Person: Muñoz García, María Belén
Loading...
First Name
María Belén
Last Name
Muñoz García
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Department
Geodinámica, Estratigrafía y Paleontología
Area
Estratigrafía
Identifiers
36 results
Search Results
Now showing 1 - 10 of 36
Item Fabric and Fluid Inclusions Characterization of a Stalagmite from Eastern Spain: A Precondition for Noble Gas Analysis by Step-Crushing Methodology(Minerals, 2024) López Elorza, Maialen; Weißbach, Therese; Muñoz García, María Belén; Kluge, Tobias; Aeschbach, Werner; Martín Chivelet, JavierFluid inclusions in stalagmites are becoming increasingly important for paleoclimate research. Within this framework, noble gas thermometry, based on noble gases dissolved in water from fluid inclusions, provides quantitative estimations of cave air paleotemperature. Two major issues of Noble Gas Temperature (NGT) determination on speleothems are (1) the potential lack of enough water for the analysis and (2) the presence of trapped gas not dissolved in water that can be released during the analysis from biphasic or all-gas fluid inclusions, as its contribution to the bulk noble gas signal can hinder NGT results. Although the step-crushing method helps to reduce the second issue, it also decreases the amount of water available for the calculations. In order to obtain reliable NGT results with low uncertainties, a major challenge is still to reach a balance between sufficient water for analysis and a small amount of “atmospheric” gas. The difficulty is that the extraction process cannot be standardized since it strongly depends on the type of sample. The objective of this work is to investigate how the characteristics of the speleothem can determine the adequacy of the extraction process. For this purpose, we consider a stalagmite from a Mediterranean cave that consists of columnar elongated calcite and contains a significant quantity of fluid inclusions, which suggests good potential for NGT analysis. Results, however, were poorly satisfactory. Trying to understand the source of the problems, an integrated study of petrography and petrophysical features was performed. The samples were found to be different depending on the stage of coalescence of crystals and thus separated into “open” and “closed” fabrics. Classic petrographic analysis and non-destructive (nuclear magnetic resonance) techniques were used to characterize the type and amount of fluid inclusions present in both types of fabrics. The study indicates that the closed fabric (total coalescence of calcite crystals) has most water trapped in water-filled, small intracrystalline fluid inclusions that usually contain very little gas. This fabric is very suitable for NGT determination, but since the amount of water is quite small, the sample should be crushed in only one step with a large number of beats to break all the inclusions. In contrast, samples with open fabric (partial coalescence of calcite crystals) contain a higher amount of water and, also, gas-filled large intercrystalline fluid inclusions. For this fabric, step-crushing of the sample is necessary. However, the low amount of water left for the second and third crushings could lead to flawed NGT results. Thus, we suggest modifying the method to get rid of part of the gas in the first crushing while leaving enough water for the following steps. This work shows the importance of characterizing speleothems and fluid inclusions, including their petrography and petrophysical characteristics, before starting NGT analysis, allowing the selection of the most favorable samples and the customization of the step-crushing procedure.Item Land surface temperature changes in Northern Iberia since 4000 yr BP, based on δ13C of speleothems(Global and Planetary Change, 2011) Martín Chivelet, Javier; Muñoz García, María Belén; Edwards, R. Lawrence; Turrero, María J.; Ortega, Ana I.The surface temperature changes for the last 4000 years in northern inland Iberia (an area particularly sensitive to climate change) are determined by a high resolution study of carbon stable isotope records of stalagmites from three caves (Kaite, Cueva del Cobre, and Cueva Mayor) separated several tens of kilometers away in N Spain. Despite the local conditions of each cave, the isotopic series show a good overall coherence, and resulted to be strongly sensitive to surface temperature changes. The record reflects alternating warmer and colder intervals, always within a temperature range of 1.6 °C. The timing and duration of the intervals were provided by 43 230Th–234U (ICP-MS) ages. Main climatic recognized periods are: (1) 3950–3000 yr BP: warm period punctuated by cool events around ~3950, 3550 and 3250 yr BP; (2) 2850–2500 yr BP cold interval (Iron Age Cold Period); (3) 2500–1650 yr BP moderate warm period (Roman Warm Period), with maximum temperatures between 2150 and 1750 yr BP; (4) 1650– 1350 yr BP cold interval (Dark Ages Cold Period), with a thermal minimum at ~1500 yr BP; (5) 1350– 750 yr BP warm period (Medieval Warm Period) punctuated by two cooler events at ~1250 and ~850 yr BP; (6) 750–100 yr BP cold period (Little Ice Age) with extremes occurring at 600–500 yr BP, 350–300 yr BP, and 150–100 yr BP; and (7) the last 150 years, characterized by rapid but no linear warming (Modern Warming). Remarkably, the presented records allow direct comparison of recent warming with former warm intervals such as the Roman or the Medieval periods. That comparison reveals the 20th century as the time with highest surface temperatures of the last 4000 years for the studied area. Spectral analysis of the time series shows consistent climatic cycles of ~400, ~900 and ~1300 yr, comparable with those recognized in the North Atlantic marine record, the Greenland ice cores, and other terrestrial records for the middle–late Holocene, suggesting common climate forcing mechanisms related to changes in solar irradiance and North Atlantic circulation patterns.Item Efectos de la separación de flujo en las secuencias de barras de meandro. Ejemplos del Oligoceno Superior de la Cuenca de Loranca(Geotemas, 2008) Muñoz García, María Belén; Díaz Molina, MargaritaEl registro estratigráfico del Eoceno-Mioceno de la cuenca de Loranca está formado por sedimentos fluviales, aluviales y lacustres. Durante el Oligoceno Superior los depósitos de ríos meandriformes del abanico fluvial de Tórtola se extendieron por el centro de la cuenca y su margen oeste. Las barras de meandro del abanico de Tórtola presentan diferencias con el modelo de facies básico, en el que la secuencia de estructuras sedimentarias está producida por una disminución de la velocidad de la corriente. Las secuencias fining-upwards graduales no son las más frecuentes en las barras de meandro del Oligoceno de la cuenca de Loranca. La estructura sedimentaria más abundante es la estratificación cruzada de pequeña escala rellenando surcos erosivos, que puede presentarse en toda la sección de la barra de meandro. La estratificación cruzada de ripples compone a su vez otras formas del lecho que se caracterizan por una morfología de crestas longitudinales. Estas formas compuestas se interpretan como formas del lecho generadas por vórtices espirales en zonas de separación de flujo.Item Estudios paleoclimáticos y paleoambientales en cuevas kársticas(2011) Martín Chivelet, Javier; Muñoz García, María Belén; Garralón, A.; Gómez, P.; Turrero, M.J.; Ortega, A.I.; Edwards, R.L.; Cheng, H.; Santisteban, J.I.; Mediavilla, R.; Pérez-Monserrat, Elena M.; Charco Romero, MaríaItem Fluid-inclusion petrography in calcite stalagmites: Implications for entrapment processes(Journal of sedimentary research, 2021) López Elorza, Maialen; Muñoz García, María Belén; González Acebrón, Laura; Martín Chivelet, JavierFluids trapped in speleothems have an enormous potential in frontier fields of paleoclimate and paleohydrological research. This potential is, however, hampered by diverse scientific and technical limitations, among which the lack of a systematic methodology for genetically characterizing fluid inclusions is a major one, as these can have different origins, and thus, the trapped fluid (usually water), different meanings. In this work, we propose a systematic petrological classification of fluid inclusions, based on: 1) the temporal relation between fluid inclusions and the host calcite, 2) the spatial relation between fluid inclusions and the “crystallites” and crystals aggregates, and 3) the phases (water, air) trapped inside fluid inclusions. The first criterion allows dividing fluid inclusions in two main categories: primary and secondary, whose identification is critical in any research based on trapped fluids. The other two criteria allow the definition of eight types of primary and four types of secondary fluid inclusions. Primary fluid inclusions contain the drip water that fed stalagmites at the time of crystal growth, and can be intercrystalline, i.e., located between adjacent crystallites, or intracrystalline, i.e., with the fluid trapped within crystallites. We differentiate six main types among the intercrystalline fluid inclusions (elongate, thorn-shaped, down-arrow, interbranch, macro-elongate, and bucket) and other two among intracrystalline inclusions (pyriform and boudin). In primary inclusions, water is the main phase, while gas is much less abundant. The presence of gas could be related to slow drip rates or degassing in the cave, but also to later leakage due to changes in temperature and humidity often occurring during inadequate handling of speleothem samples. Secondary fluid inclusions were clearly related to younger water inlet through stratigraphic disruptions or unconformities. They are formed after water infiltration, but sealed before the renewed crystal growth. We differentiate four main types of secondary inclusions: interconnected, rounded, triangular, and vertical fluid inclusions. The identification of primary and secondary fluid inclusions in speleothems is a key for interpretation in paleoclimate studies. Integration of petrological results allow establishment of three different genetic scenarios for the formation of fluid inclusions, whose identification can be relevant because of their predictive character.Item El contaje de puntos como método de estimación de la cantidad de agua de las inclusiones fluidas en espeleotemas(Geotemas, 2021) López Elorza, Maialen; Muñoz García, María Belén; Martín Chivelet, JavierLas inclusiones fluidas albergan el agua que originó el crecimiento del mineral huésped, y su estudio proporciona información relevante sobre las condiciones de crecimiento del propio mineral. En el caso de los espeleotemas, las inclusiones fluidas primarias atrapan el agua de goteo que originó el crecimiento del espeleotema. Esta agua proviene del agua meteórica que se infiltró desde el epikarst hasta la cueva, lo que supone que las inclusiones fluidas albergan el agua fósil derivada de la que precipitó en los alrededores de la cueva durante el periodo de crecimiento del espeleotema. Estas inclusiones de agua presentan una estrecha relación genética con la fábrica calcítica, y su distribución o la cantidad de agua que contienen dependen de las condiciones de crecimiento del cristal colindante. Para poder analizar todo ello, en este trabajo presentamos un nuevo método de estimación de la cantidad de agua de las inclusiones fluidas de los espeleotemas basada en el contaje de puntos petrográfico. Esta técnica permite 1) caracterizar la fábrica de calcita; 2) determinar la relación espacial entre inclusión-calcita; y por último, 3) cuantificar la cantidad de agua y aire que contienen las inclusiones. La técnica pretende ser una herramienta de gran utilidad previa a los diferentes estudios geoquímicos que se llevan a cabo en las inclusiones fluidas de los espeleotemas.Item Speleothem architectural analysis: integrated approach for stalagmite-based paleoclimate research(Sedimentary Geology, 2017) Martín Chivelet, Javier; Muñoz García, María Belén; Cruz, Juncal A.; Ortega Martínez, Ana Isabel; Turrero Jiménez, María JesúsCarbonate stalagmites have become increasingly attractive to Quaternary paleoclimate research, as they can be accurately dated by radiometric methods and concurrently yield high-resolution multi-proxy records of past climate conditions. Reliable series however require the precise characterization of stalagmite internal icrostratigraphy,4 a task too often poorly accomplished despite the recent advances in speleothem research. This weakness is due to the lack of a robust integrative methodological framework capable of integrating the wide range of petrographical and micro-stratigrafical methods currently used in speleothem characterization. For covering this need, this review introduces the Speleothem Architectural Analysis (SAA), a holistic approach inspired in well-established stratigraphic procedures such as the architectural element analysis and the sequence stratigraphy, commonly used by geoscientists for categorizing internal stratigraphic heterogeneities in sedimentary deposits. The new approach establishes a six-fold hierarchy of speleothem architectural elements and their bounding surfaces: individual crystallites (1st order), single growth layers (2nd order), speleothem fabrics (3rd order), stacking patterns sets (4th order), morphostratigraphic units (5th order), unconformity-bounded units and major unconformities (6th order). Each category of architectural element is formed in a different range of time, from intervals as short as a year/season to others of centuries or millennia. The SAA, which has the capability of incorporating any petrographic or stratigraphic classification, provides a useful, systematic, and versatile tool for unraveling the complexities of speleothem growth, and thus for genetically interpreting stalagmites in a multi-temporal scale. A detailed speleothem stratigraphy must be the basis for performing robust reconstruction of paleoclimate series. They should precede and accompany any work focused in absolute age dating or in reconstructing paleoclimate by means of any geochemical proxyItem Datación de carbonatos por el método de U/Th: ejemplos en España(Cuaternario y geomorfología, 2022) Muñoz García, María Belén; Martín Chivelet, JavierEl método de U/Th permite datar materiales diversos de hasta 600.000 años de antigüedad. En este trabajo se revisan sus fundamentos y las técnicas analíticas disponibles, centrándose en su aplicación más habitual, que es la datación de carbonatos. En concreto, se discuten su potencial y limitaciones en la datación de espeleotemas, travertinos, calcretas, cementos, corales y moluscos aprovechando los ejemplos publicados en España. El cálculo de edades mediante U/Th se basa en la serie de desintegración del 238U e involucra medidas de 238U, 234U y 230Th. Su fundamento radica en el fraccionamiento entre los radionucleidos del uranio y del torio en los sistemas naturales. En el caso de la precipitación de carbonato puro, éste incorpora uranio en el momento de su formación, pero está libre de torio inicial de tal forma que, pasado un tiempo, todo el 230Th medido en la muestra deriva de la desintegración del 234U y esta relación permite calcular la edad de formación del mineral. Teóricamente, por tanto, el carbonato a datar: (1) debe incorporar cierta cantidad de uranio en el momento de su formación, (2) no debe incorporar cantidad significativa de torio y (3) debe comportarse como un sistema cerrado. De estas premisas, la segunda y la tercera no siempre se cumplen por lo que el método se ha adaptado a estos casos añadiendo cálculos y correcciones adicionales. Dada la variedad de carbonatos susceptibles de ser datados, este método es de amplia aplicación en paleoclimatología, paleontología, arqueología, estratigrafía, geomorfología, tectónica y oceanografía, entre otras disciplinas.Item Land surface temperature changes in Northern Iberia since 4000 yr BP, based on δ13C of speleothems(Global and planetary change, 2011) Martín Chivelet, Javier; Muñoz García, María Belén; Edwards, R. Lawrence; Turrero Jiménez, María Jesús; Ortega Martínez, Ana IsabelThe surface temperature changes for the last 4000 years in northern inland Iberia (an area particularly sensitive to climate change) are determined by a high resolution study of carbon stable isotope records of stalagmites from three caves (Kaite, Cueva del Cobre, and Cueva Mayor) separated several tens of kilometers away in N Spain. Despite the local conditions of each cave, the isotopic series show a good overall coherence, and resulted to be strongly sensitive to surface temperature changes. The record reflects alternating warmer and colder intervals, always within a temperature range of 1.6 °C. The timing and duration of the intervals were provided by 43 230Th–234U (ICP-MS) ages. Main climatic recognized periods are: (1) 3950–3000 yr BP: warm period punctuated by cool events around ~3950, 3550 and 3250 yr BP; (2) 2850–2500 yr BP cold interval (Iron Age Cold Period); (3) 2500–1650 yr BP moderate warm period (Roman Warm Period), with maximum temperatures between 2150 and 1750 yr BP; (4) 1650– 1350 yr BP cold interval (Dark Ages Cold Period), with a thermal minimum at ~1500 yr BP; (5) 1350– 750 yr BP warm period (Medieval Warm Period) punctuated by two cooler events at ~1250 and ~850 yr BP; (6) 750–100 yr BP cold period (Little Ice Age) with extremes occurring at 600–500 yr BP, 350–300 yr BP, and 150–100 yr BP; and (7) the last 150 years, characterized by rapid but no linear warming (Modern Warming). Remarkably, the presented records allow direct comparison of recent warming with former warm intervals such as the Roman or the Medieval periods. That comparison reveals the 20th century as the time with highest surface temperatures of the last 4000 years for the studied area. Spectral analysis of the time series shows consistent climatic cycles of ~400, ~900 and ~1300 yr, comparable with those recognized in the North Atlantic marine record, the Greenland ice cores, and other terrestrial records for the middle–late Holocene, suggesting common climate forcing mechanisms related to changes in solar irradiance and North Atlantic circulation patterns.Item Sedimentary facies and three-dimensional reconstructions of upper Oligocene meander belts from the Loranca Basin, Spain(AAPG Bulletin, 2010) Díaz Molina, Margarita; Muñoz García, María BelénIn this article, we reconstruct and explore the three-dimensional (3-D) architecture of superimposed meander-belt sediments as an analog of subsurface reservoirs. Two exposures, named the Huete anticline and Garcinarro, were selected from the Loranca Basin, central Spain. In both of them, deposits are dominated by meandering river sediments of Oligocene age. Some point bars show fining-upward sequences of sedimentary structures and grain size typical of the helicoidal flow, but most of them present multiple vertical changes in grain size and are characterized by the occurrence of small-scale cross-stratification filling scours. The origin of these structures is related to oppositely rotating spiral vortices associated with flow separation along the convex bank of the meander bends. The 3-D architecture of superimposed meander-belt sediments allowed the reconstruction of meandering channel orientations and meander wavelength, calculation of the net/gross sandstone content, and the fraction of interconnected sandstone bodies. The 3-D architecture revealed that the interconnection areas are nearly absent when the orientations of the superimposed meander belts were perpendicular and that interconnection areas are more abundant and larger where a coincidence in the orientations of superimposed meander belts is observed. Horizontal projections of the highly interconnected areas allow calculation of the area fraction where one or more sandstone bodies could be intersected by vertical drilling. Differences in sandstone fraction between the two studied exposures were caused by the proximity to the Altomira Sierra thrust belt, which forms the western margin of the Loranca Basin.