Alluvial Environments Research Articles

Changes in soils and terrestrial landscapes of the Appalachian Basin (Conemaugh, Monongahela, and Dunkard groups), U.S.A., at the onset of the late Paleozoic climate transition

ABSTRACT Changes in global climate from the Late Pennsylvanian to early Permian resulting from the destabilization of ice sheets in the Southern Hemisphere had important effects on terrestrial landscapes around the Paleozoic world. In the northern Appalachian Basin (U.S.A.), evidence for this transition and its effects on terrestrial systems is preserved in numerous paleosols in the Conemaugh, Monongahela, and Dunkard groups that formed in various alluvial environments. Several studies along a 50 km west–east and 40 km north–south transect through southeast Ohio and southwest West Virginia resulted in the recognition of 24 different pedotypes. An up-section shift in pedotypes from Argillisols to Vertisols and Calcisols as well as an overall upward increase in the diversity of pedotypes records a significant change in soil-forming processes and landscapes. The landscapes of the Late Pennsylvanian were largely characterized by well-developed, clay-rich Alfisols of woodland ecosystems on distal floodplains bordered by poorly developed Inceptisols of early successional or marshland ecosystems on proximal floodplains. By the early Permian, these landscapes began to experience strongly seasonal climates and increasingly prolonged dry periods, resulting in the production of pronounced shrink–swell features and well-developed carbonate horizons. These landscapes were characterized by Vertisols and Inceptisols of highly heterogeneous brakeland ecosystems, with rapid changes in sedimentation, hydrology, and vegetation over short distances. Climatic conditions were prone to fluctuations between wet and dry states during the transition, resulting in a highly heterogeneous landscape that changed significantly through time.

Prediction of soil seed bank of piedmont and alluvial environments of Dera Ghazi Khan, Punjab, Pakistan.

The current focus is on the overall pattern of seed storage present in the fragments of the soil of piedmont and alluvial landscapes of the environment. The present study predicted the seed banks of both soils of alluvial and piedmont zones in different ecological conditions and evaluate the potential of seeds in the restoration of both environments. The composition of the seed bank of soil is mainly affected by the alluvial environment and the structure of cleared area shows that more species of germinating annual grasses and growable seeds with the higher total number. Extant vegetation structures have an important role in the diversity of soil seed reservoirs, whose composition corresponded with the openness of the site. When in situ soil seed bank is recruited, it helps to restore only some components of the plant community in an alluvial environment. In our current research, it was confirmed that seed richness was higher in number at lower elevation (alluvial) than that at high elevation (piedmont). Seed richness showed a significant negative correlation with anions, cations, while significantly positive with altitude that suggests the richness pattern of the overall seed bank of the area is influenced by various environmental factors.

ALLUVIAL-LACUSTRINE-MARINE COMPLEX OF MOUNT MEDVEDNICA: THE EARLY SYN-RIFT DEPOSITION AND PALAEOGEOGRAPHY (EARLY TO MIDDLE MIOCENE, NORTH CROATIAN BASIN)

Mt. Medvednica belongs to the western part of the Neogene rift-type North Croatian Basin that occupies the south-western Pannonian Basin System. The Lower to Middle Miocene continental to marine sedimentary complex was studied on Mt. Medvednica in order to interpret the early syn-rift depositional environment and reconstruct palaeogeography of the North Croatian Basin. Based on facies analysis, deposits are grouped into 16 facies based on their lithological characteristics. Six of the facies belong to the alluvial environment that is characterized by coarse-grained bedload siliciclastics. Nine facies are of lacustrine origin. They comprise: a) limestone of shallow lake carbonate bench with silty coal of vegetated marsh, b) deep lake and prodelta marl with sand and conglomerate intercalations deposited by gravity flows, and c) coarse-grained Gilbert-type delta conglomerate. The lacustrine deposits compose a transgressive-regressive sequence. The studied succession ends by facies of calcareous silt intercalated by conglomerates. These deposits belong to the marine offshore to prodelta as the consequence of establishment of the connection to the sea. The deposition was strongly controlled by allogenic factors, such as synsedimentary tectonics, climate, eustatic sea level changes and explosive volcanic activity. The alluvial deposits of Mt. Medvednica are the oldest syn-rift deposits and belong to the large alluvial plain that probably covered the entire North Croatian Basin in the Ottnangian and the Karpatian. These deposits are overlain by the lower Badenian lacustrine deposits, but the question of the existence of one large or several small lakes in the early Badenian North Croatian Basin remains open.

Quaternary Mammals from Central-Western Argentina in the Stratigraphic Context of Southern South America

This is an updated contribution to the Quaternary geology and paleontology from central-western Argentina, focused on San Luis Province. It is mostly based on unpublished data; only some fossils had previously been briefly mentioned in broader faunal contexts. The fossil-bearing sediments correspond to eolian and alluvial environments of moderate energy, dominated by sands and sandy silts. They overlie high-energy fluvial cycles and underlie edaphic horizons. They have a wide distribution, and several radiocarbon dates allow their regional correlation. Stratigraphic sequences with the precise origin of fossils allow for the improvement of lithostratigraphic and faunal correlations with the Pampean Region (central and east Argentina; La Pampa and Buenos Aires provinces), where Pleistocene assemblages are better known, but also with central-western (Cuyo Region), northwestern, and northeastern Argentina. Faunal remains correspond to large mammals, represented by xenarthrans (Cingulata and Tardigrada), macraucheniids (Litopterna), gomphotheres (Proboscidea), and equids (Perissodactyla), a typical Pleistocene mixture of native (xenarthrans and litopterns) and immigrant mammals.

Variable Ophiomorpha ichnofabric: Improving the understanding of mouth bar environments in fan-delta complex depositional settings from the Upper Cretaceous of NW South America

Fan-delta deposits, an important sedimentary component of fan-delta complexes, are scarcely described in the ancient record because it is very difficult to distinguish them from other types of coarse-grained deposits (e.g., alluvial, fluvial, or deep marine deposits). This obstacle is overcome when a well-record of physical/biogenic sedimentary structures or fossils unambiguously marks the influence of the receiving basin. However, this is usually not the case. Here, we present the Ophiomorpha ichnofabric record as a key proxy of marine influence within a generally fluvial-dominated system for improving the paleoenvironmental understanding and reconstructing animal-substrate interplay during the evolution of a fan-delta complex. The ichnological record, together with detailed sedimentological analysis, allows us to define three ichnofabric types, distributed in four levels. The stratigraphic distribution of these features points to distal alluvial environments towards the base, dominated by debris and sheet flows deposits and locally shallow braided channels; they evolve upward into well-developed braided fluvial system whose facies arrangement is related to channel fills, locally influenced by debris flows. Subsequently, a basinward migration of the sedimentary system is recorded through the occurrence of the first level with Ophiomorpha ichnofabric A, and then ichnofabrics A and B in levels 2 and 3, respectively, suggesting marine-influenced mouth bar settings. Toward the top, another steep basinward migration is evidenced by Ophiomorpha ichnofabric C in level 4, indicating wave-dominated processes in distal mouth bars environments. The record of marine-influenced and dominated levels may indicate relative sea-level fluctuations related to local or autogenic processes at the basin scale. Furthermore, the present study demonstrates the ability of Ophiomorpha tracemaker to colonize challenging sedimentary environments.

3D geological modelling of the Bologna urban area (Italy)

Urban geological modelling plays a crucial role in facilitating the sustainable utilization of the urban subsurface and the development of effective strategies for geohazard mitigation. Traditionally, geological models of urban areas rely on lithological correlations of boreholes and well data. However, in complex depositional settings such as alluvial environments, where the standard concepts of superposition and lateral continuity of strata are often violated, lithostratigraphic correlation can be challenging even over short distances, leading to considerable uncertainty in the final geological model. Therefore, in such cases, lithofacies analysis can provide a more robust categorisation of subsurface geological units as lithofacies mainly reflect the depositional process, while their associations provide a reliable picture of sedimentary bodies and their geometries. In this work, we used the lithofacies correlation approach to develop a 3D geological model of the urban area of Bologna (Italy) where a complex, thick alluvial succession makes lithological correlations very difficult. To minimize subjectivity, we re-interpreted 940 existing borehole logs in terms of depositional facies and combined stratigraphic data with geophysical HSVR (Horizontal to Vertical Spectral Ratio) measurements and surface analysis (morphology and river network) based on a DTM (Digital Terrain Model). This led to the detailed reconstruction of the subsurface depositional architecture, forming the basis for the 3D geological model. The model revealed the presence of three distinct depositional domains with different stratigraphic architectures. From west to east: Domain A (Reno River) corresponds to the gravel-dominated fill of a river valley abruptly passing to Domain B (Bologna urban area) that represents a morphological and stratigraphical divide, topographically elevated with respect to the surrounding areas and characterised by fine-grained deposits with frequent paleosols. Lastly, Domain C (Savena River) exhibits the typical alluvial fan pattern, marked by a gentle convex-up surface morphology with gravelly-sandy deposits with a low degree of lateral amalgamation. The geological model effectively explains the distribution of ground subsidence in Bologna since the 1960s, which is attributable to significant groundwater pumping. This is evident from the comparison of the model with both the ground displacement contours resulting from the 1983–1987 topographic levelling campaign and the subsidence rate map derived from the 2006–2011 Radarsat interferometric survey. Subsidence shows strong variations at the domains' boundaries, especially at the limit between Domain A (Reno River) where high values prevail, and Domain B (Bologna city centre) characterised by the lowest values.

Lidar visualization techniques for the construction of geoarchaeological deposit models: An overview and evaluation in alluvial environments

AbstractLidar has become an essential tool for the mapping and interpretation of natural and archaeological features within the landscape. It is also increasingly integrated and visualized within geoarchaeological deposit models, providing valuable topographic and stratigraphic control from the contemporary ground surface downwards. However, there is a wide range of methods available for the visualization of lidar elevation models and a review of existing research suggests that it remains unclear which are most appropriate for geoarchaeological applications. This paper addresses this issue by providing an overview and quantitative evaluation of these techniques with examples from archaeologically resource‐rich alluvial environments. Owing to the relatively low‐relief nature of the terrain within these temperate lowland flood plain environments, the results show that there is a small number of visualization methods that demonstrably improve the detection of geomorphological landforms that can be related to the variable distribution of archaeological resources. More specifically, a combination of Relative Elevation Models combined with Simple Local Relief Models offered an optimal approach that subsequently allows integration with deposit models. Whilst the presented examples are from a flood plain setting, deposit models are pertinent to a range of landscape contexts and the methodology applied here has wider applicability.

Color changes in yardang strata sediment in the Dunhuang Yardang National Geopark, Northwest China: Controlling factors and significance for sedimentary environments

Introduction: Yardang stratum is the basic material unit of yardang landforms. Due to their protracted age and complex sedimentary structure, formative yardang stratum mechanisms remain poorly understood. Color, being one of the most intuitive, easily accessible, and important lithological indicators, can be used to identify yardang strata sedimentary environments. However, the lack of quantitative analysis and systematic research have limited how chromatic environmental proxies can be extracted and interpreted.Materials and methods: The Dunhuang Yardang National Geopark was selected for this experiment. Based on chromaticity, grain-size, chemical element, organic matter, and carbonate content measurements of yardang strata sediment samples, this study used correlation analysis and chromaticity proxy extraction to quantitatively characterize associated color changes, controlling factors, and sedimentary environments.Results and discussion: Results found significant cyclic changes in chromaticity parameter curves were observed in the profiles, which is likely indicative of a dry/wet evolutionary process that occurred during different stages of the yardang sedimentary environment. Organic matter content was the main factor affecting changes in brightness, while iron oxide content directly affected yardang sediment redness and yellowness values. Due to its low value, effects of carbonate content on brightness were obscured. The grain-size characteristics indirectly affect the brightness value through the content of quartz, feldspar and organic matter. Moreover, based on modern analogy method, the brightness and redness values are proved to be effective proxies for distinguishing the yardang sedimentary environment. Accordingly, it is concluded that the sedimentary environment of Dunhuang yardang landforms is composed of sedimentation that derived from lacustrine, aeolian, and alluvial environments, and that the chromaticity parameter range and characteristic color for sedimentary environments are extracted and quantified. Findings from this study not only rectify the lack of quantitative research on yardang sediment color theory but also provide an important theoretical basis for identifying sedimentary environments in the field.

Segmentação do rio Apodi-Mossoró e alterações pedogenéticas em solos de ambientes aluviais

ABSTRACT The Apodi-Mossoró River Basin is important for the west region of the state of Rio Grande do Norte (RN), Brazil. The rapid increase in population and consequent need for space has resulted in anthropogenic actions, such as the segmentation of the river course within the municipality of Mossoró, RN. The objective of this study was to assess the effects of this segmentation on soils in alluvial environments. Soil collection points were defined in natural and anthropized areas in the Mossoró urban segment; soil profiles were described and collected; and samples of the soil 0-10 and 10-20 cm were collected. The samples were subjected to physical and chemical analyses to determine granulometry, density, aggregates, pH in water, available phosphorus (P), exchangeable bases, potential acidity, total organic carbon, nitrogen, and micronutrients (Cu and Zn). Maps of location and land use and cover were developed. The soil found in the natural area was classified as Neossolo Fluvico Psamitico eutrico, presenting typical physical and chemical characteristics of this soil class, with variable texture and P contents along the soil profile. The soil in the anthropized area was classified as Planossolo Haplico Carbonatico vertissolico, with Ap Horizon presenting a sandy loam texture, since it is a horizon formed due to anthropogenic activity in the environment. All horizons and profiles presented high pH. The evaluated areas formed different groups regarding soil physical and chemical attributes, with overlapping points that can be explained by anthropogenic actions, even in the environment considered natural.

Systematics, ecology, and biochronology of blancan horses from Sonora, northwestern Mexico

We describe a set of dental and postcranial horse material recovered from the locality Los Hornitos, northeastern Sonora, northwestern Mexico. The fossil-bearing unit consists of brown silt with intercalation of fine-grained sandstone and bioturbated incipient soils, set in an alluvial environment and considered Pliocene in age. The comparative study of the available sample indicates the presence of two species: the small-sized hipparionine Nannippus peninsulatus and the medium-sized and primitive equine Equus simplicidens. The isotope composition of δ13C and δ18O in dental enamel tooth indicates a C3–C4 mixed diet for these species and suggests the presence of woodland and open areas in Los Hornitos during the Pliocene. The less negative δ13C values observed in E. simplicidens are related to a more C4 diet, preferring to roam open habitats. The coexistence and optimal resource partitioning between these species are explained, considering their differences in dietary behavior, body size, home range, and/or vagility. The recognized horse species are typical of the Blancan North American Land Mammal Age, and their biochronological information from the southwestern United States and central Mexico establishes the probable age of the Los Hornitos at about 3.9–2.6 Ma, corresponding to the Blancan III or late early Blancan – early late Blancan.

A river and its people: The example of Lower Palaeolithic occupations of the Têt fluvial terraces

Current data on human groups from the Lower Palaeolithic periods in Western Europe show a variability in material production, represented by the disconcerting diversity of lithic technocomplexes. Since the birth of the prehistoric discipline, fluvial and alluvial environments have been considered the witnesses of prehistoric occupations during the long Quaternary period. In this article, therefore, I wish to question the link between the geomorphological unit, the fluvial terrace and the lithic productions discovered there. Here, I take the example of the early occupations of the fluvial terraces of the river Têt, which is part of the sedimentary basin of Roussillon (Pyrénées-Orientales, France). During the Pleistocene, the Têt River deposited different generations of fluvial terraces, expressed by the variety of levels present in the landscape. This study focuses on level T3b attributed to Marine Isotopic Stage (MIS) 10, which yielded several series of lithic industries on pebbles. The assemblages, from the localities of La Llabanère, Le Jas and Le Moulin à soufre, represent a total of 890 pieces. Despite a taphonomic bias linked to the stripping of alluvial levels during the Quaternary, the results of recent prospecting highlight the reliability and technological consistency of these assemblages. Technicofunctional analysis made it possible to question these lithic series and to reveal their variability, witnessing the technical adaptation of prehistoric populations to the fluvial environment and inherited technical traditions. Flaking and shaping chaînes opératoires are well represented and help to illustrate the diversity of technical expressions of the Middle Pleistocene populations. Nevertheless, contrary to previous studies, we note a clear predominance of flaking chaîne opératoire that are expressed in particular through the diversity of flake tools. Finally, these results reinforce the importance of a new methodological approach to the analysis of Lower Palaeolithic technocomplexes in Europe.

Conceptual sedimentation model as the basis of geological correlation in a case study of AT6-8 reservoirs of Beregovoye field in West Siberia

For the Beregovoye field (West Siberia, Yamalo-Nenets Autonomous Okrug), a new subsurface geologic model for AT6-8 group of reservoirs in the Lower Cretaceous (Hauterivian-Aptian) interval within Ereyamskaya formation was built following the reprocessing and reinterpretation of 2D and 3D seismic data in 2020, drilling of new wells (new wells, which were drilled after 2016, account for about 10 % of the total well stock that penetrated the AT6-8 reservoirs), updating the structural framework, additional core studies, and revising the well test results. Well log correlation in the AT6-8 interval was based on the reservoirs formation in alluvial and tidal delta plain environments. Multidirectional source areas formed disconnected zones in the net reservoir interval, which controlled the oil and gas content of these reservoirs. Taking into account the results of the geochemical survey, a stage-by-stage approach to hydrocarbon accumulations (light oil and gas condensate) formation was proposed, which led to vertically and laterally varied phase compositions of the discoveries.

Climate-Controlled Coastal Deposition of the Early Permian Liangshan Formation in Western South China

During the late Paleozoic ice age, tropical coastal depositions have been widely linked to high-frequency sea-level variations, but their linkage with the associated climate change was not fully understood. In the early Permian, two deglaciations occurred in the late Sakmarian and late Artinskian, respectively. During the late Artinskian deglacial warming and transgression, coal-bearing siliciclastic successions of the Liangshan Formation were developed in South China. Three facies associations were recognized from the Liangshan Formation successions in western South China and ascribed to coastal alluvial plain, estuarine, and deltaic environments. Detailed analysis of sedimentology, paleosol morphology, and sandstone petrology suggest a relatively dry-to-wet climate shift and estuarine to deltaic facies transition in the lower Liangshan Formation. This climate shift and facies transition can be temporally correlated based on regional stratigraphic correlations, although precise age constraints are needed to test this correlation. The estuarine interval of the lowest Liangshan Formation signified a rapid transgression during the late Artinskian deglaciation and likely formed during a relatively arid climate with locally small fluvial systems, which provided limited sediment supply. The subsequent transition to and initiation of deltaic deposition was broadly associated with the inferred climate shift and could be primarily resulted from a climate wetting-induced great increase in sediment supply, irrespective of the deglacial sea-level rise.

Plants and palynomorphs from the Lower Devonian (upper Emsian) of the Holy Cross Mountains, Poland

We present a preliminary assessment of a new Lower Devonian biota from an exposure of the Zagórze Formation at Bukowa Góra quarry in the Łysogóry Region of the Holy Cross Mountains, Poland. Abundant plant macrofossils preserved as carbonaceous compressions, adpressions, and permineralizations occur alongside a diverse assemblage of microfossils. Palynostratigraphic analysis places the fossiliferous sequences in the narrow Pro. Zone within the AP Zone of the douglastownense-eurypterota Miospore Zone, which corresponds to the upper part of the Emsian. Palynofacies analysis confirms that these sediments formed in a shallow-water, alluvial environment. The biota contains a rich assemblage of freshwater and brackish water organisms and fully terrestrial ones. Common elements include filamentous green algae, arthropods, terrestrial fungi-like filaments, nematophytes and abundant land plants. Scolecodonts and acritarchs are much rarer, suggesting limited marine influence. The new flora contains stem-group vascular plants, lycophytes and euphyllophytes. Among the permineralized remains is some of the earliest evidence of complex vascular systems, including cruciform and plate-like stelar organizations and secondary wood. We record the earliest fossil evidence of a dissected stele of the cladoxylopsid type. Innovations such as these were fundamental to the later evolution of arborescent growth in plants and the development of forest ecosystems. The biota complements and extends our knowledge of Emsian biotas in Euramerica just prior to the rapid changes that marked the Middle Devonian. It provides insights into a diverse early terrestrial community and raises further questions about the affinities and roles of arthropods and nematophytales in these ecosystems.

Modelling geoarchaeological resources in temperate alluvial environments: The capability of higher resolution satellite remote sensing techniques

Temperate river systems cover large regions of the earth's surface and provide challenging environments for the detection of archaeological remains. The deposition of alluvium above, and interbedded with, archaeological deposits means conventional forms of archaeological prospection such as geophysical survey or aerial photography are often ineffective. Consequently, archaeologists have turned to the construction of deposit models to evaluate the archaeological potential of various landforms. However, despite the high capacity of satellite multispectral data to identify alluvial landforms and archaeological deposits, the contribution that it can make towards deposit models has only received limited attention. This research assesses the capability of higher resolution satellite multispectral imagery to identify alluvial landform assemblages and subsequently facilitate the modelling of geoarchaeological resources. As image enhancements are often required to improve interpretation or classification, it includes a quantitative evaluation of 45 different processes, comprising two spectral separability measures on paired regions of interest (ROIs) from the Lower Lugg Valley, Herefordshire, UK. The results define optimal image processing techniques for the detailed geoarchaeological interpretation of alluvial environments and demonstrate that relatively simple visualisation methods (e.g. composite images) and summative techniques (Principal Components Analysis) offer some of the most effective approaches.

Petrophysics and sediment variability in a mixed alluvial to lacustrine carbonate system (Miocene, Madrid Basin, Central Spain)

AbstractThis study evaluates variations in petrophysical properties within a mixed alluvial to lacustrine carbonate system (Miocene, Madrid Basin, Central Spain). The transition from alluvial environments to lake margins settings displays a shift from alluvial, siliciclastic red sandstones and mudstones to palustrine–lacustrine mudstones to packstones. Fluctuations in lake‐water level enabled land plants to occupy the lake margins during periods of low lake levels. The palustrine carbonates include features like pseudo‐microkarst, nodular and mottled limestones; the lacustrine deposits include enlarged root cavities, desiccation cracks and channel bodies. Scarce fresh water biota comprises charophytes, gastropods and ostracods. The sediments possess high natural, irregular varying, gamma‐ray values at the alluvial–lacustrine transition, and low, but constant values at full lacustrine sites. Acoustic properties agree with lithological variations within individual facies. Porosity is the most important parameter influencing P‐wave and S‐wave velocities. The scatter in the velocity–porosity relationship links to the porosity type; macro‐porosity or microporosity. The wide range of pore types and pore sizes results in a weak porosity to permeability relationship for the carbonate‐dominated rocks with low permeability for microporous and high permeability for macro‐porous carbonates. The sandstones (probably only inhibiting interparticle porosity), and to a lesser extent the sandy wackestones to packstones, show quite a strong relationship between porosity and permeability. Elastic properties of mixed alluvial–lacustrine deposits (this study) and marine deposits (literature data) overlap as variations in pore structures and porosity values are similar. Only 16% of the marine and lacustrine carbonate sediments display Equivalent Pore Aspect Ratio values above 0.2. In travertine deposits, 83% of the samples exceed Equivalent Pore Aspect Ratio values above 0.2, which highlights that travertine deposits are dominated by larger Equivalent Pore Aspect Ratios compared to lacustrine and marine carbonate deposits. Travertines display other rock frameworks with different pore types, pore distribution and amount of porosity.

Integrating hydrogeological and second-order geo-electric indices in groundwater vulnerability mapping: A case study of alluvial environments

AVI (Aquifer vulnerability index), GOD (groundwater occurrence, overlying lithology and depth to the aquifer), GLSI (geo-electric layer susceptibility indexing) and S (longitudinal unit conductance) models were used to assess economically exploitable groundwater resource in the coastal environment of Akwa Ibom State, southern Nigeria. The models were employed in order to delineate groundwater into its category of vulnerability to contamination sources using the first- and second-order geo-electric indices as well as hydrogeological inputs. Vertical electrical sounding technique employing Schlumberger electrode configuration was carried out in 16 locations, close to logged boreholes with known aquifer core samples. Primary or first-order geo-electric indices (resistivity, thickness and depth) measured were used to determine S. The estimated aquifer hydraulic conductivity, K, calculated from grain size diameter and water resistivity values were used to calculate hydraulic resistance (C) used to estimate AVI. With the indices assigned to geo-electric parameters on the basis of their influences, GOD and FSLI were calculated using appropriate equations. The geologic sequence in the study area consists of geo-electric layers ranging from motley topsoil, argillites (clayey to fine sands) and arenites (medium to gravelly sands). Geo-electric parametric indices of aquifer overlying layers across the survey area were utilized to weigh the vulnerability of the underlying water-bearing resource to the contaminations from surface and near-surface, using vulnerability maps created. Geo-electrically derived model maps reflecting AVI, BOD, FLSI and S were compared to assess their conformity to the degree of predictability of groundwater vulnerability. The AVI model map shows range of values of log C ( −3.46—0.07) generally less than unity and hence indicating high vulnerability. GOD model tomographic map displays a range of 0.1–0.3, indicating that the aquifer with depth range of 20.5 to 113.1 m or mean depth of 72. 3 m is lowly susceptible to surface and near-surface impurities. Again, the FLSI map displays a range of FLSI index of 1.25 to 2.75, alluding that the aquifer underlying the protective layer has a low to moderate vulnerability. The S model has values ranging from 0.013 to 0.991S. As the map indicates, a fractional portion of the aquifer at the western (Ikot Abasi) part of the study area has moderate to good protection (moderate vulnerability) while weak to poor aquifer protection (high vulnerability) has poor protection. The S model in this analysis seems to overstate the degree of susceptibility to contamination than the AVI, GOD and GLSI models. From the models, the categorization of severity of aquifer vulnerability to contaminations is relatively location-dependent and can be assessed through the model tomographic maps generated.

Geo-electrically and hydrogeologically derived vulnerability assessments of aquifer resources in the hinterland of parts of Akwa Ibom State, Nigeria

The study aims at employing geo-electrically and hydrogeologically derived indices to assess the vulnerability in an alluvial environment of Obot Akara and Nsit Atai counties in the hinterland of Akwa Ibom State, Southern-eastern Nigeria. Vulnerability maps have been generated using seven indices: depth to groundwater (D); net groundwater recharge (R); aquifer media (A); soil media (S); topography (T); impact of vadose zone (I) and hydraulic conductivity acronymized as DRASTIC. The DRASTIC vulnerability index (V) was computed as the sum of the product of weights and ratings. The results indicate that, for Obot Akara site, about 20% of the aquifer is classified as medium vulnerability, about 40% is high vulnerability and very high vulnerability. . For Nsit Atai, about 60% of the aquifer is classified as medium vulnerability while 20% represents high and very high vulnerability respectively. The results of the vulnerability assessment shows that the DRASTIC quality category in percentage is contributory from the seven parameters and hence avoidable anthropogenic activities leading contamination of groundwater should be avoided while the vulnerability maps should be employed to avoid locating boreholes in areas with very high vulnerability. With appropriate software programmes, ground-based geophysical data, hydrogeological and environmental inputs, the vulnerability assessment has been made to cover both the present and future exploitable groundwater resources for the healthy and economic benefits of human existence.

The geometry, sedimentary filling and depth estimate of the Mirandiba Basin, Pernambuco, Brazil: new insights about the depositional regional gap of rift phases in the interior basins

The Mirandiba Basin has a well-defined stratigraphic sequence and its sedimentation may be directly correlated with the Jatoba Basin and some other interior basins. The sedimentation began in intracratonic conditions with a Paleozoic sequence (Tacaratu/Inaja Formations), which acted as a substrate without any genetic relationship with the basin. The fluvial Tacaratu Formation emerges beyond the limits of this basin, where a remnant core named here as Poco do Ico was found wrapped around the basement to the west of the basin. Subsequently, there was a deposition in a shallow marine environment of the Inaja Formation (Devonian) formed by the intercalation of clay/siltstones and sandstones with ichnofossils. Pre-rift sedimentation occurs over the Paleozoic sequence, characterized in the basin by the lacustrine sediments of the Alianca Formation, represented by the intercalation of shales and calcarenites with desiccation cracks and fossil fragments. In spite of depositional gap described between the local Aratu and Alagoas Stages, the presence of Salvador Formation close to the north border fault may represent a rare rift phase record in the interior basins. The post-rift sequence is represented by the Marizal Formation, deposited during the Aptian. This formation is distinguished by the intercalation of fine sandstone, siltstone and conglomerate deposited in an alluvial fan environment. The pre-rift, rift and post-rift sedimentation are embedded in the depocenter of the basin, where the main NE-SWgraben stands out. A gravity survey was carried out, which obtained a negative, asymmetric Bouguer anomaly, with gradients added to the northwest, suggesting the existence of a half-graben. The result of the gravity 3D model indicates the existence of a main depocenter in the NE-SW direction with depths of up to 400 meters. These geophysical results support the tubular well location drilled 410 m in depth that was used in this work to better characterize the basin. The joint interpretation of gravity, aeromagnetic and structural data suggest that the half-graben framework of the basin developed by the evolution of a pull-apart extension system. The structural system that gave rise to the Mirandiba Basin has the maximum compression tensioner oriented to NE-SW and the distention to NW-SE. It has a depth of around 400 meters and the depressions formed by tectonic events were filled by Post-Tacaratu sedimentation.

Filamentous eukaryotic algae from the Lower Devonian, Bukowa Góra (Holy Cross Mountains, Poland)

Palynological investigations of the upper Emsian rocks from the Bukowa Góra Quarry (Holy Cross Mountains; Poland) revealed an organic fraction classified as remains of filamentous algae. Individual cells were arranged linearly and contacted each other. Specimens occurred as short filaments having no branches. Cell walls appeared single-layered, very thin and translucent. Cell surfaces were sometimes covered with very delicate striations, possibly generated by compressional folding. A comparison of the main features of the described taxa with extant algae indicated closest relationship with the chlorophycean green algal orders Ulotrichales and Cladophorales. Representatives of these orders occupy mainly freshwater environments. Palynofacies investigation revealed high content of land origin palynomorphs with complete lack of marine components. The presence of such delicate organisms as algae in sediments might indicate very fast deposition in a proximal, very near-shore, possibly shallow water/lagoonal or alluvial environment.