Silty Sediments Research Articles

Изучение трещинных коллекторов при проведении геологоразведочных работ в северо-восточной части о. Сахалин

During a geological fieldworks in the northeast of Sakhalin Island in order to study the siliceous deposits of the Pilskaya formation and to develop a technique for locating oil deposits in unconventional fractured reservoirs, natural outcrops of Cenozoic deposits on the Schmidt Peninsula and in the Pogranichny depression were studied. Samples were taken for analytical studies (geomechanical, geochemical, lithological, etc.), structural forms (folds, minor faults, slickensides, tension gashes, joints, shear fractures), which are indicators of tectonic deformations of the rock massive, were studied. It is shown that the intensity of fracturing strongly depends on the lithology, the position of the observation point relative to disjunctive and/or plicative structures. The direction of the joints varies depending on the position relative to the elements of the local folds and on the position of the block (with a small-block structure). According to the results of field observations it is shown, that the zone of intense dislocations has an extremely insignificant thickness usually the first tens of meters. An extremely nonuniformity of the stress field in the vicinity of the Pogranichniy depression is noted, which is reflected in the nature of the dipping planes, structural patterns and parageneses. In the northern part of the syncline, numerous flowing oil shows associated with open fracturing are identified, which obviously indicates the extension regime that continues up to this day.

Experimental Study on Hydraulic Conductivity and Resistance in Silty Sediments

Hydraulic conductivity k as a function of void ratio e and particle diameter for silty sediment was experimentally investigated, and an empirical formula for the estimation of hydraulic conductivity was proposed. Seepage resistance for flow in silty sediment was deliberated. Based on the findings of the study, it was concluded that hydraulic conductivity k could be expressed as an exponential function of void ratio e and median particle diameter d50 {3.1 μm < d50 < 87 μm and 0.26 < e < 4}. It was further found that the formula of seepage resistance factor (?), a form of friction factor, varies linearly with Reynolds number (Re) for silty sediments. A family of such λ-Re curves for various particle diameter d50 is presented.

Early Palaeozoic Discinocarina: a key to the appearance of cephalopod jaws

Cephalopoda is the only class of molluscs in which virtually all its modern representatives have a pair of powerful jaws. There is little doubt that jaws have contributed to the evolutionary success of cephalopods, but their origin still remains a mystery. Though cephalopods appeared at the end of the Cambrian, the oldest unequivocal jaws have been reported to date from the Late Devonian, though they were initially interpreted as phyllopod crustaceans of the suborder Discinocarina. After their relation with ammonoids was proven, they were considered as opercula, and only later their mandibular nature was recognized and widely accepted. Finds of discinocarins from Silurian deposits are still considered as opercula of ammonoid ancestors - nautiloids of the order Orthocerida. However, according to modern ideas, there is no place within their soft body for the location of such large opercula. Moreover, the repeated appearance of very similar structures in the same evolutionary line at least twice, but in different places of the body and for different purposes seems highly improbable. A new hypothesis is proposed herein, in which the Silurian fossils, earlier assigned to Discinocarina, are not specialized opercula, but protective shields, to defend orthocerids not from the predators, but from their own prey. The chitinous plates around the mouth likely appeared in the Silurian orthocerids for protection from such damage and later, during Silurian and Devonian, most likely gradually evolved into the jaws.

The Role of Abiotic Environmental Factors in the Vertical Distribution of Macrozoobenthos at the Northeastern Black Sea Coast

In this study, an attempt is made to evaluate the impact of environmental factors on the vertical distribution of the macrozoobenthos at the northeastern shelf of the Black Sea. The samples of macrozoobenthos were taken by an Ocean grab at the depths of 10–70 m in 2014–2017 along four transects between the Abrau Peninsula and the settlement of Shepsi. The particle size distributions of the bottom sediments and the near–bottom water temperature were also measured. Two major groups of stations were distinguished according to the quantitative structure and composition of the macrozoobenthos—shallow (10–40 m), corresponding to variable temperature conditions, and deep (50–70 m), corresponding to constant temperature conditions. Two subgroups were distinguished in the shallow zone coinciding with the upper mixed layer (10–15 m) and thermocline (20–40 m). The first subgroup was characterized by sandy sediments inhabited by the community of the suspension feeder bivalve, Chamelea gallina; silty sands at the stations of the second subgroup contained a community dominated by several Veneridae species. Silty sediments were spread all over the deep-water zone; the pelophylic bivalves Parvicardium simile and Modiolula phaseolina were dominant. The ratio of silt to sand fractions in the bottom sediments and the near-bottom water temperature were critical factors in distinguishing between the groups of stations. The subgroups were distinguished according to the percentage of aleurite and pebble. The coefficient of sediment sortedness, which reflects the stability of the hydrodynamics and the rates of sedimentation, also influences the differences (mostly due to Bivalvia). The total variation explained by depth almost overlapped with the variation accounted for by other factors. The major role in distinguishing between the groups belonged to the two taxa constituting most of the biomass (Bivalvia) and the density and species diversity (Polychaeta).

A Reconstructed Subaerial Hot Spring Field in the ∼3.5 Billion-Year-Old Dresser Formation, North Pole Dome, Pilbara Craton, Western Australia.

Recent discoveries of geyserite and siliceous sinter with textural biosignatures in the ∼3.5 Ga Dresser Formation of the Pilbara Craton, Western Australia, extended the record of inhabited subaerial hot springs on Earth by ∼3 billion years, back to the time when siliceous sinter deposits are known to have formed on Mars (e.g., at Columbia Hills, Gusev Crater). Here, we present more detailed lithostratigraphic, petrographic and geochemical data collected from 100 measured sections across a ∼14 km strike length in the Dresser Formation. The data indicate deposition of a wide range of hot spring and associated deposits in a restricted interval that directly overlies a hydrothermally influenced volcanic caldera lake facies, with shoreline stromatolites. Hot spring deposits show abrupt lateral facies changes and include associated channelized clastic deposits that support fluvial, subaerial hot spring deposition. All Dresser hot spring and associated lithofacies have direct analogs with proximal, middle, and distal apron hot spring facies that are characteristic of those from New Zealand, Yellowstone National Park, USA, and Argentina. Rare earth element and yttrium geochemistry shows that the Dresser geyserite shares identical patterns with Phanerozoic hot spring sinters. This geochemical data further supports textural and contextual evidence that indicate the Dresser geyserite formed as a subaerial hot spring sinter. Further, the Dresser hot spring deposits are temporally associated with a diverse suite of textural biosignatures that indicate a thriving microbial community existed within in a Paleoarchean hot spring field. The results presented here underscore the importance of continued study of the early geological record for astrobiological research. In particular these findings reinforce the long-standing hypothesis that hydrothermal systems are optimal places to search for past life on Mars.

The Loma de Hierro Ni-laterite deposit (Venezuela): Mineralogical and chemical composition

Nickel laterite deposits developed on ultramafic rocks have traditionally been a significant source of Ni and Co and recently of Sc. Although the Loma de Hierro deposit (Venezuela) has been in operation for more than 50 years, it lacks detailed studies on the mineralogical and geochemical composition of the lateritic profile. In this study, we present a geochemical and mineral description of the main carrier phases of Ni and Co in a complete profile of the deposit. The selected weathering profile has been developed from a partially serpentinized harzburgitic protolith and has a well-developed saprolitic horizon covered by a thin limonitic horizon. The geochemical signature of the profile is characterized by a significant Mg and Si decrease towards the top of the saprolite, with a clearly visible Mg discontinuity. The main Ni-bearing minerals are secondary serpentine (1–4 wt.% NiO) and kerolite-pimelite-dominated garnierite mixtures with serpentine (18–22 wt.% NiO). Limonite is rich in goethite (0–1.85 wt. % NiO), gibbsite, and Mn-oxy-hydroxides. The latter have intermediate compositions between lithiophorite and asbolane (2–13 wt.% CoO). The highest Sc grades (40–68 ppm) were observed in the limonite with amounts positively correlated with Fe content. Rare earth elements are mainly concentrated in the upper part of the saprolite horizon (60–80 ppm), while they have a lower content in the limonite (7–45 ppm). In this horizon, rare earth elements are clearly associated with Fe, indicating adsorption and/or coprecipitation. This association was not observed in the saprolite, suggesting that other minerals (e.g., clay minerals) are controlling their concentration; more information is needed to identify the rare earth element-bearing minerals. The lateritic profile of Loma de Hierro can be classified as representative of hydrated Mg silicate deposits, and was formed in a context of continuous tectonic uplift and a low water table conditions favoring the development of a thick saprolitic horizon and the precipitation of kerolite-pimelite-dominated garnierites.

A combined multivariate approach analyzing geochemical data for knowledge discovery: The Vazante – Paracatu Zinc District, Minas Gerais, Brazil

The Vazante Group comprises a Proterozoic sequence of carbonate and siliciclastic rocks located in Minas Gerais, Brazil. It is the host of the Vazante-Paracatu Zinc District, including world-class hypogene zinc silicate deposits, in the southern part, and several Pb – Zn sulfide deposits in the northern part, all hosted in dolomitic rocks. A recent study revealed the occurrence of base metal sulfide mineralization that formed prior to the Brasiliano orogenic event in the siliciclastic rocks (Serra do Garrote Formation) that underlie these dolomite-hosted silicates and sulfide deposits. These siliciclastic rocks were considered as potential sources of elements for the hydrothermal fluids that formed the dolomite-hosted deposits, however there was little evidence of depletion of the source rocks during the orogenic event. In this paper, Random Forest is used in unsupervised mode along with t-distributed Stochastic Neighbor Embedding (t-SNE) and principal component analysis (PCA) over a lithogeochemical dataset of samples of the Serra do Garrote siliciclastic rocks collected throughout the basin to provide insights about processes related to the mineralizing system at the Vazante-Paracatu District.Multivariate analysis reveals that the Serra do Garrote Formation geochemical signature typical of pre-orogenic mineralization. This is characterized by PC1+ with association of Zn, Cd, Cu, Hg, In, V ± Sb, Se, Mo, Re, which corresponds to nearly 60% of the variance in the data. This suggest that these elements are related to a widespread and/or, long-living hydrothermal activity without an efficient mechanism to focus the metal-bearing fluids, causing basin-scale sub-economical Zn and related metal enrichment. Furthermore, PC2 and PC6 distinguish the zones with signatures interpreted to be related to depletion. PC2+ separates Cd-poor sphalerite, which is typical of the generation of sphalerite that occur in zones with textural evidence of remobilization. PC6+ with association of As, organic carbon and S, identified the zones where sphalerite was leached from the pyrite-rich layers. Areas with multivariate signatures of both pre-orogenic enrichment and syn-orogenic depletion in the source siliciclastic rocks include the Vazante-North Extension and Varginha zinc silicate deposits/occurrence, Ambrósia silicate zinc deposit and the Engenho Velho prospect. Preliminary exploration in this prospect revealed hydrothermal alteration typical of the zinc silicate deposits. This study is pioneering in applying these numerical models in possible source rocks to assist in identifying targets for exploration in basins.

Diatom-inspired self-assembly for silica thin sheets of perpendicular nanochannels

HypothesisMultistage silicate self-organization into light-weight, high-strength, hierarchically patterned diatom frustules carries hints for innovative silica-based nanomaterials. With sodium silicate in a biomimetic sol-gel system templated by a tri-surfactant system of hexadecyltrimethylammonium bromide, sodium dodecylsulfate, and poly(oxyethylene-b-oxypropylene-b-oxyethylene) (P123), mesoporous silica nanochannel plates with perpendicular channel orientation are synthesized. The formation process, analogous to that of diatom frustules, is postulated to be directed by an oriented self-assembly of the block copolymer micelles shelled with charged catanionic surfactants upon silication. ExperimentsThe postulated formation process for the oriented silica nanochannel plates was investigated using time-resolved small-angle X-ray and neutron scattering (SAXS/SANS) and freeze fracture replication transmission electron microscopy (FFR-TEM). FindingsWith fine-tuned molar ratios of the anionic, cationic, and nonionic surfactants, the catanionic combination and the nonionic copolymer form charged, prolate ternary micelles in aqueous solutions, which further develop into prototype monolayered micellar plates. The prolate shape and maximized surfactant adsorption of the complex micelles, revealed from combined SAXS/SANS analysis, are of critical importance in the subsequent micellar self-assembly upon silicate deposition. Time-resolved SAXS and FFR-TEM indicate that the silicate complex micelles coalesce laterally into the prototype micellar nanoplates, which further fuse with one another into large sheets of monolayered silicate micelles of in-plane lamellar packing. Upon silica polymerization, the in-plane lamellar packing of the micelles further transforms to 2D hexagonal packing of vertically oriented silicate channels. The unveiled structural features and their evolution not only elucidate the previously unresolved self-assembly process of through-thickness silica nanochannels but also open a new line of research mimicking free-standing frustules of diatoms.

Fatty Acid Preservation in Modern and Relict Hot-Spring Deposits in Iceland, with Implications for Organics Detection on Mars.

Hydrothermal spring deposits host unique microbial ecosystems and have the capacity to preserve microbial communities as biosignatures within siliceous sinter layers. This quality makes terrestrial hot springs appealing natural laboratories to study the preservation of both organic and morphologic biosignatures. The discovery of hydrothermal deposits on Mars has called attention to these hot springs as Mars-analog environments, driving forward the study of biosignature preservation in these settings to help prepare future missions targeting the recovery of biosignatures from martian hot-spring deposits. This study quantifies the fatty acid load in three Icelandic hot-spring deposits ranging from modern and inactive to relict. Samples were collected from both the surface and 2-18 cm in depth to approximate the drilling capabilities of current and upcoming Mars rovers. To determine the preservation potential of organics in siliceous sinter deposits, fatty acid analyses were performed with pyrolysis-gas chromatography-mass spectrometry (GC-MS) utilizing thermochemolysis with tetramethylammonium hydroxide (TMAH). This technique is available on both current and upcoming Mars rovers. Results reveal that fatty acids are often degraded in the subsurface relative to surface samples but are preserved and detectable with the TMAH pyrolysis-GC-MS method. Hot-spring mid-to-distal aprons are often the best texturally and geomorphically definable feature in older, degraded terrestrial sinter systems and are therefore most readily detectable on Mars from orbital images. These findings have implications for the detection of organics in martian hydrothermal systems as they suggest that organics might be detectable on Mars in relatively recent hot-spring deposits, but preservation likely deteriorates over geological timescales. Rovers with thermochemolysis pyrolysis-GC-MS instrumentation may be able to detect fatty acids in hot-spring deposits if the organics are relatively young; therefore, martian landing site and sample selection are of paramount importance in the search for organics on Mars.

Building an Orogen: Review of U-Pb Zircon Ages from the Calabria–Peloritani Terrane to Constrain the Timing of the Southern Variscan Belt

The application of zircon dating to the reconstruction of orogenic systems is invaluable since time constraints of the geological evolution of orogens are crucial for the proposal of geodynamic and paleogeographic models. Zircon is one of the most promising accessory minerals in geochronology of crystalline basements because of its high-closure temperature. Moreover, U-Pb data of relict and recrystallized grains indicate the maximum sedimentation age as well as the timing of metamorphism in metasediments. In addition, the U-Pb ages of magmatic zircons constrain the timescale of magmatism. The Calabria–Peloritani terrane (CPT) represents a key area in the Southern Variscan Belt, whose reconstruction is still unresolved. Therefore, a review of literature zircon age data accompanied with new data from six samples of orthogneisses, paragneisses, amphibolites, and actinolite schists, helps to constrain the evolution of this Cadomian fragment, affected by metamorphic and magmatic Variscan events. A revisiting of the timing of the geological events from Paleo-proterozoic to Permian is revealed by comparing the internal textures of zircons and their U-Pb age clusters. The detected age peaks at 2500 Ma, 1600 Ma, and 1000 Ma in the CPT were related to a provenance from West and East Gondwana realms. A sedimentation age around 630 Ma emerges for the middle-deep crust terranes of the CPT, affected by Ediacaran (579–540 Ma) intrusions, accompanied by metamorphism dated at 556–509 Ma in the host metasediments. In the following, during Ordovician–Silurian extensional tectonics, the former Cadomian terranes were at least locally affected by fluid-assisted metamorphism (around 450 Ma) whereas the upper extensional basins that formed, were infilled by sediments along with interspersed volcanic to subvolcanic products. All these pre-Silurian terranes were involved in the subduction process of the Palaeotethys–Gondwana margin beneath Laurussia. The compressive phase began around 347 Ma, with under-thrusting of the formerly Gondwana substrate that was subjected to middle-high grade metamorphism, while the Ordovician–Silurian sediments were scraped off along the front of the Southern Variscan Belt and affected by low-grade metamorphism. Decompression of the whole Variscan orogenic system started around 320 Ma, together with uplifting of the chain and emplacement of widespread granitic intrusions which ended around 280 Ma and completed the Variscan orogenic cycle in the CPT.

Biogenicity of Spicular Geyserite from Te Kopia, New Zealand: Integrated Petrography, High-Resolution Hyperspectral and Elemental Analysis.

Hyperspectral and micro X-ray fluorescence (μXRF) imagery were used to derive maps of mineralogy and elemental chemistry from a sample of a siliceous hot spring deposit, or sinter, collected from a landslide breccia deposit at the base of the Paeroa fault, which bounds the eastern Taupo Rift at Te Kopia, Taupo Volcanic Zone, New Zealand. The sample is of a known biogenic sinter layer from a paleo-vent area of a recently extinct alkali chloride hot spring. The aim of the study was to distinguish it from other horizons derived from nonbiogenic sources, which is of relevance to early and extraterrestrial life research, specifically to help assess the potential reliability of morphology as an indicator of biology in the geological record. In particular, the distribution of opal, a common mineral in hot springs deposits that is known to preserve microbial features, and the relative abundances of Al-OH clay and water (OH and H2O) were mapped from hyperspectral imagery and element distributions defined by μXRF element mapping. Layers within the sinter sample composed of spicular geyserite-a type of micro-columnar stromatolite-showed contrasting mineralogy and water content in comparison with interspicular clastic sediment. Whereas clay was found to be concentrated in the interspicular sediment, high water contents characterized the spicules. μXRF imagery also showed differences in the composition of the two components of the spicule-bearing layers, with interspicular sediment being enriched in K, Ti, Fe, and Rb relative to the spicules, which are enriched in Ga. The contrasting nature of the mapped components highlights the detailed upward-branching nature of the spicules, identical to those found in living microstromatolites. These discriminants show that the spicular component can be discerned from the geological background through hyperspectral and μXRF mapping and used to define morphological features that may survive burial diagenesis and metamorphism as a biosignature in deep time rocks.

Reconstructing the Climatic-Oceanic Environment and Exploring the Enrichment Mechanism of Organic Matter in the Black Shale across the Late Ordovician-Early Silurian Transition on the Upper Yangtze Platform Using Geochemical Proxies.

Black shale deposited in the transitional period from the Late Ordovician to Early Silurian is the most important source rock and shale gas reservoir in the Yangtze region of South China. However, the source of these sediments is still controversial. In this paper, the changes in total organic carbon (TOC), total sulfur (TS), organic carbon isotopes (δ13Corg), biomarkers, trace elements, and rare earth elements in the Ordovician–Silurian boundary strata of the XK-1 well in northern Guizhou Province, South China, have been systematically studied. The paleoenvironmental and paleoclimatic conditions of the Late Ordovician to Early Silurian and their relationship with organic matter enrichment in the Upper Yangtze Platform have been reconstructed. The distribution of biomarkers reflects that the Late Ordovician–Early Silurian shale was deposited in the marine environment and was highly contributed by marine plankton/algae and microorganisms. Paleoclimatic proxies (Sr/Cu, δ13Corg) show that the global climate system experienced significant changes from a warm-humid climate to a brief period of cold-dry climate and then back to a warm-humid climate during the Ordovician–Silurian transition. This warm and humid climate condition helps to improve the biological productivity within the photic zone of the water column during deposition. In addition, the low oxygen (reduction) conditions during the deposition of the Late Ordovician–Early Silurian deposits are characterized by low Pr/Ph values (0.39–0.79) and relatively high elemental ratios of V/Ni (1.40–5.77) and V/(V + Ni) (0.58–0.85). This paleoredox condition contributes to the preservation of organic matter during deposition of the Late Ordovician–Early Silurian deposits. Therefore, it is demonstrated that the climate and ocean fluctuated greatly during the Late Ordovician–Early Silurian transition period, and this fluctuation provided necessary control factors for marine anoxia, primary productivity, and subsequent organic-rich black shale deposition in the Upper Yangtze region during the Late Ordovician and Early Silurian intervals.

Detrital zircon U-Pb ages and Hf isotopes of Lower-Middle Devonian to Middle Jurassic sandstones in the Qinfang basin, southern South China block: Constraints on provenance and tectonic setting

• The Qinfang basin is a remnant of the Paleo-Tethyan (Ailaoshan) Ocean. • The basin is not a part of the Indochina block. • The basin and its adjacent east and west sides may share a common East Gondwana source in the period of Silurian . • The adjacent west side of the Qinfang basin may be still tectonically active at least until the Middle Jurassic . The affinity and tectonic setting of the Qinfang basin have long been an enigma. Here we conduct detrital zircon U-Pb geochronology and Hf isotope analysis of Lower-Middle Devonian to Middle Jurassic samples from the basin. Along with published age data and paleontology from the basin and its east and west sides, this study constrains the sediment provenance and tectonic setting of the basin. Sandstones of Devonian-Jurassic exhibit an age distribution with major age groups at 2700–2300 Ma (absence for Jurassic), 1200–800 Ma, 600–400 Ma, and 334–246 Ma (for Jurassic alone). Zircons (peak ~2500 Ma) were sourced from the Yangtze block, while ~1200–800 Ma grains may originate from the Yunkai massif and Jiangnan orogen. ~600–400 Ma zircons came from Yunkai massif and/or Cambrian to Silurian sediments in the basin. Carboniferous-Early Triassic (334–246 Ma) zircons were probably supplied by an older sequence in the Great Youjiang basin and the Darongshan-Shiwandashan igneous rocks. The Qinfang basin and its two sides are considered to share a common East Gondwana source in Silurian. The similarity in age spectra between Silurian-Devonian samples in the basin and Ailaoshan belt suggests that the basin is a remnant of the Paleo-Tethyan (Ailaoshan) Ocean. However, the distinct age distribution between the basin and Indochina block shows that the basin is not a part of the Indochina block. By Middle Jurassic following the final closure of the Ailaoshan Ocean in the Late Triassic, the adjacent western area may be still tectonically active, thereby feeding the basin with detritus of Early Permian.

Paleomagnetic constraints on a time-stratigraphic framework for the evolution of Ohachidaira volcano and the summit caldera, central Hokkaido, Japan

We present a revised stratigraphy of the proximal deposits around Ohachidaira volcano and their paleomagnetic directions obtained from 21 sites (193 samples). We identify four proximal pyroclastic members from Ohachidaira volcano that were produced after the early edifice-building effusive volcanism, from older to younger: (1) vent-opening mafic pyroclastic density current (PDC) deposits (Kobachidaira ignimbrite); (2) maar-forming mafic tephra-ring deposits (Mamiyadake tephra ring); (3) mafic to silicic caldera-forming deposits (Sounkyo Member); and (4) mafic PDC deposits (Kumonotaira ignimbrite). Well-grouped paleomagnetic directions obtained from the Kobachidaira ignimbrite and the Sounkyo Member indicate that each deposit was formed over a short time interval compared to geomagnetic secular variation―that is, less than a century. Conversely, scattered paleomagnetic directions of the Mamiyadake tephra ring record the secular variation of the geomagnetic field that took place over a longer time interval―that is, at least 750 yr, probably more. The Kumonotaira ignimbrite, which has a similar paleomagnetic direction to the underlying Sounkyo Member, may have been produced during the Sounkyo eruption. From comparison between our data and the previously reported paleomagnetic directions of two petrologically distinct distal ignimbrites, we conclude that the Sounkyo Member is a proximal correlative of the distal pyroxene-rich ignimbrite, and that the distal hornblende-rich ignimbrite may not be of an Ohachidaira origin. The revised stratigraphy suggests that Ohachidaira volcano is a maar-caldera complex volcano, and that the summit caldera is a flaring funnel formed incrementally by explosive erosion and syn-eruptive collapse of the vent walls. Volume estimates imply that the Sounkyo eruption fundamentally enlarged the vent and formed the caldera. Our data confirm that the comparison of paleomagnetic directions can offer a useful identification and correlation tool for the Ohachidaira pyroclastic sequences.

Characterizing the Transport of Aluminum-, Silicon- and Titanium-Containing Particles and Nanoparticles in Mainstream Tobacco Smoke.

The most commonly observed forms of aluminum, silicon and titanium in tobacco products are aluminum silicates (e.g., kaolin), silica and titanium(IV) oxide. These compounds are neither water soluble nor volatile at cigarette combustion temperatures. Rather, they are transported in mainstream tobacco smoke as particles after being freed by combustion from the tobacco filler and can induce pulmonary inflammation when inhaled. Aluminum silicate particles are the most frequently observed particles in the pulmonary macrophages of smokers and have become known as 'smokers' inclusions'. A relatively new technique, single particle triple quadrupole inductively coupled plasma-mass spectrometry was used to analyze aluminum-, silicon- and titanium-containing particle deliveries in cigarette and little cigar mainstream tobacco smoke, and to collect information on solid inorganic particles. The mass concentration of aluminum-containing particles transmitted in mainstream smoke was low (0.89-0.56 ng/cigarette), which was not surprising because aluminum silicates are not volatile. Although the collective masses (ng/cigarette) of aluminum-, silicon- and titanium-containing particles under 100 nm diameter transported in mainstream smoke were low, an abundance of 'ultrafine' particles (particles < 100 nm or nanoparticles) was observed. Limitations of the particle background equivalent diameter (the smallest detectable particle size (MassHunter 4.5 Software) due to the environmentally ubiquitous silicon background restricted the determination of silica nanoparticles, but silica particles slightly below 200 nm diameter were consistently detected. Aluminum- and titanium-containing nanoparticles were observed in all cigarette and little cigar samples, with titanium(IV) oxide particle deliveries consistently fewer in number and smaller in diameter than the other two types of particles. The highest concentrations of aluminum-containing particles (as kaolin) were in the nanoparticle range with much lower concentrations extending to the larger particle sizes (>100 nm). The number and range of particle sizes determined in mainstream smoke is consistent with pulmonary deposition of aluminum silicates described by other researchers as contributing to the 'smokers' inclusions' observed in pulmonary macrophages.

A Late Triassic aquatic community: Undichna-like and related swimming traces from a freshwater pond in the lower Elliot Formation of South Africa

Swimming and subaqueous traces and trails are reported, for the first time, from a freshwater pond community in the middle Norian lower Elliot Formation (lEF) in the main Karoo Basin of South Africa. These ichnofossils, associated abiotic tool marks, and sedimentary structures are preserved on the upper bedding plane of a fine- to medium-grained sandstone that is overlain by laminated mudstones. The assessment of the relationship between the sedimentology and ichnology of this ichnosite reveals a unique perspective into a Late Triassic ecosystem. Here, a brief time window showcases events ranging from the abandonment of a river channel, to the initiation of a floodplain pond, and its subsequent infilling by silty sediments. The trace fossil assemblages, their cross-cutting relationships and the sedimentological evidence suggest that several generations of traces formed during the silting up of this floodplain pond, a palaeoenvironment infrequently documented in the lEF. Some trails are described as similar to Undichna Anderson 1976, and can be attributed to small, swimming freshwater fish. Didactyl tracks with Grallator/Anchisauripus-like affinities are associated with both sickle-shaped digit drag marks and 3–8 cm long disorderly striations showing variable morphology (e.g., narrowly incised, straight to slightly sinuous, V-shaped grooves). Their preservation indicates wading and subaqueous behaviour of tetrapods. Other traces range from semi-circular impressions of unknown affinity to unique, yet indistinct, < 2-cm-long, partially preserved ichnofossils with three (or possibly four) slender digit impressions. Together these ichnofossils provide evidence for animals currently unrecorded in the osteological record of the lEF.

Petroleum source rocks of the Silurian deposits on the Chernov swell (Timan‑Pechora basin)

Silurian source rocks are among the least studied in the Timan-Pechora basin. This is mainly due to their occurrence at great depths (3.0–4.5 km) and the limited penetration of this stratigraphic interval by wells. Another source of information is the outcrops of the Silurian, which are known in the eastern and northeastern parts of the Timan-Pechora basin. The studied section of the Silurian deposits is exposed on the Padimeityvis River, located on the Chernov swell in the northeastern part of the basin. This article is devoted to the study of Silurian source rocks based on the results of lithological, coal petrographic studies and geochemistry of organic matter. The studied section is composed of carbonate and clay-carbonate deposits formed in shallow-water shelf conditions. Most of the section, composed of microcrystalline and microcrystalline with bioclasts limestones, is characterized by low concentrations of organic matter (Corg is generally less than 0.3 %). Elevated Corg contents (up to 1.16 %) are characteristic of clay-carbonate rock varieties, which make up about 20 % of the section. Sediments with increased concentrations of organic matter were formed in isolated and deepened areas of the bottom of the shallow-water basin as a whole. Assessment of the catagenetic transformation based on Rock-Eval pyrolysis data, coal petrographic studies, and conodont color indices showed that organic matter reached the conditions of the middle-end of the main oil generation zone (gradation MC2‑MC3). The obtained geochemical characteristics (Corg, S2, HI), taking into account a certain level of organic matter maturity, indicate that the Silurian source rocks had an average hydrocarbon potential.

Stratigraphic evolution of Silurian-Devonian deposits from Amazonas basin, north Brazil, and implication for the west Gondwana

The Silurian-Devonian transition in the southern margin of Amazonas Basin registers a transgressive-regressive succession deposited in a paleogeographic scenario adjacent to the western margin of Occidental Gondwana. The Silurian deposits from Pitinga Formation represent siltstone/sandy-claystone bed shapes distributed in bodies of tabular geometry in coarsening upward and bioturbated cycles deposited in a shoreface environment. The Devonian deposits forming Maecuru Formation represent gravel sandy beds organized in fining-upward cycles within tabular bodies deposited in a braided fluvial environment. The contact between the units is marked by an outstanding Eodevonian erosive surface related to Precordillera Orogeny. The Eodevonian discordance is also present in the stratigraphy of other Paleozoic Brazilian Basins. Pitinga Formation is associated with deglaciation events observed in the Silurian final stages. The amplitude of continental exposition generated conditions for the installation of fluvial systems in which the braided style predominates during a transition from Silurian to Devonian in the Amazonas Basin southern margin.

Models of hydrocarbon traps associated with gas chimney in Parnaíba Basin (NE Brazil)

A special frequency spectrum expansion processing (FSE) was applied to seismic lines to identify gas chimneys (GC) in the Parnaíba Basin (NE Brazil). GC are recognized by typical vertical and low frequency chaotic disturbances in the seismic data, which are interpreted as being caused by the migration of fluids or free gas. These structures are important hydrocarbon indicators and have become a powerful exploratory tool, especially for frontier basins. In this study, an abundance of GCs was found in vast areas of the Parnaíba Basin, increasing the oil potential of this important South American Paleozoic basin. The new methodology was applied to seismic lines of the Parnaíba Basin and was used to characterize the GCs with greater security, which reduces the exploratory risks and suggest the existence of a new petroleum system associated with the pre-Silurian and Silurian deposits present in the basin grabens. The seismic expressions of the GC were successfully characterized by the FSE, and the origin of the gas chimney was associated with the regional geological structural framework, especially with the Transbrasiliano Lineament (TBL). In addition, theoretical models were developed to classify exploration plays associated with the GCs based on their probabilities of success of being economic hydrocarbon accumulations. Our results indicate a good potential for new hydrocarbon discoveries in this exploration frontier basin.

Bifaces or not bifaces? Role of raw materials in the Middle Pleistocene. The example of levels E-E1, B and F (610–670 ka) at Notarchirico (Italy)

Notarchirico is the earliest Acheulean Italian site. On account of the wide variety of artefacts (cores, flakes, pebble tools and bifaces for some levels) and raw materials, it is also a key site for analysing behavioural variability in the Acheulean record before 600 ka, and for investigating the significance of occupation levels with and without bifaces. In this paper, we focus on the upper part of the sequence, which was excavated by M. Piperno in the 1980s and recently securely dated between 610 and 670 ka by 40Ar/39Ar. The deposits of Notarchirico consist of a superimposition of sandy and silty sediments, with more or less intense occupation levels interspersed with sterile layers. Here we present the technological analysis of the lithic assemblages of three paleosurfaces, F, E/E1 and B. The lithic corpus from levels F and B yielded some bifaces, whereas no bifaces were found in levels E/E1, where artefacts are mainly on small flint nodules and small limestone pebbles. Technological strategies are described in the three levels, in particular previously unpublished core technologies, and compared to the rest of the site sequence and to comparable Southern European sites. We present the different hominin strategies, their modes of adaptation to diverse types and geometries of raw materials and the concomitant cultural shifts and discussed by this way the role of activities and traditions.