distribution and nature of acting loads, and constraints for future basin modelling approaches.