Person: González Acebrón, Laura
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First Name
Laura
Last Name
González Acebrón
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Department
Geodinámica, Estratigrafía y Paleontología
Area
Estratigrafía
Identifiers
17 results
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Now showing 1 - 10 of 17
Item Cyclicity recorded in the provenance sandstones in the sedimentary infill of the Cameros basin (N. Spain)(Boletín geológico y minero, 2013) González Acebrón, Laura; Arribas Mocoroa, José; Omodeo-Salé, S.; Arribas Mocoroa, María Eugenia; Le Pera, E.; Mas Mayoral, José Ramón; López-Elorza, M.; Fernández-Díaz, P.R.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.Item Criteria for recognition of localization and timing of multiple events of hydrothermal alteration in sandstones illustrated by petrographic, fluid inclusion, and isotopic analysis of the Tera Group, Northern Spain(International journal of earth sciences, 2011) González Acebrón, Laura; Goldstein, Robert H.; Mas Mayoral, José Ramón; Arribas Mocoroa, JoséStratigraphic relations, detailed petrography, microthermometry of fluid inclusions, and fine-scale isotopic analysis of diagenetic phases indicate a complex thermal history in Tithonian fluvial sandstones and lacustrine limestones of the Tera Group (North Spain). Two different thermal events have been recognized and characterized, which are likely associated with hydrothermal events that affected the Cameros Basin during the mid- Cretaceous and the Eocene. Multiple stages of quartz cementation were identified using scanning electron microscope cathodoluminescence on sandstones and fracture fills. Primary fluid inclusions reveal homogenization temperatures (Th) from 195 to 350 C in the quartz cements of extensional fracture fillings. The high variability of Th data in each particular fluid inclusion assemblage is related to natural reequilibration of the fluid inclusions, probably due to Cretaceous hydrothermal metamorphism. Some secondary fluid inclusion assemblages show very consistent data (Th = 281–305 C) and are considered not to have reequilibrated. They are likely related to an Eocene hydrothermal event or to a retrograde stage of the Cretaceous hydrothermalism. This approach shows how multiple thermal events can be discriminated. A very steep thermal gradient of 97–214 C/km can be deduced from d18O values of ferroan calcites (d18O -14.2/-11.8% V-PDB) that postdate quartz cements in fracture fillings. Furthermore, illite crystallinity data (anchizone–epizone boundary) are out of equilibrium with high fluid inclusion Th. These observations are consistent with heat-flux related to shortlived events of hydrothermal alteration focused by permeability contrasts, rather than to regional heat-flux associated with dynamo-thermal metamorphism. These results illustrate how thermal data from fracture systems can yield thermal histories markedly different from hostrock values, a finding indicative of hydrothermal fluid flow.Item Reply to comment on González-Acebrón, L., Mas, R., Arribas, J., Gutiérrez-Mas, J.M., Pérez-Garrido, C. “Very coarse-grained beaches as a response to generalized sea level drops in a complex active tectonic setting: Pleistocene marine terraces at the Cadiz coast, SW Spain”(Marine Geology, 2019) González Acebrón, Laura; Mas Mayoral, José Ramón; Arribas Mocoroa, José; Gutiérrez-Mas, José Manuel; Pérez Garrido, CarlosA series of Pleistocene marine terraces comprised of conglomerate and coarse-grained sandstone aligned NNW-SSE along the Cadiz coast have been recognized and interpreted as formed in very coarse-grained beaches in our work (González-Acebrón et al., 2016). They unconformable overlie either Pliocene units or older Pleistocene deposits. In these terraces, five sedimentary sequences were described and dated by Sr isotopic analysis of well-preserved oysters. This dating provided an Early Pleistocene age (1.3 Ma) for the oldest marine terrace, which corresponds to Sequence 1. Aguirre (2018) does not agree with the dating of the first sequence. Instead, in Aguirre (1995) and Aguirre et al. (1995) these deposits are considered as laterally equivalent to lacustrine deposits located more than 50 km far away (Mesas de Asta, Jerez Basin), and their age (Late Pliocene-lowermost Early Pleistocene) extrapolated to Sequence 1. This is an impossible correlation given the fact that the studied deposits (Sequences 1 to 5) are marine terraces without lateral continuity inland. Finally, Aguirre's (2018) sedimentological interpretation of the deposits of Sequence 1 as part of a “wave- and tide-dominated delta” breaks down when one considers that this delta would be a mixture of non-coeval deposits (the continental deposits of Mesas de Asta together with Sequence 1 deposits).Item Role of sandstone provenance in the diagenetic albitization of feldspars A case study of the Jurassic Tera Group sandstones (Cameros Basin, NE Spain)(Sedimentary Geology, 2011) González Acebrón, Laura; Arribas Mocoroa, José; Mas Mayoral, José RamónThe Cameros Basin (Iberian Chain, NE Spain) formed during the latest Jurassic–Early Cretaceous rifting stage in an extensional regime characterized by high subsidence rates. Its sedimentary infill (thicker than 6000 m) has been subdivided into eight depositional sequences (DS) mainly composed of continental sediments. DS 1 and DS 2 represent the first rifting stage (Tera Group, Tithonian), mainly formed by fluvial and lacustrine sediments. Sandstone petrofacies evolved from quartz-sedimentolithic in DS 1 to quartz-feldspathic in DS 2 due to the rifting process. In DS 2, three different types of detrital feldspars (K-feldspars, albites and polysynthetic plagioclases) with similar sodium-rich compositions (mean: Ab94.0 An4.5 Or1.5) can be recognized. Chemically pure nonluminescent albites (AbN99%) are common. In DS 2, diagenetic albitization of both plagioclases and K-feldspars is inferred from conventional microscopy observations, cathodoluminescence and electron microprobe analyses. DS 1 contains few plagioclase grains, which showno evidence of transformation into albite.Although the albitization is characterized as diagenetic it seems to be provenance-controlled since it affects the units showing higher original plagioclase/Kfeldspar ratio (DS 2), due to the greater influence of plutonic and metamorphic source areas in DS 2. Possible Na sources are: (1) the percolation ofmoderate to high salinity residual brines fromrelated alkaline lakes developed at top of DS 2 in the eastern sector of the basin, (2) clay mineral reactions (sodium smectite to illite and chlorite) indicated by mudstone composition in the interlayered mudstones, and (3) the replacement of detrital sodium plagioclases by carbonate. These three sources can be complementary.Item Diagenetic albitization in the Tera Group, Cameros Basin (NE Spain) recorded by trace elements and spectral cathodoluminescence(Chemical geology, 2012) González Acebrón, Laura; Götze, Jens; Barca, Donatella; Arribas Mocoroa, José; Mas Mayoral, José Ramón; Pérez Garrido, CarlosThis paper deals with the diagenetic albitization of both plagioclases and K-feldspars in the Tithonian fluvial sandstones of a rift basin (Cameros Basin). The sandstones in the lower part of the rift record have not suffered this albitization process. A clear relationship is observed between sodium contents, as the main element of some feldspars and their cathodoluminescence (CL) color (the higher the sodium content, the lower is their CL intensity). In conclusion, albitization processes are detectable by decreased CL intensities and changes in the CL spectra. In addition, very different trace element compositions are obtained by laser ablation when comparing trace elements of non-albitized feldspars in sandstones of the lower part of the rift record with those of albitized feldspars in sandstones of the infill top. Non-albitized K-feldspars show Rb, Sr, Ba and Pb contents of up to 1000 ppm. In contrast, very flat profiles of trace element contents (< 250 ppm) are recorded in albitized feldspars (both K-feldspars and plagioclases). Thus, albitization implies feldspars impoverished in trace elements, including REE, which suggests that albitization is a dissolution and reprecipitation process. Further, albitized plagioclases show higher REE contents than albitized K-feldspars. We report here that REE patterns partly depend on the initial composition of the feldspar (K-feldspar or plagioclase) as a useful geochemical criterion for distinguishing albitized detrital plagioclases from albitized detrital K-feldspars. CL spectra from non-albitized and albitized K-feldspars and plagioclases revealed marked differences. Non-albitized K-feldspars present blue (main emission band at 460 nm) and brownish CL colors (590 nm), sometimes in the same grain. Brownish colors are related to weathering processes. The primary blue emission is related to Al–O−–Al centers, enhanced probably by Al incorporation due to the coupled substitution of Ba2+ + Al3+ ↔ M+ + Si4+. Weathered K-feldspars present 4.8 times lower Ba content than fresh blue luminescent ones. The brownish colors are related to the external border or fractured grain zones, altered by weathering processes. Therefore, the observed 590 nm emission is assumed to be caused by structural defects resulting from weathering and alteration. Albitized K-feldspars are usually weak luminescent with a typical CL emission band at 620 nm. Sometimes, relicts of the original blue luminescence (460 nm band) are still present. The leaching of probably both Al and Ba can be responsible for the decrease in the blue band. The characteristic 620 nm band is also dominant in albitized weak luminescent plagioclases. Two additional emission bands at 440 nm (Al–O−–Al center) and 565 nm (Mn2+) occur, when albitized plagioclases preserved their original CL characteristics (green CL color). Another spectral peak at ca. 720 nm can be explained by Fe3+ activation due to Fe3+–Al3+ substitution. The spectral CL measurements indicate that changes in luminescence due to albitization (620 nm emission) seem to be more related to structural defects than to trace element activation or quenching.Item Sandstone petrofacies in the northwestern sector of the Iberian Basin(Journal of iberian geology, 2007) Arribas Mocoroa, José; Ochoa, M.; Mas Mayoral, José Ramón; Arribas Mocoroa, María Eugenia; González Acebrón, LauraDuring the most active rifting stages in the northwestern sector of the Iberian Basin (Cameros Basin and Aragonese Branch of the Iberian Range), thick sequences of continental clastic deposits were generated. Sandstone records from Rift cycle 1 (Permo-Triassic) and Rift cycle 2 (Late Jurassic-Early Cretaceous) show similarities in composition. Based on the most recent data, this paper describes sandstone petrofacies developed during both rifting periods. Six petrofacies can be distinguished: two associated with Rift cycle 1 (PT-1 and PT-2) and four with Rift cycle 2 (JC-1 to JC-4). All six petrofacies can be classifi ed as sedimentoclastic or plutoniclastic. Sedimentoclastic petrofacies developed during early rifting stages either through the recycling of pre-rift sediments or signifi - cant palaeogeographical changes. These facies comprise a thin succession (<100 m) of clastic deposits with mature quartzose and quartzolithic sandstones containing sedimentary and metasedimentary rock fragments. Carbonate diagenesis is more common than clay mineral diagenesis. Sedimentoclastic petrofacies have been identifi ed in Rift cycle 1 (Saxonian facies, PT-1) and Rift cycle 2 (JC-1 and JC-3; Tithonian and Valanginian, respectively). In the absence of the pre-rift sedimentary cover, metasedimentoclastic petrofacies sometimes develop as a product of the erosion of the low- to medium-grade metamorphic substratum (Petrofacies JC-2, Tithonian-Berriasian). Plutoniclastic petrofacies were generated during periods of high tectonic activity and accompanied by substantial denudation and the erosion of plutonites. Forming thick stratigraphic successions (1000 to 4000 m), these feldspar-rich petrofacies show a rigid framework and clay mineral diagenesis. In Rift cycle 1, plutoniclastic petrofacies (PT-2) are associated with the Buntsandstein. This type of petrofacies also developed in Rift cycle 2 in the Cameros Basin (JC-4) from DS-5 to DS-8 (Hauterivian-Early Albian), and represents the main basin fi ll interval. Sedimentoclastic and plutoniclastic petrofacies can be grouped into three pairs of basic petrofacies. Each pair represents a ‘provenance cycle’ that records a complete clastic cycle within a rifting period. Petrofacies PT-1 and PT-2 represent the ‘provenance cycle’ during Rift-1. In the Cameros Basin, two provenance cycles may be discerned during Rift cycle 2, related both to the Tithonian-Berriasian and the Valanginian-Early Albian megasequences. Tectonics is the main factor controlling petrofacies. Other factors (e.g., maturation during transport, local supply) may modulate the compositional signatures of the petrofacies yet their main character persists and even outlines the hierarchy of the main bounding surfaces between depositional sequences in the intracontinental Iberian Rift Basin.Item Sand provenance and implications for paleodrainage in a rifted basin: the Tera Group (N. Spain)(Journal of iberian geology, 2010) González Acebrón, Laura; Arribas Mocoroa, José; Mas Mayoral, José RamónFluvial-fan and fluvial siliciclastic strata, developed during the rifting that generated the Cameros Basin (North Spain), record important provenance changes that reveal source areas compositions and locations, paleodrainage evolution and rift patterns. The Tera Group represents the first rifting stage in the Cameros Basin, containing fluvial-fan sediments at the lower part of the sedimentary fill that evolve to fluvial and lacustrine systems in the upper part of the record. Our quantitative sandstone petrographic analysis evidences the presence of three main petrofacies related closely to the rift basin evolution. At the base of the sedimentary succession, Petrofacies 1 (quartzolithic) indicates that the fluvial-fans source areas included Jurassic marine carbonates and older siliciclastic Mesozoic units, as well as metamorphic supplies from the West Asturian Leonese Zone (WALZ). Variscan basement sources of this metamorphic area (WALZ) were more abundant in the upper fluvial record (Petrofacies 2, quartzofeldspathic). Further, the influence of plutonic source areas with a mixed potassic and calcium-sodium composition is also recorded, probably related to the Central Iberian Zone (CIZ). In addition, a local sedimentary input was active during the fluvial riftand lacustrine stages (Petrofacies 2 and 3, both quartzofeldspathic), as a function of the palaeogeographical position of the Jurassic marine rocks and the level of erosion reached. Plutonic rock fragments have not been observed in the Tera Group sandstones of the western part of the basin. Thus, deeper erosion of the basement in the eastern Cameros Basin is suggested. The provenance evolution from quartzolithic to quartzofeldspathic petrofacies registered in Tera Group siliciclastic deposits is due to the higher influence of transversal supplies during the fluvial-fan stage (quartzolithic) to more important axial inputs during the fluvial stage (quartzofeldspathic). This provenance change represents the evolution from an undissected rift shoulder stage to more advanced stages of rifting (dissected rift shoulder) and during the beginning of a provenance cycle in a rifted basin. [RESUMEN] Los sedimentos de abanicos fluviales y fluviales propiamente dichos desarrollados durante el proceso de rift que generó la Cuenca de Cameros (Norte de España) registraron importantes cambios de procedencia que proporcionan información sobre la composición y localización de sus áreas fuente, la evolución del paleodrenaje y los patrones de rift. Este estudio se centra en el Grupo Tera (Tithoniense) en el sector oriental de la Cuenca de Cameros. El Grupo Tera representa el primer estadio de rift en dicha cuenca, y está constituido por sedimentos de abanicos fluviales en la parte inferior del relleno sedimentario, que evolucionan a sistemas fluviales y lacustres hacia la parte superior del registro. El estudio petrográfico cuantitativo de las areniscas indica la presencia de tres petrofacies principales que muestran una estrecha relación con la evolución del rift. En la base del registro sedimentario, la Petrofacies 1 (cuarzolítica) manifiesta que las áreas fuente de los abanicos fluviales incluyen tanto carbonatos Jurásicos marinos como unidades siliciclásticas mesozoicas previas, así como influencias metamórficas de la Zona Asturoccidental Leonesa (WALZ). Los aportes del basamento varisco procedentes de esta área fuente metamórfica (WALZ) fueron más importantes en la parte alta del registro (Petrofacies 2, cuarzofeldespática). Además, se detecta la influencia de áreas fuente plutónicas con una composición mixta (potásica y calcosódica), probablemente relacionadas con la Zona Centroibérica (CIZ). También existió un aporte sedimentario local durante los estadios fluviales y lacustres (Petrofacies 2 y 3, ambas cuarzofeldespáticas), que tuvo lugar en función de la posición paleogeográfica de las rocas marinas Jurásicas y del nivel de erosión alcanzado. Si comparamos los dos sectores de la cuenca, los fragmentos de roca plutónica no han sido observados en las areniscas del Grupo Tera en el sector occidental de la cuenca. Por lo tanto, se deduce un nivel de erosión del basamento más profundo en el sector occidental. La evolución de la procedencia desde petrofacies cuarzolíticas a petrofacies cuarzofeldespáticas registrada en los depósitos siliciclásticos del Grupo Tera se debe a una mayor influencia de los aportes transversales durante la sedimentación de los abanicos fluviales (cuarzolíticos) hacia una mayor influencia de aportes axiales durante la etapa fluvial (cuarzofeldespática). Esta variación en la procedencia representa la evolución desde un estadio de hombrera de rift no erosionada a estadios más avanzados del rifting (hombrera de rift erosionada) y el comienzo de un ciclo de procedencia en una cuenca de rift.Item Evolution of an intra-plate rift basin: the Latest Jurassic-Early Cretaceous Cameros Basin (Northwest Iberian Ranges, North Spain)(Geo-guías, Post-Meeting Field trips 28th IAS Meeting, Zaragoza, 2011) Mas Mayoral, José Ramón; Benito Moreno, María Isabel; Arribas Mocoroa, José; Alonso Millán, Ángela; Arribas Mocoroa, María Eugenia; Lohmann, K.C.; González Acebrón, Laura; Hernán, J.; Quijada, Isabel Emma; Suárez González, Pablo; Omodeo Salé, S.; Arenas, Concha; Pomar, Luis; Colombo, FerránItem REPLY: Answer to the comment of Casas et al. about González Acebrón et al.’s (2011) paper(International journal of earth sciences, 2012) González Acebrón, Laura; Goldstein, R.H.; Mas Mayoral, José Ramón; Arribas Mocoroa, JoséItem Fluid migration recorded by fluid inclusions in crack-sealed quartz veins and sandstone host rock; Cameros Basin, Spain(Journal of iberian geology, 2021) González Acebrón, Laura; López Elorza, Maialen; Mas Mayoral, José Ramón; Arribas Mocoroa, José; Omodeo-Salé, SilviaThe role of deep hydrothermal fluid circulation through fractures and their impact on the sandstone host rock is studied in an extensional sedimentary basin (Cameros Basin, Spain) affected by a post-extensional hydrothermal metamorphism. The quartzarenites of the Urbión Group constituted a hydrocarbon carrier affected by very low to low-grade hydrothermal metamorphism during Late Albian to Coniacian. This process generated abundant quartz veins and transformed the quartzarenites into quartzites. This study compares the microthermometry of the fluid inclusion asemblages (FIAs) in the veins and in the quartz grain overgrowths in the quartzites, in order to understand the behavior of the hydrothermal fluids through fractures and their effects in the host rock. Fluid inclusions in the quartz grain overgrowths contain liquid and vapor at room temperature and homogenize to the liquid (Th: 124–265 °C, H2O + NaCl system). Those of quartz veins present both liquid and vapor CO2 and an aqueous liquid phase (room temperature). Final homogenization is to the liquid (Th: 109–282 °C, H2O + NaCl + CO2, mean values of amount-of-substance fractions: 0.92, 0.01, 0.07). Large Th variation within each FIA is common, due to crack and sealing processes and to reequilibration by successive thermal pulses. In contrast, the narrow Th range in each FIA towards the top of the record indicates that these inclusions are probably not reequilibrated. Two growing stages are recognized under SEM-CL in the quartz grain overgrowths, one diagenetic and another hydrothermal, the later with FIAs showing Th similar than the veins. The results can help in the evaluation of the geo-energy resources in sedimentary basins.