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Trabajo presentado en el 8th International Conference Climate Change: The Karst Record, celebrado en Austin, Texas (Estados Unidos), del 21 al 24 de mayo de 2017, Nuclear magnetic resonance (NMR) techniques are powerful non-destructive tools to understand the internal porosity and fluid inclusions distribution of carbonate rocks. In the case of speleothems, relaxometry experiments and the reconstruction of 2D magnetic resonance images (MRI) help to complement the results obtained by petrographic analysis in microscope, where different type of fluid inclusions have been classified. Relaxometry test of 1 H nuclei of water in a porous media allows to quantify isolated cavities as fluid inclusions and, based on so called “surface effects”, the size distribution can be achieved. It is known that T1 (longitudinal) and T2 (transversal) relaxation times, indicators of pore size when a single fluid is present, are shorter in pores with a high surface-to-volume ratio (S/V). On the other hand, high intensity pixels (bright areas) are associated to water filled fluid inclusions in 2D MRI images, while low intensity pixels (black areas) are related to calcite. The technique shows a high potential to analyze different fluid inclusions bear in mind their magnitudes, allowing to classify and estimate the amount of intracrystallite and intercrystallite inclusions. Moreover, the 2D and 3D visualization of fluid inclusions distribution inside the sample by MRI images and the pre-estimation of enclosed water amount in each sample by relaxometry curves, turn this technique into a useful tool previous to stable isotope or noble gas crushing measurements of fluid inclusions under high vacuum line. In this work, two stalagmites from Cueva del Tortero (Valencia, Spain), Tortero-2 and Tortero-4, have been analyzed by this method. T1 and T2 curves of fully dried samples reveal that fluid inclusions could be classified in three groups taking their size into consideration, where short relaxation times represent small fluid inclusions and larger T1 and T2 values characterize enlarged cavities. Furthermore, the greater sensitivity that T2 displays to inclusions morphology allows to identify more deeply different types of fluid inclusions. In both samples, intracrystallite fluid inclusions are very tiny (3-15 μm) and correspond to shorter T2 values (0,2-3 ms for Tortero-4 slabs and 1-4 ms for Tortero-2). On the other hand, intercrystallite inclusions are bigger in size (20-100 μm) and they provoke T2 relaxation times between 4 and 500 ms for Tortero-4 slabs and from 8-50 ms for Tortero-2. T2 relaxation times bigger than 1000 ms are induced by enlarged porosity in both samples. Moreover, MRI images confirm that lots of intracrystallite inclusions are located in bands and in the hiatus, where the signal given by water is brighter., This work was supported by the R+D+i Program of Spain [CGL2013-43257-R] and the Complutense University [Research Group 910198]. We thank the authorities of the Generalitat Valenciana for permissions and support. Thanks are extended to Ana I. Ortega (Grupo Espeleológico Edelweiss) and Policarp Garay, for speleological advice during cave work.

Trabajo presentado en el 8th International Conference Climate Change: The Karst Record, celebrado en Austin, Texas (Estados Unidos), del 21 al 24 de mayo de 2017, Reliable paleoclimate time series based in stalagmites require the precise characterization of speleothem internal micro-stratigraphy, a task too often poorly accomplished despite the recent advances in speleothem research. This weakness is probably due to the lack of a robust integrative methodological framework capable of integrating the wide range of petrographic and micro-stratigraphic methods currently used in speleothem characterization. For covering this need, we propose the Speleothem Architectural Analysis (SAA), a holistic approach inspired in well-stablished stratigraphic procedures such as the architectural element analysis and the sequence stratigraphy, commonly used by geoscientists for categorizing the stratigraphy of sedimentary deposits. The SAA 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 seasons or years to centuries or millennia. The method provides an open and versatile tool for unravelling the complexities of speleothem growth. It generates a standardized stratigraphic framework for each stalagmite, which can be the basis for its genetic interpretation in a multi-temporal scale. This stratigraphic analysis must precede and accompany any geochemical work directed to the construction of paleoclimate series, Contribution to project CGL2013-43257-R and the UCM Research Group 910198

[EN] The intraplate Cameros rift basin in the north of Spain was formed came into being between the Tithonian and the Early Albian and contains 9 000 m of mostly continental sediments. This basin is a good example of cyclicity of different depositional sequences (DSs) in sedimentary environments, which show clear repetition in their sandstone composition (petrofacies) and diagenetic patterns. The DSs are arranged in two megasequences (MSs) separated by a tectonic unconformity. A similar vertical sandstone compositional evolution, subdivided into two stages that repeat cyclically, has been recognised in both MSs: the first comprises quartzo-sedimentolithic petrofacies and the second is made up of several quartzo-feldspathic petrofacies. This was caused by a progression from the recycling of the pre-rift sedimentary cover to the erosion of the mainly plutonic and metamorphic crystalline basement. These changes in the erosion of the different source areas were conditioned by the tectonics of the basin. Furthermore, the original sandstone framework composition conditioned the diagenetic pattern of the two stages: quartzo-sedimentolithic sandstones containing large amounts of very pervasive carbonate cement that reduce their original porosity considerably, and quartzo-feldspathic petrofacies with a rigid framework that maintained the original pores during burial diagenesis. This compositional and diagenetic pattern is probably applicable to other non-volcanic rifted basins, depending upon the original amount of carbonate rock fragments present., [ES] La cuenca intraplaca de rift de Cameros se localiza al norte de España. Se desarrolló entre el Titónico y el Albiense Inferior, depositándose 9000 m de sedimentos fundamentalmente continentales. La cuenca es un buen ejemplo de ciclicidad en los medios sedimentarios en las diferentes Secuencias Deposicionales (SD), lo que genera una clara repetición de la composición de las areniscas (petrofacies) y de las pautas diagenéticas. Las SD están organizadas en dos megasecuencias (MS) separadas por una discordancia de carácter tectónico. Ambas MS presentan una evolución vertical similar en la composición de las areniscas, generando una repetición de dos estadios: (1º) constituido por una petrofacies cuarzosedimentolítica y (2º) formado por varias petrofacies cuarzofeldespáticas. Este hecho viene motivado por el cambio desde la erosión de una cobertera sedimentaria pre-rift a la erosión del basamento cristalino, principalmente constituido por áreas fuente plutónicas y metamórficas. Estos cambios en la erosión de distintas áreas fuente están controlados por la tectónica de la cuenca. Además, la composición original del esqueleto de las areniscas condiciona el tipo de diagénesis para los dos estadios anteriormente descritos: las areniscas cuarzosedimentolíticas contienen abundante cemento de carbonato, que reduce su porosidad inicial drásticamente. Sin embargo, las areniscas cuarzofeldespáticas presentan un esqueleto más rígido que mantiene los poros originales durante la diagénesis de enterramiento. Este patrón composicional y diagenético es probablemente aplicable a otras cuencas de rift intraplaca no volcánicas, dependiendo de la cantidad inicial de fragmentos de roca carbonática.