Surficial Structures Research Articles

Reversible transformation between terrace and step sites of Pt nanoparticles on titanium under CO and O2 environments

Understanding the dynamic evolution of active sites of supported metal catalysts during catalysis is fundamentally important for improving its performance, which attracts tremendous research interests in the past decades. There are two main surficial structures for metal catalysts: terrace sites and step sites, which exhibit catalytic activity discrepancy during catalysis. Herein, by using in situ transmission electron microscopy and in situ Fourier transform infrared spectroscopy (FTIR), the transformation between surface terrace and step sites of Pt-TiO2 catalysts was studied under CO and O2 environments. We found that the {111} step sites tend to form at {111} terrace under O2 environment, while these step sites prefer to transform into terrace under CO environment at elevated temperature. Meanwhile, quantitative ratios of terrace/step sites were obtained by in situ FTIR. It was found that this transformation between terrace sites and step sites was reversible during gas treatment cycling of CO and O2. The selective adsorption of O2 and CO species at different sites, which stabilized the step/terrace sites, was found to serve as the driving force for active sites transition by density functional theory calculations. Inspired by the in situ results, an enhanced catalytic activity of Pt-TiO2 catalysts was successfully achieved through tuning surface-active sites by gas treatments.

Mineralogical, chemical and stable C and O isotope characteristics of surficial carbonate structures from the Mediterranean offshore Israel indicate microbial and thermogenic methane origin

The Eastern Mediterranean continental slope offshore Israel became a focus of exploration for, and production of, natural gas in recent years. The 2010–2011 Nautilus ROV expedition performed detailed video recordings and sampling in two areas offshore Israel: the Palmachim disturbance, southwest of Tel Aviv, and an area offshore Acre, north of Haifa. An analytical programme regarding the carbonate structures was carried out, examining the overall mineralogy, stable C and O isotopes, and Ca, Mg, and Mn concentrations. This provided information on their composition and as a result, an indication of the carbon sources and temperature of formation. The major authigenic minerals identified comprised magnesian calcite, dolomite, aragonite, and kutnohorite. The detrital minerals included quartz, clays, feldspars, and rare augite and enstatite, likely transported from the Nile estuary. The carbon isotope composition of aliquots taken from nineteen samples from these areas have an overall δ13C range from −62.0 to −0.1‰PDB, indicating a range of microbial/biogenic and thermogenic methane contributions. The range of δ18O from 2.7 to 7.0‰PDB reflects the range of temperatures of formation. The δ18O characteristics differ among areas. In general, high values; δ18O >5‰PDB are recorded from area N2 of the Palmachim disturbance, indicating low temperature of formation. Low values of δ18O (<5‰PDB) were measured from areas W2 and W3 of the Palmachim disturbance, together with samples from area N2 of the Palmachim disturbance, and samples from areas A1 and A2 offshore Acre indicate high temperature origin. Samples from an inactive chimney from area N2 range from pure dolomite to pure magnesian calcite. This trend is linked to δ13C increase from −39.9 to −0.1‰(PDB), and δ18O decrease from 6.2 to 4.7‰(PDB). These values indicate a decrease in the methane-derived carbon contribution and an increase in temperature. Kutnohorite, Ca(Mn2+, Mg, Fe 2+)(CO3)2 is a major component in samples from Acre, and less so in the Palmachim disturbance. An exploratory investigation of the relationship between Mn/Ca, δ18O and δ13C revealed that samples having Mn/Ca < 0.1(wt./wt.) have δ13C<−50‰PDB indicating a microbial methane source, while samples with Mn/Ca > 0.1 have δ13C between −35 and −22‰PDB suggesting a thermogenic origin. These results suggest that the mineralogical, isotopic δ13, δ18O, and chemical (Mn/Ca indicative of kutnohorite) characteristics of surficial carbonate structures can indicate and distinguish between deep and shallow methane sources in the Eastern Mediterranean.

Morphotectonic controls of groundwater flow regime and relating environmental impacts in Northwest Sinai, Egypt

The frequent appearance of some hydro-environmental hazard features, such as waterlogging and soil salinization along the susceptible zones at Northwest Sinai area (NWSA), has put serious challenges and obstacles for a correct and efficient land use planning of this region, for several decades. Although previous studies have shown that the whole region of Northern Sinai is greatly affected by the tectonic movements associated with the Syrian Arc folding system (SAS), NWSA is barren of any obvious surficial structures. The current work aims to investigate the effect of subsurface tectonic features on the hydrogeologic regime of NWSA.

Wrinkled Graphene Monoliths as Superabsorbing Building Blocks for Superhydrophobic and Superhydrophilic Surfaces.

Superhydrophobic and superhydrophilic surfaces are of great interest because of a large range of applications, for example, as antifogging and self-cleaning coatings, as antibiofouling paints for boats, in metal refining, and for water-oil separation. An aqueous ink based on three-dimensional graphene monoliths (Gr) can be used for constructing both superhydrophobic and superhydrophilic surfaces on arbitrary substrates with different surficial structures from the meso- to the macroscale. The surface wettability of a Gr-coated surface mainly depends on which additional layers (air for a superhydrophobic surface and water for a superhydrophilic surface) are adsorbed on the surface of the graphene sheets. Switching a Gr-coated surface between being superhydrophobic and superhydrophilic can thus be easily achieved by drying and prewetting with ethanol. The Gr-based superhydrophobic membranes or films should have great potential as efficient separators for fast and gravity-driven oil-water separation.

Microboring in a Freshwater Fluvial Unionid Bivalve Substrate

Samples of the unionid bivalve Elliptio complanata were collected from the channel of the freshwater Saint John River, from Fredericton, New Brunswick, Canada. Scanning electron microscopy imaging of prepared shell samples revealed an assemblage of microborings. No borings are noted on the periostracum or prismatic shell layers. Boring structures are instead confined to the underlying nacreous aragonitic shell material, together with its associated organic conchiolin layers. Three main styles of boring are encountered, encompassing both predominantly surficial structures and penetrative tubular borings. Surficial structures are represented by a polygonal network on an exposed conchiolin shell layer. The penetrative borings take two forms, one being simple unbranched tubes, steeply aligned (perpendicular to the shell surface) and traversing the full thickness of the nacreous shell layer. The other penetrative boring style, again occurring within the nacreous layer, comprises a complex irregular network of randomly oriented rarely branching tubular borings. Borings generally display diameters of micron scale. Biofilm and extracellular polymeric substances, with bacterial, diatomaceous and filamentous components are also observed, often displaying a close association with both the borings and the conchiolin layers within the shell. The formation of the borings may be attributed to cyanobacteria, cyanophyte or fungal progenitors.

Possible Animal Embryos from the Lower Cambrian (Stage 3) Shuijingtuo Formation, Hubei Province, South China

Fossilized animal embryos from lower Cambrian rocks provide a rare opportunity to study the ontogeny and developmental biology of early animals during the Cambrian explosion. This paper reports possible animal embryos, along with sponge spicules, hyolithelminths, and linguliformean brachiopods, from the upper Shuijingtuo Formation limestone (Cambrian Stage 3) at Changyang, Hubei Province, South China. This limestone unit has carbonate carbon and oxygen isotopic compositions similar to the upper Shuijingtuo limestone in the Yangtze Gorges area. The Shuijingtuo embryo fossils were exposed by physical fracturing, extracted with acetic acid maceration, and observed in thin sections. They were examined using light microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopic elemental mapping, and micro-focus X-ray computed tomography. Most of them are poorly preserved, with a phosphatic envelope (interpreted as a chorion or fertilization envelope) surrounding sparitic calcite. In some specimens, a polygonal pattern is present on the surface, and these are interpreted as multicelled blastula embryos. In others, sets of grooves are present on the surface of a calcitic spheroidal structure, presumably representing the calcitic interior within the chorion; these grooves are superficially similar to annulations ofMarkueliaembryos, but their biological significance is unknown. Although their phylogenetic and taxonomic placement is largely unconstrained, the Shuijingtuo animal embryos indicate that chorions are taphonomically more robust and are selectively phosphatized. Embryos within the chorions, on the other hand, can be completely lost or entirely replaced by calcite, with only poorly preserved surficial structures. This style of preservation can be explained by a taphonomic switch from early phosphatization to later calcitization. This study illustrates the importance of combining physical fracturing with widely used acid digestion methods in the study of calcitized animal embryos, and it alludes to the possibility that many empty phosphatic vesicles recovered by acid digestion from Cambrian carbonates may be fossilized chorions.

Deformation history and hydrocarbon potential of the Southwestern Gissar Range (Southern Uzbekistan)

The divergent geometry of the Southwestern Gissar Range is related to large-scale underthrusting of the hinterland units of the Tajik depression beneath Southwestern Gissar and the thrusting of orogenic crust toward the northwest over the Beshkent trough. Since the predominant style of deformation in the region consists of folding and faulting, almost all the surficial structures of the orogen are allochthonous. This can significantly hamper understanding of a deeper, sub-thrust layer of the Southwestern Gissar, which hosts major hydrocarbon sources. Regional dynamic models involving ductile layers, as well as thrust faults, folds, and strike-slip faults allowed identification of the most favorable conditions for the localization of structural traps within this highly prospective petroleum basin.

Air permeameter investigation of surficial dune structures in the Nebraska Sand Hills

A permeameter was designed and constructed, and its theory of operation was developed; it has a subsurface probe for internal permeability measurements in poorly consolidated sediments. It was used to measure the permeability of sand at five depths in the upper 1.3 m (4.3 ft) of structural features on a large vegetated composite crescentic dune in the Nebraska Sand Hills. Permeability measurements were taken at 34 locations on the dune's steep leeward face, its long windward slope, fans below the leeward face, blowouts, peaks, crests, transverse ridges, benches, and the heads of gullies. Correlation of the permeabilities with the morphology of the dune is illustrated by a plot of the depth-averaged permeabilities and dune profile along a transect perpendicular to the lee face. Some of the permeabilities do not match the values anticipated on the basis of the theory of sedimentation (and experimental results) for active crescentic dunes. Although the large-scale features of the dune studied were evidently because of the original eolian sedimentation, the permeability was found to be strongly influenced by dune degradation processes involving running water and animal activity.

Three-dimensional architecture of growth strata associated to fault-bend, fault-propagation, and décollement anticlines in non-erosional environments

Abstract The evolution of surficial structures at the toes of orogens arises from the complex interplay between tectonic and surface processes. The internal architecture of syntectonic sediments has been shown to provide useful insights on the kinematic mechanism of folding. Two-dimensional templates of growth strata patterns associated to thrust-related anticlines are available in the literature. In this paper, we show the results of three-dimensional numerical modelling of growth fault-bend folds, fault-propagation folds, fixed limb length decollement folds and fixed limb dip decollement folds. We point out that total thickness contour maps, single syntectonic layer contour maps, and above all, the computation of their directional first-derivative maps, provide useful templates for inferring the kinematic mechanism of folding when compared with similar maps from natural examples. Application of these three-dimensional numerical models includes the comparison and supervised best fit with three-dimensional seismic reflection data sets. Numerical results are contrasted with the growth strata map patterns of the Mediano, Oliana and Pico del Aguila anticlines, in the Spanish Pyrenees.

Crust and upper mantle heterogeneities in the southwest Pacific from surface wave phase velocity analysis

Direct earthquake-to-station Rayleigh and Love wave data observed on high gain broadband records are analyzed in order to improve the lateral resolution of the uppermost mantle in the southwest Pacific region. We used data of nine permanent Geoscope and Iris stations located in the southern hemisphere and nine other stations as part of two temporary networks, the first one installed in New Caledonia and Vanuatu (hereafter named Cavascope network) by ORSTOM and the EOST from Louis Pasteur University in Strasbourg (France) and the second one installed in the Fiji, Tonga and Niue islands (hereafter named Spase network) by Washington University in St. Louis (USA). In order to collect more significant details on the surficial structures, we included the analysis of short period waves down to 8 s. A multiple frequency filtering technique has been used to recover phase velocities of Rayleigh and Love waves for selected earthquakes with magnitude greater than 5.5 and with known centroid moment tensor (CMT). About 1100 well-distributed seismograms have been processed in the period range 8–100 s and corrections for topography and water depth have been applied to the observed phase velocities. The geographical distribution of phase velocity anomalies have then been computed using the tomographic method developed by Montagner [Montagner, J.P., 1986a. Regional three-dimensional structures using long-period surface waves. Ann. Geophys. 4 (B3), 283–294]. Due to a poor knowledge of dense, well-distributed, crustal thickness values and corresponding velocity models, we did not perform or speculate on the construction of an S-wave 3D velocity model; therefore, we limited this study to the interpretation of the phase velocity distribution. The location of phase velocity anomalies are well determined and the deviations are discussed within the framework of the geological context and compared with other tomographic models. At long periods, from 40 s to 100 s, our results agree well with most of previous studies: the tomographic imaging shows a large contrast between low and high phase velocities along the Solomon, New Hebrides and Fiji–Tonga trenches. The lowest phase velocity anomalies are distributed beneath northern and southern Fiji basins and the Lau basin (corresponding to the volume situated just above the dipping slabs), whereas the highest values are displayed beneath the Pacific plate and the eastern part of Indian plate downgoing under the North Fiji basin. At shorter periods, our results show that the phase velocity distributions are well correlated with the large structural crustal domains. The use of local temporary broadband stations in the central part of the studied area gives us the opportunity to observe surface waves showing well-dispersed trains, allowing extended velocity measurements down to 8 s although aliasing due to multipaths become important. The continental regions (Eastern Australia, New Guinea, Fiji islands and New Zealand) show low velocities which are likely due to thick continental crust, whereas the Tasmanian, D'Entrecasteaux, and the Northern and Southern Fiji basins are characterized by higher velocities suggesting thinner oceanic crust. Additional analysis including the anisotropic case and S-wave velocity inversion with depth is in progress.

Present‐day stress field changes along the Baikal rift and tectonic implications

Intraplate extension, in a frame of a global compressional stress field, seems linked to local lithospheric perturbations (lithospheric thinning or thickening) able to modify the resulting state of stress [Zoback, 1992]. The Baikal Rift Zone (BRZ), Siberia, is located north of the India‐Asia collision zone and exhibits no direct communication with any oceanic domain. It can thus be fully considered as an area of continental extension, dominated by the “global compressional intraplate stress field” resulting from plate driving forces. In order to address the problem of its dynamics and kinematics and their links with the India‐Asia collision, a comprehensive stress tensor analysis is presented, based on 319 focal mechanisms of earthquakes located along the whole Baikal rift. The stress field is varying at different scales of observation: when looking at central Asia (several thousands kilometers), the maximum horizontal stress SHmax directions remain rather constant (with a fan‐shape geometry) when the tectonic regime goes from compressional (Himalayas) to extensional (Baikal). When observing the Baikal rift (about 1000 km long), clear variations of the stress regime are observed, from an extensional regime in the central part of the rift to wrench ones in its northern and southern ends. Finally, at the scale of 100 km, systematic SHmax reorientations occur close to major rift faults. We thus infer that the interaction between collisional processes and inherited structures may have a strong influence on rift dynamics. We then use computed stress tensors to predict slip vectors on major rift faults. Deformation patterns show two distinct parts of the rift: the South Baikal Rift (SBR) is characterized by a constant trending (around N100°E) slip vector, meanwhile the North Baikal Rift (NBR) exhibits a complex block rotation behavior involving at least three crustal blocks. We propose to interpret these surficial structures and motions as the result of an interaction between the regional compression coming from the India‐Asia collision and the geometry of the hardly deformable Siberian platform. This particular setting can explain most of the surficial deformation patterns, which suggest a large‐scale cracking of the lithosphere in the Baikal region. Other possible sources of stress could also be considered, like deep mantellic upwelling, or trench suction linked to the Pacific subduction.

Surficial sedimentology of the Middelkerke Bank (southern North Sea)

Detailed surficial investigations over the Middelkerke Bank, a tidal sand bank in the southern North Sea, revealed the relationship between morphology, surficial structures and grain-size parameters. Data from 85 grab samples all over the bank show that on a bank normal profile, the coarser, CaCO 3 rich and badly sorted sediments are generally located near the highest point of the bank, seaward at the northern end and landward at the southern end. Sedimentary structures were studied from 239 boxcores sampled on all the morphological units of the bank: crest, flanks and adjacent channels. In the shallower parts, foreset beds are preserved while in the deeper zones, intense bioturbation arises and destroys any structure. The combination between these data and the virtual absence of wave-induced structures indicates that the main agents responsible for the bank shaping are the tidal currents.

Sonography of a glaciated continental shelf

Sonographs of the inner continental shelf off Halifax, Nova Scotia, show a large part of the inner shelf area consisting of exposed bedrock in which the inferred sequence of structural events is clearer than the record on land. Ribbed moraines overlie eroded drumlins and provide new information on the deglaciation history. Morphologic features allow a precise definition of the maximum postglacial lowstand of sealevel at -65 to -70 m. A 1000 km 2 area in eastern Canada was surveyed with a multibeam sounder EM100, manufactured by Simrad of Norway. A 100% coverage of the sea floor was achieved with 50 to 100 m track spacing, and position control was achieved using the differential global positioning system (DGPS) with an accuracy of 1-2 m. Data were corrected for ship motion, gridded at a 10 m spacing, and displayed as obliquely illuminated relief image. The sonograph revealed characteristics of the sea bed in detail for the interpretation of bedrock and surficial structures and processes. The bathymetric images may be more useful for geologic mapping than air photographs and satellite images on nearby land, where vegetation commonly obscures the geologic features.

Mercury Contamination in the Oil and Gas Industry

Mercury contamination of surficial soils and building structures is concern to the oil, natural gas, and utility industries. Spillage from mercury-filled manometers that measure pipeline pressures is a major source of mercury contamination. Because of its chemical characteristics, the mobility of mercury within the soil posed significant health and environmental impacts. Inorganic mercury strongly adsorbs onto fine soil particles and organic matter, readily volatilizes into the atmospheres, and is leachable into aqueous systems. Under acidic conditions or with microbial action, elemental mercury and mercury oxides may transform into the water-soluble organic form, methyl mercury. Soil pH and Cl concentration are key elements to speciation and chemical transformation. Adsorption is pH dependent and proportional to the cation exchange capacity. Adsorption appears to be the dominant process in mercury soil retention. Methyl mercury readily bioconcentrates in fish and shellfish, posing a threat to the food chain and human health. Mercury vapors emanating from contaminated soils or building materials also can pose worker health problems. Chemical reactions of elemental, inorganic and organic mercury with different soil types limits the remedial alternatives currently available. Three general types of response actions exists for the remediation of mercury-containing sites: (1) source removal and ex-situ treatment, (2)more » application of in-situ corrective measures and, (3) no action. Treatment alternatives include retorting/roasting, acid leaching, extraction with complexing agents, soil washing/ion exchange, gravitational separation, electroreclamation, and immobilization/stabilization. Of these, only retorting/roasting and acid leaching are considered the best demonstrated available technology.« less

Structure of the Eastern Cordillera of Colombia: Implications for Trap Styles and Regional Tectonics

The northwest margin of South America has undergone multiple phases of compressional deformation beginning in the Late Cretaceous and culminating in the Pliocene-Pleistocene. The latest phases (Miocene to Pleistocene) of this deformation created the Eastern Cordillera of Colombia. Compressional structures in the Eastern Cordillera formed traps that have petroleum exploration potential; these are generally in the form of fault-bend and fault-propagation folds containing top-sealed reservoir and mature source rocks. Trap delineation, although difficult to achieve because of the poor seismic quality obtained in the region, can be accomplished by supplementing the seismic data with geometric analysis of surficial structures. The Eastern Cordillera is asymmetrical, with the dominant tectonic transport direction towards the east. West-directed thrust faults are localized along the western flank of the Eastern Cordillera and are interpreted to be back thrusts splaying off a deep mid-crustal detachment. A regional, retrodeformable cross section across the Eastern Cordillera shows that basement-detached deformation of late Miocene to Pliocene age was followed by Pliocene to Holocene uplift of the Cordillera on high-angle, basement-involved reverse faults. These two structural styles were superimposed on preexisting Jurassic and Lower Cretaceous grabens, whose normal faults were partially inverted during the later stages of compressional deformation. A palinspastic restoration of this regional cross section indicates that approximately 150 km of shortening (40% shortening) has occurred: 105 km eastward-directed towards the Llanos basin and 45 km westward-directed towards the Middle Magdalena basin. This calculated shortening is very close to that calculated by summing microplate motions for the northwest corner of South America. Shortening in the sedimentary cover rocks exceeds that in the basement rocks by about three times. This shortening can be regionally balanced with a gently dipping, mid-crustal detachment that extends beneath the Middle Magdalena basin and Central Cordillera and which roots in the Benioff zone beneath the Western Cordillera. The presence of a mid-crustal detachment, as postulated here, provides a mechanism to transmit the shortening from the convergent plate margin in the Pacific to the Andean foreland, and is interpreted to have provided the structural link between the three ranges of the Colombian Andes. The detachment also provides a mechanism to explain the imbalance of shortening seen between Eastern Cordillera basement and the overlying strata, and implies that the Western and Central Colombian Andes have been tectonically transported eastwards a distance of at least 150 km.

Tectonics of the Venus and the early Precambrian

Analyzing the tectonics of planets and their satellites we use all the information available from the studies of the Earth and other celestial bodies such as the Moon, Mars and Mercury. An important condition in such analysis is naturally the scale of the phenomena compared. Most surface structures of Venus are known to have no direct analogues on the surface of the present Earth, with its global systems of mid-oceanic ridges, deep trenches and vast lithospheric plates. This might be due to the sharp differences in the present thermal regimes of the Earth and Venus. It has already been suggested in numerous papers that the key to the genesis of the Cytherean surficial structures must be looked for in the geodynamics of the Early Precambrian Earth. Such an approach appears very logical indeed since the rheology of the present Cytherean crust must be closer to that of the Precambrian rigid lithosphere of the Earth which is as if ‘floating’ in the low-viscous asthenosphere. An attempt has therefore been made to evaluate certain elements in the tectonics of Venus through the theological properties of its crust comparing structural formation in the low-viscous layers of the Earth crust in the Early Precambrian with data on the morphology of structures on the surface of Venus.

Surficial structures of the northern Red Sea axial valley from 23° N to 28°N: time and space evolution of neo-oceanic structures

During recent French cruises in the northern Red Sea, the surficial structures of the axial valley were studied by means of bathymetry, magnetics and single channel reflection seismics. New compilation maps have been established and comparison of the various data allow different segments of the northern Red Sea axial valley to the distinguished where only intra-evaporitic deformations (24–25 °N), large volcanic outcrops (Mabahiss deep, 25°30′–26°N) or several recent isolated volcanic intrusions (26–27 ° N) characterize different stages of evolution. This new information allows reconstruction of the evolution of oceanization cells from a simple intra-evaporitic deep to a limited oceanic rift zone such as those observed in the central Red Sea. A major characteristic of this evolution, also depicted in other young oceanic rifts, is a succession of volcanic and tectonic phases. The major event in the northern Red Sea axial valley is a recent episode of voluminous but well localized magmatism. It would represent a new stage in the Red Sea evolution and thus may have some implications on earlier phases.

A thermodynamical study of the Martian permafrost

An outstanding result of the Viking mission has been the detection of water vapor in the martian environment. The only possible reservoir for the water, where no evidence of surface frost has been detected, is the soil. Comparative morphologic analyses of periglacial terrestrial and martian terrains suggested that permafrost can play an important role in forming many surficial structures as the Valles Marineris landslides or the collapse structures in the volcanic region of Tharsis. In this paper a study of the thermodynamics which regulate the processes of thawing and freezing of the layers of permafrost on Mars has been carried out. The equation of the heat propagation has been solved under martian conditions both in the case of periodic variations of the surface temperature and in the case of an anomalous heating of the ground. Seasonal temperature variations do not allow survival of CO2 or clathrate permafrost down to a depth of 15 m. We have demonstrated the existence of a secular ‘active layer’ of about 100‐m depth.

Recent investigations of surficial and deeper crustal structures of the Eastern and Southern Alps

After a review of the surficial structures of the Eastern and Southern Alps a discussion of some important theories of the Alpidic Orogeny is presented. Geological cross sections, based as far as possible on the latest data, are then presented in detail.