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Ana Moreno Blas L. Valero‐Garcés Montserrat Jiménez‐Sánchez María José Domínguez‐Cuesta M. Pilar Mata Ana Navas Penélope González‐Sampériz Heather Stoll Pedro Farias Mario Morellón J. Pablo Corella Mayte Rico 《第四纪科学杂志》2010,25(7):1076-1091
A sedimentological and geochemical study of the Lago Enol sequence (Cantabrian Mountains, northern Spain), together with detailed geomorphological mapping, provides a first record of glacier evolution and climate change over the last 40 ka in the Picos de Europa National Park. The Enol glacier retreated from its maximum extent prior to 40 ka BP as demonstrated by the onset of proglacial lacustrine sedimentation in two glaciated depressions: the Comella hollow to the north (before 40 ka BP) and the Lago Enol (before 38 ka BP). These results support previous evidence that the maximum extent of southern European glaciers occurred earlier than in northern Europe. Alternation of homogeneous and laminated proglacial sediments during the glacier retreat illustrate a dynamic glacial evolution during the Marine Isotope Stage (MIS) 3 (40–26 ka BP). A slight warming is detected at 26 ka ago with the change from proglacial sediments (in a lake located in contact to the glacier) to glaciolacustrine sedimentation (in a non‐contact or distal lake). Finally, the onset of organic‐rich sediments took place at 18 ka ago. This last transition occurred in two phases, similarly to the North Atlantic Last Termination, suggesting a link between North Atlantic Deep Water formation oscillations and palaeohydrological variability in the Cantabrian Mountains. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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The Variscan Belt in western Europe shows an arcuate geometry that is usually named Ibero-Armorican Arc. The nucleus of this arc, known as the Asturian Arc, comprises the Cantabrian Zone which is a foreland fold and thrust belt. The Trubia River area is located in the inflexion zone of the Asturian Arc, which is a strategic structural position for unraveling the geometry and kinematics of the Variscan thrust sheets and related folds. Geological mapping, construction of stratigraphic and structural cross sections, analysis of kinematic indicators, and estimate of shortening for each cross section have been carried out. This area consists of two major antiform-synform pairs related to two imbricate thrust systems. These folds are asymmetric, tight, and their axial traces follow the trend of the Asturian Arc. They have been interpreted as fault-propagation folds. The emplacement directions measured in the Trubia River area change from north to south and converge towards the core of the Asturian Arc. The minimum shortening estimated ranges between 16.4 and 17.6 km, which corresponds to 56.9 and 59.4%. The complex cross-cutting relationships between folds and thrusts suggest that, in general, the different structural units followed a forward-breaking sequence of emplacement, with some breaching and a few out-of-sequence thrusts. The analysis of the transport vectors together with the disposition of the fold axes and post-thrusting faults that deform the thrust stack are evidence of a late deformation event that is partially or totally responsible for the arcuate form of the Asturian Arc. The timing of the Asturian Arc, amount of shortening, and sequence of emplacement of the structures are in accordance with previous regional studies of the Cantabrian Zone. 相似文献
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A strategy to predict strain across geological structures, based on previous techniques, is modified and evaluated, and a practical application is shown. The technique, which employs cross-section restoration combined with kinematic forward modelling, consists of restoring a section, placing circular strain markers on different domains of the restoration, and forward modelling the restored section with strain markers until the present-day stage is reached. The restoration algorithm employed must be also used to forward model the structure. The ellipses in the forward modelled section allow determining the strain state of the structure and may indirectly predict orientation and distribution of minor structures such as small-scale fractures. The forward model may be frozen at different time steps (different growth stages) allowing prediction of both spatial and temporal variation of strain. The method is evaluated through its application to two stages of a clay experiment, that includes strain markers, and its geometry and deformation history are well documented, providing a strong control on the results. To demonstrate the method's potential, it is successfully applied to a depth-converted seismic profile in the Central Sumatra Basin, Indonesia. This allowed us to gain insight into the deformation undergone by rollover anticlines over listric normal faults. 相似文献
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Lateglacial and Holocene palaeohydrology in the western Mediterranean region: The Lake Estanya record (NE Spain) 总被引：3，自引：0，他引：3
Mario Morelln Blas Valero-Garcs Teresa Vegas-Vilarrúbia Penlope Gonzlez-Sampriz
scar Romero Antonio Delgado-Huertas Pilar Mata Ana Moreno Mayte Rico Juan Pablo Corella 《Quaternary Science Reviews》2009,28(25-26):2582-2599
The multi-proxy analysis of sediment cores recovered in karstic Lake Estanya (42°02′ N, 0°32′ E; 670 m a. s. l., NE Spain), located in the transitional area between the humid Pyrenees and the semi-arid Central Ebro Basin, provides the first high-resolution, continuous sedimentary record in the region, extending back the last 21 000 years. The integration of sedimentary facies, elemental and isotopical geochemistry and biogenic silica, together with a robust age model based on 17 AMS radiocarbon dates, enables precise reconstruction of the main hydrological and environmental changes in the region during the last deglaciation.Arid conditions, represented by shallow lake levels, predominantly saline waters and reduced organic productivity occurred throughout the last glacial maximum (21–18 cal kyrs BP) and the lateglacial, reaching their maximum intensity during the period 18–14.5 cal kyrs BP (including Heinrich event 1) and the Younger Dryas (12.9–11.6 cal kyrs BP). Less saline conditions characterized the 14.5–12.6 cal kyrs BP period, suggesting higher effective moisture during the Bölling/Allerød. The onset of more humid conditions started at 9.4 cal kyrs, indicating a delayed hydrological response to the onset of the Holocene which is also documented in several sites of the Mediterranean Basin. Higher, although fluctuating, Holocene lake levels were punctuated by a mid Holocene arid period between 4.8 and 4.0 cal kyrs BP. A major lake-level rise occurred at 1.2 cal kyrs BP, conducive to the establishment of conditions similar to the present and interrupted by a last major water level drop, occurring around 800 cal yrs BP, which coincides with the Medieval Climate Anomaly.The main hydrological stages in Lake Estanya are in phase with most Western Mediterranean and North Atlantic continental and marine records, but our results also show similarities with other Iberian and northern African reconstructions, emphasizing peculiarities of palaeohydrological evolution of the Iberian Peninsula during the last deglaciation. 相似文献
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P. Mayte S. Jiménez-Noriega Teresa Terrazas Lauro López-Mata Arturo Sánchez-González Heike Vibrans 《山地科学学报》2017,14(11):2182-2199
Change in environmental conditions with altitudinal gradients induces morpho-anatomical variations in plants that have been poorly documented in intertropical regions. Five species with three life forms, cryptophyte (Alchemilla procumbens, Geranium seemannii), hemicryptophyte (Acaena elongata, Lupinus montanus), and phanerophyte (Symphoricarpos microphyllus), distributed along an altitudinal gradient in the Sierra Nevada of central Mexico, were studied. The aims were to identify and evaluate their morpho-anatomical modifications under the hypothesis that the sizes of individuals and of their wood and leaf cell types decrease as elevation increases. Three individuals per species per site were collected at seven locations along the altitudinal gradient (2949-3952 m). Their morpho-anatomical characters were analyzed through multiple regression analyses. Elevation was the variable that best explained anatomical changes in the leaf and wood of the five species. Canopy density and potassium content in the soil also contributed to explain the variation in anatomical variables along the gradient. As elevation increased a bimodal pattern was observed in various anatomical characters as in the leaf width of A. elongata, A. procumbens and G. seemannii and in the vessel diameter of A. procumbens, G. seemannii, and L. montanus. Other features as the vessel diameter of A. elongata, the fiber length of S. microphyllus, and the ray width of A. elongata increased as the elevation increased. Anatomical traits have a tendency to decrease in size but just toward the end of the gradient, which is probably related to changes in canopy density. The plant response to the altitudinal gradient is more focused on anatomical adaptations than morphological variation; it is also species dependent. 相似文献
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To check the behaviour of physical experiments of simple rollover anticlines over listric normal faults, several fault-slip, bed-length and area parameters are measured for different beds in two stages of evolution of two physical experiments. Given a certain amount of extension, the heave and dip of the displacement vary for different beds, whereas the throw is approximately constant for small amounts of extension and the displacement remains constant for high amounts of extension. Neither bed lengths nor areas beneath beds remain constant with increasing extension. A number of techniques allow amounts of extension and detachment depth to be estimated given one or more marker horizons, the portion of the fault between hanging-wall and footwall cut off points, the depth to detachment and/or the shear angle. These techniques are applied to the physical experiments of listric normal faults analysed. Since many of these techniques rely on parameters measured on the physical experiments such as fault slip, bed length and area, the influence of these parameters on the different magnitudes of extension and detachment depths estimated using different techniques is discussed and the accuracy of the results is compared. 相似文献
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Flood response to rainfall variability during the last 2000 years inferred from the Taravilla Lake record (Central Iberian Range, Spain) 总被引：2，自引：0，他引：2
Ana Moreno Blas L. Valero-Garcés Penélope González-Sampériz Mayte Rico 《Journal of Paleolimnology》2008,40(3):943-961
A sedimentological, geochemical and palynological study of the Taravilla Lake sequence (Central Iberian Range, NE Spain) provides
a detailed record of allochthonous terrigenous layers that intercalate within the lacustrine sediments over the last 2000 years.
These terrigenous layers are interpreted as the result of extreme hydrological events that caused higher clastic input to
the basin. Anthropogenic influence caused by fires or deforestation is rejected as the main factor generating these layers
because human impact, inferred from the pollen reconstruction, was minimal when the terrigenous layers reached their greatest
frequency. The reconstructed occurrence of these events in the Taravilla Lake record is coherent with the paleoflood history
of the Tagus River, characterized by a notable increase of extreme events at the beginning of the Little Ice Age. The Taravilla
record suggests a relationship between the occurrence of extreme hydrological events, solar variability, and the North Atlantic
Oscillation for the NE Iberian Peninsula. 相似文献
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