Heterogeneidad de facies en una rampa carbonatada del Kimmeridgiense (Jabaloyas, Este de España): análisis de campo y geomodelización tridimensional

The Upper Kimmeridgian outcrops exposed around the village of Jabaloyas (NE Spain) have been analyzed to document the facies heterogeneity across the shallow portion of a low angle carbonate ramp. The studied area covers a total surface of 12 square kilometres. Seventeen stratigraphic profiles have provided basic information to carry out the detailed facies analyses presented in this work. The studied unit corresponds to a high-frequency sequence, bounded by discontinuities that can be traced at regional scale. This sequence shows the widespread development of coral-microbial reef buildups with conical to cylindrical shape (up to 19 m thick). The characterization and interpretation of the different sort of inter-reef and post-reef facies resulted in the reconstruction of the sedimentary domains of the studied carbonate ramp, from burrowed mud-dominated skeletal facies (distal middle ramp), to grainy (skeletal, peloidal, oolitic) shoal and backshoal facies (inner ramp). The studied sequence is divided into four sedimentary episodes bounded by sharp facies changes. The lower two episodes include the vertical reef growth during rapid accommodation gain; the upper two episodes are marked by the rapid progradation of the inner ramp facies. The depositional facies and their stacking patterns in the Jabaloyas outcrops are similar to those described in the subsurface Arab D reservoirs. This Late Jurassic carbonate unit forms major hydrocarbon fields in the Middle East. For improving the geological distribution of reservoir heterogeneity in this kind of low angle carbonate ramp system, two 3D models have been created. A Fullfield Model of the overall geometry of the facies belts has allowed the quantification of vertical and lateral extension of the inter-reef and post-reef facies. A Sector Model, which includes individual reef bodies has been used to better simulate reservoir heterogeneity resulting from different diagenetic overprint.Los afloramientos del Kimmeridgiense Superior en las cercanías de Jabaloyas (NE de España) han sido estudiados para documentar la heterogeneidad de facies en las zonas más someras de una rampa carbonatada de bajo ángulo. El área de estudio cubre una superficie de 12 kilómetros cuadrados en la que se han levantado diecisiete columnas estratigráficas y se ha realizado un análisis detallado de facies. La unidad estratigráfica estudiada corresponde a una secuencia de alta frecuencia limitada por discontinuidades que pueden ser cartografiadas a escala regional. Dicha secuencia presenta bioconstrucciones arrecifales coralinas y microbianas con morfologías cónicas o cilíndricas de hasta 19 m de potencia. La caracterización e interpretación de las diferentes facies inter- y post-arrecifales ha permitido la reconstrucción de los diferentes dominios de la rampa carbonatada, desde facies no granosostenidas bioturbadas (rampa media distal), hasta facies granosostenidas (bioclásticas, peloidales, oolíticas) desarrolladas en bajíos activos y en zonas someras protegidas. La existencia de superficies bien cementadas y de cambios abruptos de facies asociados ha permitido la división de la secuencia en cuatro episodios de sedimentación. Los dos primeros incluyen el crecimiento de los arrecifes durante los periodos de ganancia de acomodación, mientras que los dos últimos vienen marcados por una rápida progradación de las facies de rampa interna. El patrón de apilamiento de esta unidad en los afloramientos de Jabaloyas muestra similitudes con aquellos descritos en los reservorios desarrollados en el Arab D, el cual genera campos de hidrocarburos de gran tamaño en Medio Oriente. Con el fin de precisar la heterogeneidad de facies a escala de reservorio en este tipo de rampas carbonatadas de bajo ángulo, se han elaborado dos modelos tridimensionales. Un modelo de campo completo ha permitido precisar la extensión y la geometría de los diferentes cinturones de facies; y un modelo sector, que incluye los cuerpos arrecifales, posteriormente utilizado para simular la heterogeneidad del reservorio con ayuda de estudios diagenéticos previos

Mechanisms of amphetamine action illuminated through optical monitoring of dopamine synaptic vesicles in Drosophila brain

Amphetamines elevate extracellular dopamine, but the underlying mechanisms remain uncertain. Here we show in rodents that acute pharmacological inhibition of the vesicular monoamine transporter (VMAT) blocks amphetamine-induced locomotion and self-administration without impacting cocaine-induced behaviours. To study VMAT’s role in mediating amphetamine action in dopamine neurons, we have used novel genetic, pharmacological and optical approaches in Drosophila melanogaster. In an ex vivo whole-brain preparation, fluorescent reporters of vesicular cargo and of vesicular pH reveal that amphetamine redistributes vesicle contents and diminishes the vesicle pH-gradient responsible for dopamine uptake and retention. This amphetamine-induced deacidification requires VMAT function and results from net H+ antiport by VMAT out of the vesicle lumen coupled to inward amphetamine transport. Amphetamine-induced vesicle deacidification also requires functional dopamine transporter (DAT) at the plasma membrane. Thus, we find that at pharmacologically relevant concentrations, amphetamines must be actively transported by DAT and VMAT in tandem to produce psychostimulant effects

14-3-3 Mediates Histone Cross-Talk during Transcription Elongation in Drosophila

Post-translational modifications of histone proteins modulate the binding of transcription regulators to chromatin. Studies in Drosophila have shown that the phosphorylation of histone H3 at Ser10 (H3S10ph) by JIL-1 is required specifically during early transcription elongation. 14-3-3 proteins bind H3 only when phosphorylated, providing mechanistic insights into the role of H3S10ph in transcription. Findings presented here show that 14-3-3 functions downstream of H3S10ph during transcription elongation. 14-3-3 proteins localize to active genes in a JIL-1–dependent manner. In the absence of 14-3-3, levels of actively elongating RNA polymerase II are severely diminished. 14-3-3 proteins interact with Elongator protein 3 (Elp3), an acetyltransferase that functions during transcription elongation. JIL-1 and 14-3-3 are required for Elp3 binding to chromatin, and in the absence of either protein, levels of H3K9 acetylation are significantly reduced. These results suggest that 14-3-3 proteins mediate cross-talk between histone phosphorylation and acetylation at a critical step in transcription elongation

Shallow-marine microporous carbonate reservoir rocks in the Middle East: relationship with seawater Mg/Ca ratio and eustatic sea level

The formation of shallow-marine microporous carbonate reservoir rocks remains poorly understood in spite of their economic importance, particularly in the Middle East. In this paper, we investigate relationships between the stratigraphic occurrence of these carbonates in the Middle East and (i) the evolution of the Mg/Ca ratio in seawater; and (ii) cyclic variations in relative sea-level. An inventory of carbonate formations in the Middle East was compiled for three geological time intervals characterised by different seawater chemistries: the Late Carboniferous to Triassic (aragonite seas); the Cretaceous (calcite seas); and the Cenozoic (transitional from calcite to aragonite seas). For each time interval, carbonate formations described as microporous have been listed. During the Cretaceous calcite sea, eleven microporous carbonate formations were deposited in the Middle East. However, no microporous carbonates were formed during the Late Carboniferous to Triassic, a time of aragonite seas. During the Cenozoic, four of the five microporous carbonate formations recorded were deposited before the transition from calcite to aragonite seas. Thus, these shallow-marine microporous carbonates appear to have developed from precursor muds which were mainly composed of low-Mg calcite crystals. Moreover, during the Cretaceous and the Cenozoic, microporous carbonate formations in the Middle East were generally associated with major transgressions and highstands of relative sea level. The relatively high stability of low-Mg calcite muds may explain why shallow-marine microporous carbonates formed during time intervals with calcite seas. In contrast to muds composed of aragonite or high-Mg calcite crystals, the original microfabric (including intercrystalline microporosity) of low-Mg calcite muds can partly survive moderate diagenesis.status: publishe

Controls on the distribution of nummulite facies: a case study from the late Ypresian el Garia formation (Kesra Plateau, Central Tunisia)

Eocene nummulite deposits along the southern Tethys margin locally constitute important hydrocarbon reservoir rocks. In order to understand the heterogeneity of these complex reservoirs, we have carried out a detailed field study of the nummulite limestones which crop out at the Kesra Plateau in Central Tunisia. The main contributions of this paper can be summarised as follows: 1. Various species of Nummulites and planktonic foraminifera were identified in late Ypresian carbonates in the Kesra area and provided accurate biostratigraphic ages. Nummulitic limestones occur in the Chouabine and El Garia Formations representing deposition over a period of about 2Ma. 2. Six depositional facies have been identified in the El Garia Formation, ranging from high-energy nummulitic grainstones to laterally-equivalent lower-energy nummulithoclastic accumulations. Variations in nummulite morphology (size and shape) were used to distinguish a number of subfacies which correspond to different depositional environments. We provide evidence that nummulite accumulations were locally sub-aerially exposed. 3. A 3D reconstruction of the Kesra Plateau outcrop identified two stacked nummulite bodies, deposited under high-energy conditions, which pass laterally into two isolated bodies in more distal parts of the platform. 4. Regional-scale observations indicate that the geometry of the late Ypresian nummulite platform was strongly influenced by the presence of the Oued Bahloul anticline structure, which formed a major environmental barrier between openmarine and more restricted settings. Facies distribution in the Kesra area was strongly controlled by the inherited topography, which reflects the reactivation of NW-SE trending faults during the Late Cretaceous and Paleocene. 5. A tentative 3D facies model illustrates the relationship between facies and fault distributions in the Kesra area. The facies map shows that the best reservoir potential is associated with palaeo-highs, and consists of nummulite limestones deposited in very shallow waters (a few metres) under high-energy conditions

Lacustrine microporous micrites of the Madrid Basin (Late Miocene, Spain) as analogues for shallow-marine carbonates of the Mishrif reservoir Formation (Cenomanian to Early Turonian, Middle East)

Shallow-marine microporous limestones account for many carbonate reservoirs. Their formation, however, remains poorly understood. Due to the lack of recent appropriate marine analogues, this study uses a lacustrine counterpart to examine the diagenetic processes controlling the development of intercrystalline microporosity. Late Miocene lacustrine microporous micrites of the Madrid Basin (Spain) have a similar matrix microfabric as Cenomanian to Early Turonian shallow-marine carbonates of the Mishrif reservoir Formation (Middle East). The primary mineralogy of the precursor mud partly explains this resemblance: low-Mg calcites were the main carbonate precipitates in the Cretaceous seawater and in Late Miocene freshwater lakes of the Madrid Basin. Based on hardness and petrophysical properties, two main facies were identified in the lacustrine limestones: a tight facies and a microporous facies. The tight facies evidences strong compaction, whereas the microporous facies does not. The petrotexture, the sedimentological content, and the mineralogical and chemical compositions are identical in both facies. The only difference lies in the presence of calcite overgrowths: they are pervasive in microporous limestones, but almost absent in tight carbonates. Early diagenetic transformations of the sediment inside a fluctuating meteoric phreatic lens are the best explanation for calcite overgrowths precipitation. Inside the lens, the dissolution of the smallest crystals in favor of overgrowths on the largest ones rigidifies the sediment and prevents compaction, while partly preserving the primary microporous network. Two factors appear essential in the genesis of microporous micrites: a precursor mud mostly composed of low-Mg calcite crystals and an early diagenesis rigidifying the microcrystalline framework prior to burial

Preservation potential of highstand coastal sedimentary bodies in a macrotidal basin : Example from the Bay of Mont-Saint-Michel, NW France

This study investigated the spatio-temporal evolution and preservation of a highstand coastal wedge in the Holocene deposits of the macrotidal Bay of Mont-Saint-Michel (NW France). Vibracores were collected in two contrasted environments of the Bay : (1) in the estuary, which is characterized by very strong tidal currents, and (2) along the north-eastern littoral, which is made up of an elongated wave-dominated barrier. Facies analysis associated with radiocarbon dating revealed marked differences in the preservation potential of sedimentary sequences in both environments. In the general framework of a very slow rise in sea level, these two environments are subject to different hydrodynamical, sediment supply and coastal morphology conditions. In the northeastern area, the coastal wedge is made of successive tidal lagoon infill sequences. Due to their back-barrier origin, each individual sequence has been preserved; the supply of sediments combined with wave dynamics are the main factors that control the way of the system functions. In the estuary, the sediment wedge comprises a single tidal channel infill sequence reaching down to the substratum. In this area, the sediment supply is very high and tidal currents are very powerful. As the active tidal channel occupies all the available space, lateral migration of the channel is the main factor that controls the temporal and spatial development and preservation of the sequence. The potential for the sequence preservation in the estuary is therefore minimal and only the last channel infill sequence is in fact preserved. Dating revealed that the tidal lagoon sequences and the tidal channel infill sequence correspond to millennial and centennial time scales respectively. This study showed that local factors such as the sediment supply and the hydrodynamics, combined with pre-existing topography, play a significant role in the preservation of coastal wedge sequences during sea-level highstand conditions. It also revealed the time scale of the preserved sequences