Papers by REBECA MARTIN GARCIA
Sedimentary Geology, 2019
International Journal of Speleology, 2012
A drapery speleothem (DRA-1) from Castañar Cave in Spain was subjected to a detailed petrographic... more A drapery speleothem (DRA-1) from Castañar Cave in Spain was subjected to a detailed petrographical study in order to identify its primary and diagenetic features. The drapery's present day characteristics are the result of the combined effects of the primary and diagenetic processes that DRA-1 underwent. Its primary minerals are calcite, aragonite and huntite. Calcite is the main constituent of the speleothem, whereas aragonite forms as frostwork over the calcite. Huntite is the main mineral of moonmilk which covers the tips of aragonite. These primary minerals have undergone a set of diagenetic processes, which include: 1) partial dissolution or corrosion that produces the formation of powdery matt-white coatings on the surface of the speleothem. These are seen under the microscope as dark and highly porous microcrystalline aggregates; 2) total dissolution produces pores of few cm 2 in size; 3) calcitization and dolomitization of aragonite result in the thickening and lost of shine of the aragonite fibres. Microscopically, calcitization is seen as rhombohedral crystals which cover and replace aragonite forming mosaics that preserve relics of aragonite precursor. Dolomitization results in the formation of microcrystalline rounded aggregates over aragonite fibres. These aggregates are formed by dolomite crystals of around 1 μm size. The sequence of diagenetic processes follows two main pathways. Pathway 1 is driven by the increase of saturation degree and Mg/Ca ratio of the karstic waters and is visible in the NW side of the drapery. This sequence of processes includes: 1) aragonite and huntite primary precipitation and 2) dolomitization. Pathway 2 is driven by a decrease in the degree of saturation of calcite and aragonite and Mg/Ca ratio of the cave waters, and it is observed in the SE side of the drapery. The diagenetic processes of the second pathway include: 1) calcitization of aragonite; 2) incomplete dissolution (micritization) of both aragonite and calcite; 3) total dissolution. This study highlights the importance of diagenetic processes on speleothems and their complexity. The correct interpretation of these processes is crucial for the understanding of possible changes in the chemistry of waters, temperature, or pCO 2 and so is critical to the correct interpretation of the paleoenvironmental significance of speleothems.
Geological Magazine, 2010
The Castañar Cave (central western Spain) formed in mixed carbonate–siliciclastic rocks of Neopro... more The Castañar Cave (central western Spain) formed in mixed carbonate–siliciclastic rocks of Neoproterozoic age. The host rock is finely bedded and shows a complex network of folds and fractures, with a prevalent N150E strike. This structure controlled the development and the maze pattern of the cave, as well as its main water routes. The cave formed more than 350 ka ago as the result of both the dissolution of interbedded carbonates and weathering of siliciclastic beds, which also promoted collapse of the overlying host rock. At present it is a totally vadose hypergenic cave, but its initial development could have been phreatic. The cave's speleothems vary widely in their morphology and mineralogy. In general, massive speleothems (stalactites, stalagmites, flowstones, etc.) are associated with the main fractures of the cave and bedding planes. These discontinuities offer a fairly continuous water supply. Other branching, fibrous, mostly aragonite speleothems, commonly occur in th...
Earth-Science Reviews, 2012
The Upper Miocene (Vallesian-Turolian) Unit II of the Teruel Graben comprises at its top a 25 m-t... more The Upper Miocene (Vallesian-Turolian) Unit II of the Teruel Graben comprises at its top a 25 m-thick sequence of palustrine deposits. Deposition of the entire unit commenced some 9 to 7 Ma ago in a halfgraben basin. Here, via a recent quarry, we examine in detail the lateral and vertical distribution of Unit II's palustrine facies and their features to determine the palaeogeography and main controls on deposit formation. Our findings suggest the deposits formed at a low-gradient lake margin with different energy levels. These energy levels controlled the type of primary deposit within the lake; wackestone to packstone sediments formed in low-energy conditions, whereas cross-bedded rudstones to floatstones formed under higher energy conditions, by erosion and redeposition of prior lacustrine deposits. Pedogenic and diagenetic modifications of the primary sediments took place during sedimentary discontinuities (SO) when the lacustrine sediments were subaerially exposed. These processes serve to explain the formation of eight different pal ustrine limestones: limestones with root traces, mottled limestones, brecciated limestones, flat pebble breccias, granular limestones, micro-karstified limestones with laminar ca1cretes, carbonate mounds and clayey limestones with laminar ca1cretes. Based on the features and thicknesses of the modified sediments five different morphological stages (I to V) of palustrine carbonates are defined. Stage I is characterized by incipient mottling and brecciation. Stage II shows mottling and strong brecciation that lead to the formation of intraclast breccias, in which the fragments are mostly "in situ". In Stage Ill, the primary fabric is totally changed; intraclasts have moved and may have lost their initial morphology. This Stage III may also be characterized by the formation of micro-karst. Stage IV is typified by the presence of coated grains and thin root mats. The chronological data available suggest that the formation of Stage III (lacustrine deposition + palustrine modification) would require about 40,000 yr. Facies and the SO record changes across short horizontal distances, and thus reflect the topography of prior sedimentation/modification events. Small (50 cm) highs with micro-karst have their SO counterparts in lower areas of the lake, in which the SO is indicated by desiccation and mottling. The topographic differences of the micro-karst were filled by intraclastic rudstones sourced by the adjacent carbonate flats. The example examined not only clearly sketches the morphology of ancient palustrine systems or wetlands, it also provides evidence that recycling of previous carbonate deposits played an important role as a sediment source, apart from biogenic or physical-chemical production processes. Our geochemical data indicate LMC (Low Magnesian Calcite) as the main component and Fe contents lower than 1%, except for the mottled areas that are richer in FeO. Stable isotope compositions provide 6 18 0 values close to-6.5%0 VPOB, and more varied 613C (-3.39 to-6.97%0 POB). Oxygen and carbon values reveal no covariation and clear trends are lacking. The homogeneity of 6 18 0 values reflects the intense effects of meteoric waters. The deposition of these palustrine limestones took place under suitable semi-arid to sub-humid climates. Climate could also have a role in determining subaerial exposure periods. However, its imprint is not easy to detect neither in the geochemical signals nor in the vertical arrangement of the facies. This could be attributed to climate changes probably occurring over shorter periods than those that can be recorded in this type of sediment, such as the astronomical precession cycles, and suggests the unsuitability of palustrine carbonates for detailed palaeoclimate analyses.
REDUCA ( …, 2010
Este tema se dedica al estudio de los procesos postsedimentarios o diagenéticos que sufren las ro... more Este tema se dedica al estudio de los procesos postsedimentarios o diagenéticos que sufren las rocas carbonáticas. Se presentan los distintos estadios y ambientes. Se parte del análisis de los factores que controlan los procesos diagenéticos y posteriormente se analiza cada uno de los procesos y los rasgos diagenéticos. Se hace especialmente hincapié en la dolomitización, como principal proceso de reemplezamiento. Otros procesos de reemplazamiento como silicificación o yesificación, se analizarán en los temas dedicados a esas rocas sedimentarias.
Advances in Research in Karst Media, 2010
In Castaiiar Cave (Caceres, Spain), coatings of red clays cover the walls of the chambers, coexis... more In Castaiiar Cave (Caceres, Spain), coatings of red clays cover the walls of the chambers, coexisting with diverse speleothems of aragonite, calcite, huntite and dolomite. The mineralogy of the clays is mainly illite, chlorite, kaolinite, smec tite, quartz and Fe oxides and hydroxides such as goethite. They can be transported into the cave by infiltration waters or form by in situ alteration of the host rock: lay ers of dolomite rich in Fe and magnesite interbedded with greywackes and shales. Present-day hydrological conditions in the cave and conditions during the forma tion of speleothems have determined that the clays have not been transported by any flooding or seepage, but mostly staying in situ, and not included into carbonate crys tal forms. Thus, most of the well-preserved speleothems are white and not stained, conforming an interesting chromatic contrast with the red clays that represent an additional attraction in this show cave.
Brazilian Journal of Development, Jun 21, 2021
Neste trabalho, discorreremos sobre poesia digital, gênero emergente do ciberespaço. Como o nome ... more Neste trabalho, discorreremos sobre poesia digital, gênero emergente do ciberespaço. Como o nome já sugere, ciberespaço significa um ambiente tecnológico, no qual as relações se constroem virtualmente. Nesse contexto, esta pesquisa trata, de modo específico, a respeito das transformações ocorridas no processo de criação e leitura de poesia, por meio de uma pesquisa bibliográfica, na abordagem qualitativa e propõe o trabalho com poesia digital com vistas a formação de leitores literários. Para tanto, utilizamos (2003), Eco (2011), Adorno (2006), Candido (2011) para tratar sobre poesia enquanto arte e como a leitura desse gênero é promovida no Brasil. Ainda discorreremos a respeito das transformações ocorridas no processo criativo (produção e recepção) de poesia em face das redes sociais e do letramento digital, pautados em Xavier (2010) e Silva et al (2012). Logo, verificamos ser imprescindível considerar esse gênero emergente no trabalho de formação de leitores, principalmente em dos nativos digitais.
ASAS DA PALAVRA, 2019
Este artigo objetiva, por meio de uma pesquisa bibliográfica, verificar como as alterações nos su... more Este artigo objetiva, por meio de uma pesquisa bibliográfica, verificar como as alterações nos suportes de leitura que ocorreram ao longo do tempo podem interferir nos modos de ler e, por conseguinte, na caracterização do leitor. Desde as inscrições em pedras até os hipertextos lidos nas telas dos computadores e smartphones, percebemos diferenças preponderantes no processo de recepção de textos as quais causam questionamentos tais como: o livro impresso, um dos suportes de escrita e leitura, será substituído por livros eletrônicos? Nesse sentido, esta pesquisa se dedicou a analisar a relação dos suportes com a leitura, de modo a apresentar diferentes tipos de leitor e as habilidades necessárias para o ato de ler, principalmente literatura, sem, no entanto, extinguir o livro físico do universo dos leitores. Para tanto, embasamos o trabalho em Chartier (1999), Terra (2015), Soares (2002), Spalding (2012), Xavier (2010) e Santaella (2004) na abordagem acerca de suportes de leitura, hip...
Acta Psiquiatrica Y Psicologica De America Latina, 2001
Viii Congreso De Posgrado En Psicologia Unam, Oct 12, 2014
El estudio de la evaluacion cognitiva ha cobrado mayor peso dentro del campo del dolor cronico. E... more El estudio de la evaluacion cognitiva ha cobrado mayor peso dentro del campo del dolor cronico. El presente estudio esta constituido por dos fases; el objetivo de la fase 1 fue identificar si la evaluacion cognitiva tiene una funcion mediadora entre la intensidad del dolor y la ansiedad, la depresion y la discapacidad. La muestra estuvo constituida por 191 pacientes con dolor cronico que asisten a la clinica del dolor del INCMNSZ, el diseno utilizado fue no experimental, transversal y correlacional. Los datos fueron analizados por un modelo de trayectorias. Los resultados mostraron que la evaluacion cognitiva negativa presento un papel mediador entre la intensidad del dolor y las variables de ansiedad y discapciadad. La fase 2 se propuso observar si en una muestra la intervencion desarrollada para la modificacion de la evaluacion cognitiva negativa se relaciona con la disminucion de sintomatologia ansiosa, depresiva y discapacidad. La muestra se compuso de 5 participantes; el diseno empleado fue de N=1 con 4 replicas y medidas repetidas con seguimiento a dos meses. Los resultados mostraron cambios clinicos significativos en las variables de ansiedad, depresion y discapacidad. Se concluye que una intervencion que se centre en la modificacion de la evaluacion cognitiva representa una alternativa efectiva de intervencion.
Revista Latinoamericana De Medicina Conductual Latin American Journal of Behavioral Medicine, Nov 2, 2015
Proyecto académico sin fines de lucro, desarrollado bajo la iniciativa de acceso abierto
Sedimentary Geology, 2011
The Ediacaran deposits (between 635 and 542 Ma) of the Central Zone of the Iberian Massif consist... more The Ediacaran deposits (between 635 and 542 Ma) of the Central Zone of the Iberian Massif consist of alter nating silidc1astic and carbonate beds. These carbonates are dolostones and magnesites which are inter preted to have been formed by the replacement of primary peritidal limestones. Through petrographic and geochemical analyses, we recognize different types of dolomites (01 to 04) and magnesites (M1 and M2). Despite distinct petrographic features of the four types of dolomite, their oxygen and carbon isotopes overlap with &180 values ranging from + 15.45 to + 17.51 %0 (SMOW) and & 13C from-0.13 to 3.21%0 PDB. Sr isotope values for 01 and 02 range from 0.7028 to 0.7091. Magnesites (M1 and M2) show oxygen values higher than + 17.87.0%0, and o313C values show the same variability as for the dolomites. 03 and 04 oxygen isotope values are between + 18.91 and 19.61, and the carbon isotope values range are similar to the other diagenetic phases. Sr isotope values for the magnesites and late dolomites (03 and 04) are 0.7095 to 0.7104, being
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Papers by REBECA MARTIN GARCIA