Large Outcrops Research Articles

Jurassic volcanism of the Chon Aike Silicic LIP in the northeastern Deseado Massif

Two compositionally different volcanic cycles are documented by geological mapping, lithofacies and petrographic analyses of Jurassic volcanic rocks in the northeastern sector of the Deseado Massif, constituting the western counterpart of the Karoo-Ferrar LIPs in Patagonia. The first cycle is of intermediate composition and is represented by andesitic lava flows, phenoandesitic moderate-grade ignimbrites and volcaniclastic deposits. These rocks constitute a previously unknown large outcrop (~100 km2) of the Bajo Pobre Formation. The second cycle (Chon Aike Formation) is acidic in composition and constituted by several pyroclastic deposits (ignimbrites and co-ignimbrite lag breccias), lavic bodies (rhyolitic lava domes, dykes, and coulees) and rhyolitic pyroclastic dykes. Structural measurements collected in the studied area suggest an extensional tectonic control on the emplacement of, at least, the Chon Aike Formation rocks. We document two major NE-striking (SE-dipping) normal faults, which constitute direct field evidence of the extensional tectonic control on the Jurassic Chon Aike Silicic LIP in the Deseado Massif at the time when southern Gondwana broke up.

Tectonomagmatic development of the Eocene Pasevh pluton (NW Iran): Implications for the Arabia-Eurasia collision

Abstract The Pasveh pluton is one of a number of intrusive complexes in the northwestern part of the Sanandaj-Sirjan Zone (SSZ), NW Iran. The major part of this complex is composed of high-K, calc-alkaline granitic rocks. The geochemical data indicate that the granitic rocks, although compositionally similar, are not cogenetic and can be divided into three groups. The first group (mesocratic granitoids) is represented by the largest outcrop in the Pasveh pluton. It is mainly composed of metaluminous magnesian monzodiorite to granodiorite with abundant MME and gabbroic enclaves. Zircon LA–ICP–MS U–Pb dating yielded Eocene crystallization ages (ca. 40 Ma) for this group. The monzodiorite (eNdt = +2.0 to +2.5), granodiorite (eNdt = +1.5 to +1.6), MME and gabbroic enclave (eNdt = +3.3 to +4.7) have distinct Nd isotopic compositions. The second group is composed of Eocene (39.7 ± 0.6 Ma), weakly peraluminous monzogranites that have Carboniferous and Cretaceous inherited zircons. Leucocratic granitic dikes of adakitic composition comprise the third group of Pasveh silicic rocks. The dikes are slightly younger (37.5 ± 0.3 Ma) than host rocks and cross-cut the mesocratic granitoids. Our results indicate that the underplating of basaltic magmas related to extensional stress in the overlying Iranian plate during the Eocene induced partial melting of the lower crust. Differences in the amount of partial melting of the source rocks are likely responsible for the volume and heterogeneity of their melt compositions. Subsequent to melt generation, it is possible that the silicic magmas mixed with mafic magmas in variable proportions to produce the hybridized rocks and enclaves. The intrusion of leucogranite dikes after the emplacement of the Pasveh pluton suggests that during or slightly after Neo-Tethys subduction there was another period of magmatism that was likely related to the melting of the subducted slab.

Fabric study in metamorphic rocks in Karangsambung, Kebumen, Central Java

Process of deFormation has an effect on both dynamic and regional metamorphic rocks. Metamorphic rock of Manunggal Formation can be found as large outcrops in Karangsambung, Central Java. In this research, we did geological mapping in the Manunggal Formation outcrop area and took rock samples. The rock samples are then analysis macroscopically to determine their metamorphic facies. From our study, we are able to identify the various degrees of metamorphism within the study area. This variation are concluded from the detailed macroscopic of mineral composition and rock texture of the rock samples from Manunggal Formation. The metamorphism process in rocks produced foliation textures on metamorphic rocks that are either foliated like phyllite and schist, or non-foliated such as green rock, serpentinite, and hornfels. All of this variation are plotted into the geological map and showing specific trend that might be related to past tectonic activity in the study area.

Geological Characterization of the Marble Commercial Varieties Outcropping in the Frigido Valley (Apuan Alps, Italy)

The Apuan Alps are studied by several authors since the nineteenth century for the presence of important geoheritage mainly represented by metamorphic polydeformed rocks, polymetallic mineralizations and large outcrops of precious natural stones. The Apuan Alps marble is a typology of ornamental stone that is worldwide known for decoration and building purposes as well as for the excellent physical-mechanical properties. This paper aims at improving the knowledge of geology, petrography and microstructures of the marble commercial variety of the Apuan Alps. In particular, this study investigated the Frigido Valley (NW Tuscany, Italy) and its nine stone-work basins: Brugiana, Capraia, Madielle, Rocchetta, Gioia, Valsora, Piastramarina, Piastreta and Forno. Seven marble commercial varieties were identified (namely white, ordinary, veined, grey, “Arabesque-like”, Calacatta and Seravezza Breccias) from these basins, corresponding to more than fifty local names according to the current nomenclature used by the workers during the exploitation work and trading.

A comparison study on landslide prediction through FAHP and Dempster–Shafer methods and their evaluation by P–A plots

One of the important issues in identifying susceptible landslide locations is to select effective factors in the landslide of studied areas. The complexity of this issue is due to the fact that each of the factors is a part of the desired criteria, and the selection among them is a multi-criteria decision-making problem, requiring a structured and systematic approach. In the study area, the presence of large outcrops, as well as relatively thick soils formed on the formations, has caused a significant level of the province to potentially have the conditions for the movement of the tides. In addition, the situation is exacerbated by inappropriate use of natural resources, and construction of numerous rural and forest roads. In this paper, multi-criteria decision-making (MCDM) such as the fuzzy analytical hierarchy process (FAHP) and Dempster–Shafer (DeS) method was used to detect susceptible landslide locations, and output maps were verified applying the prediction–area (P–A) method for landslide purposes. The study has utilized P–A plot to evaluate and compare the obtained results of FAHP and DeS methods. The results indicated that the normalized density value achieved from P–A plots was significantly higher for the FAHP than the corresponding value for the DeS. In other words, FAHP, compared to DeS, resulted in the successful detection of landslide occurrences and more accurate classification of the study area.

Badania georadarowe kemów jako przykład możliwości zastosowania metod geofizycznych do badania form zbudowanych z drobnoziarnistych osadów klastycznych = GPR surveys of kame hills as an example of geophysical methods being applied to the study of forms built of fine grained clastic sediments

The Ground Penetrating Radar (GPR) method potentially offers many possibilities for fast and reliable lithostratigraphic sediment models to be developed. From a cognitive point of view, this represents a major simplification and shortening of procedures with which information about sediments can be obtained. And from the point of view of the economy of operations, there can be a significant reduction in costs and time of research in shallow geology and the stratigraphy of areas where unconsolidated clastic sediments are of superficial occurrence. Also noteworthy is the possibility for the results of GPR surveys to be deployed in support of geological mapping, as well as in the shallow exploration of resources and hydrogeological studies.The most major advantage of the GPR method related to the possibility of the structure of forms being observed in full shape. In the absence of large outcrops, geophysical prospection of geomorphological forms is helpful, insofar as we are able to translate the results of geophysical surveys into the actual lithostratigraphic system of sediments building a specific form.Against that background, the research presented in this article forms part of the work to develop radar stratigraphy, as an important support for direct geological research (Huggenberger et al., 1994; Van Overmeeren, 1998; Beres et al., 1999, Overgaard and Jakobsen, 2001; Jakobsen and Overgaard, 2002; Neal, 2004; Lejzerowicz et al., 2014; Żuk and Sambrook Smith, 2015; Lejzerowicz et al., 2018). It also points to the research potential of the GPR method in determining the genesis of form. The discussion on the way kames form has been going on in the literature for years (Niewiarowski, 1959; 1961; Karczewski, 1971; Klajnert, 1978; Jaksa, 2003; Terpiłowski, 2008). The studies presented here do not suffice to allow the matter to be determined comprehensively, even though they do provide for verification of the opinions of previous researchers.The area forming the subject of this article is defined by Niewiarowski (1959) as the dead ice zone because of the characteristic set of forms (dead ice moraines, kames and eskers). Like modern researchers (Terpiłowski, 2008), Niewiarowski points to the importance of sub-Quaternary surface elevations in the formation of cracks in the ice sheet, with this leading on to the formation of kame hills above such elevations. This would also seem to have been one of the reasons for the formation in the mass of ice of lakes whose filling with sediment and melting ice walls took the form of kames.The great advantage of the GPR method lies in its ability to recognise macrostructural sediment patterns in glacilimic forms. This diagnosis allows for the high-probability assessment of the genesis of form, especially in the context of its position being determined in the marginal zone of the ice sheet. Also looking extremely promising is the capacity for the thickness of fine clastic sediments lying on till to be determined using GPR. It allows for the determination of the way in which a given form is rooted.Described as they are in brief only, test results for selected sites serve to confirm the great usefulness of the GPR method in the recognition of shallow lithostratigraphy of clastic sediments. Nevertheless, this should not be the only method used to recognise the geological structure of forms and sediments. Significant interpretation ambiguities mean that the GPR method should act in support of direct lithostratigraphic research, not merely serving as an alternative to it. GPR surveys offer a depiction particularly close to the real one – of sediment present in homogeneous sediments in relation to electrical parameters. Sediments ideal for GPR surveys would for example be fine dry sands or silts – and it is precisely these sediments that built most of the investigated kame forms.

Petrology and geochemistry of ophiolitic ultramafic rocks and chromitites across the Eastern Desert of Egypt: Insights into the composition and nature of a Neoproterozoic mantle and implication for the evolution of SSZ system

Large outcrops of ultramafic rocks are common in the Central Eastern Desert (CED) of Egypt and represent residual mantle sections and cumulates of dismembered Neoproterozoic oceanic lithosphere. This study integrates field observations, petrography, geochemistry and mineral chemistry to investigate ultramafic rocks of the dismembered ophiolitic rocks at four areas distributed from east to west across the CED, with the aim of gaining a better understanding the tectonic settings and mantle conditions under which the ultramafic rocks formed. The ultramafic masses studied are composed of serpentinized peridotites, serpentinites and pyroxenites, and occasionally host podiform chromitites. Preserved textures, relict primary minerals and whole-rock compositions indicate that the protoliths of these ultramafic rocks were dominated by harzburgites. The Al2O3- and CaO-depleted nature of residual harzburgites, the high Fo and NiO contents of primary olivines and the high Cr# and low TiO2 contents of fresh Cr-spinels suggest that these ultramafic rocks are remnants of depleted to highly depleted forearc mantle of suprasubduction zone (SSZ) system. Temperatures from olivine-spinel geothermometry (668–778 °C) and Al-in-orthopyroxene geothermometry (984 °C) estimated for residual harzburgites are comparable to those reported for modern forearc mantle peridotites. The range of oxygen fugacity [ΔlogƒO2 (FMQ)] values (−3.01 to +0.32) calculated for the residual harzburgites reveals heterogeneity in the Neoproterozoic mantle oxidation state and suggests that SSZ mantle was not consistently more oxidized than MOR mantle. The podiform chromitites of different ultramafic masses were formed following the interaction of residual mantle peridotites with forearc basaltic and boninitic melts, implying the evolution of Neoproterozoic SSZ system from subduction initiation to more mature island arc stage. Integration of the analyses carried out in this study shows a Neoproterozoic SSZ system where slab-derived melts evolve in composition and oxidation state from early reduced forearc basalt in the east to more oxidised boninitic melts in the west.

Cenozoic exhumation of the Neoproterozoic Sanfang batholith in South China

The 1500-km-long Jiangnan tectonic belt in China is well known for large outcrops of Proterozoic basement rocks, although the exhumation history of the exposed basement is poorly constrained. The thermochronology of the Sanfang batholith in the southernmost section of this belt was used to constrain the timing and mechanism of exhumation using apatite fission track analysis of granite samples collected along three transects. The results show that the ages of single apatite grains are much younger than the Neoproterozoic crystallization age of the Sanfang batholith. The apparent age v. elevation diagram shows two-stage cooling during the Paleogene and Miocene. The cooling stages are coincident with unconformities between the Paleogene and underlying strata, and between the Neogene and the Paleogene, with movement on high-angle normal faults. A compilation of apatite fission track data from this and previous studies suggests that the batholith was exhumed in the Cenozoic and the timing of rapid cooling is progressively younger to the east as a result of slab rollback leading to Cenozoic back-arc extension. The exhumation of the Sanfang batholith therefore indicates that Cenozoic erosion and extensional tectonics played a key part in exhuming the basement rocks and forming the present architecture of the Jiangnan tectonic belt.

Ordovician trace fossils from southern Jordan with particular consideration to the Cruziana rugosa group: Taxonomy, stratigraphy and trans-regional correlation throughout the Middle East and northern Africa

First detailed palaeoichnological research is presented from all the Ordovician formations and members of the Southern Desert of Jordan. The exclusively siliciclastic succession is of fluvial, fluvial-deltaic and fully marine origin and develops continuously from Cambrian strata until late Hirnantian glacial deposits. The ichnofauna occurs on large outcrop surfaces and is quite rich and of high diversity. Based on numerous taxonomic identifications from the excellently preserved material of various stratigraphic levels a biostratigraphic determination of the sequence is concluded as late Early to early Late Ordovician. Twenty-four ichnotaxa, two morphotypes and fifteen ichnogenera within five ethological groups based on the categories of architectural designs were identified. (1) horizontal burrows and trails (arthropod traces): Cruziana rugosa, C. furcifera, C. goldfussi, C. rouaulti, C. almadenensis, C. isp., Diplichnites cf. D. gouldi, D. morphotype A, D. morphotype B, Monomorphichnus cf. lineatus, cf. Monomorphichnus, Rusophycus didymus, R. aff. petraeus, ?R. aff. almadenensis; (2) vertical burrows: Arenicolites isp., Monocraterion isp., Rosselia socialis, Skolithos linearis; (3) plug-shaped burrows: Bergaueria perata, B. sucta; (4) horizontal branched burrows: Treptichnus cf. T. pedum; (5) horizontal burrows and trails: Gyrochorte isp., Palaeophycus tubularis, Planolites beverleyensis, Psammichnites gigas, Zoophycos isp. Whereas the ichnofauna of the Early Ordovician upper Disi Formation (Fm.) is dominated by cruzianid (C. rugosa group) and diplichnid arthopod traces (“trilobite highways”), the late Middle to early Late Ordovician Dubaydib Fm. contains distinctly smaller, nearly monoichnospecific, but completely surface covering arthropod tracks (C. almadenensis). In places, an amazing monospecific mass occurrence (Skolithos piperock ichnofabric) points to very special palaeoecological conditions during the deposition of the lower Dubaydib Fm. Ichnoassociations of the lower part of the Mudawwara Fm. (middle Late Ordovician) indicate a primarily shallow environment (e.g., Zoophycos isp.). Based on the trace fossil content and lithofacial characteristics, a correlation with North African regions is possible. So, the upper part of the Disi Fm. and the lower part of the Umm Sahm Fm. From Jordan is correlated with the Early Ordovician strata from southeastern Libya by the occurrence of C. goldfussi and C. furcifera. Additional correlations are possible by the shared occurrence of C. rouaulti with western Egypt, Sudan and western Libya. Within the Middle East (Jordan, Saudi Arabia, United Arab Emirates, Iran and Turkey), similar trace fossil assemblages composed of the C. rugosa group and related traces as well as common lithofacies characteristics point to closer palaeogeographic vicinity on a connected shallow shelf region along the costal margin of the Gondwana palaeocontinent.

Interplay of sediment supply and lake-level changes on the margin of an intrabasinal basement high in the Late Miocene Lake Pannon (Mecsek Mts., Hungary)

Lake Pannon, covering the Pannonian Basin (Hungary) during the Late Miocene, had a complex lake bottom with deeper sub-basins and intrabasinal basement highs, sometimes emerging above the lake level as islands and peninsulas. Above structural highs, the basin fill sequence usually commenced with deposition of transgressional, locally sourced coarse-grained deltas. These deposits are overlain by distally-sourced deltaic bodies associated with the prograding delta system that gradually filled up the entire basin. The transition between these two distinct delta systems was studied in a large outcrop on the edge of a former basement high (Mecsek Mts., southern Hungary). The transgressional phase is represented by the deposition of a mass flow dominated fan delta body, fed by local material from a granitic catchment area. An overlying fossil-rich, clayey unit records an episode for which sediment delivery into the basin was curtailed, possibly due to submergence of the granite body. The deposition of these two units took place between 8 and 6.8 Ma. The onset of sedimentation associated with the arrival of the distally sourced regressive delta system (around 6.8 Ma) is represented by deposition of shoreface sediments. This unit is characterized by distinctive bioturbation and storm related, sand filled scour-fills. Resedimented local material that forms mm thick, coarse laminas in the scour fills is indicative of denudation due to tectonic events and implies coupled storm-flood sedimentation. The deposition of the two distinct delta bodies and the interplay between tectonic events and lake-level changes occurred during a relatively short, ca. 1.5 Ma long time interval.

Preliminary conceptual model of the Cerro Blanco caldera-hosted geothermal system (Southern Puna, Argentina): Inferences from geochemical investigations

The Cerro Blanco Caldera (CBC) is the youngest collapse caldera system in the Southern Central Andes (Southern Puna, Argentina). The CBC is subsiding with at an average velocity of 0.87 cm/year and hosts an active geothermal system. A geochemical characterization of emitted fluids was carried out based on the chemical and isotopic compositions of fumaroles, and thermal and cold springs discharged in this volcanic area with the aim of constructing the first hydrogeochemical conceptual model and preliminary estimate the geothermal potential. The main hydrothermal reservoir, likely hosted within the pre-caldera basement rocks, has a Na+-Clˉ(HCO3)ˉ composition with estimated temperatures ≥135 °C. The unconsolidated, fine-grained Cerro Blanco ignimbrite likely acts as the cap-rock of the hydrothermal system. The presence of phreatic eruption breccias in the surrounding area of the geothermal fumaroles supports the effectiveness of the pyroclastic deposit as sealing rocks. The isotopic data of water (δ18O and δD) indicate a meteoric recharge of the hydrothermal reservoir, suggesting as recharge areas the sectors surrounding the CBC, mainly towards the W and NW where large outcrops of the pre-caldera basement exist. A fault-controlled hydraulic connection between the hot springs and the hydrothermal reservoir is proposed for the Los Hornitos area. The fumaroles show the typical compositional features of hydrothermal fluids, being dominated by water vapor with significant concentrations of H2S, CH4 and H2. Considering the high geothermal gradient of this area (∼104 °C/km) and the relatively high fraction of mantle He (∼39%) calculated on the basis of the measured R/Ra values, the hydrothermal aquifer likely receives inputs of magmatic fluids from the degassing magma chamber. The preliminary geothermal potential at CBC was evaluated with the Volume Method, calculating up to E = 11.4*1018 J. Both the scarce presence of superficial thermal manifestations and the occurrence of an efficient cap-rock likely contribute to minimize the loss of thermal energy from the reservoir. The results here presented constitute the necessary base of knowledge for further accurate assessment of the geothermal potential and ultimately the implementation of the geothermal resource as a viable energy alternative for small localities or mining facilities isolated from the National Interconnected System due to their remote localization.

A rock and an art place: the Inkas’ Collaconcho in context

Collaconcho, a large rocky outcropping located at the edge of the Inka archaeological site of Saqsaywaman, was – from an Andean perspective – both sentient and agentic. Oral histories accuse this stone of resisting Inka construction efforts and also of homicide. Over time, Inka stone carvers blanketed its surface with mostly abstract forms; of them, step motifs (siqana) predominate. Here we consider the significance of Collaconcho's ‘steps’ and what this outcropping meant to the Inkas who made it and to the indigenous Andeans who viewed it. Bearing in mind Collaconcho's location and the legend surrounding it, I suggest that its carvings may be dialogic in nature, that the Inkas sculpted the rock as a means of communicating with this venerable, powerful, and – at times – hostile being. Collaconcho, in its storied defiance and heavily carved superficies, embodied the ways the Inkas engaged oppositional forces.

Does seasonality and pool connectivity influence fish trophic ecology in knickzone habitats?

ABSTRACTKnickzones are large rock outcrops found in upstream and middle plateau river basins. This kind of geological formation, which is considered a macrohabitat, creates a complex of mesohabitats: pools, riffles and runs, with distinct characteristics. In the present work, the aim was to evaluate the influence of connectivity and seasonality on the trophic structure of the ichthyofauna found in knickzone pools. Fish were sampled in four connected and three isolated pools, during dry and rainy seasons, and the stomach contents of 20 species were analyzed. Seasonal differences in diet occurred, with greater contribution of algae and aquatic hexapod in the dry season and of plant fragments and organic matter in the rainy season. The high diet overlap found in the isolated pools may be related to more intensive biotic interactions among individuals confined in physically restricted habitats. Seasonality in combination with connectivity to the main channel influenced the trophic structure of fish assemblage in the knickzone. Knickzones dynamics are modulated by seasonal events, such as floods, and connectivity of habitats, being extremely important for the trophic interactions between species. Alterations to these dynamics, like the construction of hydroelectric power plants, can modify significantly the trophic ecology of knickzones.

Basal Moraines: Communication 1. Essential Lithological Features

The facies complex of basal moraines with glaciodynamic structures (common basal moraines) dominates among deposits of the given genetic type. These moraines represent glacial diamictons of diverse structure and lithology. Some of their features are also typical of sediments of other genetic types. Therefore, a comprehensive study of glacial diamictons and their occurrence mode on the glacial bed (unconsolidated or consolidated) within large outcrops is methodically correct. Only such studies can unravel the wide range of specific features typical of common basal moraines.

Characterization of benthic biogeochemistry and ecology at three methane seep sites on the Northern U.S. Atlantic margin

Several hundred methane seeps were recently discovered along the U.S. Atlantic margin, a passive margin without a major hydrocarbon basin. These seeps represent a compelling opportunity to compare and contrast geochemical parameters, as well as the distribution and composition of associated chemosynthetic ecosystems, across geologically distinct seeps. Specifically, this study characterized the physical, chemical, geological, and biological features at Veatch Canyon, New England, and Shallop Canyon methane seep sites using a suite of state-of-the-art sampling and communication tools: AUV Sentry, HOV Alvin, a video-equipped multicore, and a real-time telepresence connection to the Inner Space Center (ISC) at the University of Rhode Island. Water column backscatter data collected by AUV Sentry confirmed previously detected gas emission and further indicated the presence of 13 actively emitting gas seeps within the Veatch Canyon survey area, 5 within the New England survey area, and 15 within the Shallop Canyon survey area. Complementary high-resolution seafloor bathymetry and backscatter mapping data indicated highly rugose morphology at all surveyed seep sites including the presence of extensive rock outcrops and bivalve beds. Video collected by HOV Alvin provided visual confirmation of gas plumes and the presence of chemosynthetic communities, including microbial mats and mussel beds, as well as large outcrops of authigenic carbonate rock surrounding locations of discrete gas emission. Bathymodiolus was the dominant species observed at the Veatch Canyon methane seep site, while the deep-sea red crab, Chaceon quinquedens, dominated the New England and Shallop Canyon seep sites. Elevated pore water sulfide concentrations suggested stimulation of sulfate-coupled anaerobic oxidation of methane (AOM) and/or degradation of organic matter in seep sediments relative to non-seep sediments; AOM was observed directly within overlying authigenic carbonate rocks. DNA sequencing of the surface sediments revealed diverse sulfide-oxidizing bacteria similar to the taxa described previously at other methane seeps, including members of the Thiotrichales and Campylobacterales. Together, these analyses provide one of the first interdisciplinary descriptions of sites within this massive seep system, setting the stage for more targeted, hypothesis-driven investigations. In this context, telepresence facilitated interdisciplinary research between specialists at the ISC and scientists and engineers at sea, enabling researchers to transfer data and maximize research efforts with sampling tools at sea. Our findings suggest that although the geological setting is distinct, the surficial microbial and macrofaunal communities closely resemble those of previously described methane seeps.

関東平野西縁,下部更新統仏子層の切り通し大露頭(フォト)

関東平野西縁,下部更新統仏子層の切り通し大露頭(フォト)

Erratum to: Therapeutic characteristics of Galician mineral and thermal waters (NW-Spain) ascribed to their local/regional geological setting

Galicia is located in the NW corner of the Iberian Peninsula (Spain). From a geological point of view, the territory belongs to the Hercynian chain and, more specifically, to a large outcrop dominated by igneous and metamorphic rocks called the Hesperian Massif or Iberian Massif. In some sectors the Hesperian Massif is partially covered by more recent sedimentary deposits. The geology of Galicia is very complex due to the age of the rocks that make up its substrate and their diversity. Thus, the hydrogeological behaviour of the underground medium (hydrodynamic and hydrogeochemical characteristics) will determine the therapeutic properties of the water emanating from the surface. In Galicia, aquifers are generally shallow with low mineralization, except for those whose waters come from deep fractured mediums. The chemical characteristics of the water are directly related to the geological matrix. The groundwater flows through the geological medium and is mineralogically enriched by heterogeneous chemical reactions. Galicia turns out to be an area rich in the potential exploitation, applications and use of different water resources. These resources are thermal, mineral-natural and mineral-medicinal waters. In this work, we have developed a study that relates the geology, hydrogeological and hydrogeochemical characteristics of the Galician substrate and their potential therapeutic indications. To achieve that, we have chosen to study the exploited waters with higher flow rates, including the natural mineral waters for human use.

Therapeutic characteristics of Galician mineral and thermal waters (NW-Spain) ascribed to their local/regional geological setting

Galicia is located in the NW corner of the Iberian Peninsula (Spain). From a geological point of view, the territory belongs to the Hercynian chain and, more specifically, to a large outcrop dominated by igneous and metamorphic rocks called the Hesperian Massif or Iberian Massif. In some sectors the Hesperian Massif is partially covered by more recent sedimentary deposits. The geology of Galicia is very complex due to the age of the rocks that make up its substrate and their diversity. Thus, the hydrogeological behaviour of the underground medium (hydrodynamic and hydrogeochemical characteristics) will determine the therapeutic properties of the water emanating from the surface. In Galicia, aquifers are generally shallow with low mineralization, except for those whose waters come from deep fractured mediums. The chemical characteristics of the water are directly related to the geological matrix. The groundwater flows through the geological medium and is mineralogically enriched by heterogeneous chemical reactions. Galicia turns out to be an area rich in the potential exploitation, applications and use of different water resources. These resources are thermal, mineral-natural and mineral-medicinal waters. In this work, we have developed a study that relates the geology, hydrogeological and hydrogeochemical characteristics of the Galician substrate and their potential therapeutic indications. To achieve that, we have chosen to study the exploited waters with higher flow rates, including the natural mineral waters for human use.

Deepwater fish assemblages at Isla del Coco National Park and Las Gemelas Seamount, Costa Rica

The deepwater faunas of oceanic islands and seamounts of the Eastern Tropical Pacific are poorly known. From 11-22 September 2009 we conducted an exploration of the deepwater areas of the Isla del Coco Marine Conservation Area, Costa Rica and a nearby seamount using a manned submersible. The goal of the exploration was to characterize the habitats and biota, and conduct quantitative surveys of the deepwater portions of Isla del Coco National Park and Las Gemelas Seamount, located about 50km southwest of Isla del Coco. We completed a total of 22 submersible dives, spanning more than 80hr underwater, and collected a total of 36hr of video. We surveyed habitats from 50-402m and observed more than 45 species of fishes, some of which have not yet been described and are likely new to science. The diversity of fish species in deep water at Isla del Coco National Park was lower than the diversity of fishes in shallow water, and eight species groups accounted for more than 95% of the total fish biomass. The combined density of all fish species was higher at Las Gemelas Seamount (253 fishes/100m2) than at Isla del Coco National Park (138 fishes/100m2). The combined density of fishes in habitats comprised primarily of bedrock or large boulders outcrops was more than three times as high at Las Gemelas Seamount as it was at Isla del Coco National Park. This discrepancy was caused by the extremely high concentration of Anthiinae fishes in rocky habitats at Las Gemelas Seamount. Densities of fishes in the other habitats were similar between the two sites. Similarly, when estimates of fish density were plotted by slope categories the density was much greater on steep slopes, which were usually comprised of rock habitats. Also, the density of fishes was greatest on high rugosity habitats. Results of these submersible surveys indicate that seamounts in the tropical eastern Pacific Ocean may be an important source of biodiversity and that more quantitative surveys are needed to characterize the fauna of the region. Citation: Starr, R.M., K. Green & E. Sala. 2012. Deepwater fish assemblages at Coco Island National Park and Las Gemelas Seamounts, Costa Rica. Rev. Biol. Trop. 60 (Suppl. 3): 347-362. Epub 2012 Dec 01.

An integrated workflow for stress and flow modelling using outcrop-derived discrete fracture networks

Fluid flow in naturally fractured reservoirs is often controlled by subseismic-scale fracture networks. Although the fracture network can be partly sampled in the direct vicinity of wells, the inter-well scale network is poorly constrained in fractured reservoir models. Outcrop analogues can provide data for populating domains of the reservoir model where no direct measurements are available. However, extracting relevant statistics from large outcrops representative of inter-well scale fracture networks remains challenging. Recent advances in outcrop imaging provide high-resolution datasets that can cover areas of several hundred by several hundred meters, i.e. the domain between adjacent wells, but even then, data from the high-resolution models is often upscaled to reservoir flow grids, resulting in loss of accuracy. We present a workflow that uses photorealistic georeferenced outcrop models to construct geomechanical and fluid flow models containing thousands of discrete fractures covering sufficiently large areas, that does not require upscaling to model permeability. This workflow seamlessly integrates geomechanical Finite Element models with flow models that take into account stress-sensitive fracture permeability and matrix flow to determine the full permeability tensor. The applicability of this workflow is illustrated using an outcropping carbonate pavement in the Potiguar basin in Brazil, from which 1082 fractures are digitised. The permeability tensor for a range of matrix permeabilities shows that conventional upscaling to effective grid properties leads to potential underestimation of the true permeability and the orientation of principal permeabilities. The presented workflow yields the full permeability tensor model of discrete fracture networks with stress-induced apertures, instead of relying on effective properties as most conventional flow models do.