Significant Weathering Research Articles

Strain shadow “megapores” in mid-crustal ultramylonites

AbstractMylonitic shear zones are important fluid conduits in the Earth’s crust. They host transient and permeable porosity that facilitates fluid transfer and controls fluid-rock interaction. Here we present microstructural observations from a mid-crustal ultramylonite with very large pores that occupy the strain shadows of albite porphyroclasts. Our non-invasive three-dimensional X-ray microtomographic data show that the largest of these strain shadow megapores have substantial volumes of as much as ∼1.7 × 105 µm3. Given that the sample shows no signs of retrogressive overprint or weathering, these pores must be synkinematic. Importantly, the close proximity of the pores to creep cavities in dynamically recrystallized quartz ribbon grains suggests a potential hydraulic link between fluid in the strain shadow megapores and fluid in the creeping rock matrix. The evolving megapores constitute very large syndeformational local fluid reservoirs in mylonites that likely fed into the granular fluid pump established by the dynamically evolving creep cavities. Our findings add to an emerging picture of the dynamic transport properties of ultramylonitic shear zones, where the formation and destruction of porosity are intrinsically linked to microscale deformation processes. They also suggest that despite many studies on porphyroclast systems, open questions remain, especially concerning the interaction of clasts with their matrix.

Binational survey using Mytilus galloprovincialis as a bioindicator of microplastic pollution: Insights into chemical analysis and potential risk on humans

Microplastic (MP) contamination in edible mussels has raised concerns due to their potential risk to human health. Aiming to provide valuable insights regarding the occurrence, physicochemical characteristics, and human health implications of MP contamination, in the present study, two nationwide surveys of MP contamination in mussels (Mytilus galloprovincialis) were conducted in Morocco and Tunisia. The results indicated that MP frequency ranged from 79 % to 100 % in all the analyzed samples. The highest MP density was detected in mussels from Morocco (gills “GI”: 1.88 MPs/g ww−1; digestive glands “DG”: 0.92 MPs/g ww−1) compared to mussels of Tunisia (GI: 1.47 MPs g− 1; DG: 0.79 MPs g− 1). No significant differences in MP density were found between the two organs (GI and DG) for both countries. MPs were predominantly blue and black fibers, and smaller than 1000 μm. Seven polymeric types were identified, of which PET, PP, and PE were the most abundant, accounting for >87 % of all samples. Scanning Electron Microscopy (SEM) coupled with Energy dispersive X-ray (EDX) showed that most MPs have noticeable signs of weathering and inorganic components on their surface. The highest MP daily intake was found in children, while the lowest was estimated in women and men. Moreover, the annual dietary exposure of MPs through mussel consumption was estimated to be 1262.17 MPs/year in Morocco and 78.18 MPs/year in Tunisia. The potential risk assessment of MPs in mussels based on the polymer hazard index (PHI) was estimated in the high-risk levels, implying that MPs may pose health risks to humans. Overall, this research suggests that the consumption of mussels represents a considerable MP exposure route for the Moroccan and Tunisian populations.

Collection of Manuscripts in Oirat in Ulan-Khol khurul of Kalmykia

This article presents a brief overview of the collection of manuscripts in the Oirat language stored in the fund of the Ulan-Khol Temple of the Republic of Kalmykia. The collection under consideration is relatively small (50 manuscripts), but it contains very interesting materials. The manuscripts of the Ulan-Khol Temple were a part of a significant collection of Buddhist writings in Tibetan, Old Mongolian and Oirat in the library of the Shars-Bagut (Northern) Temple, which was located from 1889 to 1939 in the area of Bora, Shars-Bagut aimak located in Erketenevsky ulus. The manuscripts were transferred to the Ulan-Khol Temple by relatives of the clergymen Bodgur Ochirov (1892-1955) and Tsagan Atkhaev (1900-1981). The collection seems to be extremely heterogeneous: it includes fiction literature works, orders, prophecies, ritual texts, prayers, astrological works, texts of divination, weather signs and traditional folk medicine texts. Some collections contain texts in Oirat with Tibetan inclusions as well as ones in Tibetan with Oirat interlinear. The fact proves Kalmyk monks were equally fluent in Tibetan and Oirat. The heterogeneity of the composition of the manuscript collection of the Ulan-Khol khurul indicates that the monks of the Shars-Bagut Temple in their main practice were not only clergymen, but also astrologers, soothsayers, healers. The presented texts are a valuable source for studying traditional religious beliefs, philosophy, ethics, old written Kalmyk literature, astrology and Kalmyk cult rituals.

Geochemistry of decades-old spodumene mine tailings under a humid continental climate

Transports electrification efforts currently increase global demand for lithium, but literature about the environmental geochemistry of spodumene mine tailings is very scarce. Mine tailings from the former Québec Lithium Corporation site in La Corne, Québec, Canada, were submitted to a suite of geochemical and mineralogical characterizations to evaluate metals distribution and mobility 55 years after deposition. From 1955 to 1965, production of spodumene concentrate, lithium carbonate and other lithium salts from a spodumene-pegmatite ore left behind about 750,000 tons of non-sulfidic tailings (mostly from flotation). Core samples of the tailings were collected from 5 boreholes ranging from 5.13 to 9.75 m in depth. Results show that grain size and metals distribution is heterogeneous, with elements groups (Li–Ta–U or K–Rb) being enriched or depleted in coincident strata and zones. The mineralogical assemblage is dominated by quartz, albite and other feldspars, unrecovered spodumene (up to 12 wt%), and micas, displaying few to no signs of weathering. Sequential extraction results indicate that for most elements surveyed, including Li and Be, secondary retention mechanisms like precipitation, sorption, and ion exchange, almost exert no control on their mobility within the tailings. Silicate-hosted elements (Al, Li, Be, K, Rb) were proportionally among the least extractable. The most extractable elements are either ubiquitous in the environment (Fe, Mn) or hosted in metamict minerals (U). Apart from paste pH which tends to be relatively lower close to the surface, no relation is evident between depth or the water table level and any physical or geochemical parameter. Despite the tailings being almost unweathered, the surrounding waters contain Li concentrations up to the mg/L range. This study gives environmentally-relevant insights into the geochemistry of non-sulfidic spodumene-pegmatite mine tailings as surging worldwide demand for Li attracts interest towards new spodumene mining projects.

Girolamo Cardano’s Meteorological Predictions: Hippocratism, Weather Signs, Winds, and the Limits of Astrology

AbstractThe subject of meteorology was central to Girolamo Cardano’s thought. It held together his encyclopedism by tying the celestial realm to the sublunary world and human action. Meteorology, for Cardano, links abstract knowledge to the practical and operative. While many of his Aristotelian predecessors understood weather prediction as distinct from meteorology as a natural philosophical field, Cardano’s profound interest in conjectural arts and probabilistic reasoning led him to tie causal explanations to methods of forecasting future conditions of the air and their effects on humans, especially regarding health and disease. While it might be expected that Cardano would have emphasized astrological tools for weather forecasting, instead he went in a different direction, namely, embracing the ancient tradition of weather signs and revising Aristotelian theories of winds. At the end of his career, which he mostly spent writing commentaries on Hippocratic writings, he integrated his understanding of weather signs with Hippocratic rules of prognosis, revising traditional understandings of the causes of winds.

Plastic in digestive tracts and gills of cod and herring from the Baltic Sea

Plastic litter is widespread on our planet and is recognized as a contaminant of high concern. Plastic ingestion and retention in gills were studied in two key Baltic fish species: herring (Clupea harengus L.) and cod (Gadus morhua L.). In total, 183 fish from the southern Baltic Sea were analysed. Plastic litter was found in digestive tracts of 12.7 and 14.8% of herrings and cods, respectively. In addition, gills were shown to constitute an important transfer route of plastic to cod (9.9% of cods) but not to herring thus likely reflecting species-specific differences in fish lifestyles and/or water filtering capacity. No more than one plastic item per individual was found except for three fish with two items in their stomachs. Dominant microplastics (<5 mm) (MPs) (88.6% of all items) composed of irregular fragments, fibres and foils (61.3%, 25.8% and 12.9% of all MPs, respectively) were followed by meso- (5–25 mm) and macro-plastics (>25 mm) (5.7% each of all items). Plastic ingestion and retention in gills did not affect fish body condition assessed by Fulton's K index, although herrings that ingested plastic particles beyond the microplastic size range (i.e. >5 mm) were characterized by the lowest condition indices.All plastic items recovered from fish exhibited clear signs of weathering and surface extended due to their roughness and fragmentation which may enhance both sorption properties for chemical compounds and/or their leaching. Nevertheless, chemical contaminant levels in herring muscles were not different than in a plastic-free group.The vast majority of fibres found in fish was identified as air-borne or procedural contamination and were excluded from further analyses. In addition, the vessel's paint dust found in fish stressed the need for strict quality assurance also during fish sampling.

A Note on Verg. Georg. 1.393-397

In this paper I take a close look at the way Vergil reworks Aratus’ weather signs in Georgics 1.393-397. This in turn leads to a new interpretation of these difficult lines and allows for a political and poetical reading of the passage.

Horoscopes of the Moon: Weather Prediction as Astrology in Ptolemy’s Tetrabiblos

Abstract Ptolemy’s Tetrabiblos is not usually considered as a meteorological text. I examine the sections of the Tetrabiblos that deal with weather prediction and argue that Ptolemy considers it part of astrology. I show that the way Ptolemy categorises weather prediction differs significantly from other Greco-Roman writers, including Cicero (On Divination) and Sextus Empiricus (Against the Astrologers). I argue for these conclusions: first, that Ptolemy considers weather prediction to be part of astrology – i.e., a scientific practice which includes giving an account of the causes of phenomena with reference to the stars; to give such an account for the weather requires a practitioner to go beyond the observation and cataloguing of weather signs. Secondly, I argue that understanding weather prediction as astrology means that the distinction between horoscopic and general astrology is more fluid than is sometimes thought. Finally, I will show that Ptolemy’s views on weather prediction provide a case study for his view of astral causation.

Sacred components of hunting and fishing technologies of the indigenous peoples of the Amur-Sakhalin Region

The article, by means of the comparative-historical method, critical analysis of scholarly concepts, and use of ethnographic materials, deals with the study of the complex of beliefs and rituals of indigenous peoples of the Russian Far East (Nanais, Negidals, Nivkhs, Orochs, Udeges, Uilta, Ulchs, and Evenks) as a sacred component of their traditional and modern hunting and fishing technologies. The term ‘technology’ originates from the Ancient Greek philosophy by the development of the doctrine of ‘techne’ as an art by which things are made. Technology is based on notion and supersedes the role of the chance in human life and activities, which expedites the proc-ess of adaptation to the nature. The ritual preceding production of a tool or a vehicle is performed to improve qual-ity of the item to ensure its more productive use in hunting and fishing. In the culture of indigenous peoples of the Russian Far East, there are known examples of invocation of magic, cults, beliefs, and rituals to secure hunter’s luck in fabrication of hunter carriers, tools for hunting marine and terrestrial animals, and traps. Beliefs and rituals serve as the sacred components of the hunting and fishing technologies, which have the utmost importance for sustainable life of the indigenous population. The main conclusion is that, in spite of some differences in the economy, degree of settlement and mobility, and the level of influence of nonethnic cultures, undoubtedly, the results of hunting, fishing, off-shore seal catching, deer breeding, and foraging depend on personal experience, rational knowledge of the qualities of plants, weather signs, and migration times and habits of animals, and on the quality of the trade equipment, transport, clothes and footwear. However, these aspects are not sufficient and the hunters resort to the sacral components of the hunting and fishing technologies — transport means are ‘enli-vened’, by magic means they are imparted with the qualities of living beings — people or animals. With the help of amulets, the hunters strengthen their trade qualities — agility, perception-reaction time, and intuition. Prohibitions are observed, which are aimed at decreasing dependence on chance and increasing hunting productivity. The rational technologies, aimed at the survivance of the ethnos, are complemented by the sacred components, so that people cling to the help of supernatural powers.

Spheroidal weathering of basalt from Gebel Qatrani, Fayum Depression, Egypt

BackgroundThree stages of basalt weathering are known: early or incipient weathering, intermediate weathering and advanced weathering. The Late Oligocene basalt of Gebel Qatrani in Fayum Depression, Egypt, shows signs of early weathering, particularly exhibited in basalt spheroids found at the top of the basalt flow. The present paper gives the results of detailed petrographical, mineralogical and geochemical study of the weathering of these basalt spheroids.ResultsThe core-stones of the basalt spheroids are composed of phenocrystals of plagioclase feldspars and clinopyroxenes set in a groundmass of tiny feldspars and pyroxenes, relatively altered olivine and opaque minerals. The basalt is subalkali (tholeiitic). The outer weathered shells surrounding the core-stones are composed of partly altered feldspars and pyroxenes. The calculated weathering indices show that there is marked weathering trend from the core-stones of the spheroids to the outer shells. The chemical mobility of the elements shows marked depletion of Mg, Ca, Na and K from the core-stones to the outer shells due to the weathering of olivine, pyroxene and feldspars. The trace elements Rb, Sr, Ni, V, Cr and Zn are also depleted.ConclusionsThe weathering of basalt spheroids from Gebel Qatrani, Fayum Depression, Egypt, is of the incipient type. The degree of weathering from the core-stones of the basalt spheroids to the corresponding weathered shells indicates that the weathering occurred under predominantly semiarid to arid conditions.

МЕТЕОРОЛОГІЧНА ЛЕКСИКА В УКРАЇНСЬКІЙ І КИТАЙСЬКІЙ МОВАХ: СИСТЕМНИЙ ПЕРЕКЛАД

Within the anthropocentric paradigm of modern linguistics there is a steady interest in the human factor in language, which, among other things, is realized through the close attention of researchers to the theory of linguistic pictures of the world, which fully reflects the uniqueness of peoples Human life and activity are inseparable from nature. Nature is one, but manifests itself in various forms. In the process of learning about nature, man tries to realize both its unity and diversity. A special place in the perception of the world by man is occupied by climatic and weather phenomena that affect human behavior in the world, various aspects of his life, including economic, as well as well-being. In the IV century. BC became aware of the impact of fluctuations in weather conditions on human health. For example, Hippocrates established a close link between human disease and the weather conditions in which he lives. Over the centuries, people have gathered a variety of knowledge about nature: from misunderstanding of natural phenomena, fear of them, inherent in ancient people, to today’s scientific knowledge of nature, from the first folk signs of weather to the formation of modern science — meteorology. Nature as a source of everything necessary for man has an impact on both the material and spiritual culture of society. Therefore, knowledge of meteorological phenomena occupies an important place in the awareness of reality. The article considers the peculiarities of meteorological vocabulary in Chinese and Ukrainian languages, as well as the peculiarities of meteorological vocabulary translation in two languages.

The fall, recovery, classification, and initial characterization of the Hamburg, Michigan H4 chondrite.

The Hamburg meteorite fell on January 16, 2018, near Hamburg, Michigan, after a fireball event widely observed in the U.S. Midwest and in Ontario, Canada. Several fragments fell onto frozen surfaces of lakes and, thanks to weather radar data, were recovered days after the fall. The studied rock fragments show no or little signs of terrestrial weathering. Here, we present the initial results from an international consortium study to describe the fall, characterize the meteorite, and probe the collision history of Hamburg. About 1 kg of recovered meteorites was initially reported. Petrology, mineral chemistry, trace element and organic chemistry, and O and Cr isotopic compositions are characteristic of H4 chondrites. Cosmic ray exposure ages based on cosmogenic 3He, 21Ne, and 38Ar are ~12 Ma, and roughly agree with each other. Noble gas data as well as the cosmogenic 10Be concentration point to a small 40–60 cm diameter meteoroid. An 40Ar‐39Ar age of 4532 ± 24 Ma indicates no major impact event occurring later in its evolutionary history, consistent with data of other H4 chondrites. Microanalyses of phosphates with LA‐ICPMS give an average Pb‐Pb age of 4549 ± 36 Ma. This is in good agreement with the average SIMS Pb‐Pb phosphate age of 4535.3 ± 9.5 Ma and U‐Pb Concordia age of 4535 ± 10 Ma. The weighted average age of 4541.6 ± 9.5 Ma reflects the metamorphic phosphate crystallization age after parent body formation in the early solar system.

Practical Lexicography as a Sphere of Multidimensional Research Activity of Multi-level Students (On the Materials of a Dictionary of Folk Signs)

The article presents the experience of organizing research activities of students and schoolchildren as part of a lexicographic project implemented on the basis of the Experimental Laboratory of Educational Lexicography of the Pskov State University. The goal of the presented research project is to popularize folk culture and Russian paremiology, to develop students’ interest in the Russian language and folklore, to draw students’ attention to environmental issues, and to form their environmental awareness. The expected practical result is the preparation of a School Dictionary of Weather Signs for publication. The use of the linguo-cognitive method and structural-semantic modelling techniques allowed thematic classification of the signs for their representation in the dictionary; linguistic and cultural analysis provided the identification of ethnocultural specifics of signs; the method of linguoculturological commenting was used during the dictionary explication of the cultural background of paremias. The innovative nature of the dictionary being developed implied involving the reader in the interactive work with the material. The methods of this activity were tested at the second stage of the lexicographic project: the dictionary materials were posted on the website, and the users – schoolchildren – were invited to analyze the relevance of the signs, observing the natural environment, and present the results of their observations in the comments. These data were used in the structuring of entries and the development of linguoculturological vocabulary comments for the School Weather Vocabulary, which was prepared for publication in accordance with the project implementation plan. Thus, it was proved that practical work on a lexicographic project allows organizing a multidimensional research activity of students of different levels: higher education students who study Russian paremias in terms of their relevance, frequency, linguistic and cultural value, master the methods of lexicographic material representation, including using information technologies as part of an online project; and secondary school students who analyse the content and identify the scientific basis of weather signs, observing the environment in the course of sign verification, reflect about its contemporary state and offer their solutions to ecological problems.

Sustainable Agriculture Reflected in Cuba’s Water Quality

Water samples from 25 rivers in central Cuba are dominated by signs of rock weathering rather than fertilizer runoff, researchers working at Cuban and American institutions show.

Rapid Physicochemical Changes in Microplastic Induced by Biofilm Formation.

Risk assessment of microplastic (MP) pollution requires understanding biodegradation processes and related changes in polymer properties. In the environment, there are two-way interactions between the MP properties and biofilm communities: (i) microorganisms may prefer some surfaces, and (ii) MP surface properties change during the colonization and weathering. In a 2-week experiment, we studied these interactions using three model plastic beads (polyethylene [PE], polypropylene [PP], and polystyrene [PS]) exposed to ambient bacterioplankton assemblage from the Baltic Sea; the control beads were exposed to bacteria-free water. For each polymer, the physicochemical properties (compression, crystallinity, surface chemistry, hydrophobicity, and surface topography) were compared before and after exposure under controlled laboratory conditions. Furthermore, we characterized the bacterial communities on the MP surfaces using 16S rRNA gene sequencing and correlated community diversity to the physicochemical properties of the MP. Significant changes in PE crystallinity, PP stiffness, and PS maximum compression were observed as a result of exposure to bacteria. Moreover, there were significant correlations between bacterial diversity and some physicochemical characteristics (crystallinity, stiffness, and surface roughness). These changes coincided with variation in the relative abundance of unique OTUs, mostly related to the PE samples having significantly higher contribution of Sphingobium, Novosphingobium, and uncultured Planctomycetaceae compared to the other test materials, whereas PP and PS samples had significantly higher abundance of Sphingobacteriales and Alphaproteobacteria, indicating possible involvement of these taxa in the initial biodegradation steps. Our findings demonstrate measurable signs of MP weathering under short-term exposure to environmentally relevant microbial communities at conditions resembling those in the water column. A systematic approach for the characterization of the biodegrading capacity in different systems will improve the risk assessment of plastic litter in aquatic environments.

Stability of Cu-Sulfides in Submarine Tailing Disposals: A Case Study from Repparfjorden, Northern Norway

Mine tailings that were produced during the exploitation of the Ulveryggen siliciclastic sediment-hosted Cu deposit in northern Norway were disposed into the inner part of Repparfjorden from 1972 to 1978/1979. This study focuses on the mineralogy and geochemistry of the submarine mine tailings and underlying natural marine sediments from the inner part of Repparfjorden, as well as on the primary Ulveryggen ore. The ore mineralization from the neighboring Nussir carbonate sediment-hosted Cu deposit was studied too, due to the forthcoming mining of both deposits. Bornite and chalcopyrite are the major Cu-sulfides, and are characterized by low concentrations of potentially toxic elements including Cd, Hg, and As. The tailing material occupies the uppermost 9 cm of Repparfjorden sediments. It is characterized by predomination of a silty component with elevated Cu (up to 747.7 ppm), Ni (up to 87 ppm), and Cr (up to 417 ppm) concentrations. The high Cu concentration is related to the deposition of mine tailings. In contrast, Ni and Cr concentrations are close to those in naturally occurring stream sediments from the feeding river, Repparfjordelva, reflecting the compatibility of these elements with hosting mafic volcanics, which are widely spread in the Repparfjord Tectonic Window. Copper in the uppermost part of the sediments is bound to the acid-soluble fraction while Ni and Cr are bound to the residual fraction. Artificial placement of large masses of fine-grained material, i.e., smothering, resulted in a diminished biological activity and/or physical distortion of mostly benthic fauna, which was reflected in total organic carbon (TOC) values as low as 0.15% in the uppermost strata. Sulfide minerals are found both in natural marine sediments and in the mine tailings. They are generally well-preserved with an exception for chalcopyrite from the uppermost part of the submarine tailing, which shows signs of incipient weathering. Thermodynamic modeling confirmed that redox potential and pH are important factors in the weathering of sulfides. Available ligands contribute to the Cu speciation. In near-neutral to slightly alkaline conditions a presence of carbonates can lead to the mobilization of Cu in form of CuCO3 complexes.

Field biotite weathering rate determination using U-series disequilibria

The chemical weathering rate of silicates is a key parameter of several geochemical processes; however, the long-term field measurement of these rates remains challenging. Currently, there are several methods for quantifying field weathering rates, but each presents it's own unique set of difficulties. In this study uranium-series nuclides were used to investigate long-term biotite weathering in a soil profile. For this purpose, pseudomorph grains of biotites (including weathering products) were hand-picked from four horizons of a soil profile and from underlying granitic saprolite from the experimental Breuil-Chenue site (France).Unexpected behaviors of U and Th nuclides were recorded from these samples. An unambiguous leaching of 232Th occurs during the weathering of biotite, while reduced U release relative to Th was observed, implying an efficient redistribution of U between the primary mineral and weathering products within the pseudomorphs. The measured U-series activity ratios reflect a regular and self-consistent pattern evolution. However, the “U-series-derived-weathered-stage” is not always coherent with the weathering features of major elements and/or with the location of the samples within the soil profile. For instance, biotite from the saprolite displays U-series activity ratios typical of significantly weathered samples, while major elements present rather limited signs of weathering. These results suggest an incongruent leaching of U and Th isotopes and suggest that U- and Th-series nuclides probe some water-mineral interactions that occur before macroscopic mineral tansformation.Using an open-system leaching model, coupled (234U/238U), (234U/230Th), and (226Ra/230Th) disequilibria measured from the samples allow us to calculate a weathering duration range of 6–52 ky for most weathered samples of this soil profile. The biotite weathering rate deduced from these data ranges from 7.8 × 10−17 mol·m−2·s−1 to 6.5 × 10−16 mol·m−2·s−1, which is consistent with the range of field rates previously reported. This rate was compared to the weathering rate of biotites induced by the substitution of vegetation occuring 35 years ago in a nearby soil profile, which was about 2–3 orders of magnitude higher than the long-term rate reported above. This feature is perfectly consistent with the decrease in the weathering rate with time that was previously widely documented but that still remains debated. Our results allude to a valuable use of U-series isotopes for mineral-weathering field rate determination and report a decrease in silicate weathering rates over long- (10,000s of years) and short-term (10s of years) weathering events recorded from the same site. The results show that short term laboratory experiments can be representative of field processes, and suggest that some forms of mineral weathering reactivation, similar to that observed during laboratory experiments, may naturally occur in soils in response to high frequency perturbation processes such as land cover change.

Indigenous Knowledge and Farmer Perceptions of Climate and Ecological Changes in the Bamenda Highlands of Cameroon: Insights from the Bui Plateau

Anticipating seasonal and shorter time scale dynamics to farming practices is primordial for indigenous farmers’ resilience under extreme environmental conditions, where climate change is a menace to agro-hydro-ecological systems. This paper assesses the effectiveness of indigenous farmers’ knowledge and aptitude to read weather signs for informed decisions on their daily and seasonal activities. Such climate-proof development is anchored on indigenous people’s knowledge and perceptions in circumstances where the dearth of scientific evidence or information exists as in Cameroon. The study is based on eight focus group discussions and a survey of 597 farming households in seven agro-ecological basins on the Bui Plateau of the Bamenda Highlands. The results indicate that indigenous smallholder farmers value their ability to accurately observe and anticipate local conditions in various ways to serve their local realities more aptly than outside forecasts. Such local knowledge should thus exercise a complementary role weave in a local climate information understanding system that replicates ecological variability.

Engineering the geological evaluation of some rocks from Akure, Southwestern Nigeria as aggregates for concrete and pavement construction

The importance of rocks and rock aggregates cannot be overemphasized in construction and concrete design globally. This study evaluated the physical and mechanical characteristics of fine grained granite, porphyritic granite, quartzite, granite gneiss, migmatite gneiss and charnockite from ten different locations in Akure for their suitability as construction materials. Field observation, water absorption, specific gravity, shape indices, aggregate impact value (AIV), aggregate crushing value (ACV), Los Angeles abrasion value (LAAV), compressive strength, tensile strength and petrography of the selected rocks were evaluated. The field studies indicate fresh outcrops with little signs of weathering. Porphyritic granite shows a higher water absorption value >1%, suggestive of its unsuitability as foundation materials in water logged areas. The higher flakiness and elongation indices of porphyritic granite, quartzite and migmatite gneiss are detrimental to the higher workability and stability of mixes. AIV (14.79–23.52%), ACV (18.32–28.93%) and LAAV (25.22–34.55%) showed that granite, granite gneiss and charnockite have good soundness and hardness with greater resistance to wear. Higher strength values of all the rocks were found to be satisfactory for use in the production of aggregates for civil constructions. Petrographic analysis revealed similarities in the compositions of the rocks, with quartz being the dominant mineral. The results show that all the rock types possess the required quality standards for use as construction aggregates in highway pavements and foundations. Some of the aggregates (GG1, GG2, GF, GC, MG1, CK1 and CK2) are also suitable for bituminous mixes. Quartzite should be avoided in load bearing masonry units due to its lower strength values. The most suitable rocks proven as road and building stones are fine grained granite, granite gneiss and charnockite because of their low water absorption, low flakiness and elongation indices, low abrasion values, higher strength values (tensile strength and unconfined compressive strength) and sound petrographic characters. Thus, adequate knowledge of rocks and rock aggregates is crucial in order to prevent continuous structural failure around the globe and make the environment friendlier.

Selective weathering of cross-bedded layers forming shelters and small caves on Akopán Tepui (Venezuela): Field, laboratory and experimental evidence about diagenesis and weathering of the Matauí Formation arenites (Roraima Supergroup, Middle Proterozoic)

South-American table-top mountains (tepuis) are formed by quartzites and sandstones of Matauí Formation belonging to the Roraima Supergroup (Lower to Middle Proterozoic). Field observations in the northern part of Akopán Tepui in Venezuela revealed that unlike the beds with flat bedding, the cross-bedded layers are commonly affected by selective weathering, expressed by depressions, shelters, and even small caves. All the arenites are fine-grained; most of them are likely of aeolian origin. Hardness measurements confirmed that the cross-bedded layers are softer than the flat-bedded or structureless beds occurring above and below them.Petrographic analysis showed that the rocks are mostly fine-grained quartzites to quartz sandstones, with original sand grains overgrown by syntaxial quartz cement and bearing signs of compaction manifested by local pressure solution. Some intergranular spaces are filled by newly-formed phyllosilicates (paragonite, locally intergrown with muscovite). In the overlying beds, no porosity was observed by microscopic study and under SEM, whereas in the underlying rocks signs of slight weathering and etching of phyllosilicates was observed, together with locally widened spaces along the grain-to-grain boundaries. The samples from cross-bedded layers display weathering, the degree of which depends on the present access of flowing water. Where water has periodical access to the arenite, it shows dissolution of quartz cement (arenization), together with complete leaching and removal of the phyllosilicates due to lateritization. The intergranular spaces are considerably widened and quartz grains bear signs of strong skeletal etching and pitting. Samples from the sites where the water access ceased show mostly leaching of phyllosilicates, with weak skeletal dissolution of quartz grains without pitting.To imitate the origin of structures observed in the field, experimental modelling was performed, using artificially layered and compacted fine-grained sands, on which sodium-silicate solution was dripped. During soaking, downward preferential penetration of the solution along the cross-bedding laminae (funnel-flow) was observed in the cross-bedded layer. The resulting structures display good lithification of horizontally layered sands and relatively poorer lithification of the cross-bedded sediment between them, showing triangular-shaped overhangs and shelters, which mimic those on the Akopán Tepui.Differential weathering of otherwise petrologically very similar arenites indicates that there had to be a difference in the initial porosity in the time of the rock denudation. A preserved porosity in the cross-bedded layers was necessary for the water/rock contact to perform dissolution.