Three-dimensional flexural modelling of the Ebro Basin(NE Iberia)

The Ebro Basin, the southern foreland basin of the Pyrenees, has undergone a complex evolution in which, apart from the Pyrenees, the Iberian Range and the Catalan Coastal Ranges have played an important role, both as sediment sources and as basin confining structures. The deflected basement underlying the Ebro Basin dips north, suggesting a lithospheric-scale control on the structure of this basin. This is compatible with the results of subsidence analyses, which show that the study area is not in a local mode of isostatic compensation. In order better to understand the mechanisms that led to the present configuration of the Ebro Basin, and particularly the relevance of the various kinds of (un)loading (e.g. surrounding fold-and-thrust belts, basin topography, subsurface loads), we carried out a 3-D kinematic modelling study that accounts for the flexural state of the lithosphere, subjected to various loads applied at its lateral boundaries, and the sedimentary fill of the basin. We also included the effect of Neogene extensional tectonics along the eastern basin margin, which is related to the opening of the Valencia Trough. We show the suitability of the 3-D lithospheric-scale flexural modelling approach to the study of NE Iberia. Modelling results point to a relatively strong lithosphere in this area, with values of effective elastic thickness ranging from 10 to 35 km in the Ebro Basin, increasing towards the Pyrenees. We also find that the topographic (tectonic) load itself is insufficient to explain the observed basement deflection. Thus an extra subsurface load beneath the Pyrenees, corresponding to the underthrusted Iberian lithosphere, is required. The effect of lithospheric stretching in the Valencia Trough on the Ebro Basin is appreciable only in its eastern part, where the lithosphere was uplifted. This had considerable repercussions on the sedimentary and erosional regime of the Ebro Basin. We have analysed the link between the stretching-related, tectonically uplifted areas and the erosional patterns observed onshore northeast Iberi

Linking the northern Alps with their foreland: The latest exhumation history resolved by low-temperature thermochronology

The evolution of the Central Alpine deformation front (Subalpine Molasse) and its undeformed foreland is recently debated because of their role for deciphering the late orogenic evolution of the Alps. Its latest exhumation history is poorly understood due to the lack of late Miocene to Pliocene sediments. We constrain the late Miocene to Pliocene history of this transitional zone with apatite fission track and (U-Th)/He data. We used laser ablation inductively coupled mass spectrometry for apatite fission track dating and compare this method with previously published and unpublished external detector method fission track data. Two investigated sections across tectonic slices show that the Subalpine Molasse was tectonically active after the onset of folding of the Jura Mountains. This is much younger than hitherto assumed. Thrusting occurred at 10, 8, 6–5 Ma and potentially thereafter. This is contemporaneous with reported exhumation of the External Crystalline Massifs in the central Alps. The Jura Mountains and the Subalpine Molasse used the same detachments as the External Crystalline Massifs and are therefore kinematically coupled. Estimates on the amount of shortening and thrust displacement corroborate this idea. We argue that the tectonic signal is related to active shortening during the late stage of orogenesis

Mechanisms of extension at nonvolcanic margins: Evidence from the Galicia interior basin, west of Iberia

We have studied a nonvolcanic margin, the West Iberia margin, to understand how the mechanisms of thinning evolve with increasing extension. We present a coincident prestack depth‐migrated seismic section and a wide‐angle profile across a Mesozoic abandoned rift, the Galicia Interior Basin (GIB). The data show that the basin is asymmetric, with major faults dipping to the east. The velocity structure at both basin flanks is different, suggesting that the basin formed along a Paleozoic terrain boundary. The ratios of upper to lower crustal thickness and tectonic structure are used to infer the mechanisms of extension. At the rift flanks (stretching factor, β ≤ 2) the ratio is fairly constant, indicating that stretching of upper and lower crust was uniform. Toward the center of the basin (β ∼ 3.5–5.5), fault‐block size decreases as the crust thins and faults reach progressively deeper crustal levels, indicating a switch from ductile to brittle behavior of the lower crust. At β ≥ 3.5, faults exhume lower crustal rocks to shallow levels, creating an excess of lower crust within their footwalls. We infer that initially, extension occurred by large‐scale uniform pure shear but as extension increased, it switched to simple shear along deep penetrating faults as most of the crust was brittle. The predominant brittle deformation might have driven small‐scale flow (≤40 km) of the deepest crust to accommodate fault offsets, resulting in a smooth Moho topography. The GIB might provide a type example of nonvolcanic rifting of cold and thin crust

Obese kweekvissen krijgen zwemtraining

Vis moet zwemmen, is het adagiumvan visfysioloog Arjan Palstra, maar kweekvissen doen dat te weinig. Dus dwingt hij ze in zijn lab in Yerseke. Ze knappen ervan op en –belangrijk voor de kwekers – ze groeien harder